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1

Obligate intracellular bacterial parasites of acanthamoebae related to Chlamydia spp.  

PubMed Central

The phylogeny of obligate intracellular coccoid parasites of acanthamoebae isolated from the nasal mucosa of humans was analyzed by the rRNA approach. The primary structures of the 16S and 23S rRNA molecules of one strain were determined in almost full length. In situ hybridization with a horseradish peroxidase-labeled oligonucleotide probe targeted to a unique signature site undoubtedly correlated the retrieved 16S rRNA sequence to the respective intracellular parasite. This probe also hybridized with the second strain, suggesting a close relationship between the two intracellular parasites. Comparative sequence analysis demonstrated a distinct relationship to the genus Chlamydia. With 16S rRNA similarities of 86 to 87% to the hitherto-sequenced Chlamydia species, the intracellular parasites are likely not new species of this genus but representatives of another genus in the family of the Chlamydiaceae. Consequently, it is proposed to provisionally classify the endoparasite of Acanthamoeba sp. strain Bn9 as "Candidatus Parachlamydia acanthamoebae." From an epidemiological perspective, the results suggest that small amoebae could be environmental reservoirs and vectors for a variety of potentially pathogenic bacteria including members of the Chlamydiaceae.

Amann, R; Springer, N; Schonhuber, W; Ludwig, W; Schmid, E N; Muller, K D; Michel, R

1997-01-01

2

An Alternative Efficient Procedure for Purification of the Obligate Intracellular Fish Bacterial Pathogen Piscirickettsia salmonis  

PubMed Central

Piscirickettsia salmonis is an obligate intracellular bacterial pathogen of salmonid fish and the etiological agent of the aggressive disease salmonid rickettsial syndrome. Today, this disease, also known as piscirickettsiosis, is the cause of high mortality in net pen-reared salmonids in southern Chile. Although the bacteria can be grown in tissue culture cells, genetic analysis of the organism has been hindered because of the difficulty in obtaining P. salmonis DNA free from contaminating host cell DNA. In this report, we describe a novel procedure to purify in vitro-grown bacteria with iodixanol as the substrate to run differential centrifugation gradients which, combined with DNase I digestion, yield enough pure bacteria to do DNA analysis. The efficiency of the purification procedure relies on two main issues: semiquantitative synchrony of the P. salmonis-infected Chinook salmon embryo (CHSE-214) tissue culture cells and low osmolarity of iodixanol to better resolve bacteria from the membranous structures of the host cell. This method resulted in the isolation of intact piscirickettsia organisms and removed salmon and mitochondrial DNA effectively, with only 1.0% contamination with the latter.

Henriquez, Vitalia; Rojas, Maria Veronica; Marshall, Sergio H.

2003-01-01

3

An alternative efficient procedure for purification of the obligate intracellular fish bacterial pathogen Piscirickettsia salmonis.  

PubMed

Piscirickettsia salmonis is an obligate intracellular bacterial pathogen of salmonid fish and the etiological agent of the aggressive disease salmonid rickettsial syndrome. Today, this disease, also known as piscirickettsiosis, is the cause of high mortality in net pen-reared salmonids in southern Chile. Although the bacteria can be grown in tissue culture cells, genetic analysis of the organism has been hindered because of the difficulty in obtaining P. salmonis DNA free from contaminating host cell DNA. In this report, we describe a novel procedure to purify in vitro-grown bacteria with iodixanol as the substrate to run differential centrifugation gradients which, combined with DNase I digestion, yield enough pure bacteria to do DNA analysis. The efficiency of the purification procedure relies on two main issues: semiquantitative synchrony of the P. salmonis-infected Chinook salmon embryo (CHSE-214) tissue culture cells and low osmolarity of iodixanol to better resolve bacteria from the membranous structures of the host cell. This method resulted in the isolation of intact piscirickettsia organisms and removed salmon and mitochondrial DNA effectively, with only 1.0% contamination with the latter. PMID:14532090

Henríquez, Vitalia; Rojas, María Verónica; Marshall, Sergio H

2003-10-01

4

OspA, a lipoprotein antigen of the obligate intracellular bacterial pathogen Piscirickettsia salmonis.  

PubMed

No effective recombinant vaccines are currently available for any rickettsial diseases. In this regard the first non-ribosomal DNA sequences from the obligate intracellular pathogen Piscirickettsia salmonis are presented. Genomic DNA isolated from Percoll density gradient purified P. salmonis, was used to construct an expression library in lambda ZAP II. In the absence of preexisting DNA sequence, rabbit polyclonal antiserum raised against P. salmonis, with a bias toward P. salmonis surface antigens, was used to identify immunoreactive clones. Catabolite repression of the lac promoter was required to obtain a stable clone of a 4,983 bp insert in Escherichia coli due to insert toxicity exerted by the accompanying radA open reading frame (ORF). DNA sequence analysis of the insert revealed 1 partial and 4 intact predicted ORF's. A 486 bp ORF, ospA, encoded a 17 kDa antigenic outer surface protein (OspA) with 62% amino acid sequence homology to the genus common 17 kDa outer membrane lipoprotein of Rickettsia prowazekii, previously thought confined to members of the genus Rickettsia. Palmitate incorporation demonstrated that OspA is posttranslationally lipidated in E. coli, albeit poorly expressed as a lipoprotein even after replacement of the signal sequence with the signal sequence from lpp (Braun lipoprotein) or the rickettsial 17 kDa homologue. To enhance expression, ospA was optimized for codon usage in E. coli by PCR synthesis. Expression of ospA was ultimately improved (approximately 13% of total protein) with a truncated variant lacking a signal sequence. High level expression (approximately 42% tot. prot.) was attained as an N-terminal fusion protein with the fusion product recovered as inclusion bodies in E. coli BL21. Expression of OspA in P. salmonis was confirmed by immunoblot analysis using polyclonal antibodies generated against a synthetic peptide of OspA (110-129) and a strong antibody response against OspA was detected in convalescent sera from coho salmon (Oncorhynchus kisutch). PMID:11200233

Kuzyk, M A; Burian, J; Thornton, J C; Kay, W W

2001-01-01

5

Genome degeneration affects both extracellular and intracellular bacterial endosymbionts  

PubMed Central

The obligate intracellular bacterial endosymbionts of insects are a paradigm for reductive genome evolution. A study published recently in BMC Biology demonstrates that similar evolutionary forces shaping genome structure may also apply to extracellular endosymbionts.

Feldhaar, Heike; Gross, Roy

2009-01-01

6

Microsporidian genome analysis reveals evolutionary strategies for obligate intracellular growth  

PubMed Central

Microsporidia comprise a large phylum of obligate intracellular eukaryotes that are fungal-related parasites responsible for widespread disease, and here we address questions about microsporidia biology and evolution. We sequenced three microsporidian genomes from two species, Nematocida parisii and Nematocida sp1, which are natural pathogens of Caenorhabditis nematodes and provide model systems for studying microsporidian pathogenesis. We performed deep sequencing of transcripts from a time course of N. parisii infection. Examination of pathogen gene expression revealed compact transcripts and a dramatic takeover of host cells by Nematocida. We also performed phylogenomic analyses of Nematocida and other microsporidian genomes to refine microsporidian phylogeny and identify evolutionary events of gene loss, acquisition, and modification. In particular, we found that all microsporidia lost the tumor-suppressor gene retinoblastoma, which we speculate could accelerate the parasite cell cycle and increase the mutation rate. We also found that microsporidia acquired transporters that could import nucleosides to fuel rapid growth. In addition, microsporidian hexokinases gained secretion signal sequences, and in a functional assay these were sufficient to export proteins out of the cell; thus hexokinase may be targeted into the host cell to reprogram it toward biosynthesis. Similar molecular changes appear during formation of cancer cells and may be evolutionary strategies adopted independently by microsporidia to proliferate rapidly within host cells. Finally, analysis of genome polymorphisms revealed evidence for a sexual cycle that may provide genetic diversity to alleviate problems caused by clonal growth. Together these events may explain the emergence and success of these diverse intracellular parasites.

Cuomo, Christina A.; Desjardins, Christopher A.; Bakowski, Malina A.; Goldberg, Jonathan; Ma, Amy T.; Becnel, James J.; Didier, Elizabeth S.; Fan, Lin; Heiman, David I.; Levin, Joshua Z.; Young, Sarah; Zeng, Qiandong; Troemel, Emily R.

2012-01-01

7

Rickettsia Phylogenomics: Unwinding the Intricacies of Obligate Intracellular Life  

PubMed Central

Background Completed genome sequences are rapidly increasing for Rickettsia, obligate intracellular ?-proteobacteria responsible for various human diseases, including epidemic typhus and Rocky Mountain spotted fever. In light of phylogeny, the establishment of orthologous groups (OGs) of open reading frames (ORFs) will distinguish the core rickettsial genes and other group specific genes (class 1 OGs or C1OGs) from those distributed indiscriminately throughout the rickettsial tree (class 2 OG or C2OGs). Methodology/Principal Findings We present 1823 representative (no gene duplications) and 259 non-representative (at least one gene duplication) rickettsial OGs. While the highly reductive (?1.2 MB) Rickettsia genomes range in predicted ORFs from 872 to 1512, a core of 752 OGs was identified, depicting the essential Rickettsia genes. Unsurprisingly, this core lacks many metabolic genes, reflecting the dependence on host resources for growth and survival. Additionally, we bolster our recent reclassification of Rickettsia by identifying OGs that define the AG (ancestral group), TG (typhus group), TRG (transitional group), and SFG (spotted fever group) rickettsiae. OGs for insect-associated species, tick-associated species and species that harbor plasmids were also predicted. Through superimposition of all OGs over robust phylogeny estimation, we discern between C1OGs and C2OGs, the latter depicting genes either decaying from the conserved C1OGs or acquired laterally. Finally, scrutiny of non-representative OGs revealed high levels of split genes versus gene duplications, with both phenomena confounding gene orthology assignment. Interestingly, non-representative OGs, as well as OGs comprised of several gene families typically involved in microbial pathogenicity and/or the acquisition of virulence factors, fall predominantly within C2OG distributions. Conclusion/Significance Collectively, we determined the relative conservation and distribution of 14354 predicted ORFs from 10 rickettsial genomes across robust phylogeny estimation. The data, available at PATRIC (PathoSystems Resource Integration Center), provide novel information for unwinding the intricacies associated with Rickettsia pathogenesis, expanding the range of potential diagnostic, vaccine and therapeutic targets.

Gillespie, Joseph J.; Williams, Kelly; Shukla, Maulik; Snyder, Eric E.; Nordberg, Eric K.; Ceraul, Shane M.; Dharmanolla, Chitti; Rainey, Daphne; Soneja, Jeetendra; Shallom, Joshua M.; Vishnubhat, Nataraj Dongre; Wattam, Rebecca; Purkayastha, Anjan; Czar, Michael; Crasta, Oswald; Setubal, Joao C.; Azad, Abdu F.; Sobral, Bruno S.

2008-01-01

8

Transient Transfection and Expression in the Obligate Intracellular Parasite Toxoplasma gondii  

Microsoft Academic Search

Toxoplasma gondii is a protozoan pathogen that produces severe disease in humans and animals. This obligate intracellular parasite provides an excellent model for the study of how such pathogens are able to invade, survive, and replicate intracellularly. DNA encoding chloramphenicol acetyltransferase was introduced into T. gondii and transiently expressed with the use of three vectors based on different Toxoplasma genes.

Dominique Soldati; John C. Boothroyd

1993-01-01

9

Whole genome amplification of the obligate intracellular pathogen Coxiella burnetii using multiple displacement amplification.  

PubMed

This study demonstrates that whole genome multiple displacement amplification (MDA) is a promising technique for downstream genomic analysis of fastidious obligate intracellular pathogens such as Coxiella burnetii. The MDA technology can help in obtaining sufficient genetic material from highly infectious agent and thus minimizing repeated culturing and associated biohazard. PMID:24455771

Kumar, Sanjay; Gangoliya, Shefali Raj; Berri, Mustapha; Rodolakis, Annie; Alam, Syed Imteyaz

2013-12-01

10

Transient Transfection and Expression in the Obligate Intracellular Parasite Toxoplasma gondii  

NASA Astrophysics Data System (ADS)

Toxoplasma gondii is a protozoan pathogen that produces severe disease in humans and animals. This obligate intracellular parasite provides an excellent model for the study of how such pathogens are able to invade, survive, and replicate intracellularly. DNA encoding chloramphenicol acetyltransferase was introduced into T. gondii and transiently expressed with the use of three vectors based on different Toxoplasma genes. The ability to introduce genes and have them efficiently and faithfully expressed is an essential tool for understanding the structure-function relation of genes and their products.

Soldati, Dominique; Boothroyd, John C.

1993-04-01

11

PI3K-? inhibitors in the therapeutic intervention of diseases caused by obligate intracellular pathogens  

PubMed Central

Our increased understanding of host pathogen interactions shows that pathogens could capitalize on host cell pathways to favor entry and disease establishment. One such pathway used by Leishmania mexicana to enter into neutrophils and macrophages is the PI3K? signaling pathway. We recently showed that the use of the PI3K? inhibitor AS-605240 for the treatment of experimental L. mexicana infection in mice resulted in significantly lower parasite burdens and lesion sizes than WT untreated mice. Further, AS-605240 was found to be as effective as Sodium Stibogluconate, the drug of choice for treatment of L. mexicana infection, in reducing parasite burdens in mice. Here, we provide potential mechanisms of PI3K? blockade in promoting resistance to L. mexicana infection in mice. As a proof of principle, we propose that targeting host cell signaling pathways used in the establishment of infection could be a possible therapeutic option in the management of obligate intracellular pathogens.

Oghumu, Steve; Satoskar, Abhay R.

2013-01-01

12

Bacterial Pathogens Commandeer Rab GTPases to Establish Intracellular Niches  

PubMed Central

Intracellular bacterial pathogens deploy virulence factors termed effectors to inhibit degradation by host cells and to establish intracellular niches where growth and differentiation take place. Here, we describe mechanisms by which human bacterial pathogens (including Chlamydiae; Coxiella burnetii; Helicobacter pylori; Legionella pneumophila; Listeria monocytogenes; Mycobacteria; Pseudomonas aeruginosa, Salmonella enterica) modulate endocytic and exocytic Rab GTPases in order to thrive in host cells. Host cell Rab GTPases are critical for intracellular transport following pathogen phagocytosis or endocytosis. At the molecular level bacterial effectors hijack Rab protein function to: evade degradation, direct transport to particular intracellular locations, and monopolize host vesicles carrying molecules that are needed for a stable niche and/or bacterial growth and differentiation. Bacterial effectors may serve as specific receptors for Rab GTPases or as enzymes that post-translationally modify Rab proteins or endosomal membrane lipids required for Rab function. Emerging data indicate that bacterial effector expression is temporally and spatially regulated and multiple virulence factors may act concertedly to usurp Rab GTPase function, alter signaling and ensure niche establishment and intracellular bacterial growth, making this field an exciting area for further study.

Stein, Mary-Pat; Muller, Matthias P.; Wandinger-Ness, Angela

2012-01-01

13

Biological Properties and Cell Tropism of Chp2, a Bacteriophage of the Obligate Intracellular Bacterium Chlamydophila abortus  

Microsoft Academic Search

A number of bacteriophages belonging to the Microviridae have been described infecting chlamydiae. Phy- logenetic studies divide the Chlamydiaceae into two distinct genera, Chlamydia and Chlamydophila, containing three and six different species, respectively. In this work we investigated the biological properties and host range of the recently described bacteriophage Chp2 that was originally discovered in Chlamydophila abortus. The obligate intracellular

J. S. Everson; S. A. Garner; B. Fane; B.-L. Liu; P. R. Lambden; I. N. Clarke

2002-01-01

14

The genome of obligately intracellular Ehrlichia canis revealsthemes of complex membrane structure and immune evasion strategies  

SciTech Connect

Ehrlichia canis, a small obligately intracellular, tick-transmitted, gram-negative, a-proteobacterium is the primary etiologic agent of globally distributed canine monocytic ehrlichiosis. Complete genome sequencing revealed that the E. canis genome consists of a single circular chromosome of 1,315,030 bp predicted to encode 925 proteins, 40 stable RNA species, and 17 putative pseudogenes, and a substantial proportion of non-coding sequence (27 percent). Interesting genome features include a large set of proteins with transmembrane helices and/or signal sequences, and a unique serine-threonine bias associated with the potential for O-glycosylation that was prominent in proteins associated with pathogen-host interactions. Furthermore, two paralogous protein families associated with immune evasion were identified, one of which contains poly G:C tracts, suggesting that they may play a role in phase variation and facilitation of persistent infections. Proteins associated with pathogen-host interactions were identified including a small group of proteins (12) with tandem repeats and another with eukaryotic-like ankyrin domains (7).

Mavromatis, K.; Kuyler Doyle, C.; Lykidis, A.; Ivanova, N.; Francino, P.; Chain, P.; Shin, M.; Malfatti, S.; Larimer, F.; Copeland,A.; Detter, J.C.; Land, M.; Richardson, P.M.; Yu, X.J.; Walker, D.H.; McBride, J.W.; Kyrpides, N.C.

2005-09-01

15

Physical and Genetic Map of the Obligate Intracellular Bacterium Coxiella burnetii  

PubMed Central

Pulsed-field gel electrophoresis and PCR techniques have been used to construct a NotI macrorestriction map of the obligate intracellular bacterium Coxiella burnetii Nine Mile. The size of the chromosome has been determined to be 2,103 kb comprising 29 NotI restriction fragments. The average resolution is 72.5 kb, or about 3.5% of the genome. Experimental data support the presence of a linear chromosome. Published genes were localized on the physical map by Southern hybridization. One gene, recognized as transposable element, was found to be present in at least nine sites evenly distributed over the whole chromosome. There is only one copy of a 16S rRNA gene. The putative oriC has been located on a 27.5-kb NotI fragment. Gene organization upstream the oriC is almost identical to that of Pseudomonas putida and Bacillus subtilis, whereas gene organization downstream the oriC seems to be unique among bacteria. The physical map will be helpful in investigations of the great heterogeneity in restriction fragment length polymorphism patterns of different isolates and the great variation in genome size. The genetic map will help to determine whether gene order in different isolates is conserved.

Willems, H.; Jager, Cornelie; Baljer, Georg

1998-01-01

16

Autophagic clearance of bacterial pathogens: molecular recognition of intracellular microorganisms.  

PubMed

Autophagy is involved in several physiological and pathological processes. One of the key roles of the autophagic pathway is to participate in the first line of defense against the invasion of pathogens, as part of the innate immune response. Targeting of intracellular bacteria by the autophagic machinery, either in the cytoplasm or within vacuolar compartments, helps to control bacterial proliferation in the host cell, controlling also the spreading of the infection. In this review we will describe the means used by diverse bacterial pathogens to survive intracellularly and how they are recognized by the autophagic molecular machinery, as well as the mechanisms used to avoid autophagic clearance. PMID:24137567

Pareja, Maria Eugenia Mansilla; Colombo, Maria I

2013-01-01

17

Autophagic clearance of bacterial pathogens: molecular recognition of intracellular microorganisms  

PubMed Central

Autophagy is involved in several physiological and pathological processes. One of the key roles of the autophagic pathway is to participate in the first line of defense against the invasion of pathogens, as part of the innate immune response. Targeting of intracellular bacteria by the autophagic machinery, either in the cytoplasm or within vacuolar compartments, helps to control bacterial proliferation in the host cell, controlling also the spreading of the infection. In this review we will describe the means used by diverse bacterial pathogens to survive intracellularly and how they are recognized by the autophagic molecular machinery, as well as the mechanisms used to avoid autophagic clearance.

Mansilla Pareja, Maria Eugenia; Colombo, Maria I.

2013-01-01

18

Analysis of Fluorescent Protein Expression in Transformants of Rickettsia monacensis, an Obligate Intracellular Tick Symbiont  

PubMed Central

We developed and applied transposon-based transformation vectors for molecular manipulation and analysis of spotted fever group rickettsiae, which are obligate intracellular bacteria that infect ticks and, in some cases, mammals. Using the Epicentre EZ::TN transposon system, we designed transposons for simultaneous expression of a reporter gene and a chloramphenicol acetyltransferase (CAT) resistance marker. Transposomes (transposon-transposase complexes) were electroporated into Rickettsia monacensis, a rickettsial symbiont isolated from the tick Ixodes ricinus. Each transposon contained an expression cassette consisting of the rickettsial ompA promoter and a green fluorescent protein (GFP) reporter gene (GFPuv) or the ompB promoter and a red fluorescent protein reporter gene (DsRed2), followed by the ompA transcription terminator and a second ompA promoter CAT gene cassette. Selection with chloramphenicol gave rise to rickettsial populations with chromosomally integrated single-copy transposons as determined by PCR, Southern blotting, and sequence analysis. Reverse transcription-PCR and Northern blots demonstrated transcription of all three genes. GFPuv transformant rickettsiae exhibited strong fluorescence in individual cells, but DsRed2 transformants did not. Western blots confirmed expression of GFPuv in R. monacensis and in Escherichia coli, but DsRed2 was expressed only in E. coli. The DsRed2 gene, but not the GFPuv gene, contains many GC-rich amino acid codons that are rare in the preferred codon suite of rickettsiae, possibly explaining the failure to express DsRed2 protein in R. monacensis. We demonstrated that our vectors provide a means to study rickettsia-host cell interactions by visualizing GFPuv-fluorescent R. monacensis associated with actin tails in tick host cells.

Baldridge, Gerald D.; Burkhardt, Nicole; Herron, Michael J.; Kurtti, Timothy J.; Munderloh, Ulrike G.

2005-01-01

19

Multi locus sequence typing of Chlamydiales: clonal groupings within the obligate intracellular bacteria Chlamydia trachomatis  

PubMed Central

Background The obligate intracellular growing bacterium Chlamydia trachomatis causes diseases like trachoma, urogenital infection and lymphogranuloma venereum with severe morbidity. Several serovars and genotypes have been identified, but these could not be linked to clinical disease or outcome. The related Chlamydophila pneumoniae, of which no subtypes are recognized, causes respiratory infections worldwide. We developed a multi locus sequence typing (MLST) scheme to understand the population genetic structure and diversity of these species and to evaluate the association between genotype and disease. Results A collection of 26 strains of C. trachomatis of different serovars and clinical presentation and 18 strains of C. pneumoniae were included in the study. For comparison, sequences of C. abortus, C. psittaci, C. caviae, C. felis, C. pecorum (Chlamydophila), C. muridarum (Chlamydia) and of Candidatus protochlamydia and Simkania negevensis were also included. Sequences of fragments (400 – 500 base pairs) from seven housekeeping genes (enoA, fumC, gatA, gidA, hemN, hlfX, oppA) were analysed. Analysis of allelic profiles by eBurst revealed three non-overlapping clonal complexes among the C. trachomatis strains, while the C. pneumoniae strains formed a single group. An UPGMA tree produced from the allelic profiles resulted in three groups of sequence types. The LGV strains grouped in a single cluster, while the urogenital strains were distributed over two separated groups, one consisted solely of strains with frequent occurring serovars (E, D and F). The distribution of the different serovars over the three groups was not consistent, suggesting exchange of serovar encoding ompA sequences. In one instance, exchange of fumC sequences between strains of different groups was observed. Cluster analyses of concatenated sequences of the Chlamydophila and Chlamydia species together with those of Candidatus Protochlamydia amoebophila and Simkania negevensis resulted in a tree identical to that obtained with 23S RNA gene sequences. Conclusion These data show that C. trachomatis and C. pneumoniae are highly uniform. The difference in genetic diversity between C. trachomatis and C. pneumoniae is in concordance with a later assimilation to the human host of the latter. Our data supports the taxonomy of the order of Chlamydiales.

Pannekoek, Yvonne; Morelli, Giovanna; Kusecek, Barica; Morre, Servaas A; Ossewaarde, Jacobus M; Langerak, Ankie A; van der Ende, Arie

2008-01-01

20

Detection of Intracellular Bacterial Communities in Human Urinary Tract Infection  

PubMed Central

Background Urinary tract infections (UTIs) are one of the most common bacterial infections and are predominantly caused by uropathogenic Escherichia coli (UPEC). While UTIs are typically considered extracellular infections, it has been recently demonstrated that UPEC bind to, invade, and replicate within the murine bladder urothelium to form intracellular bacterial communities (IBCs). These IBCs dissociate and bacteria flux out of bladder facet cells, some with filamentous morphology, and ultimately establish quiescent intracellular reservoirs that can seed recurrent infection. This IBC pathogenic cycle has not yet been investigated in humans. In this study we sought to determine whether evidence of an IBC pathway could be found in urine specimens from women with acute UTI. Methods and Findings We collected midstream, clean-catch urine specimens from 80 young healthy women with acute uncomplicated cystitis and 20 asymptomatic women with a history of UTI. Investigators were blinded to culture results and clinical history. Samples were analyzed by light microscopy, immunofluorescence, and electron microscopy for evidence of exfoliated IBCs and filamentous bacteria. Evidence of IBCs was found in 14 of 80 (18%) urines from women with UTI. Filamentous bacteria were found in 33 of 80 (41%) urines from women with UTI. None of the 20 urines from the asymptomatic comparative group showed evidence of IBCs or filaments. Filamentous bacteria were present in all 14 of the urines with IBCs compared to 19 (29%) of 66 samples with no evidence of IBCs (p < 0.001). Of 65 urines from patients with E. coli infections, 14 (22%) had evidence of IBCs and 29 (45%) had filamentous bacteria, while none of the gram-positive infections had IBCs or filamentous bacteria. Conclusions The presence of exfoliated IBCs and filamentous bacteria in the urines of women with acute cystitis suggests that the IBC pathogenic pathway characterized in the murine model may occur in humans. The findings support the occurrence of an intracellular bacterial niche in some women with cystitis that may have important implications for UTI recurrence and treatment.

Rosen, David A; Hooton, Thomas M; Stamm, Walter E; Humphrey, Peter A; Hultgren, Scott J

2007-01-01

21

Bacterial Associates of Arboreal Ants and Their Putative Functions in an Obligate Ant-Plant Mutualism? †  

PubMed Central

Bacterial communities are highly diverse and have great ecological importance. In the present study, we used an in silico analysis of terminal restriction fragments (tRF) to characterize the bacterial community of the plant ant Pseudomyrmex ferrugineus. This species is an obligate inhabitant of Acacia myrmecophytes and feeds exclusively on plant-derived food sources. Ants are the dominant insect group in tropical rain forests. Associations of ants with microbes, which contribute particularly to the ants’ nitrogen nutrition, could allow these insects to live on mostly or entirely plant-based diets and could thus contribute to the explanation of the high abundances that are reached by tropical ants. We found tRF patterns representing at least 30 prokaryotic taxa, of which the Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes, Planctomycetes, Proteobacteria, and Spirochaetes comprised 93%. Because most bacterial taxa were found in all ant-derived samples studied and because the bacteria detected on the ants’ host plant revealed little overlap with this community, we regard our results as reliably representing the bacterial community that is associated with P. ferrugineus. Genera with a likely function as ant symbionts were Burkholderia, Pantoea, Weissella, and several members of the Enterobacteriaceae. The presence of these and various other groups was confirmed via independent PCR and cultivation approaches. Many of the bacteria that we detected belong to purportedly N-fixing taxa. Bacteria may represent important further partners in ant-plant mutualisms, and their influences on ant nutrition can contribute to the extraordinary abundance and evolutionary success of tropical arboreal ants.

Eilmus, Sascha; Heil, Martin

2009-01-01

22

Stable DNA transformation in the obligate intracellular parasite Toxoplasma gondii by complementation of tryptophan auxotrophy.  

PubMed Central

The protozoan parasite Toxoplasma gondii infects a wide range of vertebrate hosts and is an important opportunistic pathogen in immunocompromised humans. Although Toxoplasma is amenable to both biochemical and cellular experimental approaches, the molecular basis of its success as an intracellular parasite is poorly understood. To provide a system for molecular genetic analyses, we have developed a stable DNA transformation system for Toxoplasma based on complementation of its naturally occurring tryptophan auxotrophy. Complementation was accomplished by expressing the Escherichia coli trpB gene, encoding the beta subunit of tryptophan synthase (EC 4.2.1.20), the enzyme that catalyzes the formation of tryptophan from indole plus serine. Transformants were obtained by electroporation of a plasmid, called SAG1/trpB, containing the trpB gene flanked by Toxoplasma surface antigen 1 (SAG1) gene sequences and selection for growth on indole. Transformants were obtained with circular forms of the SAG1/trpB plasmid with efficiencies of 10(-4) per cell. Transformation with either circular or linear SAG1/trpB resulted in integration into the genome at distinct, nonhomologous sites. Trp+ transformants typically contained tandemly repeated copies of the SAG1/trpB plasmid and were stable in the absence of continued selection. The Trp phenotype provides a dominant selectable marker that should allow expression of foreign or altered genes in Toxoplasma and facilitate molecular analyses of genes important for intracellular survival. Images

Sibley, L D; Messina, M; Niesman, I R

1994-01-01

23

Genetic diversity of the obligate intracellular bacterium Chlamydophila pneumoniae by genome-wide analysis of single nucleotide polymorphisms: evidence for highly clonal population structure  

Microsoft Academic Search

BACKGROUND: Chlamydophila pneumoniae is an obligate intracellular bacterium that replicates in a biphasic life cycle within eukaryotic host cells. Four published genomes revealed an identity of > 99 %. This remarkable finding raised questions about the existence of distinguishable genotypes in correlation with geographical and anatomical origin. RESULTS: We studied the genetic diversity of C. pneumoniae by analysing synonymous single

Thomas Rattei; Stephan Ott; Michaela Gutacker; Jan Rupp; Matthias Maass; Stefan Schreiber; Werner Solbach; Thierry Wirth; Jens Gieffers

2007-01-01

24

Metabolic host responses to infection by intracellular bacterial pathogens  

PubMed Central

The interaction of bacterial pathogens with mammalian hosts leads to a variety of physiological responses of the interacting partners aimed at an adaptation to the new situation. These responses include multiple metabolic changes in the affected host cells which are most obvious when the pathogen replicates within host cells as in case of intracellular bacterial pathogens. While the pathogen tries to deprive nutrients from the host cell, the host cell in return takes various metabolic countermeasures against the nutrient theft. During this conflicting interaction, the pathogen triggers metabolic host cell responses by means of common cell envelope components and specific virulence-associated factors. These host reactions generally promote replication of the pathogen. There is growing evidence that pathogen-specific factors may interfere in different ways with the complex regulatory network that controls the carbon and nitrogen metabolism of mammalian cells. The host cell defense answers include general metabolic reactions, like the generation of oxygen- and/or nitrogen-reactive species, and more specific measures aimed to prevent access to essential nutrients for the respective pathogen. Accurate results on metabolic host cell responses are often hampered by the use of cancer cell lines that already exhibit various de-regulated reactions in the primary carbon metabolism. Hence, there is an urgent need for cellular models that more closely reflect the in vivo infection conditions. The exact knowledge of the metabolic host cell responses may provide new interesting concepts for antibacterial therapies.

Eisenreich, Wolfgang; Heesemann, Jurgen; Rudel, Thomas; Goebel, Werner

2013-01-01

25

Human Female Genital Tract Infection by the Obligate Intracellular Bacterium Chlamydia trachomatis Elicits Robust Type 2 Immunity  

PubMed Central

While Chlamydia trachomatis infections are frequently asymptomatic, mechanisms that regulate host response to this intracellular Gram-negative bacterium remain undefined. This investigation thus used peripheral blood mononuclear cells and endometrial tissue from women with or without Chlamydia genital tract infection to better define this response. Initial genome-wide microarray analysis revealed highly elevated expression of matrix metalloproteinase 10 and other molecules characteristic of Type 2 immunity (e.g., fibrosis and wound repair) in Chlamydia-infected tissue. This result was corroborated in flow cytometry and immunohistochemistry studies that showed extant upper genital tract Chlamydia infection was associated with increased co-expression of CD200 receptor and CD206 (markers of alternative macrophage activation) by endometrial macrophages as well as increased expression of GATA-3 (the transcription factor regulating TH2 differentiation) by endometrial CD4+ T cells. Also among women with genital tract Chlamydia infection, peripheral CD3+ CD4+ and CD3+ CD4- cells that proliferated in response to ex vivo stimulation with inactivated chlamydial antigen secreted significantly more interleukin (IL)-4 than tumor necrosis factor, interferon-?, or IL-17; findings that repeated in T cells isolated from these same women 1 and 4 months after infection had been eradicated. Our results thus newly reveal that genital infection by an obligate intracellular bacterium induces polarization towards Type 2 immunity, including Chlamydia-specific TH2 development. Based on these findings, we now speculate that Type 2 immunity was selected by evolution as the host response to C. trachomatis in the human female genital tract to control infection and minimize immunopathological damage to vital reproductive structures.

Vicetti Miguel, Rodolfo D.; Harvey, Stephen A. K.; LaFramboise, William A.; Reighard, Seth D.; Matthews, Dean B.; Cherpes, Thomas L.

2013-01-01

26

Evolution to a Chronic Disease Niche Correlates with Increased Sensitivity to Tryptophan Availability for the Obligate Intracellular Bacterium Chlamydia pneumoniae.  

PubMed

The chlamydiae are obligate intracellular parasites that have evolved specific interactions with their various hosts and host cell types to ensure their successful survival and consequential pathogenesis. The species Chlamydia pneumoniae is ubiquitous, with serological studies showing that most humans are infected at some stage in their lifetime. While most human infections are asymptomatic, C. pneumoniae can cause more-severe respiratory disease and pneumonia and has been linked to chronic diseases such as asthma, atherosclerosis, and even Alzheimer's disease. The widely dispersed animal-adapted C. pneumoniae strains cause an equally wide range of diseases in their hosts. It is emerging that the ability of C. pneumoniae to survive inside its target cells, including evasion of the host's immune attack mechanisms, is linked to the acquisition of key metabolites. Tryptophan and arginine are key checkpoint compounds in this host-parasite battle. Interestingly, the animal strains of C. pneumoniae have a slightly larger genome, enabling them to cope better with metabolite restrictions. It therefore appears that as the evolutionarily more ancient animal strains have evolved to infect humans, they have selectively become more "susceptible" to the levels of key metabolites, such as tryptophan. While this might initially appear to be a weakness, it allows these human C. pneumoniae strains to exquisitely sense host immune attack and respond by rapidly reverting to a persistent phase. During persistence, they reduce their metabolic levels, halting progression of their developmental cycle, waiting until the hostile external conditions have passed before they reemerge. PMID:24682324

Huston, Wilhelmina M; Barker, Christopher J; Chacko, Anu; Timms, Peter

2014-06-01

27

Characterization of an Obligate Intracellular Bacterium in the Midgut Epithelium of the Bulrush Bug Chilacis typhae (Heteroptera, Lygaeidae, Artheneinae)?  

PubMed Central

Many members of the suborder Heteroptera have symbiotic bacteria, which are usually found extracellularly in specific sacs or tubular outgrowths of the midgut or intracellularly in mycetomes. In this study, we describe the second molecular characterization of a symbiotic bacterium in a monophagous, seed-sucking stink bug of the family Lygaeidae (sensu stricto). Chilacis typhae possesses at the end of the first section of the midgut a structure which is composed of circularly arranged, strongly enlarged midgut epithelial cells. It is filled with an intracellular endosymbiont. This “mycetocytic belt” might represent an evolutionarily intermediate stage of the usual symbiotic structures found in stink bugs. Phylogenetic analysis based on the 16S rRNA and the groEL genes showed that the bacterium belongs to the Gammaproteobacteria, and it revealed a phylogenetic relationship with a secondary bacterial endosymbiont of Cimex lectularius and free-living plant pathogens such as Pectobacterium and Dickeya. The distribution and ultrastructure of the rod-shaped Chilacis endosymbiont were studied in adults and nymph stages using fluorescence in situ hybridization (FISH) and electron microscopy. The detection of symbionts at the anterior poles of developing eggs indicates that endosymbionts are transmitted vertically. A new genus and species name, “Candidatus Rohrkolberia cinguli,” is proposed for this newly characterized clade of symbiotic bacteria.

Kuechler, Stefan Martin; Dettner, Konrad; Kehl, Siegfried

2011-01-01

28

Pulsed-field gel electrophoresis determination of the genome size of obligate intracellular bacteria belonging to the genera Chlamydia, Rickettsiella, and Porochlamydia.  

PubMed Central

The chromosome length of obligate intracellular procaryotes was determined by pulsed-field gel electrophoresis of intact or NotI- and SfiI-restricted genomes. Sizes averaged 2,100, 1,720, 1,550, 2,650, and 1,450 kilobases for Rickettsiella grylli, Rickettsiella melolonthae, Porochlamydia buthi, Porochlamydia chironomi, and Chlamydia psittaci and Chlamydia trachomatis, respectively. An SfiI restriction map of the R. melolonthae genome was derived. Images

Frutos, R; Pages, M; Bellis, M; Roizes, G; Bergoin, M

1989-01-01

29

Motor-driven intracellular transport powers bacterial gliding motility  

PubMed Central

Protein-directed intracellular transport has not been observed in bacteria despite the existence of dynamic protein localization and a complex cytoskeleton. However, protein trafficking has clear potential uses for important cellular processes such as growth, development, chromosome segregation, and motility. Conflicting models have been proposed to explain Myxococcus xanthus motility on solid surfaces, some favoring secretion engines at the rear of cells and others evoking an unknown class of molecular motors distributed along the cell body. Through a combination of fluorescence imaging, force microscopy, and genetic manipulation, we show that membrane-bound cytoplasmic complexes consisting of motor and regulatory proteins are directionally transported down the axis of a cell at constant velocity. This intracellular motion is transmitted to the exterior of the cell and converted to traction forces on the substrate. Thus, this study demonstrates the existence of a conserved class of processive intracellular motors in bacteria and shows how these motors have been adapted to produce cell motility.

Sun, Mingzhai; Wartel, Morgane; Cascales, Eric; Shaevitz, Joshua W.; Mignot, Tam

2011-01-01

30

ISPsa2, the first mobile genetic element to be described and characterized in the bacterial facultative intracellular pathogen Piscirickettsia salmonis.  

PubMed

Piscirickettsia salmonis is a novel, aggressive, facultative Gram-negative bacterium that drastically affects salmon production at different latitudes, with particular impact in southern Chile. Initially, P. salmonis was described as a Rickettsia-like, obligate, intracellular Alphaproteobacteria, but it was reclassified recently as a facultative intracellular Gammaproteobacteria. This designation has prompted the independent growth of the bacterium to a pure state for detailed study of its biology, genetics and epidemiology, properties that are still relatively poorly characterized. The preliminary sequence analysis of a 992-bp fragment of pure P. salmonis DNA allowed us to characterize a novel and complete 863-bp insertion sequence in the bacterial genome (named ISPsa2), which has a novel 16/16bp perfectly inverted terminal repeat flanking a 726-bp ORF that encodes a putative transposase (Tnp-Psa). The coding sequence of the enzyme shares similarities to that described in some Bacillus species and particularly to those of the IS6 family. ISPsa2 carries its own promoter with standard -10 and -35 sequences, suggesting an interesting potential for plasticity in this pathogenic bacterium. Additionally, the presence of ISPsa2 was confirmed from three isolates of P. salmonis collected from different epizootics in Chile in 2010. PMID:21073510

Marshall, Sergio H; Henríquez, Vitalia; Gómez, Fernando A; Cárdenas, Constanza

2011-01-01

31

Directed antigen delivery as a vaccine strategy for an intracellular bacterial pathogen  

NASA Astrophysics Data System (ADS)

We have developed a vaccine strategy for generating an attenuated strain of an intracellular bacterial pathogen that, after uptake by professional antigen-presenting cells, does not replicate intracellularly and is readily killed. However, after degradation of the vaccine strain within the phagolysosome, target antigens are released into the cytosol for endogenous processing and presentation for stimulation of CD8+ effector T cells. Applying this strategy to the model intracellular pathogen Listeria monocytogenes, we show that an intracellular replication-deficient vaccine strain is cleared rapidly in normal and immunocompromised animals, yet antigen-specific CD8+ effector T cells are stimulated after immunization. Furthermore, animals immunized with the intracellular replication-deficient vaccine strain are resistant to lethal challenge with a virulent WT strain of L. monocytogenes. These studies suggest a general strategy for developing safe and effective, attenuated intracellular replication-deficient vaccine strains for stimulation of protective immune responses against intracellular bacterial pathogens. CD8+ T cell | replication-deficient | Listeria monocytogenes

Bouwer, H. G. Archie; Alberti-Segui, Christine; Montfort, Megan J.; Berkowitz, Nathan D.; Higgins, Darren E.

2006-03-01

32

The "domino theory" of gene death: gradual and mass gene extinction events in three lineages of obligate symbiotic bacterial pathogens.  

PubMed

During the adaptation of an organism to a parasitic lifestyle, various gene functions may be rendered superfluous due to the fact that the host may supply these needs. As a consequence, obligate symbiotic bacterial pathogens tend to undergo reductive genomic evolution through gene death (nonfunctionalization or pseudogenization) and deletion. Here, we examine the evolutionary sequence of gene-death events during the process of genome miniaturization in three bacterial species that have experienced extensive genome reduction: Mycobacterium leprae, Shigella flexneri, and Salmonella typhi. We infer that in all three lineages, the distribution of functional categories is similar in pseudogenes and genes but different from that of absent genes. Based on an analysis of evolutionary distances, we propose a two-step "domino effect" model for reductive genome evolution. The process starts with a gradual gene-by-gene-death sequence of events. Eventually, a crucial gene within a complex pathway or network is rendered nonfunctional triggering a "mass gene extinction" of the dependent genes. In contrast to published reports according to which genes belonging to certain functional categories are prone to nonfunctionalization more frequently and earlier than genes belonging to other functional categories, we could discern no characteristic regularity in the temporal order of function loss. PMID:16237210

Dagan, Tal; Blekhman, Ran; Graur, Dan

2006-02-01

33

An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent  

PubMed Central

The abundance of life on Earth is almost entirely due to biological photosynthesis, which depends on light energy. The source of light in natural habitats has heretofore been thought to be the sun, thus restricting photosynthesis to solar photic environments on the surface of the Earth. If photosynthesis could take place in geothermally illuminated environments, it would increase the diversity of photosynthetic habitats both on Earth and on other worlds that have been proposed to possibly harbor life. Green sulfur bacteria are anaerobes that require light for growth by the oxidation of sulfur compounds to reduce CO2 to organic carbon, and are capable of photosynthetic growth at extremely low light intensities. We describe the isolation and cultivation of a previously unknown green sulfur bacterial species from a deep-sea hydrothermal vent, where the only source of light is geothermal radiation that includes wavelengths absorbed by photosynthetic pigments of this organism.

Beatty, J. Thomas; Overmann, Jorg; Lince, Michael T.; Manske, Ann K.; Lang, Andrew S.; Blankenship, Robert E.; Van Dover, Cindy L.; Martinson, Tracey A.; Plumley, F. Gerald

2005-01-01

34

An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent.  

PubMed

The abundance of life on Earth is almost entirely due to biological photosynthesis, which depends on light energy. The source of light in natural habitats has heretofore been thought to be the sun, thus restricting photosynthesis to solar photic environments on the surface of the Earth. If photosynthesis could take place in geothermally illuminated environments, it would increase the diversity of photosynthetic habitats both on Earth and on other worlds that have been proposed to possibly harbor life. Green sulfur bacteria are anaerobes that require light for growth by the oxidation of sulfur compounds to reduce CO2 to organic carbon, and are capable of photosynthetic growth at extremely low light intensities. We describe the isolation and cultivation of a previously unknown green sulfur bacterial species from a deep-sea hydrothermal vent, where the only source of light is geothermal radiation that includes wavelengths absorbed by photosynthetic pigments of this organism. PMID:15967984

Beatty, J Thomas; Overmann, Jörg; Lince, Michael T; Manske, Ann K; Lang, Andrew S; Blankenship, Robert E; Van Dover, Cindy L; Martinson, Tracey A; Plumley, F Gerald

2005-06-28

35

Hydrogen peroxide staining to visualize intracellular bacterial infections of seedling root cells.  

PubMed

Visualization of bacteria in living plant cells and tissues is often problematic due to lack of stains that pass through living plant cell membranes and selectively stain bacterial cells. In this article, we report the use of 3,3'-diaminobenzidine tetrachloride (DAB) to stain hydrogen peroxide associated with bacterial invasion of eukaryotic cells. Tissues were counterstained with aniline blue/lactophenol to stain protein in bacterial cells. Using this staining method to visualize intracellular bacterial (Burkholderia gladioli) colonization of seedling roots of switch grass (Panicum virgatum), we compared bacterial free seedling roots and those inoculated with the bacterium. To further assess application of the technique in multiple species of vascular plants, we examined vascular plants for seedling root colonization by naturally occurring seed-transmitted bacteria. Colonization by bacteria was only observed to occur within epidermal (including root hairs) and cortical cells of root tissues, suggesting that bacteria may not be penetrating deeply into root tissues. DAB/peroxidase with counter stain aniline blue/lactophenol was effective in penetration of root cells to selectively stain bacteria. Furthermore, this stain combination permitted the visualization of the bacterial lysis process. Before any evidence of H2 O2 staining, intracellular bacteria were seen to stain blue for protein content with aniline blue/lactophenol. After H2 O2 staining became evident, bacteria were often swollen, without internal staining by aniline blue/lactophenol; this suggests loss of protein content. This staining method was effective for seedling root tissues; however, it was not effective at staining bacteria in shoot tissues due to poor penetration. Microsc. Res. Tech. 77:566-573, 2014. © 2014 Wiley Periodicals, Inc. PMID:24825573

White, James F; Torres, Mónica S; Somu, Mohini P; Johnson, Holly; Irizarry, Ivelisse; Chen, Qiang; Zhang, Ning; Walsh, Emily; Tadych, Mariusz; Bergen, Marshall

2014-08-01

36

Detection of intracellular bacterial communities in a child with Escherichia coli recurrent urinary tract infections.  

PubMed

The formation of intracellular bacterial communities (IBC) has been proposed as a new pathogenic model for urinary tract infections. Scarce reports describe this phenomenon in humans. We describe the presence of IBC in uroepithelial cells of a child with recurrent urinary infections. Urine specimen was collected from a child with Escherichia coli UTI and analyzed by light and confocal laser scanning microscopy (CLSM). The capability of this strain to produce intracellular infection in bladder tissue was confirmed in mice models. Escherichia coli phylogenetic group, presence of virulence factors genes, and its multiple locus sequence type were determined. CLSM showed large collections of morphologically coccoid and rod bacteria in eukaryotic cells cytoplasm, even seemingly protruding from the cells. Escherichia coli EC7U, ST3626, harbored type 1, P, and S/F1C fimbriae and K1 capsule genes. In this report, we confirm the presence of IBC in children with UTI, as it has been described before in women. PMID:23733378

Robino, Luciana; Scavone, Paola; Araujo, Lucia; Algorta, Gabriela; Zunino, Pablo; Vignoli, Rafael

2013-08-01

37

RIG-I Detects mRNA of Intracellular Salmonella enterica Serovar Typhimurium during Bacterial Infection  

PubMed Central

ABSTRACT The cytoplasmic helicase RIG-I is an established sensor for viral 5?-triphosphorylated RNA species. Recently, RIG-I was also implicated in the detection of intracellular bacteria. However, little is known about the host cell specificity of this process and the bacterial pathogen-associated molecular pattern (PAMP) that activates RIG-I. Here we show that RNA of Salmonella enterica serovar Typhimurium activates production of beta interferon in a RIG-I-dependent fashion only in nonphagocytic cells. In phagocytic cells, RIG-I is obsolete for detection of Salmonella infection. We further demonstrate that Salmonella mRNA reaches the cytoplasm during infection and is thus accessible for RIG-I. The results from next-generation sequencing analysis of RIG-I-associated RNA suggest that coding bacterial mRNAs represent the activating PAMP.

Schmolke, Mirco; Patel, Jenish R.; de Castro, Elisa; Sanchez-Aparicio, Maria T.; Uccellini, Melissa B.; Miller, Jennifer C.; Manicassamy, Balaji; Satoh, Takashi; Kawai, Taro; Akira, Shizuo; Merad, Miriam; Garcia-Sastre, Adolfo

2014-01-01

38

Piscirickettsia salmonis: a Gram-negative intracellular bacterial pathogen of fish.  

PubMed

Piscirickettsia salmonis is the first Gram-negative, intracellular bacterial pathogen isolated from fish and is a significant cause of mortality in salmonid fish. Recent reports of P. salmonis or P. salmonis-like organisms from new fish hosts and geographic regions have increased the interest in the bacterium. In this review, the important characteristics of the bacterium including recent taxonomic changes, features of the disease caused by the bacterium including transmission, hosts, reservoirs, diagnostic procedures, and current approaches for prevention and treatment have been discussed. The reader is also directed to other reviews concerning the bacterium and the disease it causes (Fryer & Lannan 1994, 1996; Almendras & Fuentealba 1997; Lannan, Bartholomew & Fryer 1999; House & Fryer 2002; Mauel & Miller 2002). PMID:12962234

Fryer, J L; Hedrick, R P

2003-05-01

39

A Rickettsia genome overrun by mobile genetic elements provides insight into the acquisition of genes characteristic of an obligate intracellular lifestyle.  

PubMed

We present the draft genome for the Rickettsia endosymbiont of Ixodes scapularis (REIS), a symbiont of the deer tick vector of Lyme disease in North America. Among Rickettsia species (Alphaproteobacteria: Rickettsiales), REIS has the largest genome sequenced to date (>2 Mb) and contains 2,309 genes across the chromosome and four plasmids (pREIS1 to pREIS4). The most remarkable finding within the REIS genome is the extraordinary proliferation of mobile genetic elements (MGEs), which contributes to a limited synteny with other Rickettsia genomes. In particular, an integrative conjugative element named RAGE (for Rickettsiales amplified genetic element), previously identified in scrub typhus rickettsiae (Orientia tsutsugamushi) genomes, is present on both the REIS chromosome and plasmids. Unlike the pseudogene-laden RAGEs of O. tsutsugamushi, REIS encodes nine conserved RAGEs that include F-like type IV secretion systems similar to that of the tra genes encoded in the Rickettsia bellii and R. massiliae genomes. An unparalleled abundance of encoded transposases (>650) relative to genome size, together with the RAGEs and other MGEs, comprise ~35% of the total genome, making REIS one of the most plastic and repetitive bacterial genomes sequenced to date. We present evidence that conserved rickettsial genes associated with an intracellular lifestyle were acquired via MGEs, especially the RAGE, through a continuum of genomic invasions. Robust phylogeny estimation suggests REIS is ancestral to the virulent spotted fever group of rickettsiae. As REIS is not known to invade vertebrate cells and has no known pathogenic effects on I. scapularis, its genome sequence provides insight on the origin of mechanisms of rickettsial pathogenicity. PMID:22056929

Gillespie, Joseph J; Joardar, Vinita; Williams, Kelly P; Driscoll, Timothy; Hostetler, Jessica B; Nordberg, Eric; Shukla, Maulik; Walenz, Brian; Hill, Catherine A; Nene, Vishvanath M; Azad, Abdu F; Sobral, Bruno W; Caler, Elisabet

2012-01-01

40

A Rickettsia Genome Overrun by Mobile Genetic Elements Provides Insight into the Acquisition of Genes Characteristic of an Obligate Intracellular Lifestyle  

PubMed Central

We present the draft genome for the Rickettsia endosymbiont of Ixodes scapularis (REIS), a symbiont of the deer tick vector of Lyme disease in North America. Among Rickettsia species (Alphaproteobacteria: Rickettsiales), REIS has the largest genome sequenced to date (>2 Mb) and contains 2,309 genes across the chromosome and four plasmids (pREIS1 to pREIS4). The most remarkable finding within the REIS genome is the extraordinary proliferation of mobile genetic elements (MGEs), which contributes to a limited synteny with other Rickettsia genomes. In particular, an integrative conjugative element named RAGE (for Rickettsiales amplified genetic element), previously identified in scrub typhus rickettsiae (Orientia tsutsugamushi) genomes, is present on both the REIS chromosome and plasmids. Unlike the pseudogene-laden RAGEs of O. tsutsugamushi, REIS encodes nine conserved RAGEs that include F-like type IV secretion systems similar to that of the tra genes encoded in the Rickettsia bellii and R. massiliae genomes. An unparalleled abundance of encoded transposases (>650) relative to genome size, together with the RAGEs and other MGEs, comprise ?35% of the total genome, making REIS one of the most plastic and repetitive bacterial genomes sequenced to date. We present evidence that conserved rickettsial genes associated with an intracellular lifestyle were acquired via MGEs, especially the RAGE, through a continuum of genomic invasions. Robust phylogeny estimation suggests REIS is ancestral to the virulent spotted fever group of rickettsiae. As REIS is not known to invade vertebrate cells and has no known pathogenic effects on I. scapularis, its genome sequence provides insight on the origin of mechanisms of rickettsial pathogenicity.

Joardar, Vinita; Williams, Kelly P.; Driscoll, Timothy; Hostetler, Jessica B.; Nordberg, Eric; Shukla, Maulik; Walenz, Brian; Hill, Catherine A.; Nene, Vishvanath M.; Azad, Abdu F.; Sobral, Bruno W.; Caler, Elisabet

2012-01-01

41

Correlations Between Bacterial Ecology and Mobile DNA  

PubMed Central

Several factors can affect the density of mobile DNA in bacterial genomes including rates of exposure to novel gene pools, recombination, and reductive evolution. These traits are difficult to measure across a broad range of bacterial species, but the ecological niches occupied by an organism provide some indication of the relative magnitude of these forces. Here, by analyzing 384 bacterial genomes assigned to three ecological categories (obligate intracellular, facultative intracellular, and extracellular), we address two, related questions: How does the density of mobile DNA vary across the Bacteria? And is there a statistically supported relationship between ecological niche and mobile element gene density? We report three findings. First, the fraction of mobile element genes in bacterial genomes ranges from 0 to 21% and decreases significantly: facultative intracellular > extracellular > obligate intracellular bacteria. Results further show that the obligate intracellular bacteria that host switch have a higher mobile DNA gene density than the obligate intracellular bacteria that are vertically transmitted. Second, while bacteria from the three ecological niches differ in their average mobile DNA contents, the ranges of mobile DNA found in each category overlap a surprising extent, suggesting bacteria with different lifestyles can tolerate similar amounts of mobile DNA. Third, mobile DNA gene densities increase with genome size across the entire dataset, and the significance of this correlation is dependent on the obligate intracellular bacteria. Further, mobile DNA gene densities do not correlate with evolutionary relationships in a 16S rDNA phylogeny. These findings statistically support a compelling link between mobile element evolution and bacterial ecology.

Newton, Irene L. G.

2010-01-01

42

The complete genomic sequence of Mycoplasma penetrans, an intracellular bacterial pathogen in humans  

PubMed Central

The complete genomic sequence of an intracellular bacterial pathogen, Mycoplasma penetrans HF-2 strain, was determined. The HF-2 genome consists of a 1 358 633 bp single circular chromosome containing 1038 predicted coding sequences (CDSs), one set of rRNA genes and 30 tRNA genes. Among the 1038 CDSs, 264 predicted proteins are common to the Mycoplasmataceae sequenced thus far and 463 are M.penetrans specific. The genome contains the two-component system but lacks the essential cellular gene, uridine kinase. The relatively large genome of M.penetrans HF-2 among mycoplasma species may be accounted for by both its rich core proteome and the presence of a number of paralog families corresponding to 25.4% of all CDSs. The largest paralog family is the p35 family, which encodes surface lipoproteins including the major antigen, P35. A total of 44 genes for p35 and p35 homologs were identified and 30 of them form one large cluster in the chromosome. The genetic tree of p35 paralogs suggests the occurrence of dynamic chromosomal rearrangement in paralog formation during evolution. Thus, M.penetrans HF-2 may have acquired diverse repertoires of antigenic variation-related genes to allow its persistent infection in humans.

Sasaki, Yuko; Ishikawa, Jun; Yamashita, Atsushi; Oshima, Kenshiro; Kenri, Tsuyoshi; Furuya, Keiko; Yoshino, Chie; Horino, Atsuko; Shiba, Tadayoshi; Sasaki, Tsuguo; Hattori, Masahira

2002-01-01

43

Multilocus sequence analysis (MLSA) of 'Rickettsiella agriotidis', an intracellular bacterial pathogen of Agriotes wireworms.  

PubMed

Wireworms, the polyphagous larvae of click beetles belonging to the genus Agriotes (Coleoptera: Elateridae) are severe and widespread agricultural pests that affect numerous crops globally. A new bacterial specimen identified in diseased wireworms had previously been shown by microscopy and 16S ribosomal RNA (rRNA) gene-based phylogenetic reconstruction to belong to the taxonomic genus Rickettsiella (Gammaproteobacteria) that comprises intracellular bacteria associated with and typically pathogenic for a wide range of arthropods. Going beyond these earlier results obtained from rRNA phylogenies, multilocus sequence analysis (MLSA) using a four marker scheme has been employed in the molecular taxonomic characterization of the new Rickettsiella pathotype, referred to as 'Rickettsiella agriotidis'. In combination with likelihood-based significance testing, the MLSA approach demonstrated the close phylogenetic relationship of 'R. agriotidis' to the pathotypes 'Rickettsiella melolonthae' and 'Rickettsiella tipulae', i.e., subjective synonyms of the nomenclatural type species, Rickettsiella popilliae. 'R. agriotidis' forms, therefore, part of a Rickettsiella pathotype complex that most likely represents the species R. popilliae. As there are currently no genetic data available from the R. popilliae type strain, the respective assignment cannot be corroborated directly. However, an alternative taxonomic assignment to the species Rickettsiella grylli has been positively ruled out by significance testing. MLSA has been shown to provide a more powerful tool for taxonomic delineation within the genus Rickettsiella as compared to 16S rRNA phylogenetics. However, the limitations of the present MLSA scheme for the sub-species level classification of 'R. agriotidis' and further R. popilliae synonyms has been critically evaluated. PMID:23007524

Schuster, Christina; Kleespies, Regina G; Ritter, Claudia; Feiertag, Simon; Leclerque, Andreas

2013-01-01

44

Attenuation of the Sensing Capabilities of PhoQ in Transition to Obligate Insect-Bacterial Association  

PubMed Central

Sodalis glossinidius, a maternally inherited endosymbiont of the tsetse fly, maintains genes encoding homologues of the PhoP-PhoQ two-component regulatory system. This two-component system has been extensively studied in facultative bacterial pathogens and is known to serve as an environmental magnesium sensor and a regulator of key virulence determinants. In the current study, we show that the inactivation of the response regulator, phoP, renders S. glossinidius sensitive to insect derived cationic antimicrobial peptides (AMPs). The resulting mutant strain displays reduced expression of genes involved in the structural modification of lipid A that facilitates resistance to AMPs. In addition, the inactivation of phoP alters the expression of type-III secretion system (TTSS) genes encoded within three distinct chromosomal regions, indicating that PhoP-PhoQ also serves as a master regulator of TTSS gene expression. In the absence of phoP, S. glossinidius is unable to superinfect either its natural tsetse fly host or a closely related hippoboscid louse fly. Furthermore, we show that the S. glossinidius PhoQ sensor kinase has undergone functional adaptations that result in a substantially diminished ability to sense ancestral signals. The loss of PhoQ's sensory capability is predicted to represent a novel adaptation to the static symbiotic lifestyle, allowing S. glossinidius to constitutively express genes that facilitate resistance to host derived AMPs.

Pontes, Mauricio Henriques; Smith, Kari Lyn; De Vooght, Linda; Van Den Abbeele, Jan; Dale, Colin

2011-01-01

45

Nanocarriers for antibiotics: a promising solution to treat intracellular bacterial infections.  

PubMed

In the field of antibiotherapy, intracellular infections remain difficult to eradicate mainly due to the poor intracellular penetration of most of the commonly used antibiotics. Bacteria have quickly understood that their intracellular localisation allows them to be protected from the host immune system, but also from the action of antimicrobial agents. In addition, in most cases pathogens nestle in professional phagocytic cells, and can even use them as a 'Trojan horse' to induce a secondary site of infection thereby causing persistent or recurrent infections. Thus, new strategies had to be considered in order to counteract these problems. Amongst them, nanocarriers loaded with antibiotics represent a promising approach. Nowadays, it is possible to encapsulate, incorporate or even conjugate biologically active molecules into different families of nanocarriers such as liposomes or nanoparticles in order to deliver antibiotics intracellularly and hence to treat infections. This review gives an overview of the variety of nanocarriers developed to deliver antibiotics directly into infected cells. PMID:24721232

Abed, Nadia; Couvreur, Patrick

2014-06-01

46

Intracellular and extracellular enzymatic deacylation of bacterial endotoxin during localized inflammation induced by Escherichia coli.  

PubMed Central

Acyloxyacyl hydrolase (AOAH), an enzyme that removes the secondary acyl chains of gram-negative bacterial lipid A (endotoxin), has been identified previously in human neutrophils and mouse macrophages. We report here that bovine leukocytes also contain AOAH activity. Although bovine AOAH deacylates bacterial lipopolysaccharide in a manner similar to human AOAH, it is active in vitro over a broader pH range, from 4.0 to 7.0. By using Escherichia coli infection of the bovine mammary gland as a model of localized gram-negative bacterial disease and associated tissue inflammation, AOAH activity per leukocyte increased. In addition, AOAH activity increased in the cell-free portion of infected mammary secretions. These data indicate that AOAH activity increases in leukocytes associated with inflammation induced by gram-negative bacteria and provide additional evidence of its potential involvement in the defense against the effects of bacterial endotoxin. Images

McDermott, C M; Cullor, J S; Fenwick, B W

1991-01-01

47

Enzymatic Treatment to Eliminate the Extracellular ATP for Improving the Detectability of Bacterial Intracellular ATP  

Microsoft Academic Search

A novel and effective treatment of biological samples with a combination of adenosine phosphate deaminase and apyrase was developed for reducing extracellular ATP, which has been a major problem encountered in improving the sensitivity of assays for intracellular ATP by the firefly luciferin–luciferase (L-L) method. Under the enzymatic reaction conditions, ATP and the related adenosine derivatives were converted to IMP,

Tatsuya Sakakibara; Seiji Murakami; Noriaki Hattori; Moto-o Nakajima; Kazuhiro Imai

1997-01-01

48

Molecular mechanisms of cell-cell spread of intracellular bacterial pathogens  

PubMed Central

Several bacterial pathogens, including Listeria monocytogenes, Shigella flexneri and Rickettsia spp., have evolved mechanisms to actively spread within human tissues. Spreading is initiated by the pathogen-induced recruitment of host filamentous (F)-actin. F-actin forms a tail behind the microbe, propelling it through the cytoplasm. The motile pathogen then encounters the host plasma membrane, forming a bacterium-containing protrusion that is engulfed by an adjacent cell. Over the past two decades, much progress has been made in elucidating mechanisms of F-actin tail formation. Listeria and Shigella produce tails of branched actin filaments by subverting the host Arp2/3 complex. By contrast, Rickettsia forms tails with linear actin filaments through a bacterial mimic of eukaryotic formins. Compared with F-actin tail formation, mechanisms controlling bacterial protrusions are less well understood. However, recent findings have highlighted the importance of pathogen manipulation of host cell–cell junctions in spread. Listeria produces a soluble protein that enhances bacterial protrusions by perturbing tight junctions. Shigella protrusions are engulfed through a clathrin-mediated pathway at ‘tricellular junctions’—specialized membrane regions at the intersection of three epithelial cells. This review summarizes key past findings in pathogen spread, and focuses on recent developments in actin-based motility and the formation and internalization of bacterial protrusions.

Ireton, Keith

2013-01-01

49

Bacterial Community Morphogenesis Is Intimately Linked to the Intracellular Redox State  

PubMed Central

Many microbial species form multicellular structures comprising elaborate wrinkles and concentric rings, yet the rules governing their architecture are poorly understood. The opportunistic pathogen Pseudomonas aeruginosa produces phenazines, small molecules that act as alternate electron acceptors to oxygen and nitrate to oxidize the intracellular redox state and that influence biofilm morphogenesis. Here, we show that the depth occupied by cells within colony biofilms correlates well with electron acceptor availability. Perturbations in the environmental provision, endogenous production, and utilization of electron acceptors affect colony development in a manner consistent with redox control. Intracellular NADH levels peak before the induction of colony wrinkling. These results suggest that redox imbalance is a major factor driving the morphogenesis of P. aeruginosa biofilms and that wrinkling itself is an adaptation that maximizes oxygen accessibility and thereby supports metabolic homeostasis. This type of redox-driven morphological change is reminiscent of developmental processes that occur in metazoans.

Okegbe, Chinweike; Price-Whelan, Alexa; Sakhtah, Hassan; Hunter, Ryan C.; Newman, Dianne K.

2013-01-01

50

Bacterial death induced by expression of the intracellular portion of human Fas  

Microsoft Academic Search

In attempting to produce the intracellular portion of human Fas (IC175–319) as a GST-fusion protein we found that expression of GST-IC175–319, but not GST alone or GST-IC231–298 (containing the Fas death domain), rapidly caused the death of host E. coli cells. Expression of GST-IC175–319 with a single amino acid substitution (V238N) corresponding to the mouse lprcg mutation, or E245A, which

Yili Yang; June S Hong; Astrid Eder; Jonathan D Ashwell

1999-01-01

51

The Role of Non-Cognate T Cell Stimulation during Intracellular Bacterial Infection  

PubMed Central

Intra-macrophage bacterial infections cause significant morbidity and mortality in both the developed and developing world. Protective host immune responses to these infections initially requires the activation and expansion of pathogen-specific CD4 Th1 cells within lymphoid tissues and subsequent relocation of these effector cells to sites of infection. After entering infected tissues, the elicitation of Th1 bactericidal activity can be triggered by cognate or non-cognate signals that are delivered by locally infected antigen-presenting cells and innate cells. However, the contribution of non-cognate stimulation to the resolution of bacterial infection remains poorly understood, especially in the context of a Th1 response. Here, we review the current data on Th1 cell activation and expansion in mouse models of Salmonella and Chlamydia infection and discuss the potential role of non-cognate Th1 cell stimulation in these disease models. Greater understanding of this pathway of T cell activation may lead to the design of therapeutics or vaccines to combat intra-macrophage pathogens.

McSorley, Stephen J.

2014-01-01

52

Quorum sensing-controlled buoyancy through gas vesicles: Intracellular bacterial microcompartments for environmental adaptation  

PubMed Central

Gas vesicles are gas-filled microcompartments produced by many cyanobacteria and haloarchaea to regulate buoyancy and control positioning in the water column. Recently we identified the first case of gas vesicle production by a member of the Enterobacteriaceae, Serratia sp ATCC39006. Gas vesicle production enabled colonisation of the air-liquid interface and was positively regulated in low-oxygen conditions, suggesting development of these intracellular organelles is an adpative mechanism facilitating migration to the water surface. Vesicle production was also regulated by the intercellular communication molecule N?butanoyl-L?homoserine lactone (BHL) showing that gas vesicle production is controlled at the population level, through quorum sensing, with BHL acting as a morphogen. Gas vesicle production was also reciprocally regulated with flagella-driven swarming motility by the global regulatory protein RsmA, suggesting a fork in the regulatory pathway that controls induction of these distinct modes of mobility. Here we discuss these findings in the context of the interesting physiology of Serratia 39006 and highlight future prospects for gas vesicle research in this highly tractable strain.

Ramsay, Joshua P.

2012-01-01

53

Coinfection of tick cell lines has variable effects on replication of intracellular bacterial and viral pathogens.  

PubMed

Ticks transmit various human and animal microbial pathogens and may harbour more than one pathogen simultaneously. Both viruses and bacteria can trigger, and may subsequently suppress, vertebrate host and arthropod vector anti-microbial responses. Microbial coinfection of ticks could lead to an advantage or disadvantage for one or more of the microorganisms. In this preliminary study, cell lines derived from the ticks Ixodes scapularis and Ixodes ricinus were infected sequentially with 2 arthropod-borne pathogens, Borrelia burgdorferi s.s., Ehrlichia ruminantium, or Semliki Forest virus (SFV), and the effect of coinfection on the replication of these pathogens was measured. Prior infection of tick cell cultures with the spirochaete B. burgdorferi enhanced subsequent replication of the rickettsial pathogen E. ruminantium whereas addition of spirochaetes to cells infected with E. ruminantium had no effect on growth of the latter. Both prior and subsequent presence of B. burgdorferi also had a positive effect on SFV replication. Presence of E. ruminantium or SFV had no measurable effect on B. burgdorferi growth. In tick cells infected first with E. ruminantium and then with SFV, virus replication was significantly higher across all time points measured (24, 48, 72h post infection), while presence of the virus had no detectable effect on bacterial growth. When cells were infected first with SFV and then with E. ruminantium, there was no effect on replication of either pathogen. The results of this preliminary study indicate that interplay does occur between different pathogens during infection of tick cells. Further study is needed to determine if this results from direct pathogen-pathogen interaction or from effects on host cell defences, and to determine if these observations also apply in vivo in ticks. If presence of one pathogen in the tick vector results in increased replication of another, this could have implications for disease transmission and incidence. PMID:24685441

Moniuszko, Anna; Rückert, Claudia; Alberdi, M Pilar; Barry, Gerald; Stevenson, Brian; Fazakerley, John K; Kohl, Alain; Bell-Sakyi, Lesley

2014-06-01

54

Coinfection of tick cell lines has variable effects on replication of intracellular bacterial and viral pathogens  

PubMed Central

Ticks transmit various human and animal microbial pathogens and may harbour more than one pathogen simultaneously. Both viruses and bacteria can trigger, and may subsequently suppress, vertebrate host and arthropod vector anti-microbial responses. Microbial coinfection of ticks could lead to an advantage or disadvantage for one or more of the microorganisms. In this preliminary study, cell lines derived from the ticks Ixodes scapularis and Ixodes ricinus were infected sequentially with 2 arthropod-borne pathogens, Borrelia burgdorferi s.s., Ehrlichia ruminantium, or Semliki Forest virus (SFV), and the effect of coinfection on the replication of these pathogens was measured. Prior infection of tick cell cultures with the spirochaete B. burgdorferi enhanced subsequent replication of the rickettsial pathogen E. ruminantium whereas addition of spirochaetes to cells infected with E. ruminantium had no effect on growth of the latter. Both prior and subsequent presence of B. burgdorferi also had a positive effect on SFV replication. Presence of E. ruminantium or SFV had no measurable effect on B. burgdorferi growth. In tick cells infected first with E. ruminantium and then with SFV, virus replication was significantly higher across all time points measured (24, 48, 72 h post infection), while presence of the virus had no detectable effect on bacterial growth. When cells were infected first with SFV and then with E. ruminantium, there was no effect on replication of either pathogen. The results of this preliminary study indicate that interplay does occur between different pathogens during infection of tick cells. Further study is needed to determine if this results from direct pathogen–pathogen interaction or from effects on host cell defences, and to determine if these observations also apply in vivo in ticks. If presence of one pathogen in the tick vector results in increased replication of another, this could have implications for disease transmission and incidence.

Moniuszko, Anna; Ruckert, Claudia; Alberdi, M. Pilar; Barry, Gerald; Stevenson, Brian; Fazakerley, John K.; Kohl, Alain; Bell-Sakyi, Lesley

2014-01-01

55

Invasion of the Central Nervous System by Intracellular Bacteria  

PubMed Central

Infection of the central nervous system (CNS) is a severe and frequently fatal event during the course of many diseases caused by microbes with predominantly intracellular life cycles. Examples of these include the facultative intracellular bacteria Listeria monocytogenes, Mycobacterium tuberculosis, and Brucella and Salmonella spp. and obligate intracellular microbes of the Rickettsiaceae family and Tropheryma whipplei. Unfortunately, the mechanisms used by intracellular bacterial pathogens to enter the CNS are less well known than those used by bacterial pathogens with an extracellular life cycle. The goal of this review is to elaborate on the means by which intracellular bacterial pathogens establish infection within the CNS. This review encompasses the clinical and pathological findings that pertain to the CNS infection in humans and includes experimental data from animal models that illuminate how these microbes enter the CNS. Recent experimental data showing that L. monocytogenes can invade the CNS by more than one mechanism make it a useful model for discussing the various routes for neuroinvasion used by intracellular bacterial pathogens.

Drevets, Douglas A.; Leenen, Pieter J. M.; Greenfield, Ronald A.

2004-01-01

56

Bacterial adhesion, intracellular survival and cytokine induction upon stimulation of mononuclear cells with planktonic or biofilm phase Staphylococcus epidermidis.  

PubMed

Staphylococcus epidermidis is a leading cause of hospital-acquired and biofilm-associated infections. Interactions of peripheral blood mononuclear cells (PBMCs) and monocyte-derived macrophages with planktonic or biofilm phase S. epidermidis cells were studied. Biofilm phase bacteria exhibited higher attachment, as well as, a 10-fold higher intracellular survival in monocyte-derived macrophages than their planktonic counterparts. Stimulation of PBMCs and monocyte-derived macrophages was performed with live or formalin-fixed bacterial cells. Supernatant concentration of selected cytokines was measured by Luminex(®) xMAP(™) technology at different time points. As compared to planktonic phase, biofilm phase bacteria elicited lower amounts of proinflammatory cytokines and Th1 response cytokines, such as TNF?, IL-12p40, IL-12p70 and IFN-?, whereas they enhanced production of IL-8, GM-CSF and IL-13. This phenomenon was independent of formalin pretreatment. Taken together, these results may contribute to interpretation of observed silent course of biofilm-associated infections. PMID:22360699

Spiliopoulou, Anastasia I; Kolonitsiou, Fevronia; Krevvata, Maria I; Leontsinidis, Michalis; Wilkinson, Thomas S; Mack, Dietrich; Anastassiou, Evangelos D

2012-05-01

57

Consent and Obligation.  

National Technical Information Service (NTIS)

The main purpose of this study is to question the relation between consenting and being obligated. Topics covered include: An Idea of Consent and the Range of Obligation; Conditions of Consent -- Freedom, Information, Capacity, Conditions versus principle...

T. W. Stewart

1978-01-01

58

Measuring Intergenerational Obligations  

ERIC Educational Resources Information Center

Researchers have defined intergenerational obligations in diverse ways, and they have used many labels and ways of measuring intergenerational obligations. Using vignettes, we compared responses to questions about what family members should do when another family member needed assistance ("normative obligations") with responses to questions about…

Ganong, Lawrence; Coleman, Marilyn

2005-01-01

59

A Bacterial Indole3-acetyl-L-aspartic Acid Hydrolase Inhibits Mung Bean ( Vigna radiata L.) Seed Germination Through Arginine-rich Intracellular Delivery  

Microsoft Academic Search

Indole-3-acetyl-L-aspartic acid (IAA-Asp) is a natural product in many plant species and plays many important roles in auxin\\u000a metabolism and plant physiology. IAA-Asp hydrolysis activity is, therefore, believed to affect plant physiology through changes\\u000a in IAA metabolism in plants. We applied a newly discovered technique, arginine-rich intracellular delivery (AID), to deliver\\u000a a bacterial IAA-Asp hydrolase into cells of mung bean

Kevin Liu; Han-Jung Lee; Sio San Leong; Chen-Lun Liu; Jyh-Ching Chou

2007-01-01

60

The Francisella pathogenicity island protein IglA localizes to the bacterial cytoplasm and is needed for intracellular growth  

PubMed Central

Background Francisella tularensis is a gram negative, facultative intracellular bacterium that is the etiological agent of tularemia. F. novicida is closely related to F. tularensis but has low virulence for humans while being highly virulent in mice. IglA is a 21 kDa protein encoded by a gene that is part of an iglABCD operon located on the Francisella pathogenicity island (FPI). Results Bioinformatics analysis of the FPI suggests that IglA and IglB are components of a newly described type VI secretion system. In this study, we showed that IglA regulation is controlled by the global regulators MglA and MglB. During intracellular growth IglA production reaches a maximum at about 10 hours post infection. Biochemical fractionation showed that IglA is a soluble cytoplasmic protein and immunoprecipitation experiments demonstrate that it interacts with the downstream-encoded IglB. When the iglB gene was disrupted IglA could not be detected in cell extracts of F. novicida, although IglC could be detected. We further demonstrated that IglA is needed for intracellular growth of F. novicida. A non-polar iglA deletion mutant was defective for growth in mouse macrophage-like cells, and in cis complementation largely restored the wild type macrophage growth phenotype. Conclusion The results of this study demonstrate that IglA and IglB are interacting cytoplasmic proteins that are required for intramacrophage growth. The significance of the interaction may be to secrete effector molecules that affect host cell processes.

de Bruin, Olle M; Ludu, Jagjit S; Nano, Francis E

2007-01-01

61

High-affinity Zn2+ uptake system ZnuABC is required for bacterial zinc homeostasis in intracellular environments and contributes to the virulence of Salmonella enterica.  

PubMed

To investigate the relevance of zinc in host-pathogen interactions, we have constructed Salmonella enterica mutant strains in which the znuA gene, which encodes the periplasmic component of the ZnuABC high-affinity Zn2+ transporter, was deleted. This mutation does not alter the ability of Salmonella to grow in rich media but drastically reduces its ability to multiply in media deprived of zinc. In agreement with this phenotype, ZnuA accumulates only in bacteria cultivated in environments poor in zinc. In spite of the nearly millimolar intracellular concentration of zinc, we have found that znuA is highly expressed in intracellular salmonellae recovered either from cultivated cells or from the spleens of infected mice. We have also observed that znuA mutants are impaired in their ability to grow in Caco-2 epithelial cells and that bacteria starved for zinc display decreased ability to multiply in phagocytes. A dramatic reduction in the pathogenicity of the znuA mutants was observed in Salmonella-susceptible (BALB/c) or Salmonella-resistant (DBA-2) mice infected intraperitoneally or orally. This study shows that the amount of free metals available for bacterial growth within the infected animal is limited, despite the apparent elevated concentration of free metals within cells and in plasma and suggests that Salmonella exploits the ZnuABC zinc transporter to maximize zinc availability in such conditions. These results shed new light on the complex functions of zinc in vertebrate and bacterial physiology and pave the way for a better comprehension of pathogenic mechanisms in Salmonella infections. PMID:17923515

Ammendola, Serena; Pasquali, Paolo; Pistoia, Claudia; Petrucci, Paola; Petrarca, Patrizia; Rotilio, Giuseppe; Battistoni, Andrea

2007-12-01

62

High-Affinity Zn2+ Uptake System ZnuABC Is Required for Bacterial Zinc Homeostasis in Intracellular Environments and Contributes to the Virulence of Salmonella enterica?  

PubMed Central

To investigate the relevance of zinc in host-pathogen interactions, we have constructed Salmonella enterica mutant strains in which the znuA gene, which encodes the periplasmic component of the ZnuABC high-affinity Zn2+ transporter, was deleted. This mutation does not alter the ability of Salmonella to grow in rich media but drastically reduces its ability to multiply in media deprived of zinc. In agreement with this phenotype, ZnuA accumulates only in bacteria cultivated in environments poor in zinc. In spite of the nearly millimolar intracellular concentration of zinc, we have found that znuA is highly expressed in intracellular salmonellae recovered either from cultivated cells or from the spleens of infected mice. We have also observed that znuA mutants are impaired in their ability to grow in Caco-2 epithelial cells and that bacteria starved for zinc display decreased ability to multiply in phagocytes. A dramatic reduction in the pathogenicity of the znuA mutants was observed in Salmonella-susceptible (BALB/c) or Salmonella-resistant (DBA-2) mice infected intraperitoneally or orally. This study shows that the amount of free metals available for bacterial growth within the infected animal is limited, despite the apparent elevated concentration of free metals within cells and in plasma and suggests that Salmonella exploits the ZnuABC zinc transporter to maximize zinc availability in such conditions. These results shed new light on the complex functions of zinc in vertebrate and bacterial physiology and pave the way for a better comprehension of pathogenic mechanisms in Salmonella infections.

Ammendola, Serena; Pasquali, Paolo; Pistoia, Claudia; Petrucci, Paola; Petrarca, Patrizia; Rotilio, Giuseppe; Battistoni, Andrea

2007-01-01

63

On Obligations and Abilities  

Microsoft Academic Search

In this paper, we combine deontic logic with Alternating- time Temporal Logic (ATL) into a framework that makes it possible to model and reason about obligations and abilities of agents. The way both frameworks are combined is technically straightforward: we add deontic accessibility relations to ATL models (concurrent game structures), and deontic operators to the language of ATL (an additional

Wojciech Jamroga; Wiebe Van Der Hoek; Michael Wooldridge; A. Lomuscio; D. Nute

2004-01-01

64

On public obligation.  

PubMed

Poverty has a potent and provable impact on health, education, opportunity, safety, dignity, and overall quality of life for Americans. This article argues that our obligations to ameliorate poverty are not only private, religious, and charitable, they are public and governmental as well. PMID:23189436

Nichol, Gene R

2012-01-01

65

GRANDPARENTS' ENTITLEMENTS AND OBLIGATIONS  

PubMed Central

In this article, it is argued that grandparents' obligations originate from parental obligations (i.e from the relationship they have with their children, the parents of their grandchildren) and not from the role of grandparent per se, and any entitlements flow from the extent to which these obligations are met. The position defended is, therefore, that grandparents qua grandparents are not entitled to form or continue relationships with their grandchildren. A continuation of grandparent-grandchildren relationships may be in the interests of children, but the grandparental nature of the relationship is not decisive. What counts is the extent to which relationships children have with any adults who are not their parents are is significant to them. Sometimes, however, grandparents become parents or co-parents of their grandchildren. They then gain parental rights, and as such are as entitled, ceteris parius, as any parent to expect their relationship with the child to continue. The issue of grandparents' entitlements can come to the fore when parents separate, and grandparents are unhappy with the access they have to their grandchildren. Grandparents' obligations may become a particular issue when parents die, struggle, or fail to care for their children. This article focuses particularly on these kinds of circumstances.

Draper, Heather

2013-01-01

66

The role of gammadelta T cells in induction of bacterial antigen-specific protective CD8+ cytotoxic T cells in immune response against the intracellular bacteria Listeria monocytogenes.  

PubMed Central

The role of T-cell receptor (TCR) gammadelta T cells in the induction of protective TCR alphabeta T cells against infection by the intracellular bacteria Listeria monocytogenes was analysed. We found that depletion of gammadelta T cells by anti-TCR delta monoclonal antibody treatment before intravenous immunization of mice with a sublethal dose of viable L. monocytogenes resulted in reduction of protection against secondary challenge infection in the immunized mice. The gammadelta T-cell depletion also reduced induction of protective alphabeta T cells capable of transferring the protection against challenge infection of L. monocytogenes into naive mice. Furthermore, the protective T cells that were affected by the gammadelta T-cell depletion were suggested to be CD8+ cytotoxic T cells rather than CD4+ T cells by the following observations. First, induction of cytotoxic T lymphocytes specific to a L. monocytogenes-derived H-2Kd-restricted peptide (listeriolysin O 91-99) was significantly suppressed by gammadelta T-cell depletion before immunization. Second, gammadelta T-cell depletion did not affect cytokine production and proliferation of T cells from immunized mice in response to in vitro stimulation with heat-killed Listeria which preferentially stimulates CD4+ T cells. Third, CD8+ alphabeta T cells from control immunized mice transferred protection against infection of L. monocytogenes into naive mice but only a limited degree of protection was transferred by CD8+ T cells from the gammadelta T-cell-depleted immunized mice; and fourth, CD4+ alphabeta T cells from the gammadelta T-cell-depleted mice transferred a similar level of protection as those from the control immunized mice. All these results suggest that gammadelta T cells participate in establishment of protective immunity against intracellular bacteria by supporting priming of bacterial antigen-specific CD8+ cytotoxic T cells.

Nomura, A; Matsuzaki, G; Takada, H; Hiromatsu, K; Nabeshima, S; Nakamura, T; Kishihara, K; Nomoto, K

1998-01-01

67

Lipid acquisition by intracellular Chlamydiae.  

PubMed

Chlamydia species are obligate intracellular pathogens that are important causes of human genital tract, ocular and respiratory infections. The bacteria replicate within a specialized membrane-bound compartment termed the inclusion and require host-derived lipids for intracellular growth and development. Emerging evidence indicates that Chlamydia has evolved clever strategies to fulfil its lipid needs by interacting with multiple host cell compartments and redirecting trafficking pathways to its intracellular niche. In this review, we highlight recent findings that have significantly expanded our understanding of how Chlamydia exploit lipid trafficking pathways to ensure the survival of this important human pathogen. PMID:22452394

Elwell, Cherilyn A; Engel, Joanne N

2012-07-01

68

SNARE Protein Mimicry by an Intracellular Bacterium  

PubMed Central

Many intracellular pathogens rely on host cell membrane compartments for their survival. The strategies they have developed to subvert intracellular trafficking are often unknown, and SNARE proteins, which are essential for membrane fusion, are possible targets. The obligate intracellular bacteria Chlamydia replicate within an intracellular vacuole, termed an inclusion. A large family of bacterial proteins is inserted in the inclusion membrane, and the role of these inclusion proteins is mostly unknown. Here we identify SNARE-like motifs in the inclusion protein IncA, which are conserved among most Chlamydia species. We show that IncA can bind directly to several host SNARE proteins. A subset of SNAREs is specifically recruited to the immediate vicinity of the inclusion membrane, and their accumulation is reduced around inclusions that lack IncA, demonstrating that IncA plays a predominant role in SNARE recruitment. However, interaction with the SNARE machinery is probably not restricted to IncA as at least another inclusion protein shows similarities with SNARE motifs and can interact with SNAREs. We modelled IncA's association with host SNAREs. The analysis of intermolecular contacts showed that the IncA SNARE-like motif can make specific interactions with host SNARE motifs similar to those found in a bona fide SNARE complex. Moreover, point mutations in the central layer of IncA SNARE-like motifs resulted in the loss of binding to host SNAREs. Altogether, our data demonstrate for the first time mimicry of the SNARE motif by a bacterium.

Delevoye, Cedric; Nilges, Michael; Dehoux, Pierre; Paumet, Fabienne; Perrinet, Stephanie; Dautry-Varsat, Alice; Subtil, Agathe

2008-01-01

69

Strategies of genomic integration within insect-bacterial mutualisms  

PubMed Central

Insects, the most diverse group of macroorganisms with 900,000 known species, have been a rich playground for the evolution of symbiotic associations. Symbionts of this enormous animal group include a range of microbial partners. Insects are prone to establishing relationships with intracellular bacteria, which include the most intimate, highly integrated mutualisms known in the biological world. In recent years, an explosion of genomic studies has offered new insights into the molecular, functional, and evolutionary consequences of these insect-bacterial partnerships. In this review, I highlight some insights from genome sequences of bacterial endosymbionts and select insect hosts. Notably, comparisons of facultative versus obligate bacterial mutualists have revealed distinct genome features representing different stages along a shared trajectory of genome reduction. Bacteria associated with the cedar aphid offer a snapshot of a transition from facultative to obligate mutualism, illustrating the genomic basis of this key step along the symbiotic spectrum. In addition, genomes of stable, dual bacterial symbionts reflect independent instances of astonishing metabolic integration. In these systems, synthesis of key nutrients, and perhaps basic cellular processes, require collaboration among co-residing bacteria and their insect host. These findings provide a launching point for a new era of genomic explorations of bacterial-animal symbioses. Future studies promise to reveal symbiotic strategies across a broad ecological and phylogenetic range, to clarify key transitions along a spectrum of interaction types, and to fuel new experimental approaches to dissect the mechanistic basis of intimate host-symbiont associations.

Wernegreen, Jennifer J.

2013-01-01

70

Transposon Mutagenesis of the Obligate Intracellular Pathogen Rickettsia prowazekii  

Microsoft Academic Search

Genetic analysis of Rickettsia prowazekii has been hindered by the lack of selectable markers and efficient mechanisms for generating rickettsial gene knockouts. We have addressed these problems by adapting a gene that codes for rifampin resistance for expression in R. prowazekii and by incorporating this selection into a transposon mutagenesis system suitable for generating rickettsial gene knockouts. The arr-2 gene

Aiping Qin; Aimee M. Tucker; Andria Hines; David O. Wood

2004-01-01

71

Obligately barophilic bacterium from the Mariana trench.  

PubMed Central

An amphipod (Hirondellea gigas) was retrieved with decompression in an insulated trap from an ocean depth of 10,476 m. Bacterial isolates were obtained from the dead and cold animal by using silica gel medium incubated at 1000 bars (1 bar = 10(5) Pa) and 2 degrees C. The isolate designated MT41 was found to be obligately barophilic and did not grow at a pressure close to that of 380 bars found at average depths of the sea. The optimal generation time of about 25 hr was at 2 degrees C and 690 bars. The generation time at 2 degrees C and 1,035 bars, a pressure close to that at the depth of origin, was about 33 hr. Among the conclusions are: (i) pressure is an important determinant of zonation along the water column of the sea; (ii) some obligately barophilic bacteria survive decompressions; (iii) the pressure of optimal growth at 2 degrees C appears to be less than the pressure at the depth of origin and may be diagnostic for the depth of origin; (iv) rates of reproduction are slow yet significant and an order of magnitude greater than previously thought; and (v) much of deep-sea microbiology may have been done with spurious deep-sea organisms due to warming of samples. Images

Yayanos, A A; Dietz, A S; Van Boxtel, R

1981-01-01

72

Classical Labeling of Bacterial Pathogens According to Their Lifestyle in the Host: Inconsistencies and Alternatives  

PubMed Central

An ample understanding of the complex interactions between host and pathogen will improve our ability to develop new prophylactic and therapeutic measures against infection. Precise classification of infectious agents in regards to their infective lifestyles in the host and corresponding pathogenic implications are required because clear concepts are essential to plan fruitful research. Classically, pathogenic bacteria are classified as extracellular, facultative intracellular, and obligate intracellular. In my opinion, this classification is inadequate because, as concluded from data here discussed, it is based on inconsistencies and hyper-valorizes the capacity of the infectious agent replicate in vitro in cell-free media. For a microbial pathogen, what matters is whether intra- or extracellularity is in the context of the in vivo life and in association with pathogenicity. When living as a pathogen in association with its host, what is relevant in microbiological terms is not the ability to grow in artificial cell-free bacteriological media or in environmental niches but whether the intracellular infectious agent, besides the phase of intracellular growth which is behind its label, also is able to live extracellularly in the natural settings of the extracellular territories of their hosts. To eliminate the inconsistencies associated with the classical labeling of bacterial pathogens, I propose that bacterial pathogens be labeled exclusive extracellular, dual intracellular/extracellular and exclusive intracellular based on their infective lifestyle in the host, not in the ability to grow in artificial bacteriological media.

Silva, Manuel T.

2012-01-01

73

The genome of the obligate endobacterium of an AM fungus reveals an interphylum network of nutritional interactions.  

PubMed

As obligate symbionts of most land plants, arbuscular mycorrhizal fungi (AMF) have a crucial role in ecosystems, but to date, in the absence of genomic data, their adaptive biology remains elusive. In addition, endobacteria are found in their cytoplasm, the role of which is unknown. In order to investigate the function of the Gram-negative Candidatus Glomeribacter gigasporarum, an endobacterium of the AMF Gigaspora margarita, we sequenced its genome, leading to an ?1.72-Mb assembly. Phylogenetic analyses placed Ca. G. gigasporarum in the Burkholderiaceae whereas metabolic network analyses clustered it with insect endobacteria. This positioning of Ca. G. gigasporarum among different bacterial classes reveals that it has undergone convergent evolution to adapt itself to intracellular lifestyle. The genome annotation of this mycorrhizal-fungal endobacterium has revealed an unexpected genetic mosaic where typical determinants of symbiotic, pathogenic and free-living bacteria are integrated in a reduced genome. Ca. G. gigasporarum is an aerobic microbe that depends on its host for carbon, phosphorus and nitrogen supply; it also expresses type II and type III secretion systems and synthesizes vitamin B12, antibiotics- and toxin-resistance molecules, which may contribute to the fungal host's ecological fitness. Ca. G. gigasporarum has an extreme dependence on its host for nutrients and energy, whereas the fungal host is itself an obligate biotroph that relies on a photosynthetic plant. Our work represents the first step towards unraveling a complex network of interphylum interactions, which is expected to have a previously unrecognized ecological impact. PMID:21866182

Ghignone, Stefano; Salvioli, Alessandra; Anca, Iulia; Lumini, Erica; Ortu, Giuseppe; Petiti, Luca; Cruveiller, Stéphane; Bianciotto, Valeria; Piffanelli, Pietro; Lanfranco, Luisa; Bonfante, Paola

2012-01-01

74

Phenotypic characterization and 16S rDNA identification of culturable non-obligate halophilic bacterial communities from a hypersaline lake, La Sal del Rey, in extreme South Texas (USA)  

PubMed Central

Background La Sal del Rey ("the King's Salt") is one of several naturally-occurring salt lakes in Hidalgo County, Texas and is part of the Lower Rio Grande Valley National Wildlife Refuge. The research objective was to isolate and characterize halophilic microorganisms from La Sal del Rey. Water samples were collected from the lake and a small creek that feeds into the lake. Soil samples were collected from land adjacent to the water sample locations. Sample salinity was determined using a refractometer. Samples were diluted and cultured on a synthetic saline medium to grow halophilic bacteria. The density of halophiles was estimated by viable plate counts. A collection of isolates was selected, gram-stained, tested for catalase, and characterized using API 20E® test strips. Isolates were putatively identified by sequencing the 16S rDNA. Carbon source utilization by the microbial community from each sample site was examined using EcoPlate™ assays and the carbon utilization total activity of the community was determined. Results Results showed that salinity ranged from 4 parts per thousand (ppt) at the lake water source to 420 ppt in water samples taken just along the lake shore. The density of halophilic bacteria in water samples ranged from 1.2 × 102 - 5.2 × 103 colony forming units per ml (cfu ml-1) whereas the density in soil samples ranged from 4.0 × 105 - 2.5 × 106 colony forming units per gram (cfu g-1). In general, as salinity increased the density of the bacterial community decreased. Microbial communities from water and soil samples were able to utilize 12 - 31 carbon substrates. The greatest number of substrates utilized was by water-borne communities compared to soil-based communities, especially at lower salinities. The majority of bacteria isolated were gram-negative, catalase-positive, rods. Biochemical profiles constructed from API 20E® test strips showed that bacterial isolates from low-salinity water samples (4 ppt) showed the greatest phenotypic diversity with regards to the types and number of positive tests from the strip. Isolates taken from water samples at the highest salinity (420 ppt) tended to be less diverse and have only a limited number of positive tests. Sequencing of 16S DNA displayed the presence of members of bacterial genera Bacillus, Halomonas, Pseudomonas, Exiguobacterium and others. The genus Bacillus was most commonly identified. None of the isolates were members of the Archaea probably due to dilution of salts in the samples. Conclusions The La Sal del Rey ecosystem supports a robust and diverse bacterial community despite the high salinity of the lake and soil. However, salinity does appear to a limiting factor with regards to the density and diversity of the bacterial communities that inhabit the lake and surrounding area.

2012-01-01

75

Are Aviation Obligations Driving Students Away.  

National Technical Information Service (NTIS)

Evidence suggests that the quality of aviation accessions has been falling. Decision-makers question whether the decline is the result of the active duty service obligations (ADSOs) required of aviators. In away, these lengthy obligations compensate for t...

C. S. Moore

2000-01-01

76

Intracellular proteoglycans.  

PubMed Central

Proteoglycans (PGs) are proteins with glycosaminoglycan chains, are ubiquitously expressed and have a wide range of functions. PGs in the extracellular matrix and on the cell surface have been the subject of extensive structural and functional studies. Less attention has so far been given to PGs located in intracellular compartments, although several reports suggest that these have biological functions in storage granules, the nucleus and other intracellular organelles. The purpose of this review is, therefore, to present some of these studies and to discuss possible functions linked to PGs located in different intracellular compartments. Reference will be made to publications relevant for the topics we present. It is beyond the scope of this review to cover all publications on PGs in intracellular locations.

Kolset, Svein Olav; Prydz, Kristian; Pejler, Gunnar

2004-01-01

77

12 CFR 966.2 - Issuance of consolidated obligations.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 false Issuance of consolidated obligations. 966.2 Section 966.2 Banks...HOME LOAN BANK LIABILITIES CONSOLIDATED OBLIGATIONS § 966.2 Issuance of consolidated obligations. (a) Consolidated obligations...

2009-01-01

78

12 CFR 966.2 - Issuance of consolidated obligations.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Issuance of consolidated obligations. 966.2 Section 966.2 Banks...HOME LOAN BANK LIABILITIES CONSOLIDATED OBLIGATIONS § 966.2 Issuance of consolidated obligations. (a) Consolidated obligations...

2010-01-01

79

Chemical induced intracellular hyperthermia  

US Patent & Trademark Office Database

An invention relating to therapeutic pharmacological agents and methods to chemically induce intracellular hyperthermia and/or free radicals for the diagnosis and treatment of infections, malignancy and other medical conditions. The invention relates to a process and composition for the diagnosis or killing of cancer cells and inactivation of susceptible bacterial, parasitic, fungal, and viral pathogens by chemically generating heat, and/or free radicals and/or hyperthermia-inducible immunogenic determinants by using mitochondrial uncoupling agents, especially 2,4 dinitrophenol and, their conjugates, either alone or in combination with other drugs, hormones, cytokines and radiation.

2009-12-22

80

Obligations and Liabilities of the Carrier  

Microsoft Academic Search

\\u000a The Rotterdam Rules follow the model of the Hague-Visby Rules by imposing specific obligations on the carrier, such as to\\u000a load, handle and stow the goods. However, the Rotterdam Rules impose two further obligations resulting from the extended scope\\u000a of the Rotterdam Rules: they are the obligations to receive and deliver the goods. Furthermore, under the Rotterdam Rules\\u000a the carrier

M. Fehmi Ülgener

81

MgtC as a horizontally-acquired virulence factor of intracellular bacterial pathogens: evidence from molecular phylogeny and comparative genomics.  

PubMed

MgtC is a virulence factor required for intramacrophage survival and growth in low Mg2+ medium in two pathogens that are not phylogenetically related, Salmonella typhimurium and Mycobacterium tuberculosis. In S. typhimurium, mgtC is carried by the SPI-3 pathogenicity island and hybridization studies have suggested that the distribution of mgtC among enterobacteria is limited. In the present study, we searched for the presence of mgtC-like sequences in eubacterial genomes. Analyses of MgtC-like proteins phylogeny and mgtC-like chromosomal context support the hypothesis that mgtC has been acquired by horizontal gene transfer repeatedly throughout bacterial evolution. In addition, the phylogenetic analysis revealed the existence of a subgroup of proteins, that includes the S. typhimurium and M. tuberculosis MgtC proteins, as well as MgtC-related proteins from other pathogens that are able to survive in macrophages, B. melitensis and Y. pestis. We propose that MgtC has a similar function in all these distantly related pathogens, most likely providing the ability to grow in a low Mg2+ environment. PMID:14708580

Blanc-Potard, Anne-Béatrice; Lafay, Bénédicte

2003-10-01

82

47 CFR 27.1239 - Reimbursement obligation.  

Code of Federal Regulations, 2013 CFR

...obligation. 27.1239 Section 27.1239 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES Broadband Radio Service and Educational Broadband...

2013-10-01

83

Visualization of pseudogenes in intracellular bacteria reveals the different tracks to gene destruction  

Microsoft Academic Search

BACKGROUND: Pseudogenes reveal ancestral gene functions. Some obligate intracellular bacteria, such as Mycobacterium leprae and Rickettsia spp., carry substantial fractions of pseudogenes. Until recently, horizontal gene transfers were considered to be rare events in obligate host-associated bacteria. RESULTS: We present a visualization tool that displays the relationships and positions of degraded and partially overlapping gene sequences in multiple genomes. With

Hans-Henrik Fuxelius; Alistair C Darby; Nam-Huyk Cho; Siv GE Andersson

2008-01-01

84

45 CFR 2400.65 - Teaching obligation.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Teaching obligation. 2400.65 ...Conditions § 2400.65 Teaching obligation. Upon receiving...social studies, or political science on a full-time basis...is employed indicating the teaching activities of the Fellow...

2010-10-01

85

45 CFR 2400.65 - Teaching obligation.  

Code of Federal Regulations, 2010 CFR

... 2009-10-01 false Teaching obligation. 2400.65 ...Conditions § 2400.65 Teaching obligation. Upon receiving...social studies, or political science on a full-time basis...is employed indicating the teaching activities of the Fellow...

2009-10-01

86

[The obligation of means and the obligation of results].  

PubMed

Several important decisions were made in 2000 concerning the proof of malpractice and the fundamental principles of medical responsibility. In order to guarantee indemnities for victims of medical accidents, the French courts have facilitated the implication of medical responsibility for medical accidents. The notion of a "virtual fault" was developed allowing the courts to retain the responsibility of the surgeon for instance for injury to the sublingual nerve during extraction of a wisdom tooth or for injury to the popliteal artery (March 23, 2000). These decisions not only facilitate the demonstration of malpractice but also modify the definition of responsibility, all physicians being required to use all available means. Likewise, although jurisprudence asserts that a safe result is mandatory in certain areas, the essential obligation is the absence of "fault" and not the result despite the disquieting arguments put forward by the Paris appeals court in its January 15, 1999 decree. The patient's right to a result was sustained only in well defined areas. PMID:11688200

Rougé-Maillart, C; Pessaux, P; Jousset, N; Hubert, N; Gosset, D; Penneau, M

2001-10-01

87

11 CFR 9034.5 - Net outstanding campaign obligations.  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false Net outstanding campaign obligations. 9034...MATCHING FUND ENTITLEMENTS § 9034.5 Net outstanding campaign obligations...the candidate shall submit a statement of net outstanding campaign obligations. The...

2012-01-01

88

11 CFR 9034.5 - Net outstanding campaign obligations.  

...2014-01-01 2014-01-01 false Net outstanding campaign obligations. 9034...MATCHING FUND ENTITLEMENTS § 9034.5 Net outstanding campaign obligations...the candidate shall submit a statement of net outstanding campaign obligations. The...

2014-01-01

89

11 CFR 9034.5 - Net outstanding campaign obligations.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Net outstanding campaign obligations. 9034...MATCHING FUND ENTITLEMENTS § 9034.5 Net outstanding campaign obligations...the candidate shall submit a statement of net outstanding campaign obligations. The...

2011-01-01

90

11 CFR 9034.5 - Net outstanding campaign obligations.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 2012-01-01 true Net outstanding campaign obligations. 9034...MATCHING FUND ENTITLEMENTS § 9034.5 Net outstanding campaign obligations...the candidate shall submit a statement of net outstanding campaign obligations. The...

2013-01-01

91

11 CFR 9034.5 - Net outstanding campaign obligations.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Net outstanding campaign obligations. 9034...MATCHING FUND ENTITLEMENTS § 9034.5 Net outstanding campaign obligations...the candidate shall submit a statement of net outstanding campaign obligations. The...

2010-01-01

92

31 CFR 225.5 - Pledge of definitive Government obligations.  

Code of Federal Regulations, 2010 CFR

...Pledge of definitive Government obligations. 225.5 Section 225.5...OF BONDS SECURED BY GOVERNMENT OBLIGATIONS IN LIEU OF BONDS WITH SURETIES...Pledge of definitive Government obligations. (a) Type and...

2010-07-01

93

31 CFR 225.5 - Pledge of definitive Government obligations.  

Code of Federal Regulations, 2010 CFR

...Pledge of definitive Government obligations. 225.5 Section 225.5...OF BONDS SECURED BY GOVERNMENT OBLIGATIONS IN LIEU OF BONDS WITH SURETIES...Pledge of definitive Government obligations. (a) Type and...

2009-07-01

94

12 CFR 1270.20 - Consolidated obligations are not obligations of the United States or guaranteed by the United...  

Code of Federal Regulations, 2012 CFR

... 1270.20 Section 1270.20 Banks and Banking FEDERAL HOUSING FINANCE AGENCY FEDERAL HOME LOAN BANKS LIABILITIES Book-Entry Procedure for Consolidated Obligations § 1270.20 Consolidated obligations are not obligations of the United...

2012-01-01

95

42 CFR 136.332 - Service obligation.  

Code of Federal Regulations, 2013 CFR

...HUMAN SERVICES INDIAN HEALTH SERVICE, DEPARTMENT OF HEALTH AND HUMAN SERVICES INDIAN HEALTH Indian Health Care Improvement Act Programs Subdivision J-4-Indian...Scholarship Program § 136.332 Service obligation. The service...

2013-10-01

96

40 CFR 1043.30 - General obligations.  

Code of Federal Regulations, 2013 CFR

...Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF NOX, SOX, AND PM EMISSIONS FROM MARINE ENGINES AND VESSELS SUBJECT TO THE MARPOL PROTOCOL § 1043.30 General obligations....

2013-07-01

97

19 CFR 10.512 - Importer obligations.  

Code of Federal Regulations, 2013 CFR

...HOMELAND SECURITY; DEPARTMENT OF THE TREASURY ARTICLES CONDITIONALLY FREE, SUBJECT TO A REDUCED RATE, ETC. United States-Singapore Free Trade Agreement Import Requirements § 10.512 Importer obligations. (a) General. An...

2013-04-01

98

Federal Academic Science and Engineering Obligations Decreased  

NSF Publications Database

... Obligations Decreased Slightly in FY 1996 (April 27, 1998) This data brief highlights the major ... Fiscal Year 1996. A full set of Detailed Statistical Tables covering FY 1996 and prior years will be ...

99

The Olive Fly Endosymbiont, "Candidatus Erwinia dacicola," Switches from an Intracellular Existence to an Extracellular Existence during Host Insect Development? †  

PubMed Central

As polyphagous, holometabolous insects, tephritid fruit flies (Diptera: Tephritidae) provide a unique habitat for endosymbiotic bacteria, especially those microbes associated with the digestive system. Here we examine the endosymbiont of the olive fly [Bactrocera oleae (Rossi) (Diptera: Tephritidae)], a tephritid of great economic importance. “Candidatus Erwinia dacicola” was found in the digestive systems of all life stages of wild olive flies from the southwestern United States. PCR and microscopy demonstrated that “Ca. Erwinia dacicola” resided intracellularly in the gastric ceca of the larval midgut but extracellularly in the lumen of the foregut and ovipositor diverticulum of adult flies. “Ca. Erwinia dacicola” is one of the few nonpathogenic endosymbionts that transitions between intracellular and extracellular lifestyles during specific stages of the host's life cycle. Another unique feature of the olive fly endosymbiont is that unlike obligate endosymbionts of monophagous insects, “Ca. Erwinia dacicola” has a G+C nucleotide composition similar to those of closely related plant-pathogenic and free-living bacteria. These two characteristics of “Ca. Erwinia dacicola,” the ability to transition between intracellular and extracellular lifestyles and a G+C nucleotide composition similar to those of free-living relatives, may facilitate survival in a changing environment during the development of a polyphagous, holometabolous host. We propose that insect-bacterial symbioses should be classified based on the environment that the host provides to the endosymbiont (the endosymbiont environment).

Estes, Anne M.; Hearn, David J.; Bronstein, Judith L.; Pierson, Elizabeth A.

2009-01-01

100

The olive fly endosymbiont, "Candidatus Erwinia dacicola," switches from an intracellular existence to an extracellular existence during host insect development.  

PubMed

As polyphagous, holometabolous insects, tephritid fruit flies (Diptera: Tephritidae) provide a unique habitat for endosymbiotic bacteria, especially those microbes associated with the digestive system. Here we examine the endosymbiont of the olive fly [Bactrocera oleae (Rossi) (Diptera: Tephritidae)], a tephritid of great economic importance. "Candidatus Erwinia dacicola" was found in the digestive systems of all life stages of wild olive flies from the southwestern United States. PCR and microscopy demonstrated that "Ca. Erwinia dacicola" resided intracellularly in the gastric ceca of the larval midgut but extracellularly in the lumen of the foregut and ovipositor diverticulum of adult flies. "Ca. Erwinia dacicola" is one of the few nonpathogenic endosymbionts that transitions between intracellular and extracellular lifestyles during specific stages of the host's life cycle. Another unique feature of the olive fly endosymbiont is that unlike obligate endosymbionts of monophagous insects, "Ca. Erwinia dacicola" has a G+C nucleotide composition similar to those of closely related plant-pathogenic and free-living bacteria. These two characteristics of "Ca. Erwinia dacicola," the ability to transition between intracellular and extracellular lifestyles and a G+C nucleotide composition similar to those of free-living relatives, may facilitate survival in a changing environment during the development of a polyphagous, holometabolous host. We propose that insect-bacterial symbioses should be classified based on the environment that the host provides to the endosymbiont (the endosymbiont environment). PMID:19767463

Estes, Anne M; Hearn, David J; Bronstein, Judith L; Pierson, Elizabeth A

2009-11-01

101

Sequence Conservation and Functional Constraint on Intergenic Spacers in Reduced Genomes of the Obligate Symbiont Buchnera  

Microsoft Academic Search

Analyses of genome reduction in obligate bacterial symbionts typically focus on the removal and retention of protein-coding regions, which are subject to ongoing inactivation and deletion. However, these same forces operate on intergenic spacers (IGSs) and affect their contents, maintenance, and rates of evolution. IGSs comprise both non-coding, non-functional regions, including decaying pseudogenes at varying stages of recognizability, as well

Patrick H. Degnan; Howard Ochman; Nancy A. Moran

2011-01-01

102

Review of solar obligations in China  

Microsoft Academic Search

Solar energy utilization can not only decrease conventional energy consumption but also reduce environmental pollution. China has abundant solar energy resources and has the biggest solar water heater market in the world, so it is necessary for Chinese government to enact incentive policies and measures to enlarge the utilization scale of solar water heaters. According to international experience, solar obligation

Hui Xie; Chen Zhang; Bin Hao; Shan Liu; Kunkun Zou

103

Boundary Between Bacterial Mesophilism and Thermophilism  

PubMed Central

Bausum, Howard T. (Fort Detrick, Frederick, Md.), and Thomas S. Matney. Boundary between bacterial mesophilism and thermophilism. J. Bacteriol. 90:50–53. 1965.—The temperature boundary between bacterial mesophilism and thermophilism has been identified as 44 to 52 C. Facultative thermophiles growing in the mesophilic range require a brief period of adaptation at intermediate temperatures before gaining the capacity to initiate growth at thermophilic temperatures. Obligate mesophiles cannot grow in the thermophilic temperature range, but obligate thermophiles may show limited growth at temperatures as low as 41 C.

Bausum, Howard T.; Matney, Thomas S.

1965-01-01

104

47 CFR 76.56 - Signal carriage obligations.  

Code of Federal Regulations, 2010 CFR

...Telecommunication 4 2010-10-01 2010-10-01 false Signal carriage obligations. 76.56 Section 76.56...TELEVISION SERVICE Carriage of Television Broadcast Signals § 76.56 Signal carriage obligations. (a) Carriage of...

2010-10-01

105

47 CFR 76.56 - Signal carriage obligations.  

Code of Federal Regulations, 2010 CFR

...Telecommunication 4 2009-10-01 2009-10-01 false Signal carriage obligations. 76.56 Section 76.56...TELEVISION SERVICE Carriage of Television Broadcast Signals § 76.56 Signal carriage obligations. (a) Carriage of...

2009-10-01

106

38 CFR 17.608 - Deferment of obligated service.  

Code of Federal Regulations, 2013 CFR

...obligated service. (a) Request for deferment. A participant receiving a degree from a school of medicine, osteopathy, dentistry, optometry, or podiatry, may request deferment of obligated service to complete an approved program of advanced...

2013-07-01

107

48 CFR 333.213 - Obligation to continue performance.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Obligation to continue performance. 333.213 Section 333.213 ...Acquisition Regulations System HEALTH AND HUMAN SERVICES GENERAL CONTRACTING REQUIREMENTS... 333.213 Obligation to continue performance. (a) The Contracting Officer...

2013-10-01

108

47 CFR 22.878 - Obligation to abate unacceptable interference.  

Code of Federal Regulations, 2010 CFR

... 2009-10-01 false Obligation to abate unacceptable interference. 22.878...Air-Ground Systems § 22.878 Obligation to abate unacceptable interference. This...877, shall be strictly accountable to abate the interference, with full...

2009-10-01

109

47 CFR 90.673 - Obligation to abate unacceptable interference.  

Code of Federal Regulations, 2010 CFR

... 2009-10-01 false Obligation to abate unacceptable interference. 90.673...Interference § 90.673 Obligation to abate unacceptable interference. (a) Strict...chapter, shall be strictly accountable to abate the interference, with full...

2009-10-01

110

47 CFR 90.673 - Obligation to abate unacceptable interference.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Obligation to abate unacceptable interference. 90.673...Interference § 90.673 Obligation to abate unacceptable interference. (a) Strict...chapter, shall be strictly accountable to abate the interference, with full...

2010-10-01

111

47 CFR 22.878 - Obligation to abate unacceptable interference.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Obligation to abate unacceptable interference. 22.878...Air-Ground Systems § 22.878 Obligation to abate unacceptable interference. This...877, shall be strictly accountable to abate the interference, with full...

2010-10-01

112

47 CFR 22.971 - Obligation to abate unacceptable interference.  

Code of Federal Regulations, 2010 CFR

... 2009-10-01 false Obligation to abate unacceptable interference. 22.971...Radiotelephone Service § 22.971 Obligation to abate unacceptable interference. (a) Strict...970, shall be strictly accountable to abate the interference, with full...

2009-10-01

113

47 CFR 22.971 - Obligation to abate unacceptable interference.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Obligation to abate unacceptable interference. 22.971...Radiotelephone Service § 22.971 Obligation to abate unacceptable interference. (a) Strict...970, shall be strictly accountable to abate the interference, with full...

2010-10-01

114

24 CFR 582.410 - Obligation and deobligation of funds.  

Code of Federal Regulations, 2013 CFR

...ASSISTANT SECRETARY FOR COMMUNITY PLANNING AND DEVELOPMENT, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT COMMUNITY FACILITIES SHELTER PLUS CARE Administration § 582.410 Obligation and deobligation of funds. (a) Obligation of funds....

2013-04-01

115

Bacterial DNA Sifted from the Trichoplax adhaerens (Animalia: Placozoa) Genome Project Reveals a Putative Rickettsial Endosymbiont  

PubMed Central

Eukaryotic genome sequencing projects often yield bacterial DNA sequences, data typically considered as microbial contamination. However, these sequences may also indicate either symbiont genes or lateral gene transfer (LGT) to host genomes. These bacterial sequences can provide clues about eukaryote–microbe interactions. Here, we used the genome of the primitive animal Trichoplax adhaerens (Metazoa: Placozoa), which is known to harbor an uncharacterized Gram-negative endosymbiont, to search for the presence of bacterial DNA sequences. Bioinformatic and phylogenomic analyses of extracted data from the genome assembly (181 bacterial coding sequences [CDS]) and trace read archive (16S rDNA) revealed a dominant proteobacterial profile strongly skewed to Rickettsiales (Alphaproteobacteria) genomes. By way of phylogenetic analysis of 16S rDNA and 113 proteins conserved across proteobacterial genomes, as well as identification of 27 rickettsial signature genes, we propose a Rickettsiales endosymbiont of T. adhaerens (RETA). The majority (93%) of the identified bacterial CDS belongs to small scaffolds containing prokaryotic-like genes; however, 12 CDS were identified on large scaffolds comprised of eukaryotic-like genes, suggesting that T. adhaerens might have recently acquired bacterial genes. These putative LGTs may coincide with the placozoan’s aquatic niche and symbiosis with RETA. This work underscores the rich, and relatively untapped, resource of eukaryotic genome projects for harboring data pertinent to host–microbial interactions. The nature of unknown (or poorly characterized) bacterial species may only emerge via analysis of host genome sequencing projects, particularly if these species are resistant to cell culturing, as are many obligate intracellular microbes. Our work provides methodological insight for such an approach.

Driscoll, Timothy; Gillespie, Joseph J.; Nordberg, Eric K.; Azad, Abdu F.; Sobral, Bruno W.

2013-01-01

116

34 CFR 686.43 - Obligation to repay the grant.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Obligation to repay the grant. 686.43 Section 686.43 Education...FOR COLLEGE AND HIGHER EDUCATION (TEACH) GRANT PROGRAM Service and Repayment Obligations § 686.43 Obligation to repay the grant. (a) The TEACH Grant amounts...

2013-07-01

117

An obligate osmophilic yeast from honey.  

PubMed

An obligate osmophilic yeast that requires high sugar concentrations (10 to 20% glucose) for growth was identified as Saccharomyces bisporus var. mellis. Optimum growth for this strain was at 60% glucose. Several non-assimilable compounds permitted growth at glucose concentrations below the minimum requirement and stimulated growth at glucose concentrations above the minimum. No correlation existed between growth stimulation and spheroplast stabilization capacities of the compounds examined. PMID:984813

Munitis, M T; Cabrera, E; Rodriguez-Navarro, A

1976-09-01

118

Intracellular antibodies for proteomics  

Microsoft Academic Search

The intracellular antibody technology has many applications for proteomics studies.The potential of intracellular antibodies for the systematic study of the proteome has been made possible by the development of new experimental strategies that allow the selection of antibodies under conditions of intracellular expression. The Intracellular Antibody Capture Technology (IACT) is an in vivo two-hybrid-based method originally developed for the selection

Michela Visintin; Giovanni Antonio Meli; Isabella Cannistraci; Antonino Cattaneo

2004-01-01

119

MICROSPORIDIA: Biology and Evolution of Highly Reduced Intracellular Parasites  

Microsoft Academic Search

? Abstract Microsporidia are a large group,of microbial,eukaryotes,composed exclusively of obligate intracellular parasites of other eukaryotes. Almost 150 years of microsporidian,research has led to a basic understanding,of many,aspects of mi- crosporidian biology, especially their unique and highly specialized mode of infection, where,the parasite enters its host through,a projectile tube that is expelled,at high velocity. Molecular biology and genomic,studies on microsporidia,have

Patrick J. Keeling; Naomi M. Fast

2002-01-01

120

26 CFR 1.691(e)-1 - Installment obligations transmitted at death when prior law applied.  

Code of Federal Regulations, 2013 CFR

... Installment obligations transmitted at death when prior law applied. 1.691(e... Installment obligations transmitted at death when prior law applied. (a) In general...transmission of installment obligations at the death of a holder of such obligations were...

2013-04-01

121

Reduction of ribonucleotides by the obligate intracytoplasmic bacterium Rickettsia prowazekii.  

PubMed Central

Rickettsia prowazekii, an obligate intracellular parasitic bacterium, was shown to have a ribonucleotide reductase that would allow the rickettsiae to obtain the deoxyribonucleotides needed for DNA synthesis from rickettsial ribonucleotides rather than from transport. In the presence of hydroxyurea, R. prowazekii failed to grow in mouse L929 cells or SC2 cells (a hydroxyurea-resistant cell line), which suggested that R. prowazekii contains a functional ribonucleotide reductase. This enzymatic activity was demonstrated by the conversion of ADP to dADP and CDP to dCDP, using (i) a crude extract of Renografin-purified R. prowazekii that had been harvested from infected yolk sacs and (ii) high-performance liquid chromatographic analysis. The rickettsial ribonucleotide reductase utilized ribonucleoside diphosphates as substrates, required magnesium and a reducing agent, and was inhibited by hydroxyurea. ADP reduction was stimulated by dGTP and inhibited by dATP. CDP reduction was stimulated by ATP and adenylylimido-diphosphate and inhibited by dATP and dGTP. These characteristics provided strong evidence that the rickettsial enzyme is a nonheme iron-containing enzyme similar to those found in mammalian cells and aerobic Escherichia coli.

Cai, J; Speed, R R; Winkler, H H

1991-01-01

122

Dominant Obligate Anaerobes Revealed in Lower Respiratory Tract Infection in Horses by 16S rRNA Gene Sequencing  

PubMed Central

ABSTRACT Obligate anaerobes are important etiological agents in pneumonia or pleuropneumonia in horses, because they are isolated more commonly from ill horses that have died or been euthanized than from those that survive. We performed bacterial identification and antimicrobial susceptibility testing for obligate anaerobes to establish effective antimicrobial therapy. We used 16S rRNA gene sequencing to identify 58 obligate anaerobes and compared the results with those from a phenotypic identification kit. The identification results of 16S rRNA gene sequencing were more reliable than those of the commercial kit. We concluded that genera Bacteroides and Prevotella—especially B. fragilis and P. heparinolytica—are dominant anaerobes in lower respiratory tract infection in horses; these organisms were susceptible to metronidazole, imipenem and clindamycin.

KINOSHITA, Yuta; NIWA, Hidekazu; KATAYAMA, Yoshinari; HARIU, Kazuhisa

2013-01-01

123

Dominant Obligate Anaerobes Revealed in Lower Respiratory Tract Infection in Horses by 16S rRNA Gene Sequencing.  

PubMed

Obligate anaerobes are important etiological agents in pneumonia or pleuropneumonia in horses, because they are isolated more commonly from ill horses that have died or been euthanized than from those that survive. We performed bacterial identification and antimicrobial susceptibility testing for obligate anaerobes to establish effective antimicrobial therapy. We used 16S rRNA gene sequencing to identify 58 obligate anaerobes and compared the results with those from a phenotypic identification kit. The identification results of 16S rRNA gene sequencing were more reliable than those of the commercial kit. We concluded that genera Bacteroides and Prevotella-especially B. fragilis and P. heparinolytica-are dominant anaerobes in lower respiratory tract infection in horses; these organisms were susceptible to metronidazole, imipenem and clindamycin. PMID:24366152

Kinoshita, Yuta; Niwa, Hidekazu; Katayama, Yoshinari; Hariu, Kazuhisa

2014-05-01

124

Classification Revisions Reduce Reported Federal Development Obligations  

NSF Publications Database

Such was the case with recent survey revisions provided by NIH and NASA to the National Science Foundation's (NSF's) Survey of Federal Funds for Research and Development (Federal Funds for short). The NSF Federal Funds survey does not collect S&E field data for development or R&D plant funds. The data presented in this InfoBrief are obtained from an annual census of approximately 30 Federal agencies that report obligation data to the NSF Survey of Federal Funds for Research and Development.

125

The intracellular bacteria Chlamydia hijack peroxisomes and utilize their enzymatic capacity to produce bacteria-specific phospholipids.  

PubMed

Chlamydia trachomatis is an obligate intracellular pathogen responsible for loss of eyesight through trachoma and for millions of cases annually of sexually transmitted diseases. The bacteria develop within a membrane-bounded inclusion. They lack enzymes for several biosynthetic pathways, including those to make some phospholipids, and exploit their host to compensate. Three-dimensional fluorescence microscopy demonstrates that small organelles of the host, peroxisomes, are translocated into the Chlamydia inclusion and are found adjacent to the bacteria. In cells deficient for peroxisome biogenesis the bacteria are able to multiply and give rise to infectious progeny, demonstrating that peroxisomes are not essential for bacterial development in vitro. Mass spectrometry-based lipidomics reveal the presence in C. trachomatis of plasmalogens, ether phospholipids whose synthesis begins in peroxisomes and have never been described in aerobic bacteria before. Some of the bacterial plasmalogens are novel structures containing bacteria-specific odd-chain fatty acids; they are not made in uninfected cells nor in peroxisome-deficient cells. Their biosynthesis is thus accomplished by the metabolic collaboration of peroxisomes and bacteria. PMID:24465954

Boncompain, Gaelle; Müller, Constanze; Meas-Yedid, Vannary; Schmitt-Kopplin, Philippe; Lazarow, Paul B; Subtil, Agathe

2014-01-01

126

Natural Functions of Bacterial Polyhydroxyalkanoates  

Microsoft Academic Search

\\u000a Polyhydroxyalkanoates (PHAs) are energy- and intracellular carbon-storage compounds that can be mobilized and used when carbon\\u000a is a limiting resource. Intracellular accumulation of PHA enhances the survival of several bacterial species under environmental\\u000a stress conditions imposed in water and soil, such as UV irradiation, salinity, thermal and oxidative stress, desiccation,\\u000a and osmotic shock. The ability to endure these stresses is

Susana Castro-Sowinski; Saul Burdman; Ofra Matan; Yaacov Okon

127

Strategies for Intracellular Survival of Burkholderia pseudomallei  

PubMed Central

Burkholderia pseudomallei is the causative agent of melioidosis, a disease with high mortality that is prevalent in tropical regions of the world. A key component of the pathogenesis of melioidosis is the ability of B. pseudomallei to enter, survive, and replicate within mammalian host cells. For non-phagocytic cells, bacterial adhesins have been identified both on the bacterial surface and associated with Type 4 pili. Cell invasion involves components of one or more of the three Type 3 Secretion System clusters, which also mediate, at least in part, the escape of bacteria from the endosome into the cytoplasm, where bacteria move by actin-based motility. The mechanism of actin-based motility is not clearly understood, but appears to differ from characterized mechanisms in other bacterial species. A small proportion of intracellular bacteria is targeted by host cell autophagy, involving direct recruitment of LC3 to endosomes rather than through uptake by canonical autophagosomes. However, the majority of bacterial cells are able to circumvent autophagy and other intracellular defense mechanisms such as the induction of inducible nitric oxide synthase, and then replicate in the cytoplasm and spread to adjacent cells via membrane fusion, resulting in the formation of multi-nucleated giant cells. A potential role for host cell ubiquitin in the autophagic response to bacterial infection has recently been proposed.

Allwood, Elizabeth M.; Devenish, Rodney J.; Prescott, Mark; Adler, Ben; Boyce, John D.

2011-01-01

128

Obligate Ordered Binding of Human Lactogenic Cytokines*  

PubMed Central

Class 1 cytokines bind two receptors to create an active heterotrimeric complex. It has been argued that ligand binding to their receptors is an ordered process, but a structural mechanism describing this process has not been determined. We have previously described an obligate ordered binding mechanism for the human prolactin/prolactin receptor heterotrimeric complex. In this work we expand this conceptual understanding of ordered binding to include three human lactogenic hormones: prolactin, growth hormone, and placental lactogen. We independently blocked either of the two receptor binding sites of each hormone and used surface plasmon resonance to measure human prolactin receptor binding kinetics and stoichiometries to the remaining binding surface. When site 1 of any of the three hormones was blocked, site 2 could not bind the receptor. But blocking site 2 did not affect receptor binding at site 1, indicating a requirement for receptor binding to site 1 before site 2 binding. In addition we noted variable responses to the presence of zinc in hormone-receptor interaction. Finally, we performed Förster resonance energy transfer (FRET) analyses where receptor binding at subsaturating stoichiometries induced changes in FRET signaling, indicative of binding-induced changes in hormone conformation, whereas at receptor:hormone ratios in excess of 2:1 no additional changes in FRET signaling were observed. These results strongly support a conformationally mediated obligate-ordered receptor binding for each of the three lactogenic hormones.

Voorhees, Jeffery L.; Brooks, Charles L.

2010-01-01

129

Tails of Bacterial Motility  

NASA Astrophysics Data System (ADS)

The cytoplasm of living cells provides a complex fluid environment in which intracellular bacteria live and move. By analyzing the easily visible curved actin ``comet-tail'' of polymerization-based-motility bacteria such as Listeria monocytogenes, we can learn about sub-micron structure and dynamics of the tail and of the bacterial surface enzyme that catalyzes tail formation. By characterizing the motility, we can transform such motile systems into probes of the cytoplasmic environment.

Rutenberg, Andrew; Grant, Martin

2001-03-01

130

On the nature of obligate intracellular symbiosis of rickettsiae — Rickettsia prowazekii cells import mitochondrial porin  

Microsoft Academic Search

Mitochondrial porin was identified in Rickettsia prowazekii by Western blot analysis of whole cells and membrane fractions with monoclonal antibody against porin VDAC 1 of animal mitochondria.\\u000a Using the BLAST server, no protein sequences homologous to mitochondrial porin were found among the rickettsial genomes. Rickettsiae\\u000a also do not contain their own porin. The protein imported by rickettsiae is weakly extracted

V. V. Emelyanov; M. Yu. Vyssokikh

2006-01-01

131

Purifying selection in mitochondria, free-living and obligate intracellular proteobacteria  

Microsoft Academic Search

BACKGROUND: The effectiveness of elimination of slightly deleterious mutations depends mainly on drift and recombination frequency. Here we analyze the influence of these two factors on the strength of the purifying selection in mitochondrial and proteobacterial orthologous genes taking into account the differences in the organism lifestyles. RESULTS: (I) We found that the probability of fixation of nonsynonymous substitutions (Kn\\/Ks)

Leila Mamirova; Konstantin Popadin; Mikhail S Gelfand

2007-01-01

132

A challenge for 21st century molecular biology and biochemistry: what are the causes of obligate autotrophy and methanotrophy?  

PubMed

We assess the use to which bioinformatics in the form of bacterial genome sequences, functional gene probes and the protein sequence databases can be applied to hypotheses about obligate autotrophy in eubacteria. Obligate methanotrophy and obligate autotrophy among the chemo- and photo-lithotrophic bacteria lack satisfactory explanation a century or more after their discovery. Various causes of these phenomena have been suggested, which we review in the light of the information currently available. Among these suggestions is the absence in vivo of a functional alpha-ketoglutarate dehydrogenase. The advent of complete and partial genome sequences of diverse autotrophs, methylotrophs and methanotrophs makes it possible to probe the reasons for the absence of activity of this enzyme. We review the role and evolutionary origins of the Krebs cycle in relation to autotrophic metabolism and describe the use of in silico methods to probe the partial and complete genome sequences of a variety of obligate genera for genes encoding the subunits of the alpha-ketoglutarate dehydrogenase complex. Nitrosomonas europaea and Methylococcus capsulatus, which lack the functional enzyme, were found to contain the coding sequences for the E1 and E2 subunits of alpha-ketoglutarate dehydrogenase. Comparing the predicted physicochemical properties of the polypeptides coded by the genes confirmed the putative gene products were similar to the active alpha-ketoglutarate dehydrogenase subunits of heterotrophs. These obligate species are thus genomically competent with respect to this enzyme but are apparently incapable of producing a functional enzyme. Probing of the full and incomplete genomes of some cyanobacterial and methanogenic genera and Aquifex confirms or suggests the absence of the genes for at least one of the three components of the alpha-ketoglutarate dehydrogenase complex in these obligate organisms. It is recognized that absence of a single functional enzyme may not explain obligate autotrophy in all cases and may indeed be only be one of a number of controls that impose obligate metabolism. Availability of more genome sequences from obligate genera will enable assessment of whether obligate autotrophy is due to the absence of genes for a few or many steps in organic compound metabolism. This problem needs the technologies and mindsets of the present generation of molecular microbiologists to resolve it. PMID:15449607

Wood, Ann P; Aurikko, Jukka P; Kelly, Donovan P

2004-06-01

133

Obligations of an academic and clinical oncologist: historical reflections.  

PubMed

Obligations are derived from one's core values-those fundamental, enduring, deeply held beliefs that guide one's everyday actions. Gandhi stated it more eloquently than I ever could: "Your beliefs become your thoughts, your thoughts become your words, your words become your actions, your actions become your habits, your habits become your values, your values become your destiny." So what are the obligations of the academic oncologist and clinician? I believe there are a few indubitable and fundamental obligations: professionalism, patient care, stewardship, maintenance of knowledge, productivity, and mentorship). I might add that I do not see these obligations as unique to the academician but rather applicable to all physicians. PMID:24857063

Johnson, David H

2014-01-01

134

Identification of iron-responsive proteins expressed by Chlamydia trachomatis reticulate bodies during intracellular growth.  

PubMed

The obligate intracellular bacterium Chlamydia trachomatis serovar E is the most prevalent cause of bacterial sexually transmitted disease. With an established requirement for iron, the developmental cycle arrests at the intracellular reticulate body stage during iron restriction, resulting in a phenomenon termed persistence. Persistence has implications in natural infections for altered expression of virulence factors and antigens, in addition to a potential role in producing chronic infection. In this study, chlamydial proteins in iron-restricted, infected HEC-1B cells were radiolabelled during mid-developmental cycle growth, harvested, and separated using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Of approximately 250 radiolabelled protein species visualized, densitometric analysis revealed 25 proteins that increased in expression under iron restriction compared to iron-sufficient control samples; ten protein species identified by mass spectrometry are involved in the oxidative damage response (alkyl hydroperoxide reductase, 6-phosphogluconolactonase and acyl carrier protein synthase), transcription (RNA polymerase subunit alpha and transcription anti-termination factors NusA and NusG), protein modification (peptide deformylase and trigger factor), and virulence (Chlamydia protein associating with death domains, CADD). Transcript-level expression patterns of ahpC, devB, cadd, fabF and ct538 were measured by quantitative RT-PCR throughout the developmental cycle, and each gene examined demonstrated a significant but small mid-cycle increase in transcript level in iron-restricted cultures compared to iron-replete controls. Taken together, these data suggest that the primary response of chlamydiae to reduced iron availability is to increase expression of proteins involved in protection against oxidative damage via iron-catalysed generation of reactive oxygen species and adaptation to stress by increasing expression of transcriptional machinery and other stress-responsive proteins. PMID:19118361

Dill, Brian D; Dessus-Babus, Sophie; Raulston, Jane E

2009-01-01

135

Bacterial Endosymbionts of Pyrodinium bahamense var. compressum  

Microsoft Academic Search

The study presents evidence in support of the bacterial theory associated with the toxicity of Pyrodinium bahamense var. compressum. Bacterial endosymbionts from Philippine P. bahamense var. compressum strain Pbc MZRVA 042595 were isolated and identified via 16S rDNA sequence analysis. Taxonomic diversity of the identified culturable intracellular microbiota associated with Philippine P. bahamense var. compressum was established to be limited

Ma. Patricia V. Azanza; Rhodora V. Azanza; Vanessa Mercee D. Vargas; Cynthia T. Hedreyda

2006-01-01

136

Explicit hypoxia targeting with tumor suppression by creating an "obligate" anaerobic Salmonella Typhimurium strain  

PubMed Central

Using bacteria as therapeutic agents against solid tumors is emerging as an area of great potential in the treatment of cancer. Obligate and facultative anaerobic bacteria have been shown to infiltrate the hypoxic regions of solid tumors, thereby reducing their growth rate or causing regression. However, a major challenge for bacterial therapy of cancer with facultative anaerobes is avoiding damage to normal tissues. Consequently the virulence of bacteria must be adequately attenuated for therapeutic use. By placing an essential gene under a hypoxia conditioned promoter, Salmonella Typhimurium strain SL7207 was engineered to survive only in anaerobic conditions (strain YB1) without otherwise affecting its functions. In breast tumor bearing nude mice, YB1 grew within the tumor, retarding its growth, while being rapidly eliminated from normal tissues. YB1 provides a safe bacterial vector for anti-tumor therapies without compromising the other functions or tumor fitness of the bacterium as attenuation methods normally do.

Yu, Bin; Yang, Mei; Shi, Lei; Yao, Yandan; Jiang, Qinqin; Li, Xuefei; Tang, Lei-Han; Zheng, Bo-Jian; Yuen, Kwok-Yung; Smith, David K.; Song, Erwei; Huang, Jian-Dong

2012-01-01

137

Moral Obligations from Our Oath to the US Constitution.  

National Technical Information Service (NTIS)

Every officer in the military takes an oath of office upon entry into the service. Under that oath the officer has some moral obligations. This article examines these obligations in relation to the Constitution of the United States. The article looks back...

L. A. Helgeson

1987-01-01

138

The Role Obligations of Students and Lecturers in Higher Education  

ERIC Educational Resources Information Center

The current discussion of consumerism in higher education focuses largely on what the providers are obliged to do for the consumers, against the background of rising tuition fees. This framework does not always sit comfortably with lecturers in the context of a learning and teaching relationship, as it appears to ignore the reciprocal obligations

Regan, Julie-Anne

2012-01-01

139

The Evolutionary Pathway to Obligate Scavenging in Gyps Vultures  

Microsoft Academic Search

The evolutionary pathway to obligate scavenging in Gyps vultures remains unclear. We propose that communal roosting plays a central role in setting up the information transfer network critical for obligate scavengers in ephemeral environments and that the formation of a flotilla-like foraging group is a likely strategy for foraging Gyps vultures. Using a spatial, individual-based, optimisation model we find that

Brian J. Dermody; Colby J. Tanner; Andrew L. Jackson

2011-01-01

140

In Defence of Associative Political Obligations: Part One  

Microsoft Academic Search

Part One of this article seeks to defend the idea of associative political obligations against a number of criticisms that have been advanced opposing it.The purpose of this defence is not to demonstrate that the associative account is therefore the best explanation of political obligations, but only that the principal reasons which have been given for rejecting it are much

John Horton

2007-01-01

141

Libertarianism, positive obligations and property abandonment: children's rights  

Microsoft Academic Search

The purpose of the present paper is to test this premise of no positive obligations against a challenging critique that can be made of it. To wit, abandonment of babies. That is, does the mother who abandons her baby have the positive obligation to at least place it “on the church steps”, e.g. notify all other potential care givers of

Walter Block

2004-01-01

142

Child Support Obligations and Low-Income Fathers  

ERIC Educational Resources Information Center

Using the 1994-1998 waves of the Current Population Survey--Child Support Supplement (N = 5,387), the aims of this study are to document child support obligation rates of nonresident fathers, to examine the effect of the obligation rate on child support compliance, and to calculate the trade-off between fathers' financial responsibility and…

Huang, Chien-Chung; Mincy, Ronald B.; Garfinkel, Irwin

2005-01-01

143

Cultural Generality of the Integration of Obligation and Other Motives  

ERIC Educational Resources Information Center

The purpose of the present study is twofold. One is to assess the cultural generality of the information integration rule for moral obligation. The other is to examine how people integrate moral obligation and self-interest. Two studies were implemented following the functional measurement methodology with Chinese samples. Study 1 replicated the…

Yang, Jen-Shou

2012-01-01

144

Parental Beliefs about Nonresident Fathers' Obligations and Rights  

ERIC Educational Resources Information Center

We examine whether parents rely on principles of equity or equality in making judgments about nonresident fathers' obligations and rights. The data are taken from the first wave of the Fragile Families and Child Wellbeing Study. The analysis sample includes 4,304 new mothers and 3,414 new fathers. Results indicate that fathers perceive obligations

Lin, I-Fen; McLanahan, Sara S.

2007-01-01

145

What Is to Be Done? Children's Ascriptions of Conventional Obligations  

ERIC Educational Resources Information Center

It is often not apparent what people ought to do. Three experiments explored cues that children and adults may use to identify conventional obligations. Experiment 1 addressed the hypothesis that young children identify obligations with expected outcomes. Although preschool-aged (4-5 years) children often expected consistency, they and school-aged…

Kalish, Charles W.; Cornelius, Rebecca

2007-01-01

146

Intracellular Parasite Invasion Strategies  

NASA Astrophysics Data System (ADS)

Intracellular parasites use various strategies to invade cells and to subvert cellular signaling pathways and, thus, to gain a foothold against host defenses. Efficient cell entry, ability to exploit intracellular niches, and persistence make these parasites treacherous pathogens. Most intracellular parasites gain entry via host-mediated processes, but apicomplexans use a system of adhesion-based motility called ``gliding'' to actively penetrate host cells. Actin polymerization-dependent motility facilitates parasite migration across cellular barriers, enables dissemination within tissues, and powers invasion of host cells. Efficient invasion has brought widespread success to this group, which includes Toxoplasma, Plasmodium, and Cryptosporidium.

Sibley, L. D.

2004-04-01

147

Obligate Insect Endosymbionts Exhibit Increased Ortholog Length Variation and Loss of Large Accessory Proteins Concurrent with Genome Shrinkage  

PubMed Central

Extreme genome reduction has been observed in obligate intracellular insect mutualists and is an assumed consequence of fixed, long-term host isolation. Rapid accumulation of mutations and pseudogenization of genes no longer vital for an intracellular lifestyle, followed by deletion of many genes, are factors that lead to genome reduction. Size reductions in individual genes due to small-scale deletions have also been implicated in contributing to overall genome shrinkage. Conserved protein functional domains are expected to exhibit low tolerance for mutations and therefore remain relatively unchanged throughout protein length reduction while nondomain regions, presumably under less selective pressures, would shorten. This hypothesis was tested using orthologous protein sets from the Flavobacteriaceae (phylum: Bacteroidetes) and Enterobacteriaceae (subphylum: Gammaproteobacteria) families, each of which includes some of the smallest known genomes. Upon examination of protein, functional domain, and nondomain region lengths, we found that proteins were not uniformly shrinking with genome reduction, but instead increased length variability and variability was observed in both the functional domain and nondomain regions. Additionally, as complete gene loss also contributes to overall genome shrinkage, we found that the largest proteins in the proteomes of nonhost-restricted bacteroidetial and gammaproteobacterial species often were inferred to be involved in secondary metabolic processes, extracellular sensing, or of unknown function. These proteins were absent in the proteomes of obligate insect endosymbionts. Therefore, loss of genes encoding large proteins not required for host-restricted lifestyles in obligate endosymbiont proteomes likely contributes to extreme genome reduction to a greater degree than gene shrinkage.

Kenyon, Laura J.; Sabree, Zakee L.

2014-01-01

148

Neutrophils Mediate Immunopathology and Negatively Regulate Protective Immune Responses during Fatal Bacterial Infection-Induced Toxic Shock  

PubMed Central

Ehrlichia chaffeensis is an obligate intracellular bacterium that infects primarily monocytes and macrophages and causes potentially fatal human monocytic ehrlichiosis (HME) that mimics toxic-shock-like syndrome in immunocompetent hosts. Early recruitment of neutrophils to the sites of infection is critical for the control of bacterial infection and inflammatory responses. We recently observed rapid and sustained neutrophil recruitment at a primary site of infection (peritoneum) following lethal murine ehrlichial infection compared to innocuous ehrlichial infection. We examined here the contribution of neutrophils to protective immunity or immunopathology during infection with monocytic Ehrlichia. Unexpectedly, depletion of neutrophils from lethally infected mice enhanced bacterial elimination, decreased immune-mediated pathology, and prolonged survival. Furthermore, compared to lethally infected sham controls, neutrophil depletion in infected mice resulted in amelioration of pathogenic responses, as evidenced by a decreased number of tumor necrosis factor alpha (TNF-?)-producing CD8+ T cells, which is known to mediate immunopathology and toxic shock in a murine model of fatal ehrlichiosis. Although neutrophil depletion did not influence the number of CD4+ Th1 cells and NKT cells producing gamma interferon (IFN-?), it increased the ratio of IFN-?- to IL-10-producing NKT cells as well as the ratio of IFN-? to interleukin 10 (IL-10) transcripts in the liver. This may ameliorate the net suppressive effect of IL-10 on IFN-?-mediated activation of infected macrophages and thus may account for the enhanced bacterial elimination. Finally, transcriptional analysis of gene expression in the liver indicated that neutrophils contribute to overproduction of cytokines and chemokines during fatal ehrlichiosis. In conclusion, these results revealed an unexpected role of neutrophils in supporting bacterial replication indirectly and promoting immunopathology during severe infection with an intracellular bacterium.

Yang, Qin; Ghose, Purnima

2013-01-01

149

Intracellular Ionized Calcium.  

National Technical Information Service (NTIS)

Measurement of intracellular ionized calcium concentration (Ca2+) in living cells is of considerable interest to investigators over a broad range of cell biology. Calcium has an important role in a number of cellular functions and, perhaps most interestin...

C. H. June P. S. Rabinovitch

1994-01-01

150

Review of International Experience with Renewable Energy Obligation Support Mechanisms  

SciTech Connect

The main policy instruments currently used in the EU Member States to achieve the targets set for electricity produced from renewable energy sources are: (1) the quota obligation system; (2) the feed-in tariff system; and (3) the tendering system. The current study aims to review the experience gained with the quota obligation system. The report provides an overview of the regions where obligation systems have been implemented and contains a detailed evaluation of the performance of the obligation systems in the USA, the UK and in Sweden. The obligation systems in these countries have been evaluated based on the following criteria: Effectiveness; Market efficiency; Certainty for the renewable energy industry; Cost effectiveness; Stakeholder support for the obligation system; and Equity. The evaluation of international experiences with the obligation system gives rise to a mixed picture. Although an obligation in theory is effective and cost effective, it seems too early to conclude that the system delivers these promises in practice. On the one hand this is due to the limited period of implementation that makes it hard to distinguish between the direct effect of the system and some teething problems that will be solved in due time. On the other hand, the conclusion can be drawn that the obligation is a complex system, which will only function well if designed carefully. It does seem worthwhile, however, to continue monitoring the experiences with the obligation system abroad, because this will further reveal whether the system is indeed effective and cost effective in practice. In the longer term, e.g. beyond 2010, the introduction of an obligation system in the Netherlands could be considered. Finally, as the design of support schemes is being improved, it appears that the basic concepts of both the obligation system and the feed in system have been refined in such a way that the two systems are gradually converging. An important difference between the two systems however remains, namely that an obligation system relies more on market forces whereas the feed-in system is based on a greater involvement of the government.

Wiser, R.

2005-06-01

151

12 CFR 1270.18 - Additional requirements; notice of attachment for Book-entry consolidated obligations.  

Code of Federal Regulations, 2013 CFR

...requirements; notice of attachment for Book-entry consolidated obligations. 1270...FEDERAL HOME LOAN BANKS LIABILITIES Book-Entry Procedure for Consolidated Obligations...requirements; notice of attachment for Book-entry consolidated obligations....

2013-01-01

152

12 CFR 960.4 - Obligation to Bank under all standby letters of credit.  

Code of Federal Regulations, 2010 CFR

...Obligation to Bank under all standby letters of credit. 960.4 Section 960...OFF-BALANCE SHEET ITEMS STANDBY LETTERS OF CREDIT § 960.4 Obligation to Bank under all standby letters of credit. (a) Obligation to...

2009-01-01

153

12 CFR 960.4 - Obligation to Bank under all standby letters of credit.  

Code of Federal Regulations, 2010 CFR

...Obligation to Bank under all standby letters of credit. 960.4 Section 960...OFF-BALANCE SHEET ITEMS STANDBY LETTERS OF CREDIT § 960.4 Obligation to Bank under all standby letters of credit. (a) Obligation to...

2010-01-01

154

Bacterial Vaginosis  

MedlinePLUS

... vaginosis can increase your chance of getting an STD. What is bacterial vaginosis? Bacterial vaginosis (BV) is ... contributes to BV. BV is not considered an STD, but having BV can increase your chances of ...

155

Physicians' strikes and the competing bases of physicians' moral obligations.  

PubMed

Many authors have addressed the morality of physicians' strikes on the assumption that medical practice is morally different from other kinds of occupations. This article analyzes three prominent theoretical accounts that attempt to ground such special moral obligations for physicians--practice-based accounts, utilitarian accounts, and social contract accounts--and assesses their applicability to the problem of the morality of strikes. After critiquing these views, it offers a fourth view grounding special moral obligations in voluntary commitments, and explains why this is a preferable basis for understanding physicians' moral obligations in general and especially as pertaining to strikes. PMID:24199524

MacDougall, D Robert

2013-09-01

156

Mechanisms of cellular invasion by intracellular parasites.  

PubMed

Numerous disease-causing parasites must invade host cells in order to prosper. Collectively, such pathogens are responsible for a staggering amount of human sickness and death throughout the world. Leishmaniasis, Chagas disease, toxoplasmosis, and malaria are neglected diseases and therefore are linked to socio-economical and geographical factors, affecting well-over half the world's population. Such obligate intracellular parasites have co-evolved with humans to establish a complexity of specific molecular parasite-host cell interactions, forming the basis of the parasite's cellular tropism. They make use of such interactions to invade host cells as a means to migrate through various tissues, to evade the host immune system, and to undergo intracellular replication. These cellular migration and invasion events are absolutely essential for the completion of the lifecycles of these parasites and lead to their for disease pathogenesis. This review is an overview of the molecular mechanisms of protozoan parasite invasion of host cells and discussion of therapeutic strategies, which could be developed by targeting these invasion pathways. Specifically, we focus on four species of protozoan parasites Leishmania, Trypanosoma cruzi, Plasmodium, and Toxoplasma, which are responsible for significant morbidity and mortality. PMID:24221133

Walker, Dawn M; Oghumu, Steve; Gupta, Gaurav; McGwire, Bradford S; Drew, Mark E; Satoskar, Abhay R

2014-04-01

157

Federal Academic Obligations for S&E Activities Increased More than 4% in FY 1997  

NSF Publications Database

Federal Academic Obligations for Science and Engineering Activities Increased More than 4 Percent in ... Institutions: Fiscal Year 1997 and focuses on academic science and engineering obligations. It ...

158

Sulfur Production by Obligately Chemolithoautotrophic Thiobacillus Species  

PubMed Central

Transient-state experiments with the obligately autotrophic Thiobacillus sp. strain W5 revealed that sulfide oxidation proceeds in two physiological phases, (i) the sulfate-producing phase and (ii) the sulfur- and sulfate-producing phase, after which sulfide toxicity occurs. Specific sulfur-producing characteristics were independent of the growth rate. Sulfur formation was shown to occur when the maximum oxidative capacity of the culture was approached. In order to be able to oxidize increasing amounts of sulfide, the organism has to convert part of the sulfide to sulfur (HS(sup-)(symbl)S(sup0) + H(sup+) + 2e(sup-)) instead of sulfate (HS(sup-) + 4H(inf2)O(symbl)SO(inf4)(sup2-) + 9 H(sup+) + 8e(sup-)), thereby keeping the electron flux constant. Measurements of the in vivo degree of reduction of the cytochrome pool as a function of increasing sulfide supply suggested a redox-related down-regulation of the sulfur oxidation rate. Comparison of the sulfur-producing properties of Thiobacillus sp. strain W5 and Thiobacillus neapolitanus showed that the former has twice the maximum specific sulfide-oxidizing capacity of the latter (3.6 versus 1.9 (mu)mol/mg of protein/min). Their maximum specific oxygen uptake rates were very similar. Significant mechanistic differences in sulfur production between the high-sulfur-producing Thiobacillus sp. strain W5 and the moderate-sulfur-producing species T. neapolitanus were not observed. The limited sulfide-oxidizing capacity of T. neapolitanus appears to be the reason that it can convert only 50% of the incoming sulfide to elemental sulfur.

Visser, J. M.; Robertson, L. A.; Van Verseveld, H. W.; Kuenen, J. G.

1997-01-01

159

Sterile-?- and Armadillo Motif-Containing Protein Inhibits the TRIF-Dependent Downregulation of Signal Regulatory Protein ? To Interfere with Intracellular Bacterial Elimination in Burkholderia pseudomallei-Infected Mouse Macrophages  

PubMed Central

Burkholderia pseudomallei, the causative agent of melioidosis, evades macrophage killing by suppressing the TRIF-dependent pathway, leading to inhibition of inducible nitric oxide synthase (iNOS) expression. We previously demonstrated that virulent wild-type B. pseudomallei inhibits the TRIF-dependent pathway by upregulating sterile-?- and armadillo motif-containing protein (SARM) and by inhibiting downregulation of signal regulatory protein ? (SIRP?); both molecules are negative regulators of Toll-like receptor signaling. In contrast, the less virulent lipopolysaccharide (LPS) mutant of B. pseudomallei is unable to exhibit these features and is susceptible to macrophage killing. However, the functional relationship of these two negative regulators in the evasion of macrophage defense has not been elucidated. We demonstrated here that SIRP? downregulation was observed after inhibition of SARM expression by small interfering RNA in wild-type-infected macrophages, indicating that SIRP? downregulation is regulated by SARM. Furthermore, this downregulation requires activation of the TRIF signaling pathway, as we observed abrogation of SIRP? downregulation as well as restricted bacterial growth in LPS mutant-infected TRIF-depleted macrophages. Although inhibition of SARM expression is correlated to SIRP? downregulation and iNOS upregulation in gamma interferon-activated wild-type-infected macrophages, these phenomena appear to bypass the TRIF-dependent pathway. Similar to live bacteria, the wild-type LPS is able to upregulate SARM and to prevent SIRP? downregulation, implying that the LPS of B. pseudomallei may play a crucial role in regulating the expression of these two negative regulators. Altogether, our findings show a previously unrecognized role of B. pseudomallei-induced SARM in inhibiting SIRP? downregulation-mediated iNOS upregulation, facilitating the ability of the bacterium to multiply in macrophages.

Baral, Pankaj

2013-01-01

160

A Lack of Parasitic Reduction in the Obligate Parasitic Green Alga Helicosporidium  

PubMed Central

The evolution of an obligate parasitic lifestyle is often associated with genomic reduction, in particular with the loss of functions associated with increasing host-dependence. This is evident in many parasites, but perhaps the most extreme transitions are from free-living autotrophic algae to obligate parasites. The best-known examples of this are the apicomplexans such as Plasmodium, which evolved from algae with red secondary plastids. However, an analogous transition also took place independently in the Helicosporidia, where an obligate parasite of animals with an intracellular infection mechanism evolved from algae with green primary plastids. We characterised the nuclear genome of Helicosporidium to compare its transition to parasitism with that of apicomplexans. The Helicosporidium genome is small and compact, even by comparison with the relatively small genomes of the closely related green algae Chlorella and Coccomyxa, but at the functional level we find almost no evidence for reduction. Nearly all ancestral metabolic functions are retained, with the single major exception of photosynthesis, and even here reduction is not complete. The great majority of genes for light-harvesting complexes, photosystems, and pigment biosynthesis have been lost, but those for other photosynthesis-related functions, such as Calvin cycle, are retained. Rather than loss of whole function categories, the predominant reductive force in the Helicosporidium genome is a contraction of gene family complexity, but even here most losses affect families associated with genome maintenance and expression, not functions associated with host-dependence. Other gene families appear to have expanded in response to parasitism, in particular chitinases, including those predicted to digest the chitinous barriers of the insect host or remodel the cell wall of Helicosporidium. Overall, the Helicosporidium genome presents a fascinating picture of the early stages of a transition from free-living autotroph to parasitic heterotroph where host-independence has been unexpectedly preserved.

Pombert, Jean-Francois; Blouin, Nicolas Achille; Lane, Chris; Boucias, Drion; Keeling, Patrick J.

2014-01-01

161

A lack of parasitic reduction in the obligate parasitic green alga Helicosporidium.  

PubMed

The evolution of an obligate parasitic lifestyle is often associated with genomic reduction, in particular with the loss of functions associated with increasing host-dependence. This is evident in many parasites, but perhaps the most extreme transitions are from free-living autotrophic algae to obligate parasites. The best-known examples of this are the apicomplexans such as Plasmodium, which evolved from algae with red secondary plastids. However, an analogous transition also took place independently in the Helicosporidia, where an obligate parasite of animals with an intracellular infection mechanism evolved from algae with green primary plastids. We characterised the nuclear genome of Helicosporidium to compare its transition to parasitism with that of apicomplexans. The Helicosporidium genome is small and compact, even by comparison with the relatively small genomes of the closely related green algae Chlorella and Coccomyxa, but at the functional level we find almost no evidence for reduction. Nearly all ancestral metabolic functions are retained, with the single major exception of photosynthesis, and even here reduction is not complete. The great majority of genes for light-harvesting complexes, photosystems, and pigment biosynthesis have been lost, but those for other photosynthesis-related functions, such as Calvin cycle, are retained. Rather than loss of whole function categories, the predominant reductive force in the Helicosporidium genome is a contraction of gene family complexity, but even here most losses affect families associated with genome maintenance and expression, not functions associated with host-dependence. Other gene families appear to have expanded in response to parasitism, in particular chitinases, including those predicted to digest the chitinous barriers of the insect host or remodel the cell wall of Helicosporidium. Overall, the Helicosporidium genome presents a fascinating picture of the early stages of a transition from free-living autotroph to parasitic heterotroph where host-independence has been unexpectedly preserved. PMID:24809511

Pombert, Jean-François; Blouin, Nicolas Achille; Lane, Chris; Boucias, Drion; Keeling, Patrick J

2014-05-01

162

47 CFR 25.701 - Public interest obligations.  

Code of Federal Regulations, 2013 CFR

...CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Public Interest Obligations... (1) Entities licensed to operate satellites in the 12.2 to 12.7 GHz DBS frequency... (2) Entities licensed to operate satellites in the Ku band...

2013-10-01

163

22 CFR 231.07 - Fiscal Agent obligations.  

Code of Federal Regulations, 2013 CFR

...Agent obligations. 231.07 Section 231.07 Foreign Relations AGENCY FOR INTERNATIONAL DEVELOPMENT ARAB REPUBLIC OF EGYPT LOAN GUARANTEES ISSUED UNDER THE EMERGENCY WARTIME SUPPLEMENTAL APPROPRIATIONS ACT OF 2003, PUBLIC LAW...

2013-04-01

164

24 CFR 291.565 - Continuing obligations after purchase.  

Code of Federal Regulations, 2013 CFR

...obligations after purchase. To remain in compliance with the GNND Sales Program, the law enforcement officer, teacher, or firefighter/emergency medical technician must, for the entire duration of the owner-occupancy term: (a) Continue to...

2013-04-01

165

24 CFR 576.203 - Obligation, expenditure, and payment requirements.  

Code of Federal Regulations, 2013 CFR

...SECRETARY FOR COMMUNITY PLANNING AND DEVELOPMENT, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT COMMUNITY FACILITIES EMERGENCY SOLUTIONS GRANTS PROGRAM Award and Use of Funds § 576.203 Obligation, expenditure, and payment requirements. (a)...

2013-04-01

166

29 CFR 4043.20 - Post-Event filing obligation.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Post-Event filing obligation. 4043.20 Section...CORPORATION PLAN TERMINATIONS REPORTABLE EVENTS AND CERTAIN OTHER NOTIFICATION REQUIREMENTS Post-Event Notice of Reportable Events §...

2010-07-01

167

29 CFR 4043.20 - Post-Event filing obligation.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Post-Event filing obligation. 4043.20 Section...CORPORATION PLAN TERMINATIONS REPORTABLE EVENTS AND CERTAIN OTHER NOTIFICATION REQUIREMENTS Post-Event Notice of Reportable Events §...

2009-07-01

168

29 CFR 4043.20 - Post-Event filing obligation.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Post-Event filing obligation. 4043.20 Section...CORPORATION PLAN TERMINATIONS REPORTABLE EVENTS AND CERTAIN OTHER NOTIFICATION REQUIREMENTS Post-Event Notice of Reportable Events §...

2013-07-01

169

47 CFR 27.1184 - Triggering a reimbursement obligation.  

Code of Federal Regulations, 2013 CFR

...obligation. 27.1184 Section 27.1184 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES 1710-1755 MHz, 2110-2155 MHz, 2000-2020 MHz,...

2013-10-01

170

47 CFR 27.1168 - Triggering a Reimbursement Obligation.  

Code of Federal Regulations, 2013 CFR

...Obligation. 27.1168 Section 27.1168 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES 1710-1755 MHz, 2110-2155 MHz, 2000-2020 MHz,...

2013-10-01

171

32 CFR 220.9 - Rights and obligations of beneficiaries.  

Code of Federal Regulations, 2013 CFR

...PARTY PAYERS OF REASONABLE CHARGES FOR HEALTHCARE SERVICES § 220.9 Rights and obligations...be required. (b) Availability of healthcare services unaffected. The availability of healthcare services in any facility of the...

2013-07-01

172

22 CFR 232.07 - Fiscal agent obligations.  

Code of Federal Regulations, 2013 CFR

...Fiscal agent obligations. 232.07 Section 232.07 Foreign Relations AGENCY FOR INTERNATIONAL DEVELOPMENT REPUBLIC OF TUNISIA LOAN GUARANTEES ISSUED UNDER THE DEPARTMENT OF STATE, FOREIGN OPERATIONS, AND RELATED PROGRAMS APPROPRIATIONS ACT,...

2013-04-01

173

6 CFR 25.5 - Obligations of seller.  

...ANTI-TERRORISM BY FOSTERING EFFECTIVE TECHNOLOGIES § 25.5 Obligations of seller...Terrorism when Qualified Anti-Terrorism Technologies have been deployed in defense against...Seller of a Qualified Anti-Terrorism Technology submit any information that...

2014-01-01

174

29 CFR 500.100 - Vehicle safety obligations.  

Code of Federal Regulations, 2013 CFR

... REGULATIONS MIGRANT AND SEASONAL AGRICULTURAL WORKER PROTECTION Motor Vehicle...Transportation of Migrant and Seasonal Agricultural Workers, Housing Safety and Health...obligations. Each farm labor contractor, agricultural employer and agricultural...

2013-07-01

175

45 CFR 303.6 - Enforcement of support obligations.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 2012-10-01 true Enforcement of support obligations. 303.6 Section... Public Welfare OFFICE OF CHILD SUPPORT ENFORCEMENT (CHILD SUPPORT ENFORCEMENT PROGRAM), ADMINISTRATION FOR CHILDREN...

2013-10-01

176

Improving the Navy's Material Obligation Validation Response Rate.  

National Technical Information Service (NTIS)

This thesis sought to identify reasons for customer activity non-response to Material Obligation Validation (MOV) requests submitted by the Navy Inventory Control Points (ICP). If the non-response rate can be reduced, significant savings in procurement an...

M. A. Anderson

1985-01-01

177

Bacterial Sialidase  

NASA Technical Reports Server (NTRS)

Data shows that elevated sialidase in bacterial vaginosis patients correlates to premature births in women. Bacterial sialidase also plays a significant role in the unusual colonization of Pseudomonas aeruginosa in cystic fibrosis patients. Crystals of Salmonella sialidase have been reproduced and are used for studying the inhibitor-enzyme complexes. These inhibitors may also be used to inhibit a trans-sialidase of Trypanosome cruzi, a very similar enzyme to bacterial sialidase, therefore preventing T. cruzi infection, the causitive agent of Chagas' disease. The Center for Macromolecular Crystallography suggests that inhibitors of bacterial sialidases can be used as prophylactic drugs to prevent bacterial infections in these critical cases.

2004-01-01

178

Bacterial Thermotaxis by Speed Modulation  

PubMed Central

Naturally occurring gradients often extend over relatively long distances such that their steepness is too small for bacteria to detect. We studied the bacterial behavior in such thermal gradients. We find that bacteria migrate along shallow thermal gradients due to a change in their swimming speed resulting from the effect of temperature on the intracellular pH, which also depends on the chemical environment. When nutrients are scarce in the environment the bacteria's intracellular pH decreases with temperature. As a result, the swimming speed of the bacteria decreases with temperature, which causes them to slowly drift toward the warm end of the thermal gradient. However, when serine is added to the medium at concentrations >300 ?M, the intracellular pH increases causing the swimming speed to increase continuously with temperature, and the bacteria to drift toward the cold end of the temperature gradient. This directional migration is not a result of bacterial thermotaxis in the classical sense, because the steepness of the gradients applied is below the sensing threshold of bacteria. Nevertheless, our results show that the directional switch requires the presence of the bacterial sensing receptors. This seems to be due to the involvement of the receptors in regulating the intracellular pH.

Demir, Mahmut; Salman, Hanna

2012-01-01

179

Real-time monitoring of intracellular Staphylococcus aureus replication.  

PubMed

A high-throughput system to rapidly assess the intracellular replication of Staphylococcus aureus has been developed utilizing S. aureus transformed with a dual gfp-luxABCDE reporter operon under the control of a growth-dependent promoter. Replication of tagged bacteria internalized into bovine mammary epithelial cells (MAC-T) could be measured by monitoring fluorescence and bioluminescence from the reporter operon following removal of extracellular bacteria from the plates. Bacterial replication inside cells was confirmed by a novel ex vivo time-lapse confocal microscopic method. This assay of bacterial replication was used to evaluate the efficacy of antibiotics which are commonly used to treat staphylococcal infections. Not all antibiotics tested were able to prevent intracellular replication of S. aureus and some were ineffective at preventing replication of intracellular bacteria at concentrations above the MIC determined for bacteria in broth culture. Comparison of the fluorescence and bioluminescence signals from the bacteria enabled effects on protein synthesis and metabolism to be discriminated and gave information on the entry of compounds into the eukaryotic cell, even if bacterial replication was not prevented. Elevated resistance of S. aureus to antibiotics inside host cells increases the likelihood of selecting S. aureus strains which are resistant to commonly used antimicrobial agents within the intracellular niche. The approach presented directly assesses intracellular efficacy of antibiotics and provides an evidence-based approach to antibiotic selection for prescribing physicians and medical microbiologists. PMID:14762001

Qazi, S N A; Harrison, S E; Self, T; Williams, P; Hill, P J

2004-02-01

180

Transient transformation of the obligate biotrophic rust fungus Uromyces fabae using biolistics  

Microsoft Academic Search

Obligate biotrophic pathogens like the rust fungi are important plant pathogens causing enormous losses on food, forage and biomass crops. The analysis of the molecular details underlying obligate biotrophic host–parasite interactions is mainly hampered by the fact that no system for transformation is available for most obligate biotrophic organisms. Here we report the transient transformation of Uromyces fabae, an obligate

Alma Djulic; Annette Schmid; Heike Lenz; Pia Sharma; Christin Koch; Stefan G. R. Wirsel; Ralf T. Voegele

2011-01-01

181

Employer obligations versus fulfillment and the effects on organizational citizenship and innovative work  

Microsoft Academic Search

This research investigated the relationship among discrepancies between the employers' obligations and the level of fulfillment of those obligations and the information technology (IT) professionals' citizenship and innovative work behaviors. The dimensional approach to the psychological contract was used to demonstrate the IT professional's perceptions of their employer's obligations and the level of fulfillment of those obligations. Survey data from

Sandra K. Newton; Linda I. Nowak

182

Bacterial Overgrowth  

Microsoft Academic Search

\\u000a The human gastrointestinal tract typically contains 300–500 bacterial species. Most bacterial species are acquired during\\u000a the birth process and although some changes to the flora may occur during later stages of life, the composition of the intestinal\\u000a microflora remains relatively constant. Small bowel bacterial overgrowth (SBBO) is defined as an excessive increase in the\\u000a number of bacteria in the upper

Rosemary J. Young; Jon A. Vanderhoof

183

cPLA2 Regulates the Expression of Type I Interferons and Intracellular Immunity to Chlamydia trachomatis*  

PubMed Central

Infection with the obligate bacterial intracellular pathogen Chlamydia trachomatis leads to the sustained activation of the small GTPase RAS and many of its downstream signaling components. In particular, the mitogen-activated protein kinase ERK and the calcium-dependent phospholipase cPLA2 are activated and are important for the onset of inflammatory responses. In this study we tested if activation of ERK and cPLA2 occurred as a result of RAS signaling during infection and determined the relative contribution of these signaling components to chlamydial replication and survival. We provide genetic and pharmacological evidence that during infection RAS, ERK, and, to a lesser extent, cPLA2 activation are uncoupled, suggesting that Chlamydia activates individual components of this signaling pathway in a non-canonical manner. In human cell lines, inhibition of ERK or cPLA2 signaling did not adversely impact C. trachomatis replication. In contrast, in murine cells, inhibition of ERK and cPLA2 played a significant protective role against C. trachomatis. We determined that cPLA2-deficient murine cells are permissive for C. trachomatis replication because of their impaired expression of ? interferon and the induction of immunity-related GTPases (IRG) important for the containment of intracellular pathogens. Furthermore, the MAPK p38 was primarily responsible for cPLA2 activation in Chlamydia-infected cells and IRG expression. Overall, these findings define a previously unrecognized role for cPLA2 in the induction of cell autonomous cellular immunity to Chlamydia and highlight the many non-canonical signaling pathways engaged during infection.

Vignola, Mark J.; Kashatus, David F.; Taylor, Gregory A.; Counter, Christopher M.; Valdivia, Raphael H.

2010-01-01

184

Autophagy and bacterial infectious diseases  

PubMed Central

Autophagy is a housekeeping process that maintains cellular homeostasis through recycling of nutrients and degradation of damaged or aged cytoplasmic constituents. Over the past several years, accumulating evidence has suggested that autophagy can function as an intracellular innate defense pathway in response to infection with a variety of bacteria and viruses. Autophagy plays a role as a specialized immunologic effector and regulates innate immunity to exert antimicrobial defense mechanisms. Numerous bacterial pathogens have developed the ability to invade host cells or to subvert host autophagy to establish a persistent infection. In this review, we have summarized the recent advances in our understanding of the interaction between antibacterial autophagy (xenophagy) and different bacterial pathogens.

Yuk, Jae-Min; Yoshimori, Tamotsu

2012-01-01

185

A New Role of the Complement System: C3 Provides Protection in a Mouse Model of Lung Infection with Intracellular Chlamydia psittaci  

PubMed Central

The complement system modulates the intensity of innate and specific immunity. While it protects against infections by extracellular bacteria its role in infection with obligate intracellular bacteria, such as the avian and human pathogen Chlamydia (C.) psittaci, is still unknown. In the present study, knockout mice lacking C3 and thus all main complement effector functions were intranasally infected with C. psittaci strain DC15. Clinical parameters, lung histology, and cytokine levels were determined. A subset of infections was additionally performed with mice lacking C5 or C5a receptors. Complement activation occurred before symptoms of pneumonia appeared. Mice lacking C3 were ?100 times more susceptible to the intracellular bacteria compared to wild-type mice, with all C3?/? mice succumbing to infection after day 9. At a low infective dose, C3?/? mice became severely ill after an even longer delay, the kinetics suggesting a so far unknown link of complement to the adaptive, protective immune response against chlamydiae. The lethal phenotype of C3?/? mice is not based on differences in the anti-chlamydial IgG response (which is slightly delayed) as demonstrated by serum transfer experiments. In addition, during the first week of infection, the absence of C3 was associated with partial protection characterized by reduced weight loss, better clinical score and lower bacterial burden, which might be explained by a different mechanism. Lack of complement functions downstream of C5 had little effect. This study demonstrates for the first time a strong and complex influence of complement effector functions, downstream of C3 and upstream of C5, on the outcome of an infection with intracellular bacteria, such as C. psittaci.

Bode, Jenny; Dutow, Pavel; Sommer, Kirsten; Janik, Katrin; Glage, Silke; Tummler, Burkhard; Munder, Antje; Laudeley, Robert; Sachse, Konrad W.; Klos, Andreas

2012-01-01

186

Metabolic Complementarity and Genomics of the Dual Bacterial Symbiosis of Sharpshooters  

PubMed Central

Mutualistic intracellular symbiosis between bacteria and insects is a widespread phenomenon that has contributed to the global success of insects. The symbionts, by provisioning nutrients lacking from diets, allow various insects to occupy or dominate ecological niches that might otherwise be unavailable. One such insect is the glassy-winged sharpshooter (Homalodisca coagulata), which feeds on xylem fluid, a diet exceptionally poor in organic nutrients. Phylogenetic studies based on rRNA have shown two types of bacterial symbionts to be coevolving with sharpshooters: the gamma-proteobacterium Baumannia cicadellinicola and the Bacteroidetes species Sulcia muelleri. We report here the sequencing and analysis of the 686,192–base pair genome of B. cicadellinicola and approximately 150 kilobase pairs of the small genome of S. muelleri, both isolated from H. coagulata. Our study, which to our knowledge is the first genomic analysis of an obligate symbiosis involving multiple partners, suggests striking complementarity in the biosynthetic capabilities of the two symbionts: B. cicadellinicola devotes a substantial portion of its genome to the biosynthesis of vitamins and cofactors required by animals and lacks most amino acid biosynthetic pathways, whereas S. muelleri apparently produces most or all of the essential amino acids needed by its host. This finding, along with other results of our genome analysis, suggests the existence of metabolic codependency among the two unrelated endosymbionts and their insect host. This dual symbiosis provides a model case for studying correlated genome evolution and genome reduction involving multiple organisms in an intimate, obligate mutualistic relationship. In addition, our analysis provides insight for the first time into the differences in symbionts between insects (e.g., aphids) that feed on phloem versus those like H. coagulata that feed on xylem. Finally, the genomes of these two symbionts provide potential targets for controlling plant pathogens such as Xylella fastidiosa, a major agroeconomic problem, for which H. coagulata and other sharpshooters serve as vectors of transmission.

Wu, Dongying; Daugherty, Sean C; Van Aken, Susan E; Pai, Grace H; Watkins, Kisha L; Khouri, Hoda; Tallon, Luke J; Zaborsky, Jennifer M; Dunbar, Helen E; Tran, Phat L; Moran, Nancy A

2006-01-01

187

[Using of antibodies against Microsporia Hsp70 family proteins for analysis of secretome of intracellular parasites].  

PubMed

Microsporidia is a large group of fungi-related unicellular parasites with obligate intracellular lifestyle. Unlike other protozoan intracellular parasites (Kinetoplastida and Apicomplexa), most microsporidian species develop in direct contact with the host cell cytoplasm. This fact, acquisition of unique transporters to exploit host metabolic system (alongside the strong minimization of own machinery) and predicted repertoire of microsporidia secretome altogether suggest an active role of parasite proteins in the control of infected cell. Lack of information about secretome of microsporidia intracellular stages is largely due to the methodological difficulties of working with the obligate intracellular parasites. An important problem of such study is the contamination of preparations of host cell cytoplasm by inner (nonsecreted) parasite proteins. Even the homogenization of infected tissue in mild conditions and removal of parasite cells by low-speed centrifugation may result in their partial disruption. We expressed the fragments of three Hsp70 family chaperones from the microsporidium Paranosema (Antonospora) locustae in bacteria Escherichia coli. Immunoblotting with proteins of microsporidia intracellular stages and infected host tissue (locust fat bodies) demonstrated that antibodies against recombinant polypeptides may be used to monitor the integrity of parasite cells during homogenization of infected host tissue and subsequent removal of parasites by centrifugation. PMID:23458023

Dolgikh, V V; Senderski?, I V; Pavlova, O A; Timofeev, S A; Naumov, A M

2012-01-01

188

The Interaction between IL-18 and IL-18R Limits the Magnitude of Protective Immunity and Enhances Pathogenic Responses Following Infection with Intracellular Bacteria  

PubMed Central

The binding of IL-18 to IL-18R? induces both pro-inflammatory and protective functions during infection, depending on the context in which it occurs. IL-18 is highly expressed in the liver of wild type (WT) C57BL/6 mice following lethal infection with highly virulent Ixodes Ovatus Ehrlichia (IOE), an obligate intracellular bacterium that causes acute fatal toxic shock-like syndrome. In this study, we found that IOE infection of IL-18R?-/- mice resulted in significantly less host cell apoptosis, decreased hepatic leukocyte recruitment, enhanced bacterial clearance and prolonged survival compared to infected WT mice, suggesting a pathogenic role of IL-18/IL-18R? in Ehrlichia-induced toxic shock. Although lack of IL-18R decreases the magnitude of IFN-? producing type-1 immune response, enhanced resistance of the IL-18R?-/- mice against Ehrlichia correlated with increased pro-inflammatory cytokines at sites of infection, decreased systemic IL-10 production, increased frequency of protective natural killer T (NKT) cells producing TNF-? and IFN-? and decreased frequency of pathogenic TNF-?-producing CD8+ T cells. Adoptive transfer of immune wild type CD8+ T cells increased bacterial burden in IL-18R?-/- mice following IOE infection. Furthermore, rIL-18 treatment of WT mice infected with mildly virulent Ehrlichia muris (EM) impaired bacterial clearance and enhanced liver injury. Finally, lack of IL-18R signal reduced dendritic cells (DCs) maturation and their TNF-? production, suggesting that IL-18 possibly promote the adaptive pathogenic immune responses against Ehrlichia via influencing T cell priming functions of DCs Together, these results suggest that the presence or absence of IL-18R signals governs the pathogenic versus protective immunity in a model of Ehrlichia-induced immunopathology.

Ghose, Purnima; Ali, Asim Q; Fang, Rong; Forbes, Digna; Ballard, Billy; Ismail, Nahed

2011-01-01

189

Genome Reduction and Co-evolution between the Primary and Secondary Bacterial Symbionts of Psyllids  

PubMed Central

Genome reduction in obligately intracellular bacteria is one of the most well-established patterns in the field of molecular evolution. In the extreme, many sap-feeding insects harbor nutritional symbionts with genomes that are so reduced that it is not clear how they perform basic cellular functions. For example, the primary symbiont of psyllids (Carsonella) maintains one of the smallest and most AT-rich bacterial genomes ever identified and has surprisingly lost many genes that are thought to be essential for its role in provisioning its host with amino acids. However, our understanding of this extreme case of genome reduction is limited, as genomic data for Carsonella are available from only a single host species, and little is known about the functional role of “secondary” bacterial symbionts in psyllids. To address these limitations, we analyzed complete Carsonella genomes from pairs of congeneric hosts in three divergent genera within the Psyllidae (Ctenarytaina, Heteropsylla, and Pachypsylla) as well as complete secondary symbiont genomes from two of these host species (Ctenarytaina eucalypti and Heteropsylla cubana). Although the Carsonella genomes are generally conserved in size, structure, and GC content and exhibit genome-wide signatures of purifying selection, we found that gene loss has remained active since the divergence of the host species and had a particularly large impact on the amino acid biosynthesis pathways that define the symbiotic role of Carsonella. In some cases, the presence of additional bacterial symbionts may compensate for gene loss in Carsonella, as functional gene content indicates a high degree of metabolic complementarity between co-occurring symbionts. The genomes of the secondary symbionts also show signatures of long-term evolution as vertically transmitted, intracellular bacteria, including more extensive genome reduction than typically observed in facultative symbionts. Therefore, a history of co-evolution with secondary bacterial symbionts can partially explain the ongoing genome reduction in Carsonella. However, the absence of these secondary symbionts in other host lineages indicates that the relationships are dynamic and that other mechanisms, such as changes in host diet or functional coordination with the host genome, must also be at play.

Sloan, Daniel B.; Moran, Nancy A.

2012-01-01

190

Intracellular Trafficking of Porphyrins  

PubMed Central

Hemes are porphyrins that play a critical role in diverse biological processes. Heme synthesis culminates in the mitochondrial matrix, but the eight-step biosynthetic pathway is spatially shared between the mitochondria and cytoplasm. A recent paper describes the nature of the transporter which translocates the heme precursor coproporphyrinogen III into the mitochondria for heme synthesis. The identification of ABCB6 and future studies aimed at precisely delineating the mechanism and the physiological nature of its ligand(s) will further enhance our current understanding of the intracellular movement of tetrapyrroles in eukaryotes.

Hamza, Iqbal

2014-01-01

191

Bacterial pathogens.  

PubMed

Bacterial infections are frequent complications among patients treated for cancer. The type, severity, and treatment of bacterial infections vary and depend upon the specific malignancy, associated chemotherapies, and transplantation. This chapter discusses commonly encountered bacterial pathogens as well as Nocardia and mycobacteria in patients with cancer and addresses the clinical syndromes and management. Drug-resistant bacteria are becoming an increasingly recognized problem in patients with cancer. Antimicrobial resistance in select gram-positive and gram-negative bacteria are discussed along with the mechanisms of resistance and recommended therapies. PMID:24706222

Wilson, John W

2014-01-01

192

Intracellular trafficking of integrins in cancer cells.  

PubMed

Integrins are heterodimeric cell surface receptors, which principally mediate the interaction between cells and their extracellular microenvironments. Because of their pivotal roles in cancer proliferation, survival, invasion and metastasis, integrins have been recognized as promising targets for cancer treatment. As is the case with other receptors, the localization of integrins on the cell surface has provided opportunities to block their functions by various inhibitory monoclonal antibodies. A number of small molecule agents blocking integrin-ligand binding have also been established, and some such agents are currently on the market or in clinical trials for some diseases including cancer. This review exclusively focuses on another strategy for cancer therapy, which comes from the obligate localization of integrins on the cell surface; targeting the intracellular trafficking of integrins. A number of studies have shown the essential roles of integrin trafficking in hallmarks of cancer, such as activation of oncogenic signaling pathways as well as acquisition of invasiveness. Recent findings have shown that increased integrin recycling activity is associated with some types of gain-of-function mutations of p53, a common feature of diverse types of cancers, which also indicates that targeting integrin recycling could be widely applicable and effective against many cancers. We also discuss possible therapeutic contexts where integrin trafficking can be effectively targeted, and what molecular interfaces may hopefully be druggable. PMID:23711790

Onodera, Yasuhito; Nam, Jin-Min; Sabe, Hisataka

2013-10-01

193

12 CFR 1270.4 - Issuance of consolidated obligations.  

Code of Federal Regulations, 2012 CFR

...paragraphs (b)(1) through (b)(6) of this section free from any lien or pledge, in an amount at least equal to...consolidated obligations shall be treated as if they were assets free from any lien or pledge for purposes of compliance with...

2012-01-01

194

The BOID architecture: conflicts between beliefs, obligations, intentions and desires  

Microsoft Academic Search

In this paper we introduce the so-called Beliefs-Obligations-Intentions-Desires or BOID architecture. It contains feedback loops to consider all effects of actions before committing to them, and mechanisms to resolve conflicts between the outputs of its four components. Agent types such as realistic or social agents correspond to specific types of conflict resolution embedded in the BOID archecture.

Jan Broersen; Mehdi Dastani; Joris Hulstijn; Zhisheng Huang; Leendert W. N. van der Torre

2001-01-01

195

Family Obligations in Micronesian Cultures: Implications for Educators  

ERIC Educational Resources Information Center

Micronesian people, a new group of immigrants to the USA, have a strong system of responsibilities to family members that guides their priorities and actions. When family obligations clash with school priorities, conflicts can occur. I interviewed 26 adults to learn about the relationships and responsibilities of family members to each other in…

Ratliffe, Katherine T.

2010-01-01

196

The obligations and common ground structure of practical dialogues  

Microsoft Academic Search

In this paper a theory of dialogue structure of tas k oriented conversations and its associated tagging scheme are presented. The theory introduces two linguistic str uctures supporting the dialogue that, following tra ditional terminology, we call the obligations and common ground. The theory is illustrated with the detailed an alysis of a transaction. We also describe the empirical work

Luis Alberto Pineda; Varinia M. Estrada; Sergio Rafael Coria Olguin; James F. Allen

2007-01-01

197

European air transport public service obligations: a periodic review  

Microsoft Academic Search

The ‘Third Package’ of European Union air transport liberalisation measures came into effect on 1 January 1993 and has substantially reduced the restrictions on interstate flight operations. The package of measures also includes provision for the member states to impose ‘public service obligations’ on low-density routes which were deemed necessary for the purposes of regional development. In this paper, it

Aisling Reynolds-Feighan

1995-01-01

198

Clinical review: Influenza pandemic – physicians and their obligations  

Microsoft Academic Search

An influenza pandemic threatens to be the most lethal public health crisis to confront the world. Physicians will have critical roles in diagnosis, containment and treatment of influenza, and their commitment to treat despite increased personal risks is essential for a successful public health response. The obligations of the medical profession stem from the unique skills of its practitioners, who

Devanand Anantham; Wendy McHugh; Stephen O'Neill; Lachlan Forrow

2008-01-01

199

26 CFR 1.454-1 - Obligations issued at discount.  

...increases in the amount of 50 cents on each such date, the amount accruing in that year would be $1 ($0.50 on February 1 and $0.50 on August 1). If the taxpayer owns a non-interest-bearing obligation of the character...

2014-04-01

200

Who can be morally obligated to be a vegetarian?  

Microsoft Academic Search

Kathryn Paxton George has recently argued that vegetarianism cannot be a moral obligation for most human beings, even if Tom Regan is correct in arguing that humans and certain nonhuman animals are equally inherently valuable. She holds that Regan's liberty principle permits humans to kill and eat innocent others who have a right to life, provided that doing so prevents

Evelyn Pluhar

1992-01-01

201

The Legal Obligation to Prosecute 'Rendition to Tor ture  

Microsoft Academic Search

The United States of America and Italy are currentl y in violation of binding legal obligations under the United Nations Convention against Torture and other cruel, inhuman or degrading treatment or punishment to investigate allegations of torture resulting from extraordinary rendition and to prose cute those individuals responsible. This article describes cases that aim to establish that (i) torture has

Elena Landriscina

202

Classification Revisions Reduce Reported Federal Development Obligations. InfoBrief.  

ERIC Educational Resources Information Center

This document reports on federal Research and Development (R&D) funding trends for the last 10 years and explains the sources of Federal R&D revisions. The data are obtained from an annual census of approximately 30 federal agencies that report obligation data to the National Science Foundation Survey of Federal Funds for R&D. (YDS)

Jankowski, John E.

203

Obama states obligation to act on climate change  

NASA Astrophysics Data System (ADS)

Obama states obligation to act on climate change Noting increased global temperatures, Arctic ice melt, and severe weather events, President Barack Obama said that climate change is real and called for a conversation across the country to determine what can be done about it.

Showstack, Randy

2012-11-01

204

Family Obligation and the Transition to Young Adulthood.  

ERIC Educational Resources Information Center

Examined changes in sense of family obligation (FO) among an ethnically diverse group of 745 Americans in transition from secondary school into young adulthood. Found that FO increased for all young adults, with slight variations according to ethnic and financial backgrounds. Implications of FO for employment and educational persistence depended…

Fuligni, Andrew J.; Pedersen, Sara

2002-01-01

205

Comparative Phylogeography in a Specific and Obligate Pollination Antagonism  

Microsoft Academic Search

In specific and obligate interactions the nature and abundance of a given species can have important effects on the survival and population dynamics of associated organisms. In a phylogeographic framework, we therefore expect that the fates of organisms interacting specifically are also tightly interrelated. Here we investigate such a scenario by analyzing the genetic structures of species interacting in an

Anahí Espíndola; Nadir Alvarez

2011-01-01

206

Review of International Experience with Renewable Energy Obligation Support Mechanisms.  

National Technical Information Service (NTIS)

The main policy instruments currently used in the EU Member States to achieve the targets set for electricity produced from renewable energy sources are: (1) the quota obligation system; (2) the feed-in tariff system; and (3) the tendering system. The cur...

N. H. van der Linden M. A. Uyterlinde C. Vrolijk L. J. Nilsson J. Khan

2005-01-01

207

Experimental evolution of nodule intracellular infection in legume symbionts  

PubMed Central

Soil bacteria known as rhizobia are able to establish an endosymbiosis with legumes that takes place in neoformed nodules in which intracellularly hosted bacteria fix nitrogen. Intracellular accommodation that facilitates nutrient exchange between the two partners and protects bacteria from plant defense reactions has been a major evolutionary step towards mutualism. Yet the forces that drove the selection of the late event of intracellular infection during rhizobium evolution are unknown. To address this question, we took advantage of the previous conversion of the plant pathogen Ralstonia solanacearum into a legume-nodulating bacterium that infected nodules only extracellularly. We experimentally evolved this draft rhizobium into intracellular endosymbionts using serial cycles of legume-bacterium cocultures. The three derived lineages rapidly gained intracellular infection capacity, revealing that the legume is a highly selective environment for the evolution of this trait. From genome resequencing, we identified in each lineage a mutation responsible for the extracellular–intracellular transition. All three mutations target virulence regulators, strongly suggesting that several virulence-associated functions interfere with intracellular infection. We provide evidence that the adaptive mutations were selected for their positive effect on nodulation. Moreover, we showed that inactivation of the type three secretion system of R. solanacearum that initially allowed the ancestral draft rhizobium to nodulate, was also required to permit intracellular infection, suggesting a similar checkpoint for bacterial invasion at the early nodulation/root infection and late nodule cell entry levels. We discuss our findings with respect to the spread and maintenance of intracellular infection in rhizobial lineages during evolutionary times.

Guan, Su Hua; Gris, Carine; Cruveiller, Stephane; Pouzet, Cecile; Tasse, Lena; Leru, Aurelie; Maillard, Aline; Medigue, Claudine; Batut, Jacques; Masson-Boivin, Catherine; Capela, Delphine

2013-01-01

208

Intracellular protein topogenesis  

PubMed Central

Concurrently with or shortly after their synthesis on ribosomes, numerous specific proteins are unidirectionally translocated across or asymmetrically integrated into distinct cellular membranes. Thereafter, subpopulations of these proteins need to be sorted from each other and routed for export or targeted to other intracellular membranes or compartments. It is hypothesized here that the information for these processes, termed “protein topogenesis,” is encoded in discrete “topogenic” sequences that constitute a permanent or transient part of the polypeptide chain. The repertoire of distinct topogenic sequences is predicted to be relatively small because many different proteins would be topologically equivalent—i.e., targeted to the same intracellular address. The information content of topogenic sequences would be decoded and processed by distinct effectors. Four types of topogenic sequences could be distinguished: signal sequences, stop-transfer sequences, sorting sequences, and insertion sequences. Signal sequences initiate translocation of proteins across specific membranes. They would be decoded and processed by protein translocators that, by virtue of their signal sequence-specific domain and their unique location in distinct cellular membranes, effect unidirectional translocation of proteins across specific cellular membranes. Stop-transfer sequences interrupt the translocation process that was previously initiated by a signal sequence and, by excluding a distinct segment of the polypeptide chain from translocation, yield asymmetric integration of proteins into translocation-competent membranes. Sorting sequences would act as determinants for posttranslocational traffic of subpopulations of proteins, originating in translocation-competent donor membranes (and compartments) and going to translocation-incompetent receiver membranes (and compartments). Finally, insertion sequences initiate unilateral integration of proteins into the lipid bilayer without the mediation of a distinct protein effector. Examples are given for topogenic sequences, either alone or in combination, to provide the information for the location of proteins in any of the intracellular compartments or for the asymmetric orientation of proteins and their location in any of the cellular membranes. Proposals are made concerning the evolution of topogenic sequences and the relationship of protein topogenesis to the precellular evolution of membranes and compartments.

Blobel, Gunter

1980-01-01

209

Water near intracellular surfaces  

PubMed Central

In this paper we make the following points: Water is perturbed within several angstroms of the surfaces of soluble molecules. Removal of this water can require significant amounts of work, seen as an exponentially varying "hydration force" with respect to molecular separation. The favorable and specific attractions that occur in molecular assembly or in ligand binding imply that the specific association between the molecular surfaces is stronger than the association of those surfaces with water. The specificity of biochemical association is not simply a matter of protein-protein interaction but also of competing protein-water interactions. Small structural changes in molecular surfaces can evoke large changes in the contact energy of hydrated surfaces; surface hydration and the energetics of water displacement are a likely mechanism for the contact specificity of intracellular associations integrating the cell matrix.

Parsegian, V. A.; Rau, D. C.

1984-01-01

210

Quantitative Proteomics of Intracellular Campylobacter jejuni Reveals Metabolic Reprogramming.  

PubMed

Campylobacter jejuni is the major cause of bacterial food-borne illness in the USA and Europe. An important virulence attribute of this bacterial pathogen is its ability to enter and survive within host cells. Here we show through a quantitative proteomic analysis that upon entry into host cells, C. jejuni undergoes a significant metabolic downshift. Furthermore, our results indicate that intracellular C. jejuni reprograms its respiration, favoring the respiration of fumarate. These results explain the poor ability of C. jejuni obtained from infected cells to grow under standard laboratory conditions and provide the bases for the development of novel anti microbial strategies that would target relevant metabolic pathways. PMID:22412372

Liu, Xiaoyun; Gao, Beile; Novik, Veronica; Galán, Jorge E

2012-01-01

211

Cationic Antimicrobial Peptide LL-37 Is Effective against both Extra- and Intracellular Staphylococcus aureus  

PubMed Central

The increasing resistance of bacteria to conventional antibiotics and the challenges posed by intracellular bacteria, which may be responsible for chronic and recurrent infections, have driven the need for advanced antimicrobial drugs for effective elimination of both extra- and intracellular pathogens. The purpose of this study was to determine the killing efficacy of cationic antimicrobial peptide LL-37 compared to conventional antibiotics against extra- and intracellular Staphylococcus aureus. Bacterial killing assays and an infection model of osteoblasts and S. aureus were studied to determine the bacterial killing efficacy of LL-37 and conventional antibiotics against extra- and intracellular S. aureus. We found that LL-37 was effective in killing extracellular S. aureus at nanomolar concentrations, while lactoferricin B was effective at micromolar concentrations and doxycycline and cefazolin at millimolar concentrations. LL-37 was surprisingly more effective in killing the clinical strain than in killing an ATCC strain of S. aureus. Moreover, LL-37 was superior to conventional antibiotics in eliminating intracellular S. aureus. The kinetic studies further revealed that LL-37 was fast in eliminating both extra- and intracellular S. aureus. Therefore, LL-37 was shown to be very potent and prompt in eliminating both extra- and intracellular S. aureus and was more effective in killing extra- and intracellular S. aureus than commonly used conventional antibiotics. LL-37 could potentially be used to treat chronic and recurrent infections due to its effectiveness in eliminating not only extracellular but also intracellular pathogens.

Noore, Jabeen; Noore, Adly

2013-01-01

212

INTRA-CELLULAR STAPHYLOCOCCUS AUREUS ALONE CAUSES INFECTION IN VIVO#  

PubMed Central

Chronic and recurrent bone infections occur frequently but have not been explained. Staphylococcus aureus (S. aureus) is often found among chronic and recurrent infections and may be responsible for such infections. One possible reason is that S. aureus can internalize and survive within host cells and by doing so, S. aureus can evade both host defense mechanisms and most conventional antibiotic treatments. In this study, we hypothesized that intra-cellular S. aureus could induce infections in vivo. Osteoblasts were infected with S. aureus and, after eliminating extra-cellular S. aureus, inoculated into an open fracture rat model. Bacterial cultures and radiographic observations at post-operative day 21 confirmed local bone infections in animals inoculated with intra-cellular S. aureus within osteoblasts alone. We present direct in vivo evidence that intra-cellular S. aureus could be sufficient to induce bone infection in animals; we found that intra-cellular S. aureus inoculation of as low as 102 colony forming units could induce severe bone infections. Our data may suggest that intra-cellular S. aureus can “hide” in host cells during symptom-free periods and, under certain conditions, they may escape and lead to infection recurrence. Intra-cellular S. aureus therefore could play an important role in the pathogenesis of S. aureus infections, especially those chronic and recurrent infections in which disease episodes may be separated by weeks, months, or even years.

Hamza, Therwa; Dietz, Matthew; Pham, Danh; Clovis, Nina; Danley, Suzanne; Li, Bingyun

2013-01-01

213

Intra-cellular Staphylococcus aureus alone causes infection in vivo.  

PubMed

Chronic and recurrent bone infections occur frequently but have not been explained. Staphylococcus aureus (S. aureus) is often found among chronic and recurrent infections and may be responsible for such infections. One possible reason is that S. aureus can internalize and survive within host cells and by doing so, S. aureus can evade both host defense mechanisms and most conventional antibiotic treatments. In this study, we hypothesized that intra-cellular S. aureus could induce infections in vivo. Osteoblasts were infected with S. aureus and, after eliminating extra-cellular S. aureus, inoculated into an open fracture rat model. Bacterial cultures and radiographic observations at post-operative day 21 confirmed local bone infections in animals inoculated with intra-cellular S. aureus within osteoblasts alone. We present direct in vivo evidence that intra-cellular S. aureus could be sufficient to induce bone infection in animals; we found that intra-cellular S. aureus inoculation of as low as 102 colony forming units could induce severe bone infections. Our data may suggest that intra-cellular S. aureus can "hide" in host cells during symptom-free periods and, under certain conditions, they may escape and lead to infection recurrence. Intra-cellular S. aureus therefore could play an important role in the pathogenesis of S. aureus infections, especially those chronic and recurrent infections in which disease episodes may be separated by weeks, months, or even years. PMID:23832687

Hamza, T; Dietz, M; Pham, D; Clovis, N; Danley, S; Li, B

2013-01-01

214

Genetic control of resistance to Mycobacterium intracellulare infection in mice.  

PubMed Central

The susceptibilities of various strains of mice to a highly pathogenic strain of Mycobacterium intracellulare, the Mino strain, were determined by intravenous injection of 5 X 10(6) bacteria. CFU were counted on days 1 and 21 of infection. Among 10 strains of mice, C57BL/6, C57BL/10, BALB/c, B10.BR, B10.A, and B10.D2 were susceptible, whereas DBA/2, A/J, CBA, and C3H/He were resistant. In the susceptible mouse strains, the number of bacteria increased during 21 days of infection, whereas no bacterial growth was observed in the resistant strains. Susceptible mice showed weak but positive delayed-type hypersensitivity to M. intracellulare purified protein derivative 20 days after injection of bacteria. Resistant mice developed no delayed-type hypersensitivity. Histological examination showed severe granulomatous lesions in livers or spleens of the susceptible mice after M. intracellulare injection. Analysis of F1 hybrids of susceptible and resistant strains and of F2 and backcross mice showed that the resistance to M. intracellulare seems to be controlled genetically by a single dominant gene. The pattern of distribution of resistance to M. intracellulare among the mouse strains was consistent with that of natural resistance to Mycobacterium bovis to BCG. Thus, resistance to M. intracellulare infection may be regulated by a gene linked to the Bcg gene on chromosome 1.

Goto, Y; Nakamura, R M; Takahashi, H; Tokunaga, T

1984-01-01

215

Bacterial rheotaxis  

PubMed Central

The motility of organisms is often directed in response to environmental stimuli. Rheotaxis is the directed movement resulting from fluid velocity gradients, long studied in fish, aquatic invertebrates, and spermatozoa. Using carefully controlled microfluidic flows, we show that rheotaxis also occurs in bacteria. Excellent quantitative agreement between experiments with Bacillus subtilis and a mathematical model reveals that bacterial rheotaxis is a purely physical phenomenon, in contrast to fish rheotaxis but in the same way as sperm rheotaxis. This previously unrecognized bacterial taxis results from a subtle interplay between velocity gradients and the helical shape of flagella, which together generate a torque that alters a bacterium's swimming direction. Because this torque is independent of the presence of a nearby surface, bacterial rheotaxis is not limited to the immediate neighborhood of liquid–solid interfaces, but also takes place in the bulk fluid. We predict that rheotaxis occurs in a wide range of bacterial habitats, from the natural environment to the human body, and can interfere with chemotaxis, suggesting that the fitness benefit conferred by bacterial motility may be sharply reduced in some hydrodynamic conditions.

Marcos; Fu, Henry C.; Powers, Thomas R.; Stocker, Roman

2012-01-01

216

78 FR 52308 - Harmonization of Compliance Obligations for Registered Investment Companies Required To Register...  

Federal Register 2010, 2011, 2012, 2013

...Part 4 RIN 3038-AD75 Harmonization of Compliance Obligations for Registered Investment...regulations with respect to certain compliance obligations for commodity pool operators...are effective September 23, 2013. Compliance dates: Registered CPOs seeking...

2013-08-22

217

42 CFR 137.309 - How are NEPA and NHPA obligations typically enforced?  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false How are NEPA and NHPA obligations typically enforced? 137...SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.309 How are NEPA and NHPA obligations typically...

2012-10-01

218

42 CFR 137.309 - How are NEPA and NHPA obligations typically enforced?  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false How are NEPA and NHPA obligations typically enforced? 137...SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.309 How are NEPA and NHPA obligations typically...

2010-10-01

219

42 CFR 137.309 - How are NEPA and NHPA obligations typically enforced?  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false How are NEPA and NHPA obligations typically enforced? 137...SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.309 How are NEPA and NHPA obligations typically...

2009-10-01

220

42 CFR 137.309 - How are NEPA and NHPA obligations typically enforced?  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false How are NEPA and NHPA obligations typically enforced? 137...SERVICES TRIBAL SELF-GOVERNANCE Construction Nepa Process § 137.309 How are NEPA and NHPA obligations typically...

2013-10-01

221

21 CFR 821.30 - Tracking obligations of persons other than device manufacturers: distributor requirements.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Tracking obligations of persons other than...MEDICAL DEVICES MEDICAL DEVICE TRACKING REQUIREMENTS Additional Requirements...Responsibilities § 821.30 Tracking obligations of persons other...

2010-04-01

222

21 CFR 821.30 - Tracking obligations of persons other than device manufacturers: distributor requirements.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Tracking obligations of persons other than...MEDICAL DEVICES MEDICAL DEVICE TRACKING REQUIREMENTS Additional Requirements...Responsibilities § 821.30 Tracking obligations of persons other...

2009-04-01

223

43 CFR 3137.41 - What continuing development obligations must I define in a unit agreement?  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false What continuing development obligations must I define in a unit agreement...Agreements-National Petroleum Reserve-Alaska Development § 3137.41 What continuing development obligations must I define in a unit...

2013-10-01

224

43 CFR 3137.76 - What happens if I do not meet a continuing development obligation?  

Code of Federal Regulations, 2013 CFR

...happens if I do not meet a continuing development obligation? 3137.76 Section...Agreements-National Petroleum Reserve-Alaska Development Requirements § 3137.76 ...happens if I do not meet a continuing development obligation? (a) After...

2013-10-01

225

43 CFR 3137.70 - What must I do to meet initial development obligations?  

Code of Federal Regulations, 2013 CFR

... What must I do to meet initial development obligations? 3137.70 Section...Agreements-National Petroleum Reserve-Alaska Development Requirements § 3137.70 What must I do to meet initial development obligations? (a) To meet...

2013-10-01

226

32 CFR 220.2 - Statutory obligation of third party payer to pay.  

Code of Federal Regulations, 2013 CFR

...COLLECTION FROM THIRD PARTY PAYERS OF REASONABLE CHARGES FOR HEALTHCARE SERVICES § 220.2 Statutory obligation of third party...obligation to pay the United States the reasonable charges for healthcare services provided in or through any facility of...

2013-07-01

227

26 CFR 1.662(a)-4 - Amounts used in discharge of a legal obligation.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Amounts used in discharge of a legal obligation. 1...662(a)-4 Amounts used in discharge of a legal obligation. Any...instrument, is used in full or partial discharge or satisfaction of a...

2010-04-01

228

26 CFR 1.662(a)-4 - Amounts used in discharge of a legal obligation.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 false Amounts used in discharge of a legal obligation. 1...662(a)-4 Amounts used in discharge of a legal obligation. Any...instrument, is used in full or partial discharge or satisfaction of a...

2009-04-01

229

43 CFR 3137.40 - What initial development obligations must I define in a unit agreement?  

Code of Federal Regulations, 2010 CFR

...What initial development obligations must I define in a unit agreement? 3137.40 Section...What initial development obligations must I define in a unit agreement? Your unit agreement must defineâ (a) The number of wells you...

2010-10-01

230

43 CFR 3137.71 - What must I do to meet continuing development obligations?  

Code of Federal Regulations, 2013 CFR

...What must I do to meet continuing development obligations? 3137.71 Section...Agreements-National Petroleum Reserve-Alaska Development Requirements § 3137.71 What must I do to meet continuing development obligations? (a) Once you...

2013-10-01

231

Federal Agencies' AcademicS&E Obligations Continued to Climb in FY 1995  

NSF Publications Database

Federal Agencies' Academic S&E Obligations Continued to Climb in FY 1995 (May 16, 1997) This Data ... analytic summary of Federal academic science and engineering obligations collected through the ...

232

29 CFR 37.27 - What are the obligations of small recipients regarding Equal Opportunity Officers?  

Code of Federal Regulations, 2010 CFR

...Secretary of Labor IMPLEMENTATION OF THE NONDISCRIMINATION AND EQUAL OPPORTUNITY PROVISIONS OF THE WORKFORCE INVESTMENT ACT OF 1998 (WIA) Recordkeeping and Other Affirmative Obligations of Recipients § 37.27 What are the obligations of small...

2010-07-01

233

18 CFR 292.309 - Termination of obligation to purchase from qualifying facilities.  

Code of Federal Regulations, 2010 CFR

...obligation to purchase from qualifying facilities. 292.309 Section 292.309 ...Cogeneration and Small Power Production Facilities Under Section 210 of the Public Utility...obligation to purchase from qualifying facilities. (a) After August 8,...

2009-04-01

234

78 FR 40953 - Loan Participations; Purchase, Sale and Pledge of Eligible Obligations; Purchase of Assets and...  

Federal Register 2010, 2011, 2012, 2013

...Loan Participations; Purchase, Sale and Pledge of Eligible Obligations; Purchase of Assets and Assumption of Liabilities; Extension...Loan Participations; Purchase, Sale and Pledge of Eligible Obligations; Purchase of Assets and Assumption of Liabilities,...

2013-07-09

235

26 CFR 46.4701-1 - Tax on issuer of registration-required obligation not in registered form.  

Code of Federal Regulations, 2010 CFR

...Tax on issuer of registration-required obligation not in registered form. 46.4701-1...POLICIES ISSUED BY FOREIGN INSURERS AND OBLIGATIONS NOT IN REGISTERED FORM Excise Tax on Obligations Not in Registered Form §...

2009-04-01

236

26 CFR 46.4701-1 - Tax on issuer of registration-required obligation not in registered form.  

Code of Federal Regulations, 2010 CFR

...Tax on issuer of registration-required obligation not in registered form. 46.4701-1...POLICIES ISSUED BY FOREIGN INSURERS AND OBLIGATIONS NOT IN REGISTERED FORM Excise Tax on Obligations Not in Registered Form §...

2010-04-01

237

The genome sequence of the obligately chemolithoautotrophic, facultatively anaerobic bacterium Thiobacillus denitfificans.  

SciTech Connect

The complete genome sequence of Thiobacillus denitrificans ATCC 25259 is the first to become available for an obligately chemolithoautotrophic, sulfur-compound-oxidizing, {beta}-proteobacterium. Analysis of the 2,909,809-bp genome will facilitate our molecular and biochemical understanding of the unusual metabolic repertoire of this bacterium, including its ability to couple denitrification to sulfur-compound oxidation, to catalyze anaerobic, nitrate-dependent oxidation of Fe(II) and U(IV), and to oxidize mineral electron donors. Notable genomic features include (i) genes encoding c-type cytochromes totaling 1 to 2 percent of the genome, which is a proportion greater than for almost all bacterial and archaeal species sequenced to date, (ii) genes encoding two [NiFe]hydrogenases, which is particularly significant because no information on hydrogenases has previously been reported for T. denitrificans and hydrogen oxidation appears to be critical for anaerobic U(IV) oxidation by this species, (iii) a diverse complement of more than 50 genes associated with sulfur-compound oxidation (including sox genes, dsr genes, and genes associated with the AMP-dependent oxidation of sulfite to sulfate), some of which occur in multiple (up to eight) copies, (iv) a relatively large number of genes associated with inorganic ion transport and heavy metal resistance, and (v) a paucity of genes encoding organic-compound transporters, commensurate with obligate chemolithoautotrophy. Ultimately, the genome sequence of T. denitrificans will enable elucidation of the mechanisms of aerobic and anaerobic sulfur-compound oxidation by {beta}-proteobacteria and will help reveal the molecular basis of this organism's role in major biogeochemical cycles (i.e., those involving sulfur, nitrogen, and carbon) and groundwater restoration.

Beller, H R [Lawrence Livermore National Laboratory (LLNL); Larimer, Frank W [ORNL

2006-02-01

238

31 CFR 225.4 - Pledge of book-entry Government obligations.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Pledge of book-entry Government obligations. 225...BONDS WITH SURETIES § 225.4 Pledge of book-entry Government obligations. (a...and approval of the bond official, of book-entry Government obligations....

2013-07-01

239

Nutrient availability induces contrasting allocation and starch formation in resprouting and obligate seeding shrubs  

Microsoft Academic Search

Summary 1. Woody plant responses to crown removal in fire-prone vegetation are of two types: resprouting (resprouters) or killed (obligate seeders). Obligate seeders maximize their fitness by ensuring they are reproductively mature before the next fire; resprouters invest in structures that increase their chance of surviving the next fire. 2. We tested whether seven congeneric pairs of resprouter and obligate

K. J. E. KNOX; P. J. CLARKE

2005-01-01

240

24 CFR 905.120 - Penalties for slow obligation or expenditure of CFP assistance.  

Code of Federal Regulations, 2010 CFR

... 2009-04-01 false Penalties for slow obligation or expenditure of CFP assistance...FUND PROGRAM § 905.120 Penalties for slow obligation or expenditure of CFP assistance...sanctions available to HUD, the penalties for slow obligation or expenditure of CFP...

2009-04-01

241

24 CFR 905.120 - Penalties for slow obligation or expenditure of Capital Fund program assistance.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 false Penalties for slow obligation or expenditure of Capital Fund...Capital Fund § 905.120 Penalties for slow obligation or expenditure of Capital Fund...sanctions available to HUD, the penalties for slow obligation or expenditure of CFP...

2013-04-01

242

24 CFR 905.120 - Penalties for slow obligation or expenditure of CFP assistance.  

Code of Federal Regulations, 2010 CFR

... 2010-04-01 false Penalties for slow obligation or expenditure of CFP assistance...FUND PROGRAM § 905.120 Penalties for slow obligation or expenditure of CFP assistance...sanctions available to HUD, the penalties for slow obligation or expenditure of CFP...

2010-04-01

243

Discharge against medical advice: ethical considerations and professional obligations.  

PubMed

Discharges against medical advice (AMA) account for approximately 1% of discharges for general medical patients. Patients discharged AMA have longer eventual hospital stays and worse health outcomes. These patients are also less likely to have an established relationship with a physician, tend to have poorer social supports, and are more likely to abuse alcohol and other substances. These discharges are also distressing for physicians and other health professionals. How should physicians manage their conflicted obligations to respect patients' choices and to prevent harms from befalling their patients? What are physicians' obligations to their patients who leave accepting only partial or inadequate treatment plans or no treatment at all? When should physicians question the decision-making capacity of patients who make dangerous judgments to leave the hospital? This article examines the ethical and professional implications of discharge AMA. PMID:18951403

Berger, Jeffrey T

2008-09-01

244

Duty of care is underpinned by a range of obligations.  

PubMed

The courts have long established that nurses are in a duty situation and owe a duty of care to their patients (Kent v Griffiths [2001]). Traditionally, the profession set the standard of care and nurses were required to act in accordance with a practice accepted by a responsible body of their peers (Bolam v Friern HMC [1957]).The introduction of the Human Rights Act 1998 gave rise to a positive obligation on government to ensure that laws, policies and procedures are in place to protect violations of human rights. Nurses must now inform their practice with relevant statute law, common law and professional standards in order to properly discharge their duty of care. Richard Griffith considers the law that now underpins a nurse's duty of care and uses a recent report from the Health Service Ombudsman for England to illustrate the obligations that underpin the nurse-patient relationship. PMID:24809155

Griffith, Richard

245

Cytokine Expression in Response to Bacterial Antigens in Preterm and Term Infant Cord Blood Monocytes  

Microsoft Academic Search

Background: Neonatal susceptibility to bacterial infection is associated with an immature immune system, but the role of different bacterial antigens in specific responses is largely unknown. Objective: To evaluate differences in intracellular cytokine response to physiologically relevant bacterial antigens in term and preterm infants as compared with adults. Methods: Cord blood samples from preterm and term neonates and adult peripheral

A. M. Francesca Tatad; Mirjana Nesin; John Peoples; Sandy Cheung; Hong Lin; Cristina Sison; Jeffrey Perlman; Susanna Cunningham-Rundles

2008-01-01

246

US arms control obligations under the Non-Proliferation Treaty  

SciTech Connect

Article VI of the 1968 Non-Proliferation Treaty (NPT) obligates the nuclear weapon states parties to the Treaty ''to pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race, ... to nuclear disarmament, and on a treaty on general and complete disarmament under strict and effective international control.'' The preamble to the NPT recalls the 1963 Limited Test Ban Treaty ''determination ... to achieve the discontinuance of ... explosions.'' These provisions are interpreted by a majority of the non-nuclear weapon states parties to the Treaty as an obligation of the nuclear weapon states parties to the Treaty to pursue a comprehensive test ban (CTB). However, a review of the history of the NPT negotiations and US ratification proceedings makes clear that the NPT imposes no legal obligation on the US to pursue a CTB. The US did not make a one-to-one correspondence between Article VI and any specific arms control measure; to the contrary, the US argued successfully that such a connection (to any specific measure) would be pernicious to the attempt to achieve agreement on the NPT. This interpretation, which was sustained through the negotiations and the ratification proceedings, still reflects the limits of the legal obligations the US has accepted. But, in the absence of progress on other arms control measures, which would relieve the pressure for a CTB, the majority interpretation creates political difficulties for the US and could threaten the NPT regime in the future. These problems highlight the need for the US to better defend its compliance with Article VI and to develop a long-term strategy that will permit necessary testing while assuring the survival of the NPT regime in effective form.

Not Available

1986-06-27

247

Product Individual Sorting and Identification Systems to organize WEEE obligations  

Microsoft Academic Search

With the implementation of the Waste Electrical and Electronic Equipment directive (WEEE) manufacturers of electrical equipment\\u000a are obliged to take responsibility for their appliances. At the moment different configuration of recycling systems are discussed\\u000a in Germany which have in common that the recycling costs are distributed among the manufacturers by their respective market\\u000a share. The developed concept allows an automated

Christian Butz

248

Palatal Actinomycosis and Kaposi Sarcoma in an HIV-Infected Subject with Disseminated Mycobacterium avium-intracellulare Infection  

PubMed Central

Actinomyces and Mycobacterium avium-intracellulare are facultative intracellular organisms, members of the bacterial order actinomycetales. Although Actinomyces can behave as copathogen when anatomic barriers are compromised, its coinfection with Mycobacterium avium-intracellulare has not previously been reported. We present the first reported case of palatal actinomycosis co-infection with disseminated MAC, in an HIV-infected subject with Kaposi sarcoma and diabetes. We discuss the pathogenesis of the complex condition of this subject.

Ablanedo-Terrazas, Yuria; Ormsby, Christopher E.; Reyes-Teran, Gustavo

2012-01-01

249

The relationship between family obligation and religiosity on caregiving.  

PubMed

The purpose of this study was to examine the relationship between family obligation and religiosity on the positive appraisal of caregiving among African-American, Hispanic and non-Hispanic Caucasian family caregivers of older adults. Roy's adaptation model guided formulation of the aims and study design. A cross-sectional, correlational study design was employed to examine the relationship amongst variables for the family caregiver participants. Study participants (N = 69) completed a demographic tool and four instruments the: (1) Katz index, (2) obligation scale, (3) Duke University religion index, and (4) positive appraisal of care scale. There was a significant correlation between family obligation and positive appraisal of caregiving. However, there was no relationship between the family caregiver's religiosity and positive appraisal of caregiving overall. Demographic variables were also examined to show a higher marginal mean for Hispanic primary caregivers in relation to the positive appraisal of caregiving. Future studies should consider replicating these findings in a larger sample to provide health care professionals with substantial evidence to incorporate culturally sensitive interventions aimed at promoting positive outcomes and healthy family behaviors. PMID:24314743

Epps, Fayron

2014-01-01

250

Bacterial Biofertilizers  

Microsoft Academic Search

Many bacteria and fungi can enhance plant growth. The present review is limited to plant growth promoting rhizobacteria (PGPR). However, it includes endophytic bacteria that show plant growth enhancing activity as well. Also the best studied bacterial mechanisms of plant growth promotion are discussed, with a special emphasis on biological nitrogen fixation and synthesis of phytohormones, including less understood mechanisms

LUIS E. FUENTES-RAMIREZ; Jesus Caballero-Mellado

251

Bacterial vaginosis  

Microsoft Academic Search

Bacterial vaginosis is the commonest cause of abnormal vaginal discharge in women of childbearing age, with a prevalence as high as 50% in some communities. The symptoms of discharge and offensive smell can cause considerable distress, although 50% of women are asymptomatic when diagnosed. Microbiologically the usually dominant lactobacillus flora is overwhelmed by an overgrowth of predominantly anaerobic organisms, accompanied

Phillip Hay

2010-01-01

252

A bacterial genome in transition - an exceptional enrichment of IS elements but lack of evidence for recent transposition in the symbiont Amoebophilus asiaticus  

PubMed Central

Background Insertion sequence (IS) elements are important mediators of genome plasticity and are widespread among bacterial and archaeal genomes. The 1.88 Mbp genome of the obligate intracellular amoeba symbiont Amoebophilus asiaticus contains an unusually large number of transposase genes (n = 354; 23% of all genes). Results The transposase genes in the A. asiaticus genome can be assigned to 16 different IS elements termed ISCaa1 to ISCaa16, which are represented by 2 to 24 full-length copies, respectively. Despite this high IS element load, the A. asiaticus genome displays a GC skew pattern typical for most bacterial genomes, indicating that no major rearrangements have occurred recently. Additionally, the high sequence divergence of some IS elements, the high number of truncated IS element copies (n = 143), as well as the absence of direct repeats in most IS elements suggest that the IS elements of A. asiaticus are transpositionally inactive. Although we could show transcription of 13 IS elements, we did not find experimental evidence for transpositional activity, corroborating our results from sequence analyses. However, we detected contiguous transcripts between IS elements and their downstream genes at nine loci in the A. asiaticus genome, indicating that some IS elements influence the transcription of downstream genes, some of which might be important for host cell interaction. Conclusions Taken together, the IS elements in the A. asiaticus genome are currently in the process of degradation and largely represent reflections of the evolutionary past of A. asiaticus in which its genome was shaped by their activity.

2011-01-01

253

Rickettsial Outer-Membrane Protein B (rOmpB) Mediates Bacterial Invasion through Ku70 in an Actin, c-Cbl, Clathrin and Caveolin 2-Dependent Manner  

PubMed Central

Summary Rickettsia conorii, an obligate intracellular tick-borne pathogen and the causative agent of Mediterranean spotted fever, binds to and invades non-phagocytic mammalian cells. Previous work identified Ku70 as a mammalian receptor involved in the invasion process and identified the rickettsial autotransporter protein, rOmpB, as a ligand; however, little is known about the role of Ku70-rOmpB interactions in the bacterial invasion process. Using an E. coli heterologous expression system, we show here that rOmpB mediates attachment to mammalian cells and entry in a Ku70-dependent process. A purified recombinant peptide corresponding to the rOmpB passenger domain interacts with Ku70 and serves as a competitive inhibitor of adherence. We observe that rOmpB-mediated infection culminates in actin recruitment at the bacterial foci, and that this entry process relies in part on actin polymerization likely imparted through protein tyrosine kinase and PI3-kinase-dependent activities and microtubule stability. Small-interfering RNA (siRNA) studies targeting components of the endocytic pathway reveal that entry by rOmpB is dependent on c-Cbl, clathrin and caveolin-2. Together, these results illustrate that rOmpB is sufficient to mediate Ku70-dependent invasion of mammalian cells and that clathrin- and caveolin-dependent endocytic events likely contribute to the internalization process.

Chan, Yvonne G.Y.; Cardwell, Marissa M.; Hermanas, Timothy M.; Uchiyama, Tsuneo; Martinez, Juan J.

2009-01-01

254

Rickettsial outer-membrane protein B (rOmpB) mediates bacterial invasion through Ku70 in an actin, c-Cbl, clathrin and caveolin 2-dependent manner.  

PubMed

Rickettsia conorii, an obligate intracellular tick-borne pathogen and the causative agent of Mediterranean spotted fever, binds to and invades non-phagocytic mammalian cells. Previous work identified Ku70 as a mammalian receptor involved in the invasion process and identified the rickettsial autotransporter protein, rOmpB, as a ligand; however, little is known about the role of Ku70-rOmpB interactions in the bacterial invasion process. Using an Escherichia coli heterologous expression system, we show here that rOmpB mediates attachment to mammalian cells and entry in a Ku70-dependent process. A purified recombinant peptide corresponding to the rOmpB passenger domain interacts with Ku70 and serves as a competitive inhibitor of adherence. We observe that rOmpB-mediated infection culminates in actin recruitment at the bacterial foci, and that this entry process relies in part on actin polymerization likely imparted through protein tyrosine kinase and phosphoinositide 3-kinase-dependent activities and microtubule stability. Small-interfering RNA studies targeting components of the endocytic pathway reveal that entry by rOmpB is dependent on c-Cbl, clathrin and caveolin-2. Together, these results illustrate that rOmpB is sufficient to mediate Ku70-dependent invasion of mammalian cells and that clathrin- and caveolin-dependent endocytic events likely contribute to the internalization process. PMID:19134120

Chan, Yvonne G Y; Cardwell, Marissa M; Hermanas, Timothy M; Uchiyama, Tsuneo; Martinez, Juan J

2009-04-01

255

Bacterial microcompartments.  

PubMed

Bacterial microcompartments (BMCs) are organelles composed entirely of protein. They promote specific metabolic processes by encapsulating and colocalizing enzymes with their substrates and cofactors, by protecting vulnerable enzymes in a defined microenvironment, and by sequestering toxic or volatile intermediates. Prototypes of the BMCs are the carboxysomes of autotrophic bacteria. However, structures of similar polyhedral shape are being discovered in an ever-increasing number of heterotrophic bacteria, where they participate in the utilization of specialty carbon and energy sources. Comparative genomics reveals that the potential for this type of compartmentalization is widespread across bacterial phyla and suggests that genetic modules encoding BMCs are frequently laterally transferred among bacteria. The diverse functions of these BMCs suggest that they contribute to metabolic innovation in bacteria in a broad range of environments. PMID:20825353

Kerfeld, Cheryl A; Heinhorst, Sabine; Cannon, Gordon C

2010-01-01

256

Bacterial morphogenes  

Microsoft Academic Search

Cell shape is not the product of a particular gene or protein, but the result of the collective actions of many of them. These\\u000a are involved in several processes, including peptidoglycan precursor synthesis, peptidoglycan synthesis and recycling, cell\\u000a elongation, cell septation and division site selection. The analysis of the “morphogene” content of several bacterial genomes\\u000a suggests that there are three

Jesús Mingorance; Anabel Rico; Paulino GÓmez-Puertas

257

Francisella tularensis Harvests Nutrients Derived via ATG5-Independent Autophagy to Support Intracellular Growth  

PubMed Central

Francisella tularensis is a highly virulent intracellular pathogen that invades and replicates within numerous host cell types including macrophages, hepatocytes and pneumocytes. By 24 hours post invasion, F. tularensis replicates up to 1000-fold in the cytoplasm of infected cells. To achieve such rapid intracellular proliferation, F. tularensis must scavenge large quantities of essential carbon and energy sources from the host cell while evading anti-microbial immune responses. We found that macroautophagy, a eukaryotic cell process that primarily degrades host cell proteins and organelles as well as intracellular pathogens, was induced in F. tularensis infected cells. F. tularensis not only survived macroautophagy, but optimal intracellular bacterial growth was found to require macroautophagy. Intracellular growth upon macroautophagy inhibition was rescued by supplying excess nonessential amino acids or pyruvate, demonstrating that autophagy derived nutrients provide carbon and energy sources that support F. tularensis proliferation. Furthermore, F. tularensis did not require canonical, ATG5-dependent autophagy pathway induction but instead induced an ATG5-independent autophagy pathway. ATG5-independent autophagy induction caused the degradation of cellular constituents resulting in the release of nutrients that the bacteria harvested to support bacterial replication. Canonical macroautophagy limits the growth of several different bacterial species. However, our data demonstrate that ATG5-independent macroautophagy may be beneficial to some cytoplasmic bacteria by supplying nutrients to support bacterial growth.

Ziehr, Benjamin; Taft-Benz, Sharon; Moorman, Nathaniel; Kawula, Thomas

2013-01-01

258

Azithromycin effectiveness against intracellular infections of Francisella  

PubMed Central

Background Macrolide antibiotics are commonly administered for bacterial respiratory illnesses. Azithromycin (Az) is especially noted for extremely high intracellular concentrations achieved within macrophages which is far greater than the serum concentration. Clinical strains of Type B Francisella (F.) tularensis have been reported to be resistant to Az, however our laboratory Francisella strains were found to be sensitive. We hypothesized that different strains/species of Francisella (including Type A) may have different susceptibilities to Az, a widely used and well-tolerated antibiotic. Results In vitro susceptibility testing of Az confirmed that F. tularensis subsp. holarctica Live Vaccine Strain (LVS) (Type B) was not sensitive while F. philomiragia, F. novicida, and Type A F. tularensis (NIH B38 and Schu S4 strain) were susceptible. In J774A.1 mouse macrophage cells infected with F. philomiragia, F. novicida, and F. tularensis LVS, 5 ?g/ml Az applied extracellularly eliminated intracellular Francisella infections. A concentration of 25 ?g/ml Az was required for Francisella-infected A549 human lung epithelial cells, suggesting that macrophages are more effective at concentrating Az than epithelial cells. Mutants of RND efflux components (tolC and ftlC) in F. novicida demonstrated less sensitivity to Az by MIC than the parental strain, but the tolC disc-inhibition assay demonstrated increased sensitivity, indicating a complex role for the outer-membrane transporter. Mutants of acrA and acrB mutants were less sensitive to Az than the parental strain, suggesting that AcrAB is not critical for the efflux of Az in F. novicida. In contrast, F. tularensis Schu S4 mutants ?acrB and ?acrA were more sensitive than the parental strain, indicating that the AcrAB may be important for Az efflux in F. tularensis Schu S4. F. novicida LPS O-antigen mutants (wbtN, wbtE, wbtQ and wbtA) were found to be less sensitive in vitro to Az compared to the wild-type. Az treatment prolonged the survival of Galleria (G.) mellonella infected with Francisella. Conclusion These studies demonstrate that Type A Francisella strains, as well as F. novicida and F. philomiragia, are sensitive to Az in vitro. Francisella LPS and the RND efflux pump may play a role in Az sensitivity. Az also has antimicrobial activity against intracellular Francisella, suggesting that the intracellular concentration of Az is high enough to be effective against multiple strains/species of Francisella, especially in macrophages. Az treatment prolonged survival an in vivo model of Francisella-infection.

2010-01-01

259

Intracellular Antibody Neutralizes Listeria Growth  

Microsoft Academic Search

We previously reported that treatment of mice with a neutralizing mAb against listeriolysin O (LLO), the pore-forming toxin of Listeria monocytogenes, provided resistance to this intracellular bacterium. We evaluated whether anti-LLO mAb would affect Listeria handling by macrophages, essential cells in Listeria resistance. Macrophages infected in the presence of anti-LLO mAb showed a marked reduction in intracellular Listeria growth, with

Brian T Edelson; Emil R Unanue

2001-01-01

260

Optimal killing for obligate killers: the evolution of life histories and virulence of semelparous parasites.  

PubMed Central

Many viral, bacterial and protozoan parasites of invertebrates first propagate inside their host without releasing any transmission stages and then kill their host to release all transmission stages at once. Life history and the evolution of virulence of these obligately killing parasites are modelled, assuming that within-host growth is density dependent. We find that the parasite should kill the host when its per capita growth rate falls to the level of the host mortality rate. The parasite should kill its host later when the carrying capacity, K, is higher, but should kill it earlier when the parasite-independent host mortality increases or when the parasite has a higher birth rate. When K(t), for parasite growth, is not constant over the duration of an infection, but increases with time, the parasite should kill the host around the stage when the growth rate of the carrying capacity decelerates strongly. In case that K(t) relates to host body size, this deceleration in growth is around host maturation.

Ebert, D; Weisser, W W

1997-01-01

261

Sequence Conservation and Functional Constraint on Intergenic Spacers in Reduced Genomes of the Obligate Symbiont Buchnera  

PubMed Central

Analyses of genome reduction in obligate bacterial symbionts typically focus on the removal and retention of protein-coding regions, which are subject to ongoing inactivation and deletion. However, these same forces operate on intergenic spacers (IGSs) and affect their contents, maintenance, and rates of evolution. IGSs comprise both non-coding, non-functional regions, including decaying pseudogenes at varying stages of recognizability, as well as functional elements, such as genes for sRNAs and regulatory control elements. The genomes of Buchnera and other small genome symbionts display biased nucleotide compositions and high rates of sequence evolution and contain few recognizable regulatory elements. However, IGS lengths are highly correlated across divergent Buchnera genomes, suggesting the presence of functional elements. To identify functional regions within the IGSs, we sequenced two Buchnera genomes (from aphid species Uroleucon ambrosiae and Acyrthosiphon kondoi) and applied a phylogenetic footprinting approach to alignments of orthologous IGSs from a total of eight Buchnera genomes corresponding to six aphid species. Inclusion of these new genomes allowed comparative analyses at intermediate levels of divergence, enabling the detection of both conserved elements and previously unrecognized pseudogenes. Analyses of these genomes revealed that 232 of 336 IGS alignments over 50 nucleotides in length displayed substantial sequence conservation. Conserved alignment blocks within these IGSs encompassed 88 Shine-Dalgarno sequences, 55 transcriptional terminators, 5 Sigma-32 binding sites, and 12 novel small RNAs. Although pseudogene formation, and thus IGS formation, are ongoing processes in these genomes, a large proportion of intergenic spacers contain functional sequences.

Degnan, Patrick H.; Ochman, Howard; Moran, Nancy A.

2011-01-01

262

Desulfurispira natronophila gen. nov. sp. nov.: an obligately anaerobic dissimilatory sulfur-reducing bacterium from soda lakes  

PubMed Central

Anaerobic enrichment cultures with elemental sulfur as electron acceptor and either acetate or propionate as electron donor and carbon source at pH 10 and moderate salinity inoculated with sediments from soda lakes in Kulunda Steppe (Altai, Russia) resulted in the isolation of two novel members of the bacterial phylum Chrysiogenetes. The isolates, AHT11 and AHT19, represent the first specialized obligate anaerobic dissimilatory sulfur respirers from soda lakes. They use either elemental sulfur/polysulfide or arsenate as electron acceptor and a few simple organic compounds as electron donor and carbon source. Elemental sulfur is reduced to sulfide through intermediate polysulfide, while arsenate is reduced to arsenite. The bacteria belong to the obligate haloalkaliphiles, with a pH growth optimum from 10 to 10.2 and a salt range from 0.2 to 3.0 M Na+ (optimum 0.4–0.6 M). According to the phylogenetic analysis, the two strains were close to each other, but distinct from the nearest relative, the haloalkaliphilic sulfur-reducing bacterium Desulfurispirillum alkaliphilum, which was isolated from a bioreactor. On the basis of distinct phenotype and phylogeny, the soda lake isolates are proposed as a new genus and species, Desulfurispira natronophila (type strain AHT11T = DSM22071T = UNIQEM U758T). Electronic supplementary material The online version of this article (doi:10.1007/s00792-010-0314-7) contains supplementary material, which is available to authorized users.

Muyzer, G.

2010-01-01

263

Amoebal Endosymbiont Neochlamydia Genome Sequence Illuminates the Bacterial Role in the Defense of the Host Amoebae against Legionella pneumophila  

PubMed Central

Previous work has shown that the obligate intracellular amoebal endosymbiont Neochlamydia S13, an environmental chlamydia strain, has an amoebal infection rate of 100%, but does not cause amoebal lysis and lacks transferability to other host amoebae. The underlying mechanism for these observations remains unknown. In this study, we found that the host amoeba could completely evade Legionella infection. The draft genome sequence of Neochlamydia S13 revealed several defects in essential metabolic pathways, as well as unique molecules with leucine-rich repeats (LRRs) and ankyrin domains, responsible for protein-protein interaction. Neochlamydia S13 lacked an intact tricarboxylic acid cycle and had an incomplete respiratory chain. ADP/ATP translocases, ATP-binding cassette transporters, and secretion systems (types II and III) were well conserved, but no type IV secretion system was found. The number of outer membrane proteins (OmcB, PomS, 76-kDa protein, and OmpW) was limited. Interestingly, genes predicting unique proteins with LRRs (30 genes) or ankyrin domains (one gene) were identified. Furthermore, 33 transposases were found, possibly explaining the drastic genome modification. Taken together, the genomic features of Neochlamydia S13 explain the intimate interaction with the host amoeba to compensate for bacterial metabolic defects, and illuminate the role of the endosymbiont in the defense of the host amoebae against Legionella infection.

Ishida, Kasumi; Sekizuka, Tsuyoshi; Hayashida, Kyoko; Matsuo, Junji; Takeuchi, Fumihiko; Kuroda, Makoto; Nakamura, Shinji; Yamazaki, Tomohiro; Yoshida, Mitsutaka; Takahashi, Kaori; Nagai, Hiroki; Sugimoto, Chihiro; Yamaguchi, Hiroyuki

2014-01-01

264

Obligate symbionts activate immune system development in the tsetse fly  

PubMed Central

Many insects rely on the presence of symbiotic bacteria for proper immune system function. However, the molecular mechanisms that underlie this phenomenon are poorly understood. Adult tsetse flies (Glossina spp.) house 3 symbiotic bacteria that are vertically transmitted from mother to offspring during this insect's unique viviparous mode of reproduction. Larval tsetse that undergo intrauterine development in the absence of their obligate mutualist, Wigglesworthia, exhibit a compromised immune system during adulthood. In this study we characterize the immune phenotype of tsetse that develop in the absence of all of their endogenous symbiotic microbes. Aposymbiotic tsetse (GmmApo) present a severely compromised immune system that is characterized by the absence of phagocytic hemocytes and atypical expression of immunity-related genes. Correspondingly, these flies quickly succumb to infection with normally non-pathogenic E. coli. The susceptible phenotype exhibited by GmmApo adults can be reversed when they receive hemocytes transplanted from wild-type donor flies prior to infection. Furthermore, the process of immune system development can be restored in intrauterine GmmApo larvae when their moms are fed a diet supplemented with Wigglesworthia cell extracts. Our finding that molecular components of Wigglesworthia exhibit immunostimulatory activity within tsetse is representative of a novel evolutionary adaptation that steadfastly links an obligate symbiont with it's host.

Weiss, Brian L.; Maltz, Michele; Aksoy, Serap

2012-01-01

265

The Evolutionary Pathway to Obligate Scavenging in Gyps Vultures  

PubMed Central

The evolutionary pathway to obligate scavenging in Gyps vultures remains unclear. We propose that communal roosting plays a central role in setting up the information transfer network critical for obligate scavengers in ephemeral environments and that the formation of a flotilla-like foraging group is a likely strategy for foraging Gyps vultures. Using a spatial, individual-based, optimisation model we find that the communal roost is critical for establishing the information network that enables information transfer owing to the spatial-concentration of foragers close to the roost. There is also strong selection pressure for grouping behaviour owing to the importance of maintaining network integrity and hence information transfer during foraging. We present a simple mechanism for grouping, common in many animal species, which has the added implication that it negates the requirement for roost-centric information transfer. The formation of a flotilla-like foraging group also improves foraging efficiency through the reduction of overlapping search paths. Finally, we highlight the importance of consideration of information transfer mechanisms in order to maximise the success of vulture reintroduction programmes.

Dermody, Brian J.; Tanner, Colby J.; Jackson, Andrew L.

2011-01-01

266

Acquisition of an animal gene by microsporidian intracellular parasites  

PubMed Central

Parasites have adapted to their specialised way of life by a number of means, including the acquisition of genes by horizontal gene transfer. These newly acquired genes seem to come from a variety of sources, but seldom from the host, even in the most intimate associations between obligate intracellular parasite and host [1]. Microsporidian intracellular parasites have acquired a handful of genes, mostly from bacteria, that help them take energy from their hosts or protect them from the environment [2,3]. To date, however, no animal genes have been documented in any microsporidian genome. Here, we have surveyed the genome of the microsporidian Encephalitozoon romaleae, which parasitises arthropods for evidence of animal genes. We found one protein-encoding gene that is absent from publicly available sequence data from other microsporidia. The gene encodes a component of the purine salvage pathway, and has been independently acquired by other parasites through horizontal gene transfer from other donors. In this case, however, the gene shows a very strong phylogenetic signal for arthropod origin.

Selman, Mohammed; Pombert, Jean-Francois; Solter, Leellen; Farinelli, Laurent; Weiss, Louis M.; Keeling, Patrick; Corradi, Nicolas

2013-01-01

267

Bacterial olfaction.  

PubMed

Sensing their environment is a crucial ability of all life forms. In higher eukaryotes the sensing of airborne volatile compounds, or olfaction, is well developed. In plants, slime moulds and yeast there is also compelling evidence that these organisms can smell their environment and respond accordingly. Here we show that bacteria are also capable of olfaction. Bacillus licheniformis was able to sense airborne volatile metabolites produced by neighbouring bacterial cultures and cells could respond to this chemical information in a coordinated way. When Bacillus licheniformis was grown in a microtitre plate adjacent to a bacterial culture of the same or a different species, growing in complex medium, biofilm formation and pigment production were elicited by volatile molecules. A weaker response occurred in increasingly distant wells. The emitted volatile molecule was identified as ammonia. These data demonstrate that B. licheniformis has evolved the ability collect information about its environment from the surrounding air and physiologically respond to it in a manner similar to olfaction. This is the first time that a behavioural response triggered by odorant molecules received through the gas phase is described in bacteria. PMID:20721987

Nijland, Reindert; Burgess, J Grant

2010-09-01

268

Metallochaperones regulate intracellular copper levels.  

PubMed

Copper (Cu) is an important enzyme co-factor that is also extremely toxic at high intracellular concentrations, making active efflux mechanisms essential for preventing Cu accumulation. Here, we have investigated the mechanistic role of metallochaperones in regulating Cu efflux. We have constructed a computational model of Cu trafficking and efflux based on systems analysis of the Cu stress response of Halobacterium salinarum. We have validated several model predictions via assays of transcriptional dynamics and intracellular Cu levels, discovering a completely novel function for metallochaperones. We demonstrate that in addition to trafficking Cu ions, metallochaperones also function as buffers to modulate the transcriptional responsiveness and efficacy of Cu efflux. This buffering function of metallochaperones ultimately sets the upper limit for intracellular Cu levels and provides a mechanistic explanation for previously observed Cu metallochaperone mutation phenotypes. PMID:23349626

Pang, W Lee; Kaur, Amardeep; Ratushny, Alexander V; Cvetkovic, Aleksandar; Kumar, Sunil; Pan, Min; Arkin, Adam P; Aitchison, John D; Adams, Michael W W; Baliga, Nitin S

2013-01-01

269

Metallochaperones Regulate Intracellular Copper Levels  

PubMed Central

Copper (Cu) is an important enzyme co-factor that is also extremely toxic at high intracellular concentrations, making active efflux mechanisms essential for preventing Cu accumulation. Here, we have investigated the mechanistic role of metallochaperones in regulating Cu efflux. We have constructed a computational model of Cu trafficking and efflux based on systems analysis of the Cu stress response of Halobacterium salinarum. We have validated several model predictions via assays of transcriptional dynamics and intracellular Cu levels, discovering a completely novel function for metallochaperones. We demonstrate that in addition to trafficking Cu ions, metallochaperones also function as buffers to modulate the transcriptional responsiveness and efficacy of Cu efflux. This buffering function of metallochaperones ultimately sets the upper limit for intracellular Cu levels and provides a mechanistic explanation for previously observed Cu metallochaperone mutation phenotypes.

Pang, W. Lee; Kaur, Amardeep; Ratushny, Alexander V.; Cvetkovic, Aleksandar; Kumar, Sunil; Pan, Min; Arkin, Adam P.; Aitchison, John D.; Adams, Michael W. W.; Baliga, Nitin S.

2013-01-01

270

Ultrastructural and Immunocytochemical Study of the Uptake and Distribution of Bacterial Lipopolysaccharide in Human Monocytes.  

National Technical Information Service (NTIS)

Interaction of bacterial lipopolysaccharide (LPS) with monocytes stimulates production of a variety of mediators that are involved in the pathogenesis of septic shock and wound repair. The mechanisms of LPS uptake and intracellular distribution of LPS in ...

Y. H. Kang R. S. Dwivedi C. H. Lee

1990-01-01

271

25 CFR 163.42 - Obligated service and breach of contract.  

Code of Federal Regulations, 2011 CFR

...DEPARTMENT OF THE INTERIOR LAND AND WATER GENERAL FORESTRY REGULATIONS Forestry Education, Education Assistance, Recruitment...Obligated service. (1) Individuals completing forestry education programs with an...

2011-04-01

272

Intracellular recording in behaving animals  

PubMed Central

Electrophysiological recordings from behaving animals provide an unparalleled view into the functional role of individual neurons. Intracellular approaches can be especially revealing as they provide information about a neuron’s inputs and intrinsic cellular properties, which together determine its spiking output. Recent technical developments have made intracellular recording possible during an ever-increasing range of behaviors in both head-fixed and freely moving animals. These recordings have yielded fundamental insights into the cellular and circuit mechanisms underlying neural activity during natural behaviors in such areas as sensory perception, motor sequence generation, and spatial navigation, forging a direct link between cellular and systems neuroscience.

Long, Michael A.; Lee, Albert K.

2011-01-01

273

Dynamic Reorganization of Metabolic Enzymes into Intracellular Bodies  

PubMed Central

Both focused and large-scale cell biological and biochemical studies have revealed that hundreds of metabolic enzymes across diverse organisms form large intracellular bodies. These proteinaceous bodies range in form from fibers and intracellular foci—such as those formed by enzymes of nitrogen and carbon utilization and of nucleotide biosynthesis—to high-density packings inside bacterial microcompartments and eukaryotic microbodies. Although many enzymes clearly form functional mega-assemblies, it is not yet clear for many recently discovered cases whether they represent functional entities, storage bodies, or aggregates. In this article, we survey intracellular protein bodies formed by metabolic enzymes, asking when and why such bodies form and what their formation implies for the functionality—and dysfunctionality—of the enzymes that comprise them. The panoply of intracellular protein bodies also raises interesting questions regarding their evolution and maintenance within cells. We speculate on models for how such structures form in the first place and why they may be inevitable.

O'Connell, Jeremy D.; Zhao, Alice; Ellington, Andrew D.; Marcotte, Edward M.

2013-01-01

274

Nutrient salvaging and metabolism by the intracellular pathogen Legionella pneumophila.  

PubMed

The Gram-negative bacterium Legionella pneumophila is ubiquitous in freshwater environments as a free-swimming organism, resident of biofilms, or parasite of protozoa. If the bacterium is aerosolized and inhaled by a susceptible human host, it can infect alveolar macrophages and cause a severe pneumonia known as Legionnaires' disease. A sophisticated cell differentiation program equips L. pneumophila to persist in both extracellular and intracellular niches. During its life cycle, L. pneumophila alternates between at least two distinct forms: a transmissive form equipped to infect host cells and evade lysosomal degradation, and a replicative form that multiplies within a phagosomal compartment that it has retooled to its advantage. The efficient changeover between transmissive and replicative states is fundamental to L. pneumophila's fitness as an intracellular pathogen. The transmission and replication programs of L. pneumophila are governed by a number of metabolic cues that signal whether conditions are favorable for replication or instead trigger escape from a spent host. Several lines of experimental evidence gathered over the past decade establish strong links between metabolism, cellular differentiation, and virulence of L. pneumophila. Herein, we focus on current knowledge of the metabolic components employed by intracellular L. pneumophila for cell differentiation, nutrient salvaging and utilization of host factors. Specifically, we highlight the metabolic cues that are coupled to bacterial differentiation, nutrient acquisition systems, and the strategies utilized by L. pneumophila to exploit host metabolites for intracellular replication. PMID:24575391

Fonseca, Maris V; Swanson, Michele S

2014-01-01

275

Female-biased obligate strategies in a partially migratory population.  

PubMed

Partial migration occurs when a breeding population consists of seasonal migrants and year-round residents. Although it is common among birds, the basis of individual movement decisions within partially migratory populations is still unresolved. Over 4 years, we used state of the art tracking techniques, a combination of geolocators and radio transmitters, to follow individual European blackbirds Turdus merula year round from a partially migratory population to determine individual strategies and departure and arrival dates. The individual-based tracking combined with measures of energetic and hormonal (corticosterone) state enabled us to distinguish between obligate and facultative migration and to test several classical hypotheses of partial migration: the 'Arrival Time'-, 'Dominance'- and 'Thermal Tolerance'-hypotheses. Two distinct periods of departures from the breeding grounds were observed during the study; one in early autumn, and another during the midst of winter. Although blackbirds that migrated in autumn were never observed overwintering within 300 km of the study site, four individuals that departed in the winter were observed within 40 km. Females were significantly more likely to migrate in autumn than males but there was no difference in the age or body size of migrants and non migrants in autumn. Just prior to autumn migration, migrants had higher fat scores than non migrants and tended to have higher concentrations of baseline corticosterone, but similar concentrations of triglycerides. Unlike autumn migrants, we found no difference between the tendencies of males versus females to depart in winter, nor did we find any difference in body size or age of individuals that departed in the winter. Autumn migration was sex biased and resembled obligate migration. Our results provide strong support for the 'Arrival Time' hypothesis for partial migration in the autumn. We found no clear support for the 'Dominance' or 'Thermal Tolerance' hypotheses. By tracking individuals year round, we were able to identify a second period of departures. Overall, these results suggest the co-occurrence of obligate autumn migrants, winter movements and sedentary individuals within a single population. PMID:23363245

Fudickar, Adam M; Schmidt, Andreas; Hau, Michaela; Quetting, Michael; Partecke, Jesko

2013-07-01

276

Intracellular Neutralization of Virus by Immunoglobulin A Antibodies  

NASA Astrophysics Data System (ADS)

IgA is thought to neutralize viruses at the epithelial surface of mucous membranes by preventing their attachment. Since IgA, a polymeric immunoglobulin, is transported through the lining of epithelial cells by the polymeric-immunoglobulin receptor and since viruses are obligate intracellular parasites, we hypothesized that IgA antibodies may also interfere with viral replication by binding to newly synthesized viral proteins within infected cells. Polarized monolayers of Madin-Darby canine kidney epithelial cells expressing the polymeric-immunoglobulin receptor were infected on the apical surface with Sendai virus. Anti-Sendai virus IgA monoclonal antibody delivered from the basolateral surface colocalized with viral protein within the cell, as documented by immunofluorescence. More importantly, anti-viral IgA reduced virus titers >1000-fold (P < 0.0001) in apical supernatants and >10-fold (P < 0.0001) in cell lysates from monolayers treated with anti-viral IgA compared with those treated with either anti-viral IgG or an irrelevant IgA monoclonal antibody. We believe that the differences in viral titers between cell layers treated with specific IgA, which enters the epithelial cell by binding to the polymeric-immunoglobulin receptor, and those treated with specific IgG, which does not enter the cells, or irrelevant IgA indicate that specific intracellular IgA antibodies can inhibit viral replication. Thus, in addition to the classical role of humoral antibodies in extracellular defense, IgA antibody may be able to neutralize microbial pathogens intracellularly, giving IgA a role in host defense that has traditionally been reserved for cell-mediated immunity.

Mazanec, Mary B.; Kaetzel, Charlotte S.; Lamm, Michael E.; Fletcher, David; Nedrud, John G.

1992-08-01

277

Asparagine assimilation is critical for intracellular replication and dissemination of Francisella.  

PubMed

In order to develop a successful infectious cycle, intracellular bacterial pathogens must be able to adapt their metabolism to optimally utilize the nutrients available in the cellular compartments and tissues where they reside. Francisella tularensis, the agent of the zoonotic disease tularaemia, is a highly infectious bacterium for a large number of animal species. This bacterium replicates in its mammalian hosts mainly in the cytosol of infected macrophages. We report here the identification of a novel amino acid transporter of the major facilitator superfamily of secondary transporters that is required for bacterial intracellular multiplication and systemic dissemination. We show that inactivation of this transporter does not affect phagosomal escape but prevents multiplication in the cytosol of all cell types tested. Remarkably, the intracellular growth defect of the mutant was fully and specifically reversed by addition of asparagine or asparagine-containing dipeptides as well as by simultaneous addition of aspartic acid and ammonium. Importantly, bacterial virulence was also restored in vivo, in the mouse model, by asparagine supplementation. This work unravels thus, for the first time, the importance of asparagine for cytosolicmultiplication of Francisella. Amino acid transporters are likely to constitute underappreciated players in bacterial intracellular parasitism. PMID:24134488

Gesbert, Gael; Ramond, Elodie; Rigard, Mélanie; Frapy, Eric; Dupuis, Marion; Dubail, Iharilalao; Barel, Monique; Henry, Thomas; Meibom, Karin; Charbit, Alain

2014-03-01

278

T-Cell-Independent Humoral Immunity Is Sufficient for Protection against Fatal Intracellular Ehrlichia Infection  

Microsoft Academic Search

Although humoral immunity has been shown to contribute to host defense during intracellular bacterial infections, its role has generally been ancillary. Instead, CD4 T cells are often considered to play the dominant role in protective immunity via their production of type I cytokines. Our studies of highly pathogenic Ehrlichia bacteria isolated from Ixodes ovatus (IOE) reveal, however, that this paradigm

Constantine Bitsaktsis; Bisweswar Nandi; Rachael Racine; Katherine C. MacNamara; Gary Winslow

2007-01-01

279

Analysis of Ten Brucella Genomes Reveals Evidence for Horizontal Gene Transfer Despite a Preferred Intracellular Lifestyle  

Microsoft Academic Search

The facultative intracellular bacterial pathogen Brucella infects a wide range of warm-blooded land and marine vertebrates and causes brucellosis. Currently, there are nine recognized Brucella species based on host preferences and phenotypic differences. The availability of 10 different genomes consisting of two chromosomes and representing six of the species allowed for a detailed comparison among themselves and relatives in the

Alice R. Wattam; Kelly P. Williams; Eric E. Snyder; Nalvo F. Almeida; Maulik Shukla; A. W. Dickerman; O. R. Crasta; R. Kenyon; J. Lu; J. M. Shallom; H. Yoo; T. A. Ficht; R. M. Tsolis; C. Munk; R. Tapia; C. S. Han; J. C. Detter; D. Bruce; T. S. Brettin; Bruno W. Sobral; Stephen M. Boyle; Joao C. Setubal

2009-01-01

280

Comparative Phylogeography in a Specific and Obligate Pollination Antagonism  

PubMed Central

In specific and obligate interactions the nature and abundance of a given species can have important effects on the survival and population dynamics of associated organisms. In a phylogeographic framework, we therefore expect that the fates of organisms interacting specifically are also tightly interrelated. Here we investigate such a scenario by analyzing the genetic structures of species interacting in an obligate plant-insect pollination lure-and-trap antagonism, involving Arum maculatum (Araceae) and its specific psychodid (Diptera) visitors Psychoda phalaenoides and Psycha grisescens. Because the interaction is asymmetric (i.e., only the plant depends on the insect), we expect the genetic structure of the plant to be related with the historical pollinator availability, yielding incongruent phylogeographic patterns between the interacting organisms. Using insect mtDNA sequences and plant AFLP genome fingerprinting, we inferred the large-scale phylogeographies of each species and the distribution of genetic diversities throughout the sampled range, and evaluated the congruence in their respective genetic structures using hierarchical analyses of molecular variances (AMOVA). Because the composition of pollinator species varies in Europe, we also examined its association with the spatial genetic structure of the plant. Our findings indicate that while the plant presents a spatially well-defined genetic structure, this is not the case in the insects. Patterns of genetic diversities also show dissimilar distributions among the three interacting species. Phylogeographic histories of the plant and its pollinating insects are thus not congruent, a result that would indicate that plant and insect lineages do not share the same glacial and postglacial histories. However, the genetic structure of the plant can, at least partially, be explained by the type of pollinators available at a regional scale. Differences in life-history traits of available pollinators might therefore have influenced the genetic structure of the plant, the dependent organism, in this antagonistic interaction.

Espindola, Anahi; Alvarez, Nadir

2011-01-01

281

Palladium-mediated intracellular chemistry  

Microsoft Academic Search

Many important intracellular biochemical reactions are modulated by transition metals, typically in the form of metalloproteins. The ability to carry out selective transformations inside a cell would allow researchers to manipulate or interrogate innumerable biological processes. Here, we show that palladium nanoparticles trapped within polystyrene microspheres can enter cells and mediate a variety of Pd0-catalysed reactions, such as allylcarbamate cleavage

Rahimi M. Yusop; Asier Unciti-Broceta; Emma M. V. Johansson; Rosario M. Sánchez-Martín; Mark Bradley

2011-01-01

282

Intracellular survival of Vibrio anguillarum  

Microsoft Academic Search

The intracellular survival of a Vibrio anguillarum strain, ingested by head kidney phagocytes and peripheral leukocytes of grouper, Epinephelus awoara, was assessed in vitro by comparing with that of V. parahaemolyticus and Staphylococcus albus. There was an increase in numbers of V. alginolyticus in macrophages from head kidney and peripheral leukocytes during the first 30min after infection, followed by a

Wenbo Chen; Yingxue Qin; Qingpi Yan

2010-01-01

283

Structural and functional studies of the early T lymphocyte activation 1 (Eta-1) gene. Definition of a novel T cell-dependent response associated with genetic resistance to bacterial infection  

PubMed Central

We describe a murine cDNA, designated Early T lymphocyte activation 1 (ETA-1) which is abundantly expressed after activation of T cells. Eta- 1 encodes a highly acidic secreted product having structural features of proteins that bind to cellular adhesion receptors. The Eta-1 gene maps to a locus on murine chromosome 5 termed Ric that confers resistance to infection by Rickettsia tsutsugamushi (RT), an obligate intracellular bacterium that is the etiological agent for human scrub typhus. With one exception, inbred mouse strains that expressed the Eta- 1a allele were resistant to RT infection (RicR), and inbred strains expressing the Eta-1b allele were susceptible (RicS). These findings suggest that Eta-1 is the gene inferred from previous studies of the Ric locus (5). Genetic resistance to RT infection is associated with a strong Eta-1 response in vivo and inhibition of early bacterial replication. Eta-1 gene expression appears to be part of a surprisingly rapid T cell-dependent response to bacterial infection that may precede classical forms of T cell-dependent immunity.

1989-01-01

284

QS-type bacterial signal molecules of nonpeptide origin  

Microsoft Academic Search

This review classifies and analyzes the literature data on bacterial autoinducers (AI), the signal molecules produced and\\u000a secreted by bacterial cells and responsible for intercellular communication (quorum sensing, QS). The most important families\\u000a of nonpeptide AI are discussed, including N-acyl homoserine lactones, derivatives of 2-methyl-2,3,4,5-tetrahydroxy tetrahydrofuran, indole and quinoline derivatives,\\u000a and adrenalinerelated compounds. The data is provided on the intracellular

A. O. Shpakov

2009-01-01

285

The role of autophagy in the intracellular survival of Campylobacter concisus  

PubMed Central

Campylobacter concisus is an emerging pathogen that has been associated with gastrointestinal diseases. Given the importance of autophagy for the elimination of intracellular bacteria and the subversion of this process by pathogenic bacteria, we investigated the role of autophagy in C. concisus intracellular survival. Gentamicin protection assays were employed to assess intracellular levels of C. concisus within Caco-2 cells, following autophagy induction and inhibition. To assess the interaction between C. concisus and autophagosomes, confocal microscopy, scanning electron microscopy, and transmission electron microscopy were employed. Expression levels of 84 genes involved in the autophagy process were measured using qPCR. Autophagy inhibition resulted in two- to four-fold increases in intracellular levels of C. concisus within Caco-2 cells, while autophagy induction resulted in a significant reduction in intracellular levels or bacterial clearance. C. concisus strains with low intracellular survival levels showed a dramatic increase in these levels upon autophagy inhibition. Confocal microscopy showed co-localization of the bacterium with autophagosomes, while transmission electron microscopy identified intracellular bacteria persisting within autophagic vesicles. Further, qPCR showed that following infection, 13 genes involved in the autophagy process were significantly regulated, and a further five showed borderline results, with an overall indication towards a dampening effect exerted by the bacterium on this process. Our data collectively indicates that while autophagy is important for the clearance of C. concisus, some strains may manipulate this process to benefit their intracellular survival.

Burgos-Portugal, Jose A.; Mitchell, Hazel M.; Castano-Rodriguez, Natalia; Kaakoush, Nadeem O.

2014-01-01

286

The role of autophagy in the intracellular survival of Campylobacter concisus.  

PubMed

Campylobacter concisus is an emerging pathogen that has been associated with gastrointestinal diseases. Given the importance of autophagy for the elimination of intracellular bacteria and the subversion of this process by pathogenic bacteria, we investigated the role of autophagy in C. concisus intracellular survival. Gentamicin protection assays were employed to assess intracellular levels of C. concisus within Caco-2 cells, following autophagy induction and inhibition. To assess the interaction between C. concisus and autophagosomes, confocal microscopy, scanning electron microscopy, and transmission electron microscopy were employed. Expression levels of 84 genes involved in the autophagy process were measured using qPCR. Autophagy inhibition resulted in two- to four-fold increases in intracellular levels of C. concisus within Caco-2 cells, while autophagy induction resulted in a significant reduction in intracellular levels or bacterial clearance. C. concisus strains with low intracellular survival levels showed a dramatic increase in these levels upon autophagy inhibition. Confocal microscopy showed co-localization of the bacterium with autophagosomes, while transmission electron microscopy identified intracellular bacteria persisting within autophagic vesicles. Further, qPCR showed that following infection, 13 genes involved in the autophagy process were significantly regulated, and a further five showed borderline results, with an overall indication towards a dampening effect exerted by the bacterium on this process. Our data collectively indicates that while autophagy is important for the clearance of C. concisus, some strains may manipulate this process to benefit their intracellular survival. PMID:24918042

Burgos-Portugal, Jose A; Mitchell, Hazel M; Castaño-Rodríguez, Natalia; Kaakoush, Nadeem O

2014-01-01

287

Intracellular Helicobacter pylori in gastric epithelial progenitors  

PubMed Central

Helicobacter pylori is generally viewed as an extracellular pathogen. We have analyzed the tropism of H. pylori clinical isolates in a gnotobiotic transgenic mouse model of human chronic atrophic gastritis, a preneoplastic condition. These mice lack acid-producing parietal cells and have an amplified population of dividing gastric epithelial progenitors (GEPs) that express NeuAc?2,3Gal?1,4-glycans recognized by H. pylori adhesins. Scanning confocal and transmission electron microscopic studies of stomachs that had been colonized for 1 month or 1 year revealed intracellular bacterial collections (IBCs) in a small subset of multi- and oligopotential epithelial progenitors. Transmission electron microscopic and multilabel immunohistochemical analyses disclosed bacteria with several morphotypes, including spiral-shaped, in the cytoplasm and endosomes. Several stages in IBC evolution were documented, from a few solitary bacteria to consolidated populations in dividing and nondividing GEPs, to microorganisms traversing breaches in the GEP plasma cell membrane. IBC formation was not a unique feature of H. pylori strains isolated from patients with chronic atrophic gastritis. The notion that adult mammalian epithelial progenitors can function as a repository for H. pylori broadens the view of host habitats available to this and perhaps other pathogens.

Oh, Jung D.; Karam, Sherif M.; Gordon, Jeffrey I.

2005-01-01

288

Cytochemical Differences in Bacterial Glycocalyx  

NASA Astrophysics Data System (ADS)

To examine new cytochemical aspects of the bacterial adhesion, a strain 41452/01 of the oral commensal Streptococcus sanguis and a wild strain of Staphylococcus aureus were grown with and without sucrose supplementation for 6 days. Osmiumtetraoxyde (OsO4), uranyl acetate (UA), ruthenium red (RR), cupromeronic blue (CB) staining with critical electrolytic concentrations (CECs), and the tannic acid-metal salt technique (TAMST) were applied for electron microscopy. Cytochemically, only RR-positive fimbriae in S. sanguis were visualized. By contrast, some types of fimbriae staining were observed in S. aureus glycocalyx: RR-positive, OsO4-positive, tannophilic and CB-positive with ceasing point at 0.3 M MgCl2. The CB staining with CEC, used for the first time for visualization of glycoproteins of bacterial glycocalyx, also reveals intacellular CB-positive substances-probably the monomeric molecules, that is, subunits forming the fimbriae via extracellular assembly. Thus, glycosylated components of the biofilm matrix can be reliably related to single cells. The visualization of intracellular components by CB with CEC enables clear distinction between S. aureus and other bacteria, which do not produce CB-positive substances. The small quantities of tannophilic substances found in S. aureus makes the use of TAMST for the same purpose difficult. The present work protocol enables, for the first time, a partial cytochemical differentiation of the bacterial glycocalyx.

Krautgartner, Wolf Dietrich; Vitkov, Ljubomir; Hannig, Matthias; Pelz, Klaus; Stoiber, Walter

2005-02-01

289

Bacterial communities of two parthenogenetic aphid species cocolonizing two host plants across the Hawaiian Islands.  

PubMed

Aphids (Hemiptera: Aphididae) have been the focus of several studies with respect to their interactions with inherited symbionts, but bacterial communities of most aphid species are still poorly characterized. In this research, we used bar-coded pyrosequencing to characterize bacterial communities in aphids. Specifically, we examined the diversity of bacteria in two obligately parthenogenetic aphid species (the melon aphid, Aphis gossypii, and the cardamom aphid, Pentalonia caladii) cocolonizing two plant species (taro, Colocasia esculenta, and ginger, Alpinia purpurata) across four Hawaiian Islands (Hawaii, Kauai, Maui, and Oahu). Results from this study revealed that heritable symbionts dominated the bacterial communities for both aphid species. The bacterial communities differed significantly between the two species, and A. gossypii harbored a more diverse bacterial community than P. caladii. The bacterial communities also differed across aphid populations sampled from the different islands; however, communities did not differ between aphids collected from the two host plants. PMID:21965398

Jones, Ryan T; Bressan, Alberto; Greenwell, April M; Fierer, Noah

2011-12-01

290

Bacterial Communities of Two Parthenogenetic Aphid Species Cocolonizing Two Host Plants across the Hawaiian Islands ?  

PubMed Central

Aphids (Hemiptera: Aphididae) have been the focus of several studies with respect to their interactions with inherited symbionts, but bacterial communities of most aphid species are still poorly characterized. In this research, we used bar-coded pyrosequencing to characterize bacterial communities in aphids. Specifically, we examined the diversity of bacteria in two obligately parthenogenetic aphid species (the melon aphid, Aphis gossypii, and the cardamom aphid, Pentalonia caladii) cocolonizing two plant species (taro, Colocasia esculenta, and ginger, Alpinia purpurata) across four Hawaiian Islands (Hawaii, Kauai, Maui, and Oahu). Results from this study revealed that heritable symbionts dominated the bacterial communities for both aphid species. The bacterial communities differed significantly between the two species, and A. gossypii harbored a more diverse bacterial community than P. caladii. The bacterial communities also differed across aphid populations sampled from the different islands; however, communities did not differ between aphids collected from the two host plants.

Jones, Ryan T.; Bressan, Alberto; Greenwell, April M.; Fierer, Noah

2011-01-01

291

Acquisition of nutrients by Chlamydiae: unique challenges of living in an intracellular compartment  

PubMed Central

Summary The Chlamydiae are obligate intracellular pathogen that replicate within a membrane-bound vacuole, termed the “inclusion”. From this compartment, bacteria acquire essential nutrients by selectively redirecting transport vesicles and hijacking intracellular organelles. Re-routing is achieved by several mechanisms including proteolysis-mediated fragmentation of the Golgi apparatus, recruitment of Rab GTPases and SNAREs, and translocation of cytoplasmic organelles into the inclusion lumen. Given Chlamydiae’s extended co-evolution with eukaryotic cells, it is likely that co-option of multiple cellular pathways is a strategy to provide redundancy in the acquisition of essential nutrients from the host and has contributed to the success of these highly adapted pathogens.

Saka, Hector Alex; Valdivia, Raphael H.

2011-01-01

292

Cytotoxic Cells Kill Intracellular Bacteria through Granulysin-Mediated Delivery of Granzymes.  

PubMed

When killer lymphocytes recognize infected cells, perforin delivers cytotoxic proteases (granzymes) into the target cell to trigger apoptosis. What happens to intracellular bacteria during this process is unclear. Human, but not rodent, cytotoxic granules also contain granulysin, an antimicrobial peptide. Here, we show that granulysin delivers granzymes into bacteria to kill diverse bacterial strains. In Escherichia coli, granzymes cleave electron transport chain complex I and oxidative stress defense proteins, generating reactive oxygen species (ROS) that rapidly kill bacteria. ROS scavengers and bacterial antioxidant protein overexpression inhibit bacterial death. Bacteria overexpressing a GzmB-uncleavable mutant of the complex I subunit nuoF or strains that lack complex I still die, but more slowly, suggesting that granzymes disrupt multiple vital bacterial pathways. Mice expressing transgenic granulysin are better able to clear Listeria monocytogenes. Thus killer cells play an unexpected role in bacterial defense. PMID:24906149

Walch, Michael; Dotiwala, Farokh; Mulik, Sachin; Thiery, Jerome; Kirchhausen, Tomas; Clayberger, Carol; Krensky, Alan M; Martinvalet, Denis; Lieberman, Judy

2014-06-01

293

Bacterial vaginosis.  

PubMed Central

Bacterial vaginosis (BV) is the most common of the vaginitides affecting women of reproductive age. It appears to be due to an alteration in the vaginal ecology by which Lactobacillus spp., the predominant organisms in the healthy vagina, are replaced by a mixed flora including Prevotella bivia, Prevotella disiens, Porphyromonas spp., Mobiluncus spp., and Peptostreptococcus spp. All of these organisms except Mobiluncus spp. are also members of the endogenous vaginal flora. While evidence from treatment trials does not support the notion that BV is sexually transmitted, recent studies have shown an increased risk associated with multiple sexual partners. It has also been suggested that the pathogenesis of BV may be similar to that of urinary tract infections, with the rectum serving as a reservoir for some BV-associated flora. The organisms associated with BV have also been recognized as agents of female upper genital tract infection, including pelvic inflammatory disease, and the syndrome BV has been associated with adverse outcome of pregnancy, including premature rupture of membranes, chorioamnionitis, and fetal loss; postpartum endometritis; cuff cellulitis; and urinary tract infections. The mechanisms by which the BV-associated flora causes the signs of BV are not well understood, but a role for H2O2-producing Lactobacillus spp. in protecting against colonization by catalase-negative anaerobic bacteria has been recognized. These and other aspects of BV are reviewed.

Spiegel, C A

1991-01-01

294

Enzymatic Permeabilization of the Thecate Dinoflagellate Alexandrium minutum (Dinophyceae) Yields Detection of Intracellularly Associated Bacteria via Catalyzed Reporter Deposition-Fluorescence In Situ Hybridization  

Microsoft Academic Search

The enzymatic permeabilization procedure described here allows the detection of intracellular bacteria in the thecate dinoflagellate Alexandrium minutum by using catalyzed reporter deposition-fluorescence in situ hybridization. The combined use of propidium iodide and calcofluor for confocal laser scanning microscopy, together with general and specific fluorescent bacterial probes, demonstrated the intracellular presence of bacteria, including members of the phylum Bacteroidetes.

L. Palacios; I. Marin

2008-01-01

295

Enzymatic Permeabilization of the Thecate Dinoflagellate Alexandrium minutum (Dinophyceae) Yields Detection of Intracellularly Associated Bacteria via Catalyzed Reporter Deposition-Fluorescence In Situ Hybridization?  

PubMed Central

The enzymatic permeabilization procedure described here allows the detection of intracellular bacteria in the thecate dinoflagellate Alexandrium minutum by using catalyzed reporter deposition-fluorescence in situ hybridization. The combined use of propidium iodide and calcofluor for confocal laser scanning microscopy, together with general and specific fluorescent bacterial probes, demonstrated the intracellular presence of bacteria, including members of the phylum Bacteroidetes.

Palacios, Lucia; Marin, Irma

2008-01-01

296

Enzymatic permeabilization of the thecate dinoflagellate Alexandrium minutum (Dinophyceae) yields detection of intracellularly associated bacteria via catalyzed reporter deposition-fluorescence in situ hybridization.  

PubMed

The enzymatic permeabilization procedure described here allows the detection of intracellular bacteria in the thecate dinoflagellate Alexandrium minutum by using catalyzed reporter deposition-fluorescence in situ hybridization. The combined use of propidium iodide and calcofluor for confocal laser scanning microscopy, together with general and specific fluorescent bacterial probes, demonstrated the intracellular presence of bacteria, including members of the phylum Bacteroidetes. PMID:18263745

Palacios, Lucía; Marín, Irma

2008-04-01

297

Contractual obligations and the sharing of confidential health information in sport  

Microsoft Academic Search

As an employee, a sports doctor has obligations to their employer, but also professional and widely accepted obligations of a doctor to the patient (in this case the individual team member). The conflict is evident when sports doctors are asked by an athlete to keep personal health information confidential from the coach and team management, and yet both doctor and

L Anderson

2008-01-01

298

Limiting the Scope of Moral Obligations to Help: A Cross-Cultural Investigation.  

ERIC Educational Resources Information Center

Surveyed U.S. and Indian college students regarding the moral obligation to save someone's life by donating bone marrow. Indians were more likely to consider donation morally required. Both groups limited obligation to help out-group members. Indians regarded donating more highly when it arose from duty. Americans regarded donating more highly…

Baron, Jonathan; Miller, Joan G.

2000-01-01

299

Newcomer Psychological Contracts and Employee Socialization Activities: Does Perceived Balance in Obligations Matter?  

ERIC Educational Resources Information Center

We sought to determine the extent to which one's beliefs about the relationship between an employee and an organization at the start of employment influence subsequent socialization activities. The balance of employee exchange relationships, employee perceptions of both their own obligations and the employers' obligations, were collected from 120…

Payne, Stephanie C.; Culbertson, Satoris S.; Boswell, Wendy R.; Barger, Eric J.

2008-01-01

300

Extending XACML authorisation model to support policy obligations handling in distributed application  

Microsoft Academic Search

The paper summarises the recent developments and discussions in the Grid and networking security community to build interoperable and scalable authorisation infrastructure for distributed applications. The paper provides a short overview of the XACML policy format and policy obligations definition in the XACML specification. The paper analyses the basic use cases for obligations in computer Grids and on-demand network resource

Yuri Demchenko; Oscar Koeroo; Cees De Laat; Hakon Sagehaug

2008-01-01

301

The Role of Family Obligations and School Adjustment in Explaining the Immigrant Paradox  

ERIC Educational Resources Information Center

This study examined the role of family obligations and school adjustment in explaining immigrant adolescents' adaptation. Despite a relatively low socio-economic status, immigrant adolescents have been found to have a pattern of adaptation superior to that of national adolescents. Immigrant adolescents' strong sense of family obligations and…

van Geel, Mitch; Vedder, Paul

2011-01-01

302

Mass public health programmes and the obligations of sponsoring and participating organisations  

Microsoft Academic Search

The obligations of organisations associated with policy formation and implementation of international mass public health programmes are explored. Lines of responsibility are considered to become unclear because of the large number of agencies associated with such programmes. A separation of the relevant obligations among the bodies responsible for the formulation (usually an international non-governmental organisation) and those responsible for the

A Dawson; Y Paul

2006-01-01

303

26 CFR 1.103-16 - Obligations of certain volunteer fire departments.  

Code of Federal Regulations, 2013 CFR

...equipment not to be used in providing fire fighting services, interest on the obligation...obligation for funds to purchase a new fire truck, a new ambulance, and rescue equipment not to be used for fighting fires. Funds to be used for the...

2013-04-01

304

42 CFR 52b.7 - How is the grantee obligated to use the facility?  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false How is the grantee obligated to use the facility? 52b.7...CONSTRUCTION GRANTS § 52b.7 How is the grantee obligated to use the facility? (a) The grantee shall use the facility (or that...

2012-10-01

305

42 CFR 52b.7 - How is the grantee obligated to use the facility?  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false How is the grantee obligated to use the facility? 52b.7...CONSTRUCTION GRANTS § 52b.7 How is the grantee obligated to use the facility? (a) The grantee shall use the facility (or that...

2013-10-01

306

The Lived Experience of How Adult Nursing Students Blend Lifestyle Obligations with Nursing School Expectations  

ERIC Educational Resources Information Center

Many adult nursing students have lifestyle obligations that require integration with nursing school programs in order to graduate and fulfill their dreams of becoming a nurse. Fourteen participants shared their stories of how they were able to blend their lifestyles commitments with nursing school. Student interaction between lifestyle obligations

Coutrier, Karen A.

2011-01-01

307

31 CFR 203.6 - Obligations of TT&L depositaries.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Obligations of TT&L depositaries. 203.6 Section 203.6 Money and...General Information § 203.6 Obligations of TT&L depositaries. A TT&L depositary must: (a) Administer a TIP main...

2013-07-01

308

14 CFR 240.2 - Obligation of air carriers, foreign air carriers, and ticket agents.  

Code of Federal Regulations, 2011 CFR

...2014-01-01 2014-01-01 false Obligation of air carriers, foreign air carriers, and ticket agents. 240.2 Section 240...OF ACCOUNTS AND PROPERTY § 240.2 Obligation of air carriers, foreign air carriers, and ticket...

2014-01-01

309

Health professionals' enactment of their accountability obligations: Doing the best they can  

Microsoft Academic Search

In the current context of health care, health professionals' accountability obligations may be more extensive than the degree of autonomy that they are permitted to exercise. To date, how professionals fulfil their obligations with regard to this potential for dissonance has not been investigated. The purpose of this Grounded Theory study was to examine how one professional group, occupational therapists,

Andrew R. Freeman; Carol L. McWilliam; Joyce R. MacKinnon; Sandra DeLuca; Susan G. Rappolt

2009-01-01

310

42 CFR 62.11 - When can a scholarship program payment obligation be discharged in bankruptcy?  

Code of Federal Regulations, 2011 CFR

In accordance with section 754(d)(3) of the Act, any payment obligation incurred under § 62.10 may not be discharged in bankruptcy under title XI of the United States Code until 5 years after the date on which the payment obligation is...

2012-10-01

311

Conceptualising Hy-Bivalent Subjectivities to Facilitate an Examination of Australian Government Mutual Obligations Policies  

ERIC Educational Resources Information Center

This paper illustrates how the work of feminist theorists Valerie Walkerdine, Helen Lucey and June Melody, Beverly Skeggs, and Nancy Fraser were used together to examine the lived effects of Australian government Mutual Obligations policies. As "active" welfare policies, Mutual Obligations construct particular relations between themselves and…

Edwards, Jan

2006-01-01

312

Cognitive Representations of Obligation and Prohibition Signs when They Provide the Same Amount of Semantic Information  

ERIC Educational Resources Information Center

The aim of this research was to test whether there is an inherent difficulty in understanding prohibition signs rather than obligation signs. In the experiment conducted, participants decided whether simple car movements presented on a computer screen were allowed or not according to either obligation or prohibition traffic signs. The information…

Castro, C.; Moreno-Rios, S.; Tornay, F. J.

2012-01-01

313

An Extended Role-Based Access Control Model for Delegating Obligations  

NASA Astrophysics Data System (ADS)

The main aim of access control models is to provide means to simplify the management of the security policy, which is a fastidious and error-prone task. Supporting delegation is considered as an important mean to decentralize the administration and therefore to allow security policy to be more flexible and easier to manipulate. Our main contribution is the proposition of a unified model to the administration and delegation of obligations. Managing such delegations implies more requirements than managing traditional privileges delegation. In fact, delegating obligations may include two interpretations: the delegation of the obligation and the delegation of the responsibility related to this obligation. Therefore, it is important to deal with these two notions separately. Moreover, since delegating an obligation involves the delegation of sanctions, then the consent of the user who receives this delegation may be required in some cases. We address in this paper these requirements and we propose a formalism to deal with them.

Ben-Ghorbel-Talbi, Meriam; Cuppens, Frédéric; Cuppens-Boulahia, Nora; Bouhoula, Adel

314

Observer perceptions of moral obligations in groups with a history of victimization.  

PubMed

The authors investigated when observers assign contemporary group members moral obligations based on their group's victimization history. In Experiment 1, Americans perceived Israelis as obligated to help Sudanese genocide victims and as guiltworthy for not helping if reminded of the Holocaust and its descendants were linked to this history. In Experiment 2, participants perceived Israelis as more obligated to help and guiltworthy for not helping when the Holocaust was presented as a unique victimization event compared with when genocide was presented as pervasive. Experiments 3 and 4 replicated the effects of Experiment 1 with Cambodians as the victimized group. Experiment 5 demonstrated that participants perceived Cambodians as having more obligations under high just world threat compared with low just world threat. Perceiving victimized groups as incurring obligations is one just world restoration method of providing meaning to collective injustice. PMID:22427385

Warner, Ruth H; Branscombe, Nyla R

2012-07-01

315

Microsporidia Are Natural Intracellular Parasites of the Nematode Caenorhabditis elegans  

PubMed Central

For decades the soil nematode Caenorhabditis elegans has been an important model system for biology, but little is known about its natural ecology. Recently, C. elegans has become the focus of studies of innate immunity and several pathogens have been shown to cause lethal intestinal infections in C. elegans. However none of these pathogens has been shown to invade nematode intestinal cells, and no pathogen has been isolated from wild-caught C. elegans. Here we describe an intracellular pathogen isolated from wild-caught C. elegans that we show is a new species of microsporidia. Microsporidia comprise a large class of eukaryotic intracellular parasites that are medically and agriculturally important, but poorly understood. We show that microsporidian infection of the C. elegans intestine proceeds through distinct stages and is transmitted horizontally. Disruption of a conserved cytoskeletal structure in the intestine called the terminal web correlates with the release of microsporidian spores from infected cells, and appears to be part of a novel mechanism by which intracellular pathogens exit from infected cells. Unlike in bacterial intestinal infections, the p38 MAPK and insulin/insulin-like growth factor (IGF) signaling pathways do not appear to play substantial roles in resistance to microsporidian infection in C. elegans. We found microsporidia in multiple wild-caught isolates of Caenorhabditis nematodes from diverse geographic locations. These results indicate that microsporidia are common parasites of C. elegans in the wild. In addition, the interaction between C. elegans and its natural microsporidian parasites provides a system in which to dissect intracellular intestinal infection in vivo and insight into the diversity of pathogenic mechanisms used by intracellular microbes.

Troemel, Emily R; Felix, Marie-Anne; Whiteman, Noah K; Barriere, Antoine; Ausubel, Frederick M

2008-01-01

316

Bacterial concrete  

NASA Astrophysics Data System (ADS)

Cracks in concrete are inevitable and are one of the inherent weaknesses of concrete. Water and other salts seep through these cracks, corrosion initiates, and thus reduces the life of concrete. So there was a need to develop an inherent biomaterial, a self-repairing material which can remediate the cracks and fissures in concrete. Bacterial concrete is a material, which can successfully remediate cracks in concrete. This technique is highly desirable because the mineral precipitation induced as a result of microbial activities is pollution free and natural. As the cell wall of bacteria is anionic, metal accumulation (calcite) on the surface of the wall is substantial, thus the entire cell becomes crystalline and they eventually plug the pores and cracks in concrete. This paper discusses the plugging of artificially cracked cement mortar using Bacillus Pasteurii and Sporosarcina bacteria combined with sand as a filling material in artificially made cuts in cement mortar which was cured in urea and CaCl2 medium. The effect on the compressive strength and stiffness of the cement mortar cubes due to the mixing of bacteria is also discussed in this paper. It was found that use of bacteria improves the stiffness and compressive strength of concrete. Scanning electron microscope (SEM) is used to document the role of bacteria in microbiologically induced mineral precipitation. Rod like impressions were found on the face of calcite crystals indicating the presence of bacteria in those places. Energy- dispersive X-ray (EDX) spectra of the microbial precipitation on the surface of the crack indicated the abundance of calcium and the precipitation was inferred to be calcite (CaCO3).

Ramakrishnan, Venkataswamy; Ramesh, K. P.; Bang, S. S.

2001-04-01

317

Settling Down: The Genome of Serratia symbiotica from the Aphid Cinara tujafilina Zooms in on the Process of Accommodation to a Cooperative Intracellular Life.  

PubMed

Particularly interesting cases of mutualistic endosymbioses come from the establishment of co-obligate associations of more than one species of endosymbiotic bacteria. Throughout symbiotic accommodation from a free-living bacterium, passing through a facultative stage and ending as an obligate intracellular one, the symbiont experiences massive genomic losses and phenotypic adjustments. Here, we scrutinized the changes in the coevolution of Serratia symbiotica and Buchnera aphidicola endosymbionts in aphids, paying particular attention to the transformations undergone by S. symbiotica to become an obligate endosymbiont. Although it is already known that S. symbiotica is facultative in Acyrthosiphon pisum, in Cinara cedri it has established a co-obligate endosymbiotic consortium along with B. aphidicola to fulfill the aphid's nutritional requirements. The state of this association in C. tujafilina, an aphid belonging to the same subfamily (Lachninae) that C. cedri, remained unknown. Here, we report the genome of S. symbiotica strain SCt-VLC from the aphid C. tujafilina. While being phylogenetically and genomically very closely related to the facultative endosymbiont S. symbiotica from the aphid A. pisum, it shows a variety of metabolic, genetic, and architectural features, which point toward this endosymbiont being one step closer to an obligate intracellular one. We also describe in depth the process of genome rearrangements suffered by S. symbiotica and the role mobile elements play in gene inactivations. Finally, we postulate the supply to the host of the essential riboflavin (vitamin B2) as key to the establishment of S. symbiotica as a co-obligate endosymbiont in the aphids belonging to the subfamily Lachninane. PMID:24951564

Manzano-Marín, Alejandro; Latorre, Amparo

2014-01-01

318

Bacterial start site prediction  

Microsoft Academic Search

With the growing number of completely sequenced bacterial genes, accurate gene prediction in bacterial genomes remains an important problem. Although the existing tools predict genes in bacterial genomes with high overall accuracy, their ability to pinpoint the translation start site remains unsatisfactory. In this paper, we present a novel approach to bacterial start site prediction that takes into account multiple

Sridhar S. Hannenhalli; William S. Hayes; Artemis G. Hatzigeorgiou; James W. Fickett

1999-01-01

319

DNA topology and adaptation of Salmonella typhimurium to an intracellular environment.  

PubMed Central

The expression of genes coding for determinants of DNA topology in the facultative intracellular pathogen Salmonella typhimurium was studied during adaptation by the bacteria to the intracellular environment of J774A.1 macrophage-like cells. A reporter plasmid was used to monitor changes in DNA supercoiling during intracellular growth. Induction of the dps and spv genes, previously shown to be induced in the macrophage, was detected, as was expression of genes coding for DNA gyrase, integration host factor and the nucleoid-associated protein H-NS. The topA gene, coding for the DNA relaxing enzyme topoisomerase I, was not induced. Reporter plasmid data showed that bacterial DNA became relaxed following uptake of S. typhimurium cells by the macrophage. These data indicate that DNA topology in S. typhimurium undergoes significant changes during adaptation to the intracellular environment. A model describing how this process may operate is discussed.

Marshall, D G; Bowe, F; Hale, C; Dougan, G; Dorman, C J

2000-01-01

320

Stochastic models of intracellular transport  

NASA Astrophysics Data System (ADS)

The interior of a living cell is a crowded, heterogenuous, fluctuating environment. Hence, a major challenge in modeling intracellular transport is to analyze stochastic processes within complex environments. Broadly speaking, there are two basic mechanisms for intracellular transport: passive diffusion and motor-driven active transport. Diffusive transport can be formulated in terms of the motion of an overdamped Brownian particle. On the other hand, active transport requires chemical energy, usually in the form of adenosine triphosphate hydrolysis, and can be direction specific, allowing biomolecules to be transported long distances; this is particularly important in neurons due to their complex geometry. In this review a wide range of analytical methods and models of intracellular transport is presented. In the case of diffusive transport, narrow escape problems, diffusion to a small target, confined and single-file diffusion, homogenization theory, and fractional diffusion are considered. In the case of active transport, Brownian ratchets, random walk models, exclusion processes, random intermittent search processes, quasi-steady-state reduction methods, and mean-field approximations are considered. Applications include receptor trafficking, axonal transport, membrane diffusion, nuclear transport, protein-DNA interactions, virus trafficking, and the self-organization of subcellular structures.

Bressloff, Paul C.; Newby, Jay M.

2013-01-01

321

Unprecedented loss of ammonia assimilation capability in a urease-encoding bacterial mutualist  

PubMed Central

Background Blochmannia are obligately intracellular bacterial mutualists of ants of the tribe Camponotini. Blochmannia perform key nutritional functions for the host, including synthesis of several essential amino acids. We used Illumina technology to sequence the genome of Blochmannia associated with Camponotus vafer. Results Although Blochmannia vafer retains many nutritional functions, it is missing glutamine synthetase (glnA), a component of the nitrogen recycling pathway encoded by the previously sequenced B. floridanus and B. pennsylvanicus. With the exception of Ureaplasma, B. vafer is the only sequenced bacterium to date that encodes urease but lacks the ability to assimilate ammonia into glutamine or glutamate. Loss of glnA occurred in a deletion hotspot near the putative replication origin. Overall, compared to the likely gene set of their common ancestor, 31 genes are missing or eroded in B. vafer, compared to 28 in B. floridanus and four in B. pennsylvanicus. Three genes (queA, visC and yggS) show convergent loss or erosion, suggesting relaxed selection for their functions. Eight B. vafer genes contain frameshifts in homopolymeric tracts that may be corrected by transcriptional slippage. Two of these encode DNA replication proteins: dnaX, which we infer is also frameshifted in B. floridanus, and dnaG. Conclusions Comparing the B. vafer genome with B. pennsylvanicus and B. floridanus refines the core genes shared within the mutualist group, thereby clarifying functions required across ant host species. This third genome also allows us to track gene loss and erosion in a phylogenetic context to more fully understand processes of genome reduction.

2010-01-01

322

29 CFR 37.16 - What is this part's effect on a recipient's obligations under other laws, and what limitations...  

Code of Federal Regulations, 2013 CFR

...effect on a recipient's obligations under other laws, and what limitations...effect on a recipient's obligations under other laws, and what limitations...or her race, color, religion, sex, national origin, age, disability, political...

2013-07-01

323

Obligation of Funds for Ship Maintenance and Repair at the U.S. Pacific Fleet Maintenance Activities.  

National Technical Information Service (NTIS)

Our overall audit objective was to evaluate whether the Department of the Navy correctly obligated funds for ship maintenance and repair. Specifically, we determined whether the Department of the Navy obligated funds for ship maintenance and repair in acc...

2008-01-01

324

43 CFR 3137.74 - What must I do after BLM approves my continuing development obligations plan?  

Code of Federal Regulations, 2013 CFR

...after BLM approves my continuing development obligations plan? 3137.74...Petroleum Reserve-Alaska Development Requirements § 3137.74 ...after BLM approves my continuing development obligations plan? No...

2013-10-01

325

26 CFR 1.6049-6 - Statements to recipients of interest payments and holders of obligations for attributed original...  

Code of Federal Regulations, 2013 CFR

...obligations for attributed original issue discount. 1.6049-6 Section 1.6049-6...obligations for attributed original issue discount. (a) Requirement of furnishing statement...interest (other than original issue discount) to any person during a calendar...

2013-04-01

326

45 CFR 2553.83 - What financial obligation does the Corporation incur for non-Corporation funded projects?  

Code of Federal Regulations, 2010 CFR

...Welfare 4 2009-10-01 2009-10-01 false What financial obligation does the Corporation incur for non-Corporation... Non-Corporation Funded Projects § 2553.83 What financial obligation does the Corporation incur for...

2009-10-01

327

45 CFR 2552.113 - What financial obligation does the Corporation incur for non-Corporation funded projects?  

Code of Federal Regulations, 2010 CFR

...Welfare 4 2009-10-01 2009-10-01 false What financial obligation does the Corporation incur for non-Corporation...Foster Grandparent Program Projects § 2552.113 What financial obligation does the Corporation incur for...

2009-10-01

328

45 CFR 2553.83 - What financial obligation does the Corporation incur for non-Corporation funded projects?  

Code of Federal Regulations, 2010 CFR

...Welfare 4 2010-10-01 2010-10-01 false What financial obligation does the Corporation incur for non-Corporation... Non-Corporation Funded Projects § 2553.83 What financial obligation does the Corporation incur for...

2010-10-01

329

45 CFR 2552.113 - What financial obligation does the Corporation incur for non-Corporation funded projects?  

Code of Federal Regulations, 2010 CFR

...Welfare 4 2010-10-01 2010-10-01 false What financial obligation does the Corporation incur for non-Corporation...Foster Grandparent Program Projects § 2552.113 What financial obligation does the Corporation incur for...

2010-10-01

330

26 CFR 5f.103-1 - Obligations issued after December 31, 1982, required to be in registered form.  

Code of Federal Regulations, 2010 CFR

... Obligations issued after December 31, 1982, required to be in registered form. ...TAX EQUITY AND FISCAL RESPONSIBILITY ACT OF 1982 § 5f.103-1 Obligations issued after December 31, 1982, required to be in registered form....

2009-04-01

331

26 CFR 5f.103-1 - Obligations issued after December 31, 1982, required to be in registered form.  

Code of Federal Regulations, 2010 CFR

... Obligations issued after December 31, 1982, required to be in registered form. ...TAX EQUITY AND FISCAL RESPONSIBILITY ACT OF 1982 § 5f.103-1 Obligations issued after December 31, 1982, required to be in registered form....

2010-04-01

332

31 CFR 1060.300 - Reporting obligations on foreign bank relationships with Iranian-linked financial institutions...  

Code of Federal Regulations, 2013 CFR

...false Reporting obligations on foreign bank relationships with Iranian-linked financial...300 Reporting obligations on foreign bank relationships with Iranian-linked financial...receiving a written request from FinCEN, a bank (as defined in 31 CFR...

2013-07-01

333

31 CFR 354.2 - Law governing rights and obligations of Federal Reserve Banks, and Sallie Mae; rights of any...  

Code of Federal Regulations, 2013 CFR

...rights and obligations of Federal Reserve Banks, and Sallie Mae; rights of any Person against Federal Reserve Banks and Sallie Mae. 354.2 Section 354...rights and obligations of Federal Reserve Banks, and Sallie Mae; rights of any...

2013-07-01

334

24 CFR 81.92 - Law governing rights and obligations of United States, Federal Reserve Banks, and GSEs; rights of...  

Code of Federal Regulations, 2013 CFR

...obligations of United States, Federal Reserve Banks, and GSEs; rights of any Person against United States, Federal Reserve Banks, and GSEs; Law governing other interests...obligations of United States, Federal Reserve Banks, and GSEs; rights of any Person...

2013-04-01

335

Forest-obligate Sabethes mosquitoes suggest palaeoecological perturbations.  

PubMed

The origin of tropical forest diversity has been hotly debated for decades. Although specific mechanisms vary, many such explanations propose some vicariance in the distribution of species during glacial cycles and several have been supported by genetic evidence in Neotropical taxa. However, no consensus exists with regard to the extent or time frame of the vicariance events. Here, we analyse the cytochrome oxidase II mitochondrial gene of 250 Sabethes albiprivus B mosquitoes sampled from western Sao Paulo in Brazil. There was very low population structuring among collection sites (Phi(ST)=0.03, P=0.04). Historic demographic analyses and the contemporary geographic distribution of genetic diversity suggest that the populations sampled are not at demographic equilibrium. Three distinct mitochondrial clades were observed in the samples, one of which differed significantly in its geographic distribution relative to the other two within a small sampling area (approximately 70 x 35 km). This fact, supported by the inability of maximum likelihood analyses to achieve adequate fits to simple models for the population demography of the species, suggests a more complex history, possibly involving disjunct forest refugia. This hypothesis is supported by a genetic signal of recent population growth, which is expected if population sizes of this forest-obligate insect increased during the forest expansions that followed glacial periods. Although a time frame cannot be reliably inferred for the vicariance event leading to the three genetic clades, molecular clock estimates place this at approximately 1 Myr before present. PMID:18506202

Pedro, P M; Sallum, M A; Butlin, R K

2008-08-01

336

Health facilities' obligations when a patient refuses treatment.  

PubMed

Recent cases involving the decisions of Elizabeth Bouvia and G. Ross Henninger to starve themselves to death highlight the ethical obligations of patients, health care facilities, and the courts. When a patient seeks the hospital's cooperation in his or her attempt to commit suicide, society's responsibility is not merely to restrain the patient from suicide but to offer physical care, financial aid, and personal support. The hospital's duty is to intervene, and the court's responsibility is to allow such intervention. The most compassionate way in which the hospital can help is to force-feed the patient. If a patient is mentally competent, the refusal to eat is morally wrong. The patient is morally not permitted to commit suicide, though the avoidance of treatment may be justified in cases when force-feeding would be considered an extraordinary means, because of the patient's age or physical condition, for example. If a patient is incompetent, the refusal to eat is not a fully rational act; for the hospital to refrain from force-feeding would not be considered cooperation in suicide, since the incompetent patient cannot commit suicide. To avoid court rulings that order compliance with a patient's wishes, health care facilities in the future may have to require patients or their families to agree in writing to treatment by ordinary means. PMID:10268324

Gallagher, J

1984-09-01

337

The 'obligate diploid' Candida albicans forms mating-competent haploids.  

PubMed

Candida albicans, the most prevalent human fungal pathogen, is considered to be an obligate diploid that carries recessive lethal mutations throughout the genome. Here we demonstrate that C. albicans has a viable haploid state that can be derived from diploid cells under in vitro and in vivo conditions, and that seems to arise through a concerted chromosome loss mechanism. Haploids undergo morphogenetic changes like those of diploids, including the yeast-hyphal transition, chlamydospore formation and a white-opaque switch that facilitates mating. Haploid opaque cells of opposite mating type mate efficiently to regenerate the diploid form, restoring heterozygosity and fitness. Homozygous diploids arise spontaneously by auto-diploidization, and both haploids and auto-diploids show a similar reduction in fitness, in vitro and in vivo, relative to heterozygous diploids, indicating that homozygous cell types are transient in mixed populations. Finally, we constructed stable haploid strains with multiple auxotrophies that will facilitate molecular and genetic analyses of this important pathogen. PMID:23364695

Hickman, Meleah A; Zeng, Guisheng; Forche, Anja; Hirakawa, Matthew P; Abbey, Darren; Harrison, Benjamin D; Wang, Yan-Ming; Su, Ching-hua; Bennett, Richard J; Wang, Yue; Berman, Judith

2013-02-01

338

Managing Incidental Genomic Findings: Legal Obligations of Clinicians  

PubMed Central

Purpose Clinical whole exome and whole genome sequencing will result in a broad range of incidental findings (IFs), but clinicians’ obligations to identify and disclose such findings are a matter of debate. We sought legal cases that could offer insights into clinicians’ legal liability. Methods We searched for cases in which IFs were related to the cause of action, using the search engines WestLaw, WestLaw Next, Lexis, and Lexis Advance. Results We found no case law related to IFs from genetic testing, but identified eight cases involving IFs in medical imaging. These cases suggest that clinicians may face liability for failing to disclose IFs that would have offered an opportunity for interventions to improve health outcome, if (1) under the applicable standard of care, they fail to identify or appreciate the significance of the IF; or 2) they negligently fail to notify other clinicians and/or the patient of the identified IF. Other cases support liability for failure to refer appropriately to a clinician with greater expertise. Conclusions Clinicians may face liability if they fail to disclose incidental information that could inform interventions to improve health outcome; information lacking clinical actionability is likely to have less import.

Clayton, Ellen Wright; Haga, Susanne; Kuszler, Patricia; Bane, Emily; Shutske, Krysta; Burke, Wylie

2013-01-01

339

Bacterial elicitation and evasion of plant innate immunity  

Microsoft Academic Search

Recent research on plant responses to bacterial attack has identified extracellular and intracellular host receptors that recognize conserved pathogen-associated molecular patterns and more specialized virulence proteins, respectively. These findings have shed light on our understanding of the molecular mechanisms by which bacteria elicit host defences and how pathogens have evolved to evade or suppress these defences.

Robert B. Abramovitch; Jeffrey C. Anderson; Gregory B. Martin

2006-01-01

340

Bacterial elicitation and evasion of plant innate immunity  

PubMed Central

Recent research on plant responses to bacterial attack has identified extracellular and intracellular host receptors that recognize conserved pathogen-associated molecular patterns and more specialized virulence proteins, respectively. These findings have shed light on our understanding of the molecular mechanisms by which bacteria elicit host defences and how pathogens have evolved to evade or suppress these defences.

Abramovitch, Robert B.; Anderson, Jeffrey C.; Martin, Gregory B.

2010-01-01

341

The effects of macrophage source on the mechanism of phagocytosis and intracellular survival of Leishmania  

PubMed Central

Leishmania spp. protozoa are obligate intracellular parasites that replicate in macrophages during mammalian infection. Efficient phagocytosis and survival in macrophages are important determinants of parasite virulence. Macrophage lines differ dramatically in their ability to sustain intracellular Leishmania infantum chagasi (Lic). We report that the U937 monocytic cell line supported the intracellular replication and cell-to-cell spread of Lic during 72 hours after parasite addition, whereas primary human monocyte-derived macrophages (MDMs) did not. Electron microscopy and live cell imaging illustrated that Lic promastigotes anchored to MDMs via their anterior ends and were engulfed through symmetrical pseudopods. In contrast, U937 cells bound Lic in diverse orientations, and extended membrane lamellae to reorient and internalize parasites through coiling phagocytosis. Lic associated tightly with the parasitophorous vacuole (PV) membrane in both cell types. PVs fused with LAMP-1-expressing compartments 24 hours after phagocytosis by MDMs, whereas U937 cell PVs remained LAMP-1 negative. The expression of one phagocytic receptor (CR3) was higher in MDMs than U937 cells, leading us to speculate that parasite uptake proceeds through dissimilar pathways between these cells. We hypothesize that the mechanism of phagocytosis differs between primary versus immortalized human macrophage cells, with corresponding differences in the subsequent intracellular fate of the parasite.

Hsiao, Chia-Hung Christine; Ueno, Norikiyo; Shao, Jian Q.; Schroeder, Kristin R.; Moore, Kenneth C.; Donelson, John E.; Wilson, Mary E.

2011-01-01

342

Cyclic Dimeric GMP Signaling Regulates Intracellular Aggregation, Sessility, and Growth of Ehrlichia chaffeensis ? §  

PubMed Central

Cyclic dimeric GMP (c-di-GMP), a bacterial second messenger, is known to regulate bacterial biofilm and sessility. Replication of an obligatory intracellular pathogen, Ehrlichia chaffeensis, is characterized by formation of bacterial aggregates called morulae inside membrane-bound inclusions. When E. chaffeensis matures into an infectious form, morulae become loose to allow bacteria to exit from host cells to infect adjacent cells. E. chaffeensis expresses a sensor kinase, PleC, and a cognate response regulator, PleD, which can produce c-di-GMP. A hydrophobic c-di-GMP antagonist, 2?-O-di(tert-butyldimethysilyl)-c-di-GMP (CDGA) inhibits E. chaffeensis internalization into host cells by facilitating degradation of some bacterial surface proteins via endogenous serine proteases. In the present study, we found that PleC and PleD were upregulated synchronously during exponential growth of bacteria, concomitant with increased morula size. While CDGA did not affect host cells, when infected cells were treated with CDGA, bacterial proliferation was inhibited, morulae became less compact, and the intracellular movement of bacteria was enhanced. Concurrently, CDGA treatment facilitated the extracellular release of bacteria with lower infectivity than those spontaneously released from sham-treated cells. Addition of CDGA to isolated inclusions induced dispersion of the morulae, degradation of an inclusion matrix protein TRP120, and bacterial intrainclusion movement, all of which were blocked by a serine protease inhibitor. These results suggest that c-di-GMP signaling regulates aggregation and sessility of E. chaffeensis within the inclusion through stabilization of matrix proteins by preventing the serine protease activity, which is associated with bacterial intracellular proliferation and maturation.

Kumagai, Yumi; Matsuo, Junji; Cheng, Zhihui; Hayakawa, Yoshihiro; Rikihisa, Yasuko

2011-01-01

343

Influence of dTMP on the Phenotypic Appearance and Intracellular Persistence of Staphylococcus aureus?  

PubMed Central

Thymidine-dependent small-colony variants (SCVs) of Staphylococcus aureus are frequently associated with persistent and recurrent infections in cystic fibrosis patients. The phenotypic appearance of S. aureus SCVs or normal-colony variants (NCVs) is postulated to be affected by the intracellular amount of dTMP. This hypothesis was proven by metabolic pathway assays revealing altered intracellular dTMP concentrations, followed by investigation of the associated phenotype. Inhibition of the staphylococcal thymidylate synthase, which generated intracellular dTMP from dUMP, using 5-fluorouracil and co-trimoxazole resulted in an SCV phenotype. Inhibition of a nucleoside transporter, which provided the bacterial cell with extracellular thymidine, caused growth inhibition of SCVs. In turn, reversion of SCVs to NCVs was achieved by supplying extracellular dTMP. High-performance liquid chromatography additionally confirmed the intracellular lack of dTMP in SCVs, in contrast to NCVs. Moreover, the dTMP concentration is postulated to influence the intracellular persistence of S. aureus. Cell culture experiments with cystic fibrosis cells revealed that clinical and co-trimoxazole-induced SCVs with a diminished amount of dTMP showed significantly better intracellular persistence than NCVs. In conclusion, these results show that the dTMP concentration plays a key role in both the phenotypic appearance and the intracellular persistence of S. aureus.

Zander, Johannes; Besier, Silke; Saum, Stephan H.; Dehghani, Faramarz; Loitsch, Stefan; Brade, Volker; Wichelhaus, Thomas A.

2008-01-01

344

Bacterial synthesis of biodegradable polyhydroxyalkanoates.  

PubMed

Various bacterial species accumulate intracellular polyhydroxyalkanoates (PHAs) granules as energy and carbon reserves inside their cells. PHAs are biodegradable, environmentally friendly and biocompatible thermoplastics. Varying in toughness and flexibility, depending on their formulation, they can be used in various ways similar to many nonbiodegradable petrochemical plastics currently in use. They can be used either in pure form or as additives to oil-derived plastics such as polyethylene. However, these bioplastics are currently far more expensive than petrochemically based plastics and are therefore used mostly in applications that conventional plastics cannot perform, such as medical applications. PHAs are immunologically inert and are only slowly degraded in human tissue, which means they can be used as devices inside the body. Recent research has focused on the use of alternative substrates, novel extraction methods, genetically enhanced species and mixed cultures with a view to make PHAs more commercially attractive. PMID:17578408

Verlinden, R A J; Hill, D J; Kenward, M A; Williams, C D; Radecka, I

2007-06-01

345

INsPECT, an open-source and versatile software for automated quantification of (Leishmania) intracellular parasites.  

PubMed

Intracellular protozoan parasites are causative agents of infectious diseases that constitute major health problems for developing countries. Leishmania sp., Trypanosoma cruzi or Toxoplasma gondii are all obligate intracellular protozoan parasites that reside and multiply within the host cells of mammals, including humans. Following up intracellular parasite proliferation is therefore an essential and a quotidian task for many laboratories working on primary screening of new natural and synthetic drugs, analyzing drug susceptibility or comparing virulence properties of natural and genetically modified strains. Nevertheless, laborious manual microscopic counting of intracellular parasites is still the most commonly used approach. Here, we present INsPECT (Intracellular ParasitE CounTer), an open-source and platform independent software dedicated to automate infection level measurement based on fluorescent DNA staining. It offers the possibility to choose between different types of analyses (fluorescent DNA acquisitions only or in combination with phase contrast image set to further separate intra- from extracellular parasites), and software running modes (automatic or custom). A proof-of-concept study with intracellular Leishmania infantum parasites stained with DAPI (4',6-diamidino-2-phenylindole) confirms a good correspondence between digital results and the "gold standard" microscopic counting method with Giemsa. Interestingly, this software is versatile enough to accurately detect intracellular T. gondii parasites on images acquired with High Content Screening (HCS) systems. In conclusion, INsPECT software is proposed as a new fast and simple alternative to the classical intracellular Leishmania quantification methods and can be adapted for mid to large-scale drug screening against different intracellular parasites. PMID:24831235

Yazdanparast, Ehsan; Dos Anjos, Antonio; Garcia, Deborah; Loeuillet, Corinne; Shahbazkia, Hamid Reza; Vergnes, Baptiste

2014-05-01

346

INsPECT, an Open-Source and Versatile Software for Automated Quantification of (Leishmania) Intracellular Parasites  

PubMed Central

Intracellular protozoan parasites are causative agents of infectious diseases that constitute major health problems for developing countries. Leishmania sp., Trypanosoma cruzi or Toxoplasma gondii are all obligate intracellular protozoan parasites that reside and multiply within the host cells of mammals, including humans. Following up intracellular parasite proliferation is therefore an essential and a quotidian task for many laboratories working on primary screening of new natural and synthetic drugs, analyzing drug susceptibility or comparing virulence properties of natural and genetically modified strains. Nevertheless, laborious manual microscopic counting of intracellular parasites is still the most commonly used approach. Here, we present INsPECT (Intracellular ParasitE CounTer), an open-source and platform independent software dedicated to automate infection level measurement based on fluorescent DNA staining. It offers the possibility to choose between different types of analyses (fluorescent DNA acquisitions only or in combination with phase contrast image set to further separate intra- from extracellular parasites), and software running modes (automatic or custom). A proof-of-concept study with intracellular Leishmania infantum parasites stained with DAPI (4?,6-diamidino-2-phenylindole) confirms a good correspondence between digital results and the “gold standard” microscopic counting method with Giemsa. Interestingly, this software is versatile enough to accurately detect intracellular T. gondii parasites on images acquired with High Content Screening (HCS) systems. In conclusion, INsPECT software is proposed as a new fast and simple alternative to the classical intracellular Leishmania quantification methods and can be adapted for mid to large-scale drug screening against different intracellular parasites.

Yazdanparast, Ehsan; Dos Anjos, Antonio; Garcia, Deborah; Loeuillet, Corinne; Shahbazkia, Hamid Reza; Vergnes, Baptiste

2014-01-01

347

Forced resurgence and targeting of intracellular uropathogenic Escherichia coli reservoirs.  

PubMed

Intracellular quiescent reservoirs of uropathogenic Escherichia coli (UPEC), which can seed the bladder mucosa during the acute phase of a urinary tract infection (UTI), are protected from antibiotic treatments and are extremely difficult to eliminate. These reservoirs are a potential source for recurrent UTIs that affect millions annually. Here, using murine infection models and the bladder cell exfoliant chitosan, we demonstrate that intracellular UPEC populations shift within the stratified layers of the urothelium during the course of a UTI. Following invasion of the terminally differentiated superficial layer of epithelial cells that line the bladder lumen, UPEC can multiply and disseminate, eventually establishing reservoirs within underlying immature host cells. If given access, UPEC can invade the superficial and immature bladder cells equally well. As infected immature host cells differentiate and migrate towards the apical surface of the bladder, UPEC can reinitiate growth and discharge into the bladder lumen. By inducing the exfoliation of the superficial layers of the urothelium, chitosan stimulates rapid regenerative processes and the reactivation and efflux of quiescent intracellular UPEC reservoirs. When combined with antibiotics, chitosan treatment significantly reduces bacterial loads within the bladder and may therefore be of therapeutic value to individuals with chronic, recurrent UTIs. PMID:24667805

Blango, Matthew G; Ott, Elizabeth M; Erman, Andreja; Veranic, Peter; Mulvey, Matthew A

2014-01-01

348

Forced Resurgence and Targeting of Intracellular Uropathogenic Escherichia coli Reservoirs  

PubMed Central

Intracellular quiescent reservoirs of uropathogenic Escherichia coli (UPEC), which can seed the bladder mucosa during the acute phase of a urinary tract infection (UTI), are protected from antibiotic treatments and are extremely difficult to eliminate. These reservoirs are a potential source for recurrent UTIs that affect millions annually. Here, using murine infection models and the bladder cell exfoliant chitosan, we demonstrate that intracellular UPEC populations shift within the stratified layers of the urothelium during the course of a UTI. Following invasion of the terminally differentiated superficial layer of epithelial cells that line the bladder lumen, UPEC can multiply and disseminate, eventually establishing reservoirs within underlying immature host cells. If given access, UPEC can invade the superficial and immature bladder cells equally well. As infected immature host cells differentiate and migrate towards the apical surface of the bladder, UPEC can reinitiate growth and discharge into the bladder lumen. By inducing the exfoliation of the superficial layers of the urothelium, chitosan stimulates rapid regenerative processes and the reactivation and efflux of quiescent intracellular UPEC reservoirs. When combined with antibiotics, chitosan treatment significantly reduces bacterial loads within the bladder and may therefore be of therapeutic value to individuals with chronic, recurrent UTIs.

Blango, Matthew G.; Ott, Elizabeth M.; Erman, Andreja; Veranic, Peter; Mulvey, Matthew A.

2014-01-01

349

The Legionella effector RidL inhibits retrograde trafficking to promote intracellular replication.  

PubMed

The bacteria causing Legionnaires' disease, Legionella pneumophila, replicate intracellularly within unique Legionella-containing vacuoles (LCVs). LCV formation involves a type IV secretion system (T4SS) that translocates effector proteins into host cells. We show that the T4SS effector RidL localizes to LCVs, supports intracellular bacterial growth, and alters retrograde trafficking, in which selected proteins are transported from endosomes to the Golgi. The retromer complex that mediates retrograde trafficking localizes to LCVs independently of RidL and restricts intracellular bacterial growth. RidL binds the Vps29 retromer subunit and the lipid PtdIns(3)P, which localizes retromer components to membranes. Additionally, specific retromer cargo receptors and sorting nexins that mediate protein capture and membrane remodeling preferentially localize to LCVs in the absence of ridL. Ectopic RidL production inhibits retrograde trafficking, and L. pneumophila blocks retrograde transport at endosome exit sites in a ridL-dependent manner. Collectively, these findings suggest that RidL inhibits retromer function to promote intracellular bacterial replication. PMID:23870312

Finsel, Ivo; Ragaz, Curdin; Hoffmann, Christine; Harrison, Christopher F; Weber, Stephen; van Rahden, Vanessa A; Johannes, Ludger; Hilbi, Hubert

2013-07-17

350

31 CFR 225.3 - Pledge of Government obligations in lieu of a bond with surety or sureties.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Pledge of Government obligations in lieu of a bond with surety or...ACCEPTANCE OF BONDS SECURED BY GOVERNMENT OBLIGATIONS IN LIEU OF BONDS WITH SURETIES § 225.3 Pledge of Government obligations in lieu of a bond with surety...

2010-07-01

351

31 CFR 225.3 - Pledge of Government obligations in lieu of a bond with surety or sureties.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Pledge of Government obligations in lieu of a bond with surety or...ACCEPTANCE OF BONDS SECURED BY GOVERNMENT OBLIGATIONS IN LIEU OF BONDS WITH SURETIES § 225.3 Pledge of Government obligations in lieu of a bond with surety...

2009-07-01

352

Protein intrinsic disorder in the acetylome of intracellular and extracellular Toxoplasma gondii.  

PubMed

Toxoplasma gondii is an obligate intracellular parasite of the phylum Apicomplexa, which includes a number of species of medical and veterinary importance. Inhibitors of lysine deacetylases (KDACs) exhibit potent antiparasitic activity, suggesting that interference with lysine acetylation pathways holds promise for future drug targeting. Using high resolution LC-MS/MS to identify parasite peptides enriched by immunopurification with acetyl-lysine antibody, we recently produced an acetylome of the proliferative intracellular stage of Toxoplasma. In this study, we used similar approaches to greatly expand the Toxoplasma acetylome by identifying acetylated proteins in non-replicating extracellular tachyzoites. The functional breakdown of acetylated proteins in extracellular parasites is similar to intracellular parasites, with an enrichment of proteins involved in metabolism, translation, and chromatin biology. Altogether, we have now detected over 700 acetylation sites on a wide variety of parasite proteins of diverse function in multiple subcellular compartments. We found 96 proteins uniquely acetylated in intracellular parasites, 216 uniquely acetylated in extracellular parasites, and 177 proteins acetylated in both states. Our findings suggest that dramatic changes occur at the proteomic level as tachyzoites transition from the intracellular to the extracellular environment, similar to reports documenting significant changes in gene expression during this transition. The expanded dataset also allowed a thorough analysis of the degree of protein intrinsic disorder surrounding lysine residues targeted for this post-translational modification. These analyses indicate that acetylated lysines in proteins from extracellular and intracellular tachyzoites are largely located within similar local environments, and that lysine acetylation preferentially occurs in intrinsically disordered or flexible regions. PMID:23403842

Xue, Bin; Jeffers, Victoria; Sullivan, William J; Uversky, Vladimir N

2013-04-01

353

Protein intrinsic disorder in the acetylome of intracellular and extracellular Toxoplasma gondii  

PubMed Central

Toxoplasma gondii is an obligate intracellular parasite of the phylum Apicomplexa, which includes a number of species of medical and veterinary importance. Inhibitors of lysine deacetylases (KDACs) exhibit potent antiparasitic activity, suggesting that interference with lysine acetylation pathways hold promise for future drug targeting. Using high resolution LC-MS/MS to identify parasite peptides enriched by immunopurification with acetyl-lysine antibody, we recently produced an acetylome of the proliferative intracellular stage of Toxoplasma. In this study, we used similar approaches to greatly expand the Toxoplasma acetylome by identifying acetylated proteins in non-replicating extracellular tachyzoites. The functional breakdown of acetylated proteins in extracellular parasites is similar to intracellular parasites, with an enrichment of proteins involved in metabolism, translation, and chromatin biology. Altogether, we have now detected over 700 acetylation sites on a wide variety of parasite proteins of diverse function in multiple subcellular compartments. We found 96 proteins uniquely acetylated in intracellular parasites, 216 uniquely acetylated in extracellular parasites, and 177 proteins acetylated in both states. Our findings suggest that dramatic changes occur at the proteomic level as tachyzoites transition from the intracellular to extracellular environment, similar to reports documenting significant changes in gene expression during this transition. The expanded dataset also allowed a thorough analysis of the degree of protein intrinsic disorder surrounding lysine residues targeted for this post-translational modification. These analyses indicate that acetylated lysines in proteins from extracellular and intracellular tachyzoites are largely located within similar local environments, and that lysine acetylation preferentially occurs in intrinsically disordered or flexible regions.

Xue, Bin; Jeffers, Victoria; Sullivan, William J.; Uversky, Vladimir N.

2013-01-01

354

Intracellular ion channels and cancer  

PubMed Central

Several types of channels play a role in the maintenance of ion homeostasis in subcellular organelles including endoplasmatic reticulum, nucleus, lysosome, endosome, and mitochondria. Here we give a brief overview of the contribution of various mitochondrial and other organellar channels to cancer cell proliferation or death. Much attention is focused on channels involved in intracellular calcium signaling and on ion fluxes in the ATP-producing organelle mitochondria. Mitochondrial K+ channels (Ca2+-dependent BKCa and IKCa, ATP-dependent KATP, Kv1.3, two-pore TWIK-related Acid-Sensitive K+ channel-3 (TASK-3)), Ca2+ uniporter MCU, Mg2+-permeable Mrs2, anion channels (voltage-dependent chloride channel VDAC, intracellular chloride channel CLIC) and the Permeability Transition Pore (MPTP) contribute importantly to the regulation of function in this organelle. Since mitochondria play a central role in apoptosis, modulation of their ion channels by pharmacological means may lead to death of cancer cells. The nuclear potassium channel Kv10.1 and the nuclear chloride channel CLIC4 as well as the endoplasmatic reticulum (ER)-located inositol 1,4,5-trisphosphate (IP3) receptor, the ER-located Ca2+ depletion sensor STIM1 (stromal interaction molecule 1), a component of the store-operated Ca2+ channel and the ER-resident TRPM8 are also mentioned. Furthermore, pharmacological tools affecting organellar channels and modulating cancer cell survival are discussed. The channels described in this review are summarized on Figure 1. Overall, the view is emerging that intracellular ion channels may represent a promising target for cancer treatment.

Leanza, Luigi; Biasutto, Lucia; Manago, Antonella; Gulbins, Erich; Zoratti, Mario; Szabo, Ildiko

2013-01-01

355

Modelling intracellular H(+) ion diffusion.  

PubMed

Intracellular pH, an important modulator of cell function, is regulated by plasmalemmal proteins that transport H(+), or its equivalent, into or out of the cell. The pH(i) is also stabilised by high-capacity, intrinsic buffering on cytoplasmic proteins, oligopeptides and other solutes, and by the extrinsic CO(2)/HCO(3)(-) (carbonic) buffer. As mobility of these buffers is lower than for the H(+) ion, they restrict proton diffusion. In this paper we use computational approaches, based on the finite difference and finite element methods (FDM and FEM, respectively), for analysing the spatio-temporal behaviour of [H(+)] when it is locally perturbed. We analyse experimental data obtained for various cell-types (cardiac myocytes, duodenal enterocytes, molluscan neurons) where pH(i) has been imaged confocally using intracellular pH-sensitive dyes. We design mathematical algorithms to generate solutions for two-dimensional diffusion that fit data in terms of an apparent intracellular H(+) diffusion coefficient, D(H)(app). The models are used to explore how the spatial distribution of [H(+)](i) is affected by membrane H(+)-equivalent transport and by cell geometry. We then develop a mechanistic model, describing spatio-temporal changes of [H(+)](i) in a cardiac ventricular myocyte in terms of H(+)-shuttling on mobile buffers and H(+)-anchoring on fixed buffers. We also discuss how modelling may include the effects of extrinsic carbonic-buffering. Overall, our computational approach provides a framework for future analyses of the physiological consequences of pH(i) non-uniformity. PMID:12865074

Swietach, Pawel; Zaniboni, Massimiliano; Stewart, Andrew K; Rossini, Alessandra; Spitzer, Kenneth W; Vaughan-Jones, Richard D

2003-10-01

356

Pharmacology of intracellular signalling pathways  

PubMed Central

This article provides a brief and somewhat personalized review of the dramatic developments that have occurred over the last 45 years in our understanding of intracellular signalling pathways associated with G-protein-coupled receptor activation. Signalling via cyclic AMP, the phosphoinositides and Ca2+ is emphasized and these systems have already been revealed as new pharmacological targets. The therapeutic benefits of most of such targets are, however, yet to be realized, but it is certain that the discipline of pharmacology needs to widen its boundaries to meet these challenges in the future.

Nahorski, Stefan R

2006-01-01

357

Barcoding Hedgehog for Intracellular Transport  

NSDL National Science Digital Library

Hedgehog, an essential protein for the development of many vertebrate and invertebrate organs, signals at both short and long distances to control growth and patterning. The mechanism by which it moves between source and target cells is not known, but characterization of the covalent modification of its N terminus with palmitate and of its C terminus with cholesterol has led to the suggestion that the lipophilic properties of the modified protein serve to regulate movement after its secretion into the extracellular space. Another interpretation and model is that the C-terminal cholesterol acts to target Hedgehog to an intracellular trafficking pathway that prepares Hedgehog for release in an encapsulated form.

Thomas B. Kornberg (San Francisco;University of California REV)

2011-11-22

358

Direct measurement of intracellular pressure.  

PubMed

A method to directly measure the intracellular pressure of adherent, migrating cells is described in this unit. This approach is based on the servo-null method where a microelectrode is introduced into the cell to directly measure the physical pressure of the cytoplasm. We also describe the initial calibration of the microelectrode, as well as the application of the method to cells migrating inside three-dimensional (3-D) extracellular matrix (ECM). Curr. Protoc. Cell Biol. 63:12.9.1-12.9.9. © 2014 by John Wiley & Sons, Inc. PMID:24894836

Petrie, Ryan J; Koo, Hyun

2014-01-01

359

Federal Funds for Research and Development: Federal Obligations for Research by Agency and Detailed Field of S&E: Fiscal Years 1970-2000  

NSF Publications Database

... Format Federal Funds for Research and Development: Federal Obligations for Research by Agency and ... pdf) Federal Funds for Research and Development: Federal Obligations for Research by Agency and ...

360

Federal Funds for Research and Development: Federal Obligations for Research to Universities and Colleges by Agency and Detailed Field of S&E: Fiscal Years 1973-2000  

NSF Publications Database

... Format Federal Funds for Research and Development: Federal Obligations for Research to Universities ... pdf) Federal Funds for Research and Development: Federal Obligations for Research to Universities ...

361

Federal Funds for Research and Development: Federal Obligations for Research to Universities and Colleges by Agency and Detailed Field of Science and Engineering: Fiscal Years 1973-2001  

NSF Publications Database

... Format Federal Funds for Research and Development: Federal Obligations for Research to Universities ... pdf) Federal Funds for Research and Development: Federal Obligations for Research to Universities ...

362

Pulmonary abnormalities in obligate heterozygotes for cystic fibrosis.  

PubMed Central

Parents of children with cystic fibrosis have been reported to have a high prevalence of increased airway reactivity, but these studies were done in a select young, healthy, symptomless population. In the present study respiratory symptoms were examined in 315 unselected parents of children with cystic fibrosis and 162 parents of children with congenital heart disease (controls). The cardinal symptom of airway reactivity, wheezing, was somewhat more prevalent in cystic fibrosis parents than in controls, but for most subgroups this increased prevalence did not reach statistical significance. Among those who had never smoked, 38% of obligate heterozygotes for cystic fibrosis but only 25% of the controls reported wheezing (p less than 0.05). The cystic fibrosis parents who had never smoked but reported wheezing had lower FEV1 and FEF25-75, expressed as a percentage of the predicted value, than control parents; and an appreciable portion of the variance in pulmonary function was contributed by the interaction of heterozygosity for cystic fibrosis with wheezing. For cystic fibrosis parents, but not controls, the complaint of wheezing significantly contributed to the prediction of pulmonary function (FEV1 and FEF25-75). In addition, parents of children with cystic fibrosis reported having lung disease before the age of 16 more than twice as frequently as control parents. Other respiratory complaints, including dyspnoea, cough, bronchitis, and hay fever, were as common in controls as in cystic fibrosis heterozygotes. These data are consistent with the hypothesis that heterozygosity for cystic fibrosis is associated with increased airway reactivity and its symptoms, and that the cystic fibrosis heterozygotes who manifest airway reactivity and its symptoms may be at risk for poor pulmonary function.

Davis, P B; Vargo, K

1987-01-01

363

The Chlamydia psittaci Genome: A Comparative Analysis of Intracellular Pathogens  

PubMed Central

Background Chlamydiaceae are a family of obligate intracellular pathogens causing a wide range of diseases in animals and humans, and facing unique evolutionary constraints not encountered by free-living prokaryotes. To investigate genomic aspects of infection, virulence and host preference we have sequenced Chlamydia psittaci, the pathogenic agent of ornithosis. Results A comparison of the genome of the avian Chlamydia psittaci isolate 6BC with the genomes of other chlamydial species, C. trachomatis, C. muridarum, C. pneumoniae, C. abortus, C. felis and C. caviae, revealed a high level of sequence conservation and synteny across taxa, with the major exception of the human pathogen C. trachomatis. Important differences manifest in the polymorphic membrane protein family specific for the Chlamydiae and in the highly variable chlamydial plasticity zone. We identified a number of psittaci-specific polymorphic membrane proteins of the G family that may be related to differences in host-range and/or virulence as compared to closely related Chlamydiaceae. We calculated non-synonymous to synonymous substitution rate ratios for pairs of orthologous genes to identify putative targets of adaptive evolution and predicted type III secreted effector proteins. Conclusions This study is the first detailed analysis of the Chlamydia psittaci genome sequence. It provides insights in the genome architecture of C. psittaci and proposes a number of novel candidate genes mostly of yet unknown function that may be important for pathogen-host interactions.

Saluz, Hans Peter

2012-01-01

364

Intracellular Proton Access in a Cl?/H+ Antiporter  

PubMed Central

Chloride-transporting membrane proteins of the CLC family appear in two distinct mechanistic flavors: H+-gated Cl? channels and Cl?/H+ antiporters. Transmembrane H+ movement is an essential feature of both types of CLC. X-ray crystal structures of CLC antiporters show the Cl? ion pathway through these proteins, but the H+ pathway is known only inferentially by two conserved glutamate residues that act as way-stations for H+ in its path through the protein. The extracellular-facing H+ transfer glutamate becomes directly exposed to aqueous solution during the transport cycle, but the intracellular glutamate E203, Gluin, is buried within the protein. Two regions, denoted “polar” and “interfacial,” at the intracellular surface of the bacterial antiporter CLC-ec1 are examined here as possible pathways by which intracellular aqueous protons gain access to Gluin. Mutations at multiple residues of the polar region have little effect on antiport rates. In contrast, mutation of E202, a conserved glutamate at the protein–water boundary of the interfacial region, leads to severe slowing of the Cl?/H+ antiport rate. An X-ray crystal structure of E202Y, the most strongly inhibited of these substitutions, shows an aqueous portal leading to Gluin physically blocked by cross-subunit interactions; moreover, this mutation has only minimal effect on a monomeric CLC variant, which necessarily lacks such interactions. The several lines of experiments presented argue that E202 acts as a water-organizer that creates a proton conduit connecting intracellular solvent with Gluin.

Lim, Hyun-Ho; Shane, Tania; Miller, Christopher

2012-01-01

365

Real-Time monitoring of intracellular wax ester metabolism  

PubMed Central

Background Wax esters are industrially relevant molecules exploited in several applications of oleochemistry and food industry. At the moment, the production processes mostly rely on chemical synthesis from rather expensive starting materials, and therefore solutions are sought from biotechnology. Bacterial wax esters are attractive alternatives, and especially the wax ester metabolism of Acinetobacter sp. has been extensively studied. However, the lack of suitable tools for rapid and simple monitoring of wax ester metabolism in vivo has partly restricted the screening and analyses of potential hosts and optimal conditions. Results Based on sensitive and specific detection of intracellular long-chain aldehydes, specific intermediates of wax ester synthesis, bacterial luciferase (LuxAB) was exploited in studying the wax ester metabolism in Acinetobacter baylyi ADP1. Luminescence was detected in the cultivation of the strain producing wax esters, and the changes in signal levels could be linked to corresponding cell growth and wax ester synthesis phases. Conclusions The monitoring system showed correlation between wax ester synthesis pattern and luminescent signal. The system shows potential for real-time screening purposes and studies on bacterial wax esters, revealing new aspects to dynamics and role of wax ester metabolism in bacteria.

2011-01-01

366

16 CFR 240.11 - Wholesaler or third party performance of seller's obligations.  

Code of Federal Regulations, 2010 CFR

...Commercial Practices FEDERAL TRADE COMMISSION GUIDES AND TRADE PRACTICE RULES GUIDES FOR ADVERTISING ALLOWANCES AND OTHER MERCHANDISING PAYMENTS AND SERVICES § 240.11 Wholesaler or third party performance of seller's obligations. A seller may...

2010-01-01

367

31 CFR 547.407 - Payments from blocked accounts to satisfy obligations prohibited.  

Code of Federal Regulations, 2010 CFR

...Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY DEMOCRATIC REPUBLIC OF THE CONGO SANCTIONS REGULATIONS Interpretations § 547.407 Payments from blocked accounts to satisfy obligations...

2010-07-01

368

Federal Academic Science and Engineering Obligations Up More Than 6 Percent in FY 1998  

NSF Publications Database

... This Data Brief presents Federal academic science and engineering obligations data from 19 agencies ... Nonprofit Institutions. In this annual survey, data are collected on Federal S&E support by funding ...

369

Signatures of adaptation to obligate biotrophy in the Hyaloperonospora arabidopsidis genome  

PubMed Central

Many oomycete and fungal plant pathogens are obligate biotrophs, which extract nutrients only from living plant tissue and cannot grow apart from their hosts. Although these pathogens cause significant crop losses, little is known about the molecular basis or evolution of obligate biotrophy. Here, we report the genome sequence of the oomycete Hyaloperonospora arabidopsidis (Hpa), an obligate biotroph and natural pathogen of Arabidopsis thaliana. In comparison to genomes of related, hemi-biotrophic Phytophthora species, the Hpa genome exhibits dramatic reductions in genes encoding: 1) RXLR effectors and other secreted pathogenicity proteins; 2) enzymes for assimilation of inorganic nitrogen and sulphur; 3) proteins associated with zoospore formation and motility. These attributes comprise a genomic signature of evolution towards obligate biotrophy.

Ishaque, Naveed; Boot, Nico; Cabral, Adriana; Kemen, Eric; Thines, Marco; Ah-Fong, Audrey; Anderson, Ryan; Badejoko, Wole; Bittner-Eddy, Peter; Boore, Jeffrey L.; Chibucos, Marcus C.; Coates, Mary; Dehal, Paramvir; Delehaunty, Kim; Dong, Suomeng; Downton, Polly; Dumas, Bernard; Fabro, Georgina; Fronick, Catrina; Fuerstenberg, Susan I.; Fulton, Lucinda; Gaulin, Elodie; Govers, Francine; Hughes, Linda; Humphray, Sean; Jiang, Rays H. Y.; Judelson, Howard; Kamoun, Sophien; Kyung, Kim; Meijer, Harold; Minx, Patrick; Morris, Paul; Nelson, Joanne; Phuntumart, Vipa; Qutob, Dinah; Rehmany, Anne; Rougon-Cardoso, Alejandra; Ryden, Peter; Torto-Alalibo, Trudy; Studholme, David; Wang, Yuanchao; Win, Joe; Wood, Jo; Clifton, Sandra W.; Rogers, Jane; Van den Ackerveken, Guido; Jones, Jonathan D. G.; McDowell, John M.; Beynon, Jim; Tyler, Brett M.

2014-01-01

370

77 FR 11345 - Harmonization of Compliance Obligations for Registered Investment Companies Required To Register...  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION 17 CFR Part 4 Harmonization of Compliance Obligations for Registered Investment...proposing certain provisions to facilitate compliance by registered investment companies with...Proposed Changes to Registration and Compliance Regime for Commodity Pool...

2012-02-24

371

76 FR 56271 - Notice of Release From Federal Grant Assurance Obligations for Livermore Municipal Airport...  

Federal Register 2010, 2011, 2012, 2013

...Assurance Obligations for Livermore Municipal Airport, Livermore, CA AGENCY: Federal Aviation...ACTION: Notice of request to release airport land...release of approximately 4.5 acres of airport property at the Livermore Municipal...

2011-09-12

372

75 FR 70081 - Notice of Release From Federal Grant Assurance Obligations for Tucson International Airport...  

Federal Register 2010, 2011, 2012, 2013

...Assurance Obligations for Tucson International Airport, Tucson, AZ AGENCY: Federal Aviation...ACTION: Notice of request to release airport land...of approximately 2,000 square feet of airport property at Tucson International...

2010-11-16

373

77 FR 12906 - Notice of Release From Federal Grant Assurance Obligations at Fresno Yosemite International...  

Federal Register 2010, 2011, 2012, 2013

...Obligations at Fresno Yosemite International Airport, Fresno, CA AGENCY: Federal Aviation...ACTION: Notice of request to release airport land...release of approximately 16.02 acres of airport property at the Fresno Yosemite...

2012-03-02

374

78 FR 8220 - Notice of Release From Quitclaim Deed and Federal Grant Assurance Obligations for Delano...  

Federal Register 2010, 2011, 2012, 2013

...Assurance Obligations for Delano Municipal Airport, Delano, CA AGENCY: Federal Aviation...ACTION: Notice of Request to Release Airport Land...release of approximately 9.89 acres of airport property at Delano Municipal...

2013-02-05

375

76 FR 36482 - Affirmative Action and Nondiscrimination Obligations of Contractors and Subcontractors Regarding...  

Federal Register 2010, 2011, 2012, 2013

...and 60-300 RIN 1250-AA00 Affirmative Action and Nondiscrimination Obligations...regulations implementing the affirmative action provisions of the Vietnam Era...proposed rule entitled ``Affirmative Action and Nondiscrimination...

2011-06-22

376

77 FR 7108 - Affirmative Action and Nondiscrimination Obligations of Contractors and Subcontractors Regarding...  

Federal Register 2010, 2011, 2012, 2013

...Part 60-741 RIN 1250-AA02 Affirmative Action and Nondiscrimination Obligations...implementing the nondiscrimination and affirmative action regulations of section 503...proposed rule entitled, ``Affirmative Action and Nondiscrimination...

2012-02-10

377

45 CFR 660.5 - What is the Director's obligation with respect to Federal interagency coordination?  

Code of Federal Regulations, 2013 CFR

...5 Public Welfare Regulations Relating to Public Welfare (Continued) NATIONAL SCIENCE FOUNDATION INTERGOVERNMENTAL REVIEW OF THE NATIONAL SCIENCE FOUNDATION PROGRAMS AND ACTIVITIES § 660.5 What is the Director's obligation...

2013-10-01

378

43 CFR 3287.2 - When may BLM grant a suspension of unit obligations?  

Code of Federal Regulations, 2013 CFR

...suspension of initial drilling obligations due to a unit operator's inability to obtain an electrical sales contract, or when poor economics affect the electrical generation market, limiting the opportunity to obtain a viable sales contract. BLM may grant a...

2013-10-01

379

76 FR 74721 - Reexamination of Roaming Obligations of Commercial Mobile Radio Service Providers and Other...  

Federal Register 2010, 2011, 2012, 2013

...Reexamination of Roaming Obligations of Commercial Mobile Radio Service Providers and Other Providers of Mobile Data Services AGENCY: Federal Communications...facilities-based providers of commercial mobile data services to offer data roaming...

2011-12-01

380

76 FR 63561 - Reexamination of Roaming Obligations of Commercial Mobile Radio Service Providers and Other...  

Federal Register 2010, 2011, 2012, 2013

...Reexamination of Roaming Obligations of Commercial Mobile Radio Service Providers and Other Providers of Mobile Data Services; Public Information Collection...resolving data roaming disputes with commercial mobile data service providers. DATES: 47 CFR...

2011-10-13

381

20 CFR 655.22 - Obligations of H-2B employers.  

Code of Federal Regulations, 2010 CFR

...EMPLOYMENT OF FOREIGN WORKERS IN THE UNITED STATES...United States (H-2B Workers) § 655.22 Obligations...offering terms and working conditions normal to U.S. workers similarly employed...national origin, age, sex, religion,...

2010-04-01

382

20 CFR 655.22 - Obligations of H-2B employers.  

Code of Federal Regulations, 2010 CFR

...EMPLOYMENT OF FOREIGN WORKERS IN THE UNITED STATES...United States (H-2B Workers) § 655.22 Obligations...offering terms and working conditions normal to U.S. workers similarly employed...national origin, age, sex, religion,...

2009-04-01

383

29 CFR 37.20 - What is a grant applicant's obligation to provide a written assurance?  

Code of Federal Regulations, 2010 CFR

...EQUAL OPPORTUNITY PROVISIONS OF THE WORKFORCE INVESTMENT ACT OF 1998 (WIA) Recordkeeping and Other Affirmative Obligations of...following laws: Section 188 of the Workforce Investment Act of 1998 (WIA), which prohibits discrimination against all...

2010-07-01

384

Federal Academic Science and Engineering Obligations Increased 10 Percent in FY 2000  

NSF Publications Database

... equipment for S&E instruction; (4) general support for S&E; and (5) other S&E activities. Funding ... S&E obligations. HHS, NSF, and DOD together provided 81 percent of total Federal academic S&E ...

385

34 CFR 535.57 - How shall the fellowship recipient account for the obligation?  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false How shall the fellowship recipient account for the obligation...EDUCATION BILINGUAL EDUCATION: GRADUATE FELLOWSHIP PROGRAM What Conditions Must Be Met by Fellows? § 535.57 How shall the fellowship recipient account for the...

2013-07-01

386

45 CFR 96.14 - Time period for obligation and expenditure of grant funds.  

Code of Federal Regulations, 2011 CFR

...allotted shall remain available for obligation during the succeeding fiscal year for all block grants except: (1) Primary care. Amounts are available only if the Secretary determines that the State acted in accordance with section...

2011-10-01

387

45 CFR 96.14 - Time period for obligation and expenditure of grant funds.  

Code of Federal Regulations, 2010 CFR

...allotted shall remain available for obligation during the succeeding fiscal year for all block grants except: (1) Primary care. Amounts are available only if the Secretary determines that the State acted in accordance with section...

2010-10-01

388

Bacteriophage-aided intracellular killing of engulfed methicillin-resistant Staphylococcus aureus (MRSA) by murine macrophages.  

PubMed

Phages are known to effectively kill extracellularly multiplying bacteria as they do not have the ability of intracellular penetration within the animal cells. However, the present manuscript focuses on studying the impact of surface-adsorbed phage particles on the killing of engulfed Staphylococcus aureus inside phagocytic cells. Mouse peritoneal macrophages were isolated and cultured, followed by evaluation of their ability of bacterial uptake and killing. The intracellular killing potential of macrophages in the presence of unadsorbed free phage as well as phage adsorbed onto S. aureus 43300 was studied. Phage added alone to macrophage preparation did not influence intracellular killing of engulfed S. aureus by macrophages. However, phage adsorbed onto host bacterial cells (utilizing host bacteria as a vehicle to carry the lytic phage into the phagocytic compartment) brought about time-dependent and titre-dependent significant reduction in the number of viable intracellular cocci. Phage particles that shuttled inside the macrophage along with bacteria also significantly reduced cytotoxic damage caused by methicillin-resistant S. aureus (MRSA). This in turn enhanced the bactericidal killing potential of phagocytic cells. In earlier studies the inability of phages to kill intracellular bacteria has been thought to be a major drawback of phage therapy. For the first time results of this study confirm the killing ability of the broad host range lytic phage MR-5 of both extracellular as well as intracellular engulfed S. aureus inside macrophages. This approach shall not only restrict intracellular proliferation of staphylococci within the myeloid cells but also protect the host from further relapse of infection and treatment failures. PMID:24633444

Kaur, Sandeep; Harjai, Kusum; Chhibber, Sanjay

2014-05-01

389

Evolution of bacterial genomes.  

PubMed

This review examines evolution of bacterial genomes with an emphasis on RNA based life, the transition to functional DNA and small evolving genomes (possible plasmids) that led to larger, functional bacterial genomes. PMID:9111921

Trevors, J T

1997-03-01

390

Dual mechanisms of metabolite acquisition by the obligate intracytosolic pathogen Rickettsia prowazekii reveal novel aspects of triose phosphate transport.  

PubMed

Rickettsia prowazekii is an obligate intracytosolic pathogen and the causative agent of epidemic typhus fever in humans. As an evolutionary model of intracellular pathogenesis, rickettsiae are notorious for their use of transport systems that parasitize eukaryotic host cell biochemical pathways. Rickettsial transport systems for substrates found only in eukaryotic cell cytoplasm are uncommon among free-living microorganisms and often possess distinctive mechanisms. We previously reported that R. prowazekii acquires triose phosphates for phospholipid biosynthesis via the coordinated activities of a novel dihydroxyacetone phosphate transport system and an sn-glycerol-3-phosphate dehydrogenase (K. M. Frohlich et al., J. Bacteriol. 192:4281-4288, 2010). In the present study, we have determined that R. prowazekii utilizes a second, independent triose phosphate acquisition pathway whereby sn-glycerol-3-phosphate is directly transported and incorporated into phospholipids. Herein we describe the sn-glycerol-3-phosphate and dihydroxyacetone phosphate transport systems in isolated R. prowazekii with respect to kinetics, energy coupling, transport mechanisms, and substrate specificity. These data suggest the existence of multiple rickettsial triose phosphate transport systems. Furthermore, the R. prowazekii dihydroxyacetone phosphate transport systems displayed unexpected mechanistic properties compared to well-characterized triose phosphate transport systems from plant plastids. Questions regarding possible roles for dual-substrate acquisition pathways as metabolic virulence factors in the context of a pathogen undergoing reductive evolution are discussed. PMID:23772074

Frohlich, Kyla M; Audia, Jonathon P

2013-08-01

391

Cloning and expression of the superoxide dismutase gene from the obligate anaerobic bacterium Desulfovibrio vulgaris (Miyazaki F).  

PubMed

We identified the SOD gene in the obligate anaerobic bacterium Desulfovibrio vulgaris (Miyazaki F) and constructed a high-level expression system in Escherichia coli. A 2.6-kbp DNA fragment isolated from D. vulgaris (Miyazaki F) by double digestion with EcoRI and SmaI contained the SOD gene and part of another open reading frame. The amino acid sequence deduced from the SOD gene, which was composed of 238 amino acid residues, showed high homogeneity with iron-containing SOD (Fe-SOD) and predicted that the amino terminus of this protein would carry an export signal peptide. We produced the precursor form of SOD (PSOD) and the mature form of SOD (MSOD), which lacked the putative signal peptide. In E. coli, PSOD was present in insoluble inclusion bodies, and its putative signal peptide was not cleaved. In contrast, MSOD contained one iron per mononer and formed a dimer, which exhibited an SOD activity of 850 U/mg. Furthermore, D. vulgaris soluble extract showed a band of SOD activity on native polyacrylamide gel that migrated to the same point as MSOD. The intracellular localization of SOD and its role in D. vulgaris are also discussed. PMID:12761175

Nakanishi, Takeshi; Inoue, Hideo; Kitamura, Masaya

2003-03-01

392

Extending XACML Authorisation Model to Support Policy Obligations Handling in Distributed Applications  

Microsoft Academic Search

The paper summarises the recent and on-going developments and discussions in the Grid security community to built interoperable and scalable AuthZ infrastructure for distributed applications. The paper provides a short overview of the XACML policy format and policy obligations definition in the XACML specification. The paper analyses the basic use cases for obligations in computer Grids and on-demand network resource

Yuri Demchenko; Cees de Laat; Oscar Koeroo; Hakon Sagehaug

393

Immunization with bacterial antigens: piscirickettsiosis.  

PubMed

Piscirickettsiosis is a septicaemic disease of salmonid fish caused by the obligated intracellular rickettsia, Piscirickettsia salmonis. This disease was first reported in 1989 in salmon cultured in sea water netpens in southern Chile where it is still a major problem causing high mortality among cultured salmonids. In recent years related agents have been reported in farmed salmonids from Ireland, Canada and Norway. Mortality, however, at these locations has been reported to be low. Because of the recent description of piscirickettsiosis and its aetiological agent, knowledge about the immune response of fish against this organism is limited. At present, there is only one paper in the literature dealing with this subject. To standardise challenge methods for testing the efficacy of vaccination, lethal dose 50% and infectivity dose 50% were determined for coho salmon (Oncorhynchus kisutch) and rainbow trout (O. mykiss) using intraperitoneal (i.p.) injections of P. salmonis. Experiments using bath challenge methods failed to reproduce the disease using rainbow trout although low levels of infection in their tissues were found. In a field trial, using formalin killed bacterins injected i.p. into pre-smolt coho salmon, the fish were naturally challenged by placing them in sea water where endemic piscirickettsiosis occurred. The results showed that some of the vaccinated fish groups experienced lower cumulative mortality than the non-vaccinated control group (X < 0.05), suggesting an immunoprotective response in these animals. A trial was also conducted with formalin-killed bacterins in rainbow trout using different antigen concentrations with and without booster injections. Fish were challenged by IP injection of P. salmonis. Vaccinated fish showed less mortality than their respective infected control. Unfortunately the challenge was not strong enough because mortality in the infected control fish was low (20%). Antibody levels measured by radio-immuno-assay increased until day 40 post vaccination. The highest levels of antibody were obtained in the sera of fish vaccinated with concentrated antigen using booster injections. PMID:9270845

Smith, P A; Contreras, J R; Larenas, J J; Aguillon, J C; Garces, L H; Perez, B; Fryer, J L

1997-01-01

394

Bacterial Nail Infection (Paronychia)  

MedlinePLUS

newsletter | contact Share | Nail Infection, Bacterial (Paronychia) Information for adults A A A Nail-fold swelling and large pus-filled lesions are typical ... bacterial paronychia. Overview Paronychia, commonly known as bacterial nail infection, is inflammation of the region of the ...

395

Bacterial linguistic communication and social intelligence.  

PubMed

Bacteria have developed intricate communication capabilities (e.g. quorum-sensing, chemotactic signaling and plasmid exchange) to cooperatively self-organize into highly structured colonies with elevated environmental adaptability. We propose that bacteria use their intracellular flexibility, involving signal transduction networks and genomic plasticity, to collectively maintain linguistic communication: self and shared interpretations of chemical cues, exchange of chemical messages (semantic) and dialogues (pragmatic). Meaning-based communication permits colonial identity, intentional behavior (e.g. pheromone-based courtship for mating), purposeful alteration of colony structure (e.g. formation of fruiting bodies), decision-making (e.g. to sporulate) and the recognition and identification of other colonies - features we might begin to associate with a bacterial social intelligence. Such a social intelligence, should it exist, would require going beyond communication to encompass unknown additional intracellular processes to generate inheritable colonial memory and commonly shared genomic context. PMID:15276612

Ben Jacob, Eshel; Becker, Israela; Shapira, Yoash; Levine, Herbert

2004-08-01

396

Anomalous dynamics in intracellular transport  

NASA Astrophysics Data System (ADS)

This talk will describe quantitative analyses of particle tracking data for systems with cytoskeletally associated molecular motors to better understand the motions contributing to intracellular transport and, more generally, means for characterizing systems far from equilibrium. In particular, we have studied the motions of insulin-containing vesicles (granules) in a pancreatic beta cell line. We find subdiffusive behavior with correlations in both space and time. These data can be modeled by subordinating an ergodic random walk process to a non-ergodic one. We relate the dynamics to the underlying microtubule structure by imaging in the presence of the drug vinblastine. Our results provide a simple physical mechanism for how diverse pools of insulin granules and, in turn, biphasic secretion could arise. Time permitting, these dynamics will be compared with those of actomyosin assemblies.

Dinner, Aaron

2013-03-01

397

Intracellular Na? and cardiac metabolism.  

PubMed

In heart failure, alterations of excitation-contraction underlie contractile dysfunction. One important defect is an elevation of the intracellular Na(+) concentration in cardiac myocytes ([Na(+)]i), which has an important impact on cytosolic and mitochondrial Ca(2+) homeostasis. While elevated [Na(+)]i is thought to compensate for decreased Ca(2+) load of the sarcoplasmic reticulum (SR), it yet negatively affects energy supply-and-demand matching and can even induce mitochondrial oxidative stress. Here, we review the mechanisms underlying these pathophysiological changes. The chain of events may constitute a vicious cycle of ion dysregulation, oxidative stress and energetic deficit, resembling characteristic cellular deficits that are considered key hallmarks of the failing heart. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes". PMID:23727097

Bay, Johannes; Kohlhaas, Michael; Maack, Christoph

2013-08-01

398

Protein toxins from plants and bacteria: probes for intracellular transport and tools in medicine.  

PubMed

A number of protein toxins produced by bacteria and plants enter eukaryotic cells and inhibit protein synthesis enzymatically. These toxins include the plant toxin ricin and the bacterial toxin Shiga toxin, which we will focus on in this article. Although a threat to human health, toxins are valuable tools to discover and characterize cellular processes such as endocytosis and intracellular transport. Bacterial infections associated with toxin production are a problem worldwide. Increased knowledge about toxins is important to prevent and treat these diseases in an optimal way. Interestingly, toxins can be used for diagnosis and treatment of cancer. PMID:20385131

Sandvig, Kirsten; Torgersen, Maria L; Engedal, Nikolai; Skotland, Tore; Iversen, Tore-Geir

2010-06-18

399

Bacterial moonlighting proteins and bacterial virulence.  

PubMed

Implicit in the central dogma is the hypothesis that each protein gene product has but one function. However, over the past decade, it has become clear that many proteins have one or more unique functions, over-and-above the principal biological action of the specific protein. This phenomenon is now known as protein moonlighting and many well-known proteins such as metabolic enzymes and molecular chaperones are now recognised as moonlighting proteins. A growing number of bacterial species are being found to have moonlighting proteins and the moonlighting activities of such proteins can contribute to bacterial virulence behaviour. The glycolytic enzymes, glyceraldehyde-3-phosphate dehydrogenase (GAPD) and enolase, and the cell stress proteins: chaperonin 60, Hsp70 and peptidyl prolyl isomerase, are among the most common of the bacterial moonlighting proteins which play a role in bacterial virulence. Moonlighting activities include adhesion and modulation of cell signalling processes. It is likely that only the tip of the bacterial moonlighting iceberg has been sighted and the next decade will bring with it many new discoveries of bacterial moonlighting proteins with a role in bacterial virulence. PMID:22143554

Henderson, Brian; Martin, Andrew

2013-01-01

400

Eradication of intracellular Francisella tularensis in THP-1 human macrophages with a novel autophagy inducing agent  

PubMed Central

Background Autophagy has been shown recently to play an important role in the intracellular survival of several pathogenic bacteria. In this study, we investigated the effect of a novel small-molecule autophagy-inducing agent, AR-12, on the survival of Francisella tularensis, the causative bacterium of tularemia in humans and a potential bioterrorism agent, in macrophages. Methods and results Our results show that AR-12 induces autophagy in THP-1 macrophages, as indicated by increased autophagosome formation, and potently inhibits the intracellular survival of F. tularensis (type A strain, Schu S4) and F. novicida in macrophages in association with increased bacterial co-localization with autophagosomes. The effect of AR-12 on intracellular F. novicida was fully reversed in the presence of the autophagy inhibitor, 3-methyl adenine or the lysosome inhibitor, chloroquine. Intracellular F. novicida were not susceptible to the inhibitory activity of AR-12 added at 12 h post-infection in THP-1 macrophages, and this lack of susceptibility was independent of the intracellular location of bacteria. Conclusion Together, AR-12 represents a proof-of-principle that intracellular F. tularensis can be eradicated by small-molecule agents that target innate immunity.

2009-01-01

401

Intracellularly Induced Cyclophilins Play an Important Role in Stress Adaptation and Virulence of Brucella abortus  

PubMed Central

Brucella is an intracellular bacterial pathogen that causes the worldwide zoonotic disease brucellosis. Brucella virulence relies on its ability to transition to an intracellular lifestyle within host cells. Thus, this pathogen must sense its intracellular localization and then reprogram gene expression for survival within the host cell. A comparative proteomic investigation was performed to identify differentially expressed proteins potentially relevant for Brucella intracellular adaptation. Two proteins identified as cyclophilins (CypA and CypB) were overexpressed in the intracellular environment of the host cell in comparison to laboratory-grown Brucella. To define the potential role of cyclophilins in Brucella virulence, a double-deletion mutant was constructed and its resulting phenotype was characterized. The Brucella abortus ?cypAB mutant displayed increased sensitivity to environmental stressors, such as oxidative stress, pH, and detergents. In addition, the B. abortus ?cypAB mutant strain had a reduced growth rate at lower temperature, a phenotype associated with defective expression of cyclophilins in other microorganisms. The B. abortus ?cypAB mutant also displays reduced virulence in BALB/c mice and defective intracellular survival in HeLa cells. These findings suggest that cyclophilins are important for Brucella virulence and survival in the host cells.

Garcia Fernandez, Lucia; DelVecchio, Vito G.; Briones, Gabriel

2013-01-01

402

Linking the Transcriptional Profiles and the Physiological States of Mycobacterium tuberculosis during an Extended Intracellular Infection  

PubMed Central

Intracellular pathogens such as Mycobacterium tuberculosis have evolved strategies for coping with the pressures encountered inside host cells. The ability to coordinate global gene expression in response to environmental and internal cues is one key to their success. Prolonged survival and replication within macrophages, a key virulence trait of M. tuberculosis, requires dynamic adaptation to diverse and changing conditions within its phagosomal niche. However, the physiological adaptations during the different phases of this infection process remain poorly understood. To address this knowledge gap, we have developed a multi-tiered approach to define the temporal patterns of gene expression in M. tuberculosis in a macrophage infection model that extends from infection, through intracellular adaptation, to the establishment of a productive infection. Using a clock plasmid to measure intracellular replication and death rates over a 14-day infection and electron microscopy to define bacterial integrity, we observed an initial period of rapid replication coupled with a high death rate. This was followed by period of slowed growth and enhanced intracellular survival, leading finally to an extended period of net growth. The transcriptional profiles of M. tuberculosis reflect these physiological transitions as the bacterium adapts to conditions within its host cell. Finally, analysis with a Transcriptional Regulatory Network model revealed linked genetic networks whereby M. tuberculosis coordinates global gene expression during intracellular survival. The integration of molecular and cellular biology together with transcriptional profiling and systems analysis offers unique insights into the host-driven responses of intracellular pathogens such as M. tuberculosis.

Rohde, Kyle H.; Veiga, Diogo F. T.; Caldwell, Shannon; Balazsi, Gabor; Russell, David G.

2012-01-01

403

Guidelines for the diagnosis of tick-borne bacterial diseases in Europe  

Microsoft Academic Search

Ticks are obligate haematophagous acarines that parasitise every class of vertebrate (including man) and have a worldwide distribution. An increasing awareness of tick-borne diseases among clinicians and scientific researchers has led to the recent description of a number of emerging tick-borne bacterial diseases. Since the identification of Borrelia burgdorferi as the agent of Lyme disease in 1982, 11 tick-borne human

P. Brouqui; F. Bacellar; G. Baranton; R. J. Birtles; A. Bjoersdorff; J. R. Blanco; G. Caruso; M. Cinco; P. E. Fournier; E. Francavilla; M. Jensenius; J. Kazar; H. Laferl; A. Lakos; S. Lotric Furlan; M. Maurin; J. A. Oteo; P. Parola; C. Perez-Eid; O. Peter; D. Postic; D. Raoult; A. Tellez; Y. Tselentis; B. Wilske

2004-01-01

404

Validation of a stable recombinant antibodies repertoire for the direct selection of functional intracellular reagents  

Microsoft Academic Search

We have previously generated a semi-synthetic single-chain variable fragments (scFv) phage display library built on a thermodynamically stable single-framework scaffold. All scFv antibodies selected from this repertoire showed high thermodynamic stability and were expressed as soluble molecules in bacterial cytoplasm. In this work, two complementary methodologies have been adopted to assess the functionality of library-derived scFvs as intracellular antibodies and

Maria Elena Villani; Mariasole Di Carli; Marcello Donini; Giorgio Traversini; Chiara Lico; Rosella Franconi; Eugenio Benvenuto; Angiola Desiderio

2008-01-01

405

Circulating dendritic cell number and intracellular TNF-? production in women with type 2 diabetes  

Microsoft Academic Search

Human dendritic cell (DC) subsets perform specialized functions for surveillance against bacterial and viral infections essential\\u000a for the management of type 2 diabetes (T2D). Production of tumor necrosis factor-alpha (TNF-?) by DCs acts in autocrine fashion\\u000a to regulate DC maturation and promotes the inflammatory response. This study was designed to compare circulating DC number\\u000a and intracellular TNF-? production between post-menopausal

Sally E. BlankEmily; Emily Carolyn Johnson; Carol H. Wysham

406

Thioredoxin 80-Activated-Monocytes (TAMs) Inhibit the Replication of Intracellular Pathogens  

Microsoft Academic Search

BackgroundThioredoxin 80 (Trx80) is an 80 amino acid natural cleavage product of Trx, produced primarily by monocytes. Trx80 induces differentiation of human monocytes into a novel cell type, named Trx80-activated-monocytes (TAMs).Principal FindingsIn this investigation we present evidence for a role of TAMs in the control of intracellular bacterial infections. As model pathogens we have chosen Listeria monocytogenes and Brucella abortus

Ximena Cortes-Bratti; Eugénie Bassères; Fabiola Herrera-Rodriguez; Silvia Botero-Kleiven; Giuseppe Coppotelli; Jens B. Andersen; Maria G. Masucci; Arne Holmgren; Esteban Chaves-Olarte; Teresa Frisan; Javier Avila-Cariño

2011-01-01

407

Obligate autotrophy in the ammonia oxidizing bacterium Nitrosomonas europaea.  

SciTech Connect

Closing report for project DOE-FG02-03ER15436. The project studied obligate autotrophy in the ammonia oxidizing bacterium Nitrosomonas europaea. Nitrosomonas europaea can obtain all of its energy and reductant for growth from the oxidation of ammonia to nitrite and is, therefore, classified as a chemolithotroph. This bacterium is also an autotroph, which can derive all cellular carbon from carbon dioxide. N. europaea seems incapable of growth with other carbon or energy sources. This restricted capability is surprising given that ammonia is a poor energy source. The main goal of the project was to examine the basis of autotrophy in N. europaea or, thought of another way, to determine the barriers to heterotrophy. The approach was enabled by the N. europaea genome sequence, stimulating new ways of thinking about this physiological paradox—an insistence on a single, albeit poor, energy source. Objective 1 was to examine the expression and regulation of the genes coding for alpha-ketoglutarate dehydrogenase, determine if the enzyme’s activity is present, and determine whether alteration of the expression levels influences autotrophic growth. Although Nitrosomonas europaea lacks measurable alpha-ketoglutarate dehydrogenase activity, the genome sequence revealed the presence of the genes encoding the enzyme. A knockout mutation was created in the sucA gene encoding the E1 subunit. Compared to wild-type cells, the mutant strain showed an accelerated loss of ammonia monooxygenase and hydroxylamine oxidoreductase activities upon entering stationary phase. In addition, unlike wild-type cells, the mutant strain showed a marked lag in the ability to resume growth in response to pH adjustments in late stationary phase. The results were published in Hommes N.G., Kurth E. G., Sayavedra-Soto L.A., and Arp D.J. (2006) Disruption of sucA, which encodes a subunit of alpha-ketoglutarate dehydrogenase, affects the survival of Nitrosomonas europaea in stationary phase. Journal of Bacteriology 188:343-347. Objective 2 was to determine the basis of fructose stimulation of growth on ammonia, examine fructose metabolism, and determine the impact of other compounds on growth on ammonia. Previous studies showed that N. europaea can utilize limited amounts of certain organic compounds, including amino acids, pyruvate, and acetate, although no organic compound has been reported to support the growth of N. europaea. The genomic sequence of N. europaea revealed a potential permease for fructose. N. europaea utilized fructose and other compounds as carbon sources to support growth. Cultures were incubated in the presence of fructose or other organic compounds in sealed bottles purged of CO(2). In these cultures, addition of either fructose or pyruvate as the sole carbon source resulted in a two- to threefold increase in optical density and protein content in 3 to 4 days. Studies with [(14)C]fructose showed that >90% of the carbon incorporated by the cells during growth was derived from fructose. Cultures containing mannose, glucose, glycerol, mannitol, citrate, or acetate showed little or no growth. N. europaea was not able to grow with fructose as an energy source, although the presence of fructose did provide an energy benefit to the cells. These results show that N. europaea can be grown in carbon dioxide free medium by using fructose and pyruvate as carbon sources and may now be considered a facultative chemolithoorganotroph. The results were published in Hommes N.G., Sayavedra-Soto L.A. and Arp. D.J. (2003). Chemolithotrophic growth of Nitrosomonas europaea on fructose. Journal of Bacteriology. 185:6809-2773. Objective 3 attempted to grow N. europaea heterotrophically through pathways predicted by the genome. Experiments with mutant strains and complementation studies were performed to test whether N. europaea can utilize other carbon sources. N. europaea was not able to grow heterotrophically in the conditions tested in this objective.

Daniel James Arp; Luis Alberto Sayavedra-Soto

2006-01-01

408

Distinguishing cells in a sample by inactivating extracellular enzyme before releasing intracellular enzyme  

US Patent & Trademark Office Database

A method for detecting the absence or presence of cells of interest in a liquid sample is provided. The method comprises providing a sample suspected of containing cells of interest that contain an intracellular enzyme with a measurable activity. The sample further comprises an extracellular medium that also includes an extracellular enzyme with the measurable activity. The method further comprises the steps of treating the liquid sample with a reagent that inactivates the measurable activity in the extracellular medium but does not inactivate the measurable activity in the cells of interest, lysing the cells of interest to release the intracellular enzyme, and measuring the measurable activity. Thus, the measurable activity of the intracellular enzyme can be measured without interference from the extracellular enzyme. The invention is particularly useful for treatment of bacterially-infected blood using a detection assay based on adenylate kinase activity.

2013-01-08

409

Tailoring Silver Nanodots for Intracellular Staining  

PubMed Central

Through tailored oligonucleotide scaffolds, Ag nanocluster syntheses have yielded thermally and cell culture stable silver cluster-based emitters. Optimizing ssDNA stability has enabled creation of highly concentrated and spectrally pure nanocluster emitters with strong intracellular emission. Both fixed and live-cell staining become possible, and intracellular delivery is demonstrated both through conjugation to cell penetrating peptides and via microinjection.

Choi, Sungmoon; Yu, Junhua; Patel, Sandeep A.; Tzeng, Yih-Ling; Dickson, Robert M.

2011-01-01

410

Bacterial endosymbionts of Pyrodinium bahamense var. compressum.  

PubMed

The study presents evidence in support of the bacterial theory associated with the toxicity of Pyrodinium bahamense var. compressum. Bacterial endosymbionts from Philippine P. bahamense var. compressum strain Pbc MZRVA 042595 were isolated and identified via 16S rDNA sequence analysis. Taxonomic diversity of the identified culturable intracellular microbiota associated with Philippine P. bahamense var. compressum was established to be limited to the Phyla Proteobacteria, Actinobacteria, and Firmicutes. Major endosymbionts identified included Moraxella spp., Erythrobacter spp., and Bacillus spp., whereas Pseudomonas putida, Micrococcus spp., and Dietzia maris were identified as minor isolates. All identified strains except D. maris, P. putida, and Micrococcus spp. were shown to contain either saxitoxin or neo saxitoxin or both at levels < or =73 ng/10(7) bacterial cells based on high-performance liquid chromatography analysis. Paralytic shellfish poisoning-like physiologic reactions in test animals used in the mouse assay were recorded for the endosymbionts except for P. putida. The study is the first to elucidate the possible contribution of bacterial endosymbionts in the toxicity of P. bahamense var. compressum isolated in the Philippines. PMID:16944340

Azanza, Ma Patricia V; Azanza, Rhodora V; Vargas, Vanessa Mercee D; Hedreyda, Cynthia T

2006-11-01

411

Anomalous high native resistance to athymic mice to bacterial pathogens.  

PubMed Central

Congenitally athymic (nude) mice exhibited an anomalous high resistance against infections with the facultative intracellular parasite Listeria monocytogenes and other bacterial pathogens. Protection against lethal infection was demonstrated to result from the presence of naturally occurring activated macrophages in the reticuloendothelial organs of the nude mice. This was exemplified after intravenous challenge by enhanced bacterial clearance from the blood and augmented bacterial killing in the spleens and livers of nude mice as compared with immunologically competent control mice. Resident peritoneal macrophages of nude mice were not activated in terms of phagocytic, bactericidal, or tumoricidal potential. The development of activated fixed tissue macrophages appears to arise as a result of the T-lymphocyte deficiency since thymus implantation abrogated the enhanced resistance of nude mice. Antibiotic elimination of intestinal bacteria also modified resistance to bacterial infection, indicating a role of environmental factors on macrophage activation. Several possible mechanisms leading to macrophage activation and heightened resistance to infection in nude mice are offered.

Nickol, A D; Bonventre, P F

1977-01-01

412

Dynamics of intracellular information decoding  

NASA Astrophysics Data System (ADS)

A variety of cellular functions are robust even to substantial intrinsic and extrinsic noise in intracellular reactions and the environment that could be strong enough to impair or limit them. In particular, of substantial importance is cellular decision-making in which a cell chooses a fate or behavior on the basis of information conveyed in noisy external signals. For robust decoding, the crucial step is filtering out the noise inevitably added during information transmission. As a minimal and optimal implementation of such an information decoding process, the autocatalytic phosphorylation and autocatalytic dephosphorylation (aPadP) cycle was recently proposed. Here, we analyze the dynamical properties of the aPadP cycle in detail. We describe the dynamical roles of the stationary and short-term responses in determining the efficiency of information decoding and clarify the optimality of the threshold value of the stationary response and its information-theoretical meaning. Furthermore, we investigate the robustness of the aPadP cycle against the receptor inactivation time and intrinsic noise. Finally, we discuss the relationship among information decoding with information-dependent actions, bet-hedging and network modularity.

Kobayashi, Tetsuya J.; Kamimura, Atsushi

2011-10-01

413

Intracellular copper transport in mammals.  

PubMed

Copper is an essential cofactor for approximately a dozen cuproenzymes in which copper is bound to specific amino acid residues in an active site. However, free cuprous ions react readily with hydrogen peroxide to yield the deleterious hydroxyl radical. Therefore, copper homeostasis is regulated very tightly, and unbound copper is extremely low in concentration. Copper imported by the plasma membrane transport protein Ctr1 rapidly binds to intracellular copper chaperone proteins. Atox1 delivers copper to the secretory pathway and docks with either copper-transporting ATPase ATP7B in the liver or ATP7A in other cells. ATP7B directs copper to plasma ceruloplasmin or to biliary excretion in concert with a newly discovered chaperone, Murr1, the protein missing in canine copper toxicosis. ATP7A directs copper within the transgolgi network to the proteins dopamine beta-monooxgenase, peptidylglycine alpha-amidating monooxygenase, lysyl oxidase, and tyrosinase, depending on the cell type. CCS is the copper chaperone for Cu,Zn-superoxide dismutase; it delivers copper in the cytoplasm and intermitochondrial space. Cox17 delivers copper to mitochondria to cytochrome c oxidase via the chaperones Cox11, Sco1, and Sco2. Other copper chaperones may exist and might include metallothionein and amyloid precursor protein (APP). Genetic and nutritional studies have illustrated the essential nature of these copper-binding proteins; alterations in their levels are associated with severe pathology. PMID:15113935

Prohaska, Joseph R; Gybina, Anna A

2004-05-01

414

Intracellular signalling during female gametogenesis.  

PubMed

Female reproductive potential is dictated by the size of the primordial follicle pool and the correct regulation of oocyte maturation and activation--events essential for production of viable offspring. Although a substantial body of work underpins our understanding of these processes, the molecular mechanisms of follicular and oocyte development are not fully understood. This review summarizes recent findings which have improved our conception of how folliculogenesis and oocyte competence are regulated, and discusses their implications for assisted reproductive techniques. We highlight evidence provided by genetically modified mouse models and in vitro studies which have refined our understanding of Pi3k/Akt and mTOR signalling in the oocyte and have discovered a role for Jak/Stat/Socs signalling in granulosa cells during primordial follicle activation. We also appraise a novel role for the metal ion zinc in the regulation of meiosis I and meiosis II progression through early meiosis inhibitor (Emi2) and Mos-Mapk signalling, and examine studies which expand our understanding of intracellular calcium signalling and extrinsic Plc? in stimulating oocyte activation. PMID:23247812

Sobinoff, A P; Sutherland, J M; Mclaughlin, E A

2013-05-01

415

Avoiding the cost of males in obligately asexual Daphnia pulex (Leydig).  

PubMed Central

Asexual organisms are thought to gain an advantage by avoiding the cost of producing males. In the cladoceran Daphnia pulex (Leydig), male production is determined by the environment and is independent of the origin of the asexual obligate parthenogens from the sexual cyclical parthenogens. If there is a cost to producing males, successful obligate parthenogens should have reduced or eliminated male production. Field and laboratory observations showed that obligate parthenogens have much-reduced male production compared to cyclical parthenogens. Although the reduction or elimination of males in the obligate parthenogens suggests that the cost of males is avoided, the coexistence of sexual and asexual forms of D. pulex may be partially explained by cyclical parthenogens compensating for the cost of males by having greater fecundity. In addition, the absence of a mating constraint for the obligate parthenogens may favour an increased allocation to asexual diapausing eggs earlier in the season compared to the cyclical parthenogens which require mating with males to produce sexual diapausing eggs. No difference in the production of diapausing eggs was observed, probably because males were abundant in populations of cyclical parthenogens and do not appear to limit the production of sexual diapausing eggs. D. pulex is a useful system for determining the ecological consequences of abandoning sexual reproduction and explaining the coexistence of sexual and asexual forms of a species.

Innes, D J; Fox, C J; Winsor, G L

2000-01-01

416

Uptake and Intracellular Trafficking of Superantigens in Dendritic Cells  

PubMed Central

Bacterial superantigens (SAgs) are exotoxins produced mainly by Staphylococcus aureus and Streptococcus pyogenes that can cause toxic shock syndrome (TSS). According to current paradigm, SAgs interact directly and simultaneously with T cell receptor (TCR) on the T cell and MHC class II (MHC-II) on the antigen-presenting cell (APC), thereby circumventing intracellular processing to trigger T cell activation. Dendritic cells (DCs) are professional APCs that coat nearly all body surfaces and are the most probable candidate to interact with SAgs. We demonstrate that SAgs are taken up by mouse DCs without triggering DC maturation. SAgs were found in intracellular acidic compartment of DCs as biologically active molecules. Moreover, SAgs co-localized with EEA1, RAB-7 and LAMP-2, at different times, and were then recycled to the cell membrane. DCs loaded with SAgs are capable of triggering in vitro lymphocyte proliferation and, injected into mice, stimulate T cells bearing the proper TCR in draining lymph nodes. Transportation and trafficking of SAgs in DCs might increase the local concentration of these exotoxins where they will produce the highest effect by promoting their encounter with both MHC-II and TCR in lymph nodes, and may explain how just a few SAg molecules can induce the severe pathology associated with TSS.

Fernandez-Lynch, Maria J.; Jancic, Carolina; Vermeulen, Monica; Geffner, Jorge; Mariuzza, Roy A.; Fernandez, Marisa M.; Malchiodi, Emilio L.

2013-01-01

417

Intrauterine bacterial findings in postpartum cows with retained fetal membranes.  

PubMed

Eleven Swedish postpartum cows with retained fetal membranes (RFM) were studied to determine the intrauterine bacterial flora. Bacteriological examination was performed from twice weekly uterine biopsies. A total of 161 biopsies were collected during the first 8 weeks postpartum of which 82 (50.9%) were found with bacterial growth. Seventy-one of the 82 bacteria-positive biopsies (86.6%) showed mixed infections whereas the remaining 11 (13.4%) were pure cultures. Generally, a total of 322 isolates belonging to 12 different genera of bacteria, 6 facultative and 6 obligate anaerobic pathogens were identified. Mixed infections were most frequent for Actinomyces pyogenes together with obligate anaerobic bacteria, especially Bacteroides levii/spp. and Fusobacterium necrophorum. All of the studied cows had an infection that involved the first two genera of bacteria, whereas F. necrophorum was found in 8 of the 11 animals. The present work suggests that a possible pathogenic synergism between A. pyogenes and the two main Gram-negative anaerobes might have caused early endometritis and/or persistent infection. PMID:7732744

Bekana, M; Jonsson, P; Ekman, T; Kindahl, H

1994-11-01

418

Biodegradability of bacterial surfactants  

Microsoft Academic Search

This work aimed at evaluating the biodegradability of different bacterial surfactants in liquid medium and in soil microcosms.\\u000a The biodegradability of biosurfactants by pure and mixed bacterial cultures was evaluated through CO2 evolution. Three bacterial strains, Acinetobacter baumanni LBBMA ES11, Acinetobacter haemolyticus LBBMA 53 and Pseudomonas sp. LBBMA 101B, used the biosurfactants produced by Bacillus sp. LBBMA 111A (mixed lipopeptide),

Tânia M. S. Lima; Lorena C. Procópio; Felipe D. Brandão; André M. X. Carvalho; Marcos R. Tótola; Arnaldo C. Borges

2011-01-01

419

Demonstrating Bacterial Flagella.  

ERIC Educational Resources Information Center

Describes an effective laboratory method for demonstrating bacterial flagella that utilizes the Proteus mirabilis organism and a special harvesting technique. Includes safety considerations for the laboratory exercise. (MDH)

Porter, John R.; And Others

1992-01-01

420

Small intestinal bacterial overgrowth.  

PubMed

Small intestinal bacterial overgrowth (SIBO) syndrome is characterized in its florid form by diarrhoea and weight loss. The most common underlying factors are dysmotility, small intestinal obstruction, blind or afferent loops. Small intestinal bacterial overgrowth can be diagnosed by: 1) culture of jejunum aspirate for bacterial counts, 2) 14C-D-xylose breath testing, 3) non-invasive hydrogen breath testing using glucose or lactulose or 4) 14C-glycocholic acid breath testing. The treatment usually consists of the eradication of bacterial overgrowth with repeated course of antimicrobials, correction of associated nutritional deficiencies and, when possible, correction of the underlying predisposing conditions. PMID:18609165

Rana, S V; Bhardwaj, S B

2008-01-01

421

Autophagy targeting of Listeria monocytogenes and the bacterial countermeasure.  

PubMed

Autophagy acts as an intrinsic defense system against intracellular bacterial survival. Recently, multiple cellular pathways that target intracellular bacterial pathogens to autophagy have been described. These include the Atg5/LC3 pathway, which targets Shigella, the ubiquitin (Ub)-NDP52-LC3 pathway, which targets Group A Streptococcus (GAS) and Salmonella typhimurium, the Ub-p62-LC3 pathway, which targets Mycobacterium tuberculosis, Listeria monocytogenes and S. typhimurium, and the diacylglycerol-dependent pathway, which targets S. typhimurium. In addition, the bacterial invasion process is targeted by the NOD1 or NOD2-Atg16LLC3 pathway. Bacterial pathogens with an intracytosolic lifestyle, i.e., those capable of inducing actin polymerization and cell-to-cell spreading, also employ diverse tactics to evade autophagic recognition. Thus, Shigella, L. monocytogenes and Burkholderia pseudomallei deploy highly evolved systems to evade autophagic recognition and growth restriction. Here, we briefly review current knowledge of host recognition of L. monocytogenes by the innate immune system, and highlight how autophagic recognition by the host is overcome by bacterial countermeasures. PMID:21193840

Ogawa, Michinaga; Yoshikawa, Yuko; Mimuro, Hitomi; Hain, Torsten; Chakraborty, Trinad; Sasakawa, Chihiro

2011-03-01

422

Cell Extract-Containing Medium for Culture of Intracellular Fastidious Bacteria  

PubMed Central

The culture of fastidious microorganisms is a critical step in infectious disease studies. As a proof-of-concept experiment, we evaluated an empirical medium containing eukaryotic cell extracts for its ability to support the growth of Coxiella burnetii. Here, we demonstrate the exponential growth of several bacterial strains, including the C. burnetii Nine Mile phase I and phase II strains, and C. burnetii isolates from humans and animals. Low-oxygen-tension conditions and the presence of small hydrophilic molecules and short peptides were critical for facilitating growth. Moreover, bacterial antigenicity was conserved, revealing the potential for this culture medium to be used in diagnostic tests and in the elaboration of vaccines against C. burnetii. We were also able to grow the majority of previously tested intracellular and fastidious bacterial species, including Tropheryma whipplei, Mycobacterium bovis, Leptospira spp., Borrelia spp., and most putative bioterrorism agents. However, we were unable to culture Rickettsia africae and Legionella spp. in this medium. The versatility of this medium should encourage its use as a replacement for the cell-based culture systems currently used for growing several facultative and putative intracellular bacterial species.

Singh, Sudhir; Kowalczewska, Malgorzata; Edouard, Sophie; Eldin, Carole; Perreal, Celine; Weber, Pascal; Azza, Said

2013-01-01

423

Cell extract-containing medium for culture of intracellular fastidious bacteria.  

PubMed

The culture of fastidious microorganisms is a critical step in infectious disease studies. As a proof-of-concept experiment, we evaluated an empirical medium containing eukaryotic cell extracts for its ability to support the growth of Coxiella burnetii. Here, we demonstrate the exponential growth of several bacterial strains, including the C. burnetii Nine Mile phase I and phase II strains, and C. burnetii isolates from humans and animals. Low-oxygen-tension conditions and the presence of small hydrophilic molecules and short peptides were critical for facilitating growth. Moreover, bacterial antigenicity was conserved, revealing the potential for this culture medium to be used in diagnostic tests and in the elaboration of vaccines against C. burnetii. We were also able to grow the majority of previously tested intracellular and fastidious bacterial species, including Tropheryma whipplei, Mycobacterium bovis, Leptospira spp., Borrelia spp., and most putative bioterrorism agents. However, we were unable to culture Rickettsia africae and Legionella spp. in this medium. The versatility of this medium should encourage its use as a replacement for the cell-based culture systems currently used for growing several facultative and putative intracellular bacterial species. PMID:23740722

Singh, Sudhir; Kowalczewska, Malgorzata; Edouard, Sophie; Eldin, Carole; Perreal, Céline; Weber, Pascal; Azza, Said; Raoult, Didier

2013-08-01

424

A cross-cultural study of noblesse oblige in economic decision-making.  

PubMed

A cornerstone of economic theory is that rational agents are self-interested, yet a decade of research in experimental economics has shown that economic decisions are frequently driven by concerns for fairness, equity, and reciprocity. One aspect of other-regarding behavior that has garnered attention is noblesse oblige, a social norm that obligates those of higher status to be generous in their dealings with those of lower status. The results of a cross-cultural study are reported in which marked noblesse oblige was observed on a reciprocal-contract decision-making task. Participants from seven countries that vary along hierarchical and individualist/collectivist social dimensions were more tolerant of non-reciprocation when they adopted a high-ranking perspective compared with a low-ranking perspective. PMID:23749462

Fiddick, Laurence; Cummins, Denise Dellarosa; Janicki, Maria; Lee, Sean; Erlich, Nicole

2013-09-01

425

Obligations, internalization, and excuse making: integrating the triangle model and self-determination theory.  

PubMed

Schlenker's triangle model (Schlenker, Britt, Pennington, Murphy, & Doherty, 1994, Schlenker, Pontari, & Christopher, 2001) identifies three excuses people use to avoid taking responsibility after failure: that one had no control in the situation, that the obligation was unclear, and that it was not really one's obligation. Three retrospective studies tested the presumed negative association between excuse making and responsibility taking. The studies also examined the effects of self-determination theory's concept of motivational internalization (Deci & Ryan, 2000) upon these variables. A complex but replicable pattern emerged, such that responsibility taking and motivational internalization correlated with adaptive outcomes such as future commitment and positive expectancy and excuse making did not. Of particular interest, perceiving that the person levying the obligation internalized motivation predicted responsibility taking, in all three studies. Implications for the triangle model, as well as for theories of maturity and personality development, are considered. PMID:17359242

Sheldon, Kennon M; Schachtman, Todd R

2007-04-01

426

Federal Obligations for R&D and R&D Plant Expected to Reach Over $105 Billion in FY 2004  

NSF Publications Database

... 3 Source Data: Excel file Applied Research Federal obligations for applied research during the ... or applied. Basic research is performed without specific applications in mind; applied research is ...

427

Induction of Specific CD8 T Cells against Intracellular Bacteria by CD8 T-Cell-Oriented Immunization Approaches.  

PubMed

For protection against intracellular bacteria such as Mycobacterium tuberculosis and Listeria monocytogenes, the cellular arm of adaptive immunity is necessary. A variety of immunization methods have been evaluated and are reported to induce specific CD8(+) T cells against intracellular bacterial infection. Modified BCG vaccines have been examined to enhance CD8(+) T-cell responses. Naked DNA vaccination is a promising strategy to induce CD8(+) T cells. In addition to this strategy, live attenuated intracellular bacteria such as Shigella, Salmonella, and Listeria have been utilized as carriers of DNA vaccines in animal models. Vaccination with dendritic cells pulsed with antigenic peptides or the cells introduced antigen genes by virus vectors such as retroviruses is also a powerful strategy. Furthermore, vaccination with recombinant lentivirus has been attempted to induce specific CD8(+) T cells. Combinations of these strategies (prime-boost immunization) have been studied for the efficient induction of intracellular bacteria-specific CD8(+) T cells. PMID:20508818

Nagata, Toshi; Koide, Yukio

2010-01-01

428

Experimental Disturbance of Foraminiferal-Bacterial Interactions  

NASA Astrophysics Data System (ADS)

In experiments with living foraminifera, sediment is often sieved prior to incubation in microcosms. This is done to get rid of larger predators, which disturb the sediment and destroy the meiofaunal assemblage. However, the actual sieving results in a sudden disturbance of the obligate anaerobic bacteria. While sieved, they are subjected to aerobe conditions. But also the strictly aerobic bacteria are at a disadvantage when loading the homogenized sediment in microcosms. Normally, their population occurs abundantly in the top oxygenated layer with a thickness of a couple of mm. At the onset of the experiment, however, the aerobe population is mixed through the sediment to become relatively reduced in the top layer. The effects of these disturbances are ill known but might affect the outcome of the experimental foraminiferal and biogeochemical studies substantially. Benthic foraminifera migrate to their natural in-sediment position within three weeks after disturbance. The geochemistry is restored even quicker to the natural situation and it is assumed generally that equilibrium in the sediment has re-established after three weeks (Ernst et al., 2000, Duijnstee et al., 2001). However, some studies suggest that bacterial activity does not recover from the sieving process (Federly et al., 1986; Findley et al., 1990; Gilbert et al., 1995; Schafer et al., 2001) and our data indicate that the bacterial population suffers greatly. We tested an experimental design that has less influence on the bacterial standing stock. The sieving procedure was avoided, intact sediment columns were retrieved from the sea floor and macrofauna was removed by flushing the cores with Argon. In this way the structure of the sediment was kept intact, and no specific groups of bacteria are advantaged at the start of the experiment. The impact of the experimental designs on the outcome of foraminiferal studies is discussed.

Langezaal, A. M.; van Bergen, P. F.; van der Zwaan, G. J.

2003-04-01

429

Stomatobaculum longum gen. nov., sp. nov., an obligately anaerobic bacterium from the human oral cavity.  

PubMed

A strictly anaerobic Gram-stain-variable but positive by structure, non-spore-forming bacterium designated Lachnospiraceae bacterium ACC2 strain DSM 24645(T) was isolated from human subgingival dental plaque. Bacterial cells were 4-40 µm long non-motile rods, often swollen and forming curved filaments up to 200 µm. Cells contained intracellular, poorly crystalline, nanometre-sized iron- and sulfur-rich particles. The micro-organism was able to grow on yeast extract, trypticase peptone, milk, some sugars and organic acids. The major metabolic end-products of glucose fermentation were butyrate, lactate, isovalerate and acetate. The growth temperature and pH ranges were 30-42 °C and 4.9-7.5, respectively. Major fatty acids were C14?:?0, C14?:?0 DMA (dimethyl aldehyde), C16?:?0, C16?:?1?7c DMA. The whole-cell hydrolysate contained meso-diaminopimelic acid, indicating peptidoglycan type A1?. The DNA G+C content was calculated to be 55.05 mol% from the whole-genome sequence and 55.3 mol% as determined by HPLC. There were no predicted genes responsible for biosynthesis of respiratory lipoquinones, mycolic acids and lipopolysaccharides. Genes associated with synthesis of teichoic and lipoteichoic acids, diaminopimelic acid, polar lipids and polyamines were present. According to the 16S rRNA gene sequence phylogeny, strain DSM 24645(T) formed, together with several uncultured oral clones, a separate branch within the family Lachnospiraceae, with the highest sequence similarity to the type strain of Moryella indoligenes at 94.2?%. Based on distinct phenotypic and genotypic characteristics, we suggest that strain DSM 24645(T) represents a novel species in a new genus, for which the name Stomatobaculum longum gen. nov., sp. nov. is proposed. The type strain of Stomatobaculum longum is DSM 24645(T) (?=?HM-480(T); deposited in BEI Resources, an NIH collection managed by the ATCC). PMID:22843721

Sizova, Maria V; Muller, Paul; Panikov, Nicolai; Mandalakis, Manolis; Hohmann, Tine; Hazen, Amanda; Fowle, William; Prozorov, Tanya; Bazylinski, Dennis A; Epstein, Slava S

2013-04-01

430

Stochastic resonance in an intracellular genetic perceptron.  

PubMed

Intracellular genetic networks are more intelligent than was first assumed due to their ability to learn. One of the manifestations of this intelligence is the ability to learn associations of two stimuli within gene-regulating circuitry: Hebbian-type learning within the cellular life. However, gene expression is an intrinsically noisy process; hence, we investigate the effect of intrinsic and extrinsic noise on this kind of intracellular intelligence. We report a stochastic resonance in an intracellular associative genetic perceptron, a noise-induced phenomenon, which manifests itself in noise-induced increase of response in efficiency after the learning event under the conditions of optimal stochasticity. PMID:24730883

Bates, Russell; Blyuss, Oleg; Zaikin, Alexey

2014-03-01

431

Manganese (Mn) Oxidation Increases Intracellular Mn in Pseudomonas putida GB-1  

PubMed Central

Bacterial manganese (Mn) oxidation plays an important role in the global biogeochemical cycling of Mn and other compounds, and the diversity and prevalence of Mn oxidizers have been well established. Despite many hypotheses of why these bacteria may oxidize Mn, the physiological reasons remain elusive. Intracellular Mn levels were determined for Pseudomonas putida GB-1 grown in the presence or absence of Mn by inductively coupled plasma mass spectrometry (ICP-MS). Mn oxidizing wild type P. putida GB-1 had higher intracellular Mn than non Mn oxidizing mutants grown under the same conditions. P. putida GB-1 had a 5 fold increase in intracellular Mn compared to the non Mn oxidizing mutant P. putida GB-1-007 and a 59 fold increase in intracellular Mn compared to P. putida GB-1 ?2665 ?2447. The intracellular Mn is primarily associated with the less than 3 kDa fraction, suggesting it is not bound to protein. Protein oxidation levels in Mn oxidizing and non oxidizing cultures were relatively similar, yet Mn oxidation did increase survival of P. putida GB-1 when oxidatively stressed. This study is the first to link Mn oxidation to Mn homeostasis and oxidative stress protection.

Banh, Andy; Chavez, Valarie; Doi, Julia; Nguyen, Allison; Hernandez, Sophia; Ha, Vu; Jimenez, Peter; Espinoza, Fernanda; Johnson, Hope A.

2013-01-01

432

INTRACELLULAR OXIDATION-REDUCTION STUDIES  

PubMed Central

Twenty-five oxidation-reduction indicators were injected in oxidized or reduced form into Amoeba dubia and Amœba proteus under controlled conditions of oxygen access. (1) Under anaerobiosis the ameba was able to reduce completely all the reversible oxidation-reduction indicators down to and including indigo disulfonate. (2) Under anaerobiosis the ameba was unable to reoxidize six of the most easily oxidizable indicators. (3) Under aerobiosis the ameba was able to reduce completely all the indicators down to and including 1-naphthol-2-sulfonate indo-2, 6-dichlorophenol. Toluylene blue, methylene blue and indigo tetrasulfonate were sometimes completely and sometimes only partly reduced, depending on the quantity of indicator injected and the duration of observation. (4) The time of reduction varied approximately with the size of the injection. Reduction was more rapid under anaerobiosis than under aerobiosis, more rapid in active than in sluggish cells and was retarded by toxic compounds. (5) Sulfonated compounds were somewhat toxic, as a rule. In interpreting reduction phenomena of micro injection, it is necessary to take into consideration the intensity, capacity and rate factors. It then becomes apparent that the ameba has a high reducing potential lying on the rH scale below the zone of indigo disulfonate. The reducing capacity of the ameba seems to be relatively great in the region of the simple indophenols and of a progressively diminishing magnitude as the zone of the indigos is approached. Material of high reduction potential appears to be generated within the ameba at a measurable rate. These phenomena, observed in the interior of the cell with the aid of indicators, parallel very closely those found in reduction electrode studies on bacterial cultures.

Cohen, Barnett; Chambers, Robert; Reznikoff, Paul

1928-01-01

433

A Method for Functional Trans-Complementation of Intracellular Francisella tularensis  

PubMed Central

Francisella tularensis is a highly infectious bacterial pathogen that invades and replicates within numerous host cell types. After uptake, F. tularensis bacteria escape the phagosome, replicate within the cytosol, and suppress cytokine responses. However, the mechanisms employed by F. tularensis to thrive within host cells are mostly unknown. Potential F. tularensis mutants involved in host-pathogen interactions are typically discovered by negative selection screens for intracellular replication or virulence. Mutants that fulfill these criteria fall into two categories: mutants with intrinsic intracellular growth defects and mutants that fail to modify detrimental host cell processes. It is often difficult and time consuming to discriminate between these two possibilities. We devised a method to functionally trans-complement and thus identify mutants that fail to modify the host response. In this assay, host cells are consistently and reproducibly infected with two different F. tularensis strains by physically tethering the bacteria to antibody-coated beads. To examine the efficacy of this protocol, we tested phagosomal escape, cytokine suppression, and intracellular replication for F. tularensis ?ripA and ?pdpC. ?ripA has an intracellular growth defect that is likely due to an intrinsic defect and fails to suppress IL-1? secretion. In the co-infection model, ?ripA was unable to replicate in the host cell when wild-type bacteria infected the same cell, but cytokine suppression was rescued. Therefore, ?ripA intracellular growth is due to an intrinsic bacterial defect while cytokine secretion results from a failed host-pathogen interaction. Likewise, ?pdpC is deficient for phagosomal escape, intracellular survival and suppression of IL-1? secretion. Wild-type bacteria that entered through the same phagosome as ?pdpC rescued all of these phenotypes, indicating that ?pdpC failed to properly manipulate the host. In summary, functional trans-complementation using bead-bound bacteria co-infections is a method to rapidly identify mutants that fail to modify a host response. Francisella tularensis is a facultative intracellular bacterial pathogen and is the causative agent of the disease tularemia. F. tularensis enters host cells through phagocytosis, escapes the phagosome, and replicates in the host cell cytosol while suppressing cytokine secretion [1]–[4]. Although substantial progress has been made in understanding the intracellular life cycle of F. tularensis, the F. tularensis proteins responsible for manipulating many host cell pathways are unknown. Identifying novel host-pathogen effector proteins is difficult because there is no rapid method to reliably distinguish between bacterial proteins that modify host processes and proteins that are involved in bacterial processes that are required for the bacteria to survive or replicate in the intracellular environment. The ability to identify mutants that are deficient for host-pathogen interactions is important because it can aid in prioritizing the investigation of genes of interest and in downstream experimental design. Moreover, certain mutant phenotypes, such as decreased phagosomal escape, hinder investigation of other potential phenotypes. A method to specifically complement these phenotypes would allow for further characterizations of certain F. tularensis mutants. Thus we sought to develop a method to easily identify and functionally complement mutants that are deficient for interactions with the host.

Steele, Shaun; Taft-Benz, Sharon; Kawula, Thomas

2014-01-01

434

A method for functional trans-complementation of intracellular Francisella tularensis.  

PubMed

Francisella tularensis is a highly infectious bacterial pathogen that invades and replicates within numerous host cell types. After uptake, F. tularensis bacteria escape the phagosome, replicate within the cytosol, and suppress cytokine responses. However, the mechanisms employed by F. tularensis to thrive within host cells are mostly unknown. Potential F. tularensis mutants involved in host-pathogen interactions are typically discovered by negative selection screens for intracellular replication or virulence. Mutants that fulfill these criteria fall into two categories: mutants with intrinsic intracellular growth defects and mutants that fail to modify detrimental host cell processes. It is often difficult and time consuming to discriminate between these two possibilities. We devised a method to functionally trans-complement and thus identify mutants that fail to modify the host response. In this assay, host cells are consistently and reproducibly infected with two different F. tularensis strains by physically tethering the bacteria to antibody-coated beads. To examine the efficacy of this protocol, we tested phagosomal escape, cytokine suppression, and intracellular replication for F. tularensis ?ripA and ?pdpC. ?ripA has an intracellular growth defect that is likely due to an intrinsic defect and fails to suppress IL-1? secretion. In the co-infection model, ?ripA was unable to replicate in the host cell when wild-type bacteria infected the same cell, but cytokine suppression was rescued. Therefore, ?ripA intracellular growth is due to an intrinsic bacterial defect while cytokine secretion results from a failed host-pathogen interaction. Likewise, ?pdpC is deficient for phagosomal escape, intracellular survival and suppression of IL-1? secretion. Wild-type bacteria that entered through the same phagosome as ?pdpC rescued all of these phenotypes, indicating that ?pdpC failed to properly manipulate the host. In summary, functional trans-complementation using bead-bound bacteria co-infections is a method to rapidly identify mutants that fail to modify a host response. Francisella tularensis is a facultative intracellular bacterial pathogen and is the causative agent of the disease tularemia. F. tularensis enters host cells through phagocytosis, escapes the phagosome, and replicates in the host cell cytosol while suppressing cytokine secretion [1]-[4]. Although substantial progress has been made in understanding the intracellular life cycle of F. tularensis, the F. tularensis proteins responsible for manipulating many host cell pathways are unknown. Identifying novel host-pathogen effector proteins is difficult because there is no rapid method to reliably distinguish between bacterial proteins that modify host processes and proteins that are involved in bacterial processes that are required for the bacteria to survive or replicate in the intracellular environment. The ability to identify mutants that are deficient for host-pathogen interactions is important because it can aid in prioritizing the investigation of genes of interest and in downstream experimental design. Moreover, certain mutant phenotypes, such as decreased phagosomal escape, hinder investigation of other potential phenotypes. A method to specifically complement these phenotypes would allow for further characterizations of certain F. tularensis mutants. Thus we sought to develop a method to easily identify and functionally complement mutants that are deficient for interactions with the host. PMID:24505427

Steele, Shaun; Taft-Benz, Sharon; Kawula, Thomas

2014-01-01

435

Bistability and Bacterial Infections  

Microsoft Academic Search

Bacterial infections occur when the natural host defenses are overwhelmed by invading bacteria. The main component of the host defense is impaired when neutrophil count or function is too low, putting the host at great risk of developing an acute infection. In people with intact immune systems, neutrophil count increases during bacterial infection. However, there are two important clinical cases

Roy Malka; Eliezer Shochat; Vered Rom-Kedar; Robert Planque

2010-01-01

436

Bistable Bacterial Growth Rate in Response to Antibiotics with Low Membrane Permeability  

NASA Astrophysics Data System (ADS)

We demonstrate that growth rate bistability for bacterial cells growing exponentially at a fixed external antibiotic concentration can emerge when the cell wall permeability for the drug is low and the growth rate sensitivity to the intracellular drug concentration is high. Under such conditions, an initially high growth rate can remain high, due to dilution of the intracellular drug concentration by rapid cell volume increase, while an initially low growth rate can remain low, due to slow cell volume increase and insignificant drug dilution. Our findings have implications for the testing of novel antibiotics on growing bacterial strains.

Elf, Johan; Nilsson, Karin; Tenson, Tanel; Ehrenberg, Måns

2006-12-01

437

Induction of a stringent metabolic response in intracellular stages of Leishmania mexicana leads to increased dependence on mitochondrial metabolism.  

PubMed

Leishmania parasites alternate between extracellular promastigote stages in the insect vector and an obligate intracellular amastigote stage that proliferates within the phagolysosomal compartment of macrophages in the mammalian host. Most enzymes involved in Leishmania central carbon metabolism are constitutively expressed and stage-specific changes in energy metabolism remain poorly defined. Using (13)C-stable isotope resolved metabolomics and (2)H2O labelling, we show that amastigote differentiation is associated with reduction in growth rate and induction of a distinct stringent metabolic state. This state is characterized by a global decrease in the uptake and utilization of glucose and amino acids, a reduced secretion of organic acids and increased fatty acid ?-oxidation. Isotopomer analysis showed that catabolism of hexose and fatty acids provide C4 dicarboxylic acids (succinate/malate) and acetyl-CoA for the synthesis of glutamate via a compartmentalized mitochondrial tricarboxylic acid (TCA) cycle. In vitro cultivated and intracellular amastigotes are acutely sensitive to inhibitors of mitochondrial aconitase and glutamine synthetase, indicating that these anabolic pathways are essential for intracellular growth and virulence. Lesion-derived amastigotes exhibit a similar metabolism to in vitro differentiated amastigotes, indicating that this stringent response is coupled to differentiation signals rather than exogenous nutrient levels. Induction of a stringent metabolic response may facilitate amastigote survival in a nutrient-poor intracellular niche and underlie the increased dependence of this stage on hexose and mitochondrial metabolism. PMID:24465208

Saunders, Eleanor C; Ng, William W; Kloehn, Joachim; Chambers, Jennifer M; Ng, Milica; McConville, Malcolm J

2014-01-01

438

A focal adhesion factor directly linking intracellularly motile Listeria monocytogenes and Listeria ivanovii to the actin-based cytoskeleton of mammalian cells.  

PubMed Central

The surface-bound ActA polypeptide of the intracellular bacterial pathogen Listeria monocytogenes is the sole listerial factor needed for recruitment of host actin filaments by intracellularly motile bacteria. Here we report that following Listeria infection the host vasodilator-stimulated phosphoprotein (VASP), a microfilament- and focal adhesion-associated substrate of both the cAMP- and cGMP-dependent protein kinases, accumulates on the surface of intracytoplasmic bacteria prior to the detection of F-actin 'clouds'. VASP remains associated with the surface of highly motile bacteria, where it is polarly located, juxtaposed between one extremity of the bacterial surface and the front of the actin comet tail. Since actin filament polymerization occurs only at the very front of the tail, VASP exhibits properties of a host protein required to promote actin polymerization. Purified VASP binds directly to the ActA polypeptide in vitro. A ligand-overlay blot using purified radiolabelled VASP enabled us to identify the ActA homologue of the related intracellular motile pathogen, Listeria ivanovii, as a protein with a molecular mass of approximately 150 kDa. VASP also associates with actin filaments recruited by another intracellularly motile bacterial pathogen, Shigella flexneri. Hence, by the simple expedient of expressing surface-bound attractor molecules, bacterial pathogens effectively harness cytoskeletal components to achieve intracellular movement. Images

Chakraborty, T; Ebel, F; Domann, E; Niebuhr, K; Gerstel, B; Pistor, S; Temm-Grove, C J; Jockusch, B M; Reinhard, M; Walter, U

1995-01-01

439

Reduction of Intracellular Glutathione Content and Radiosensitivity,  

National Technical Information Service (NTIS)

The intracellular glutathione (GSH) content in HeLa, CHO and V79 cells was reduced by incubating the cells in growth medium containing buthionine sulfoximine (BSO) or diethyl maleate (DEM). Clonogenicity, single strand DNA breaks (ssb), and double strand ...

O. Vos G. P. van der Schans W. S. D. Roos-Verheij

1986-01-01

440

Nanoparticles for intracellular-targeted drug delivery  

NASA Astrophysics Data System (ADS)

Nanoparticles (NPs) are very promising for the intracellular delivery of anticancer and immunomodulatory drugs, stem cell differentiation biomolecules and cell activity modulators. Although initial studies in the area of intracellular drug delivery have been performed in the delivery of DNA, there is an increasing interest in the use of other molecules to modulate cell activity. Herein, we review the latest advances in the intracellular-targeted delivery of short interference RNA, proteins and small molecules using NPs. In most cases, the drugs act at different cellular organelles and therefore the drug-containing NPs should be directed to precise locations within the cell. This will lead to the desired magnitude and duration of the drug effects. The spatial control in the intracellular delivery might open new avenues to modulate cell activity while avoiding side-effects.

Paulo, Cristiana S. O.; Pires das Neves, Ricardo; Ferreira, Lino S.

2011-12-01

441

The Cytoskeleton and Intracellular Motility in Plants  

Microsoft Academic Search

Novel information concerning intracellular motility in plants and the mechanisms of cytoskeleton-based organelle and macromolecule movements are briefly considered. The involvement of basic molecular motors and other possible driving forces for various types of movement are discussed.

N. L. Klyachko

2005-01-01

442

Lysosomes and Intracellular Digestion in Sea Stars.  

National Technical Information Service (NTIS)

The study of lysosomes and intracellular digestion in sea stars seemed ideal. Echinoderms occupy an intermediate position in the phylogenetic progression from protozoan to mammal. A single sea star can cleanly provide a large amount of relatively homogeno...

G. S. Araki

1969-01-01

443

Intracellular dyes mask immunoreactivity of hippocampal interneurons.  

PubMed

The results of several studies have suggested that local circuit neurons, or interneurons, of area CA1 of hippocampus use gamma-aminobutyric acid (GABA) as their neurotransmitter. However, when these cells were labelled by intracellular dye injection, and examined immunocytochemically with antisera raised against GABA, none of the interneurons were immunoreactive. Numerous non-injected interneurons in the same tissue section were clearly immunoreactive. These results suggest that intracellular dyes interfere with immunocytochemical staining of hippocampal interneurons. PMID:2927710

Scharfman, H E; Kunkel, D D; Schwartzkroin, P A

1989-01-01

444

Studying Biomolecule Localization by Engineering Bacterial Cell Wall Curvature  

PubMed Central

In this article we describe two techniques for exploring the relationship between bacterial cell shape and the intracellular organization of proteins. First, we created microchannels in a layer of agarose to reshape live bacterial cells and predictably control their mean cell wall curvature, and quantified the influence of curvature on the localization and distribution of proteins in vivo. Second, we used agarose microchambers to reshape bacteria whose cell wall had been chemically and enzymatically removed. By combining microstructures with different geometries and fluorescence microscopy, we determined the relationship between bacterial shape and the localization for two different membrane-associated proteins: i) the cell-shape related protein MreB of Escherichia coli, which is positioned along the long axis of the rod-shaped cell; and ii) the negative curvature-sensing cell division protein DivIVA of Bacillus subtilis, which is positioned primarily at cell division sites. Our studies of intracellular organization in live cells of E. coli and B. subtilis demonstrate that MreB is largely excluded from areas of high negative curvature, whereas DivIVA localizes preferentially to regions of high negative curvature. These studies highlight a unique approach for studying the relationship between cell shape and intracellular organization in intact, live bacteria.

Renner, Lars D.; Eswaramoorthy, Prahathees; Ramamurthi, Kumaran S.; Weibel, Douglas B.

2013-01-01

445

Intracellular bacteria and adverse pregnancy outcomes.  

PubMed

This review considers the role of intracellular bacteria in adverse pregnancy outcomes, such as miscarriage, stillbirths, and preterm labour. The cause of miscarriage, stillbirth and preterm labour often remains unexplained. Intracellular bacteria that grow either poorly or not at all on media used routinely to detect human pathogens could be the aetiological agents of these obstetric conditions. For example, Listeria monocytogenes and Coxiella burnetti are intracellular bacteria that have a predilection for the fetomaternal unit and may induce fatal disease in the mother and/or fetus. Both are important foodborne or zoonotic pathogens in pregnancy. Preventive measures, diagnostic tools and treatment will be reviewed. Moreover, we will also address the importance in adverse pregnancy outcomes of other intracellular bacteria, including Brucella abortus and various members of the order Chlamydiales. Indeed, there is growing evidence that Chlamydia trachomatis, Chlamydia abortus and Chlamydia pneumoniae infections may also result in adverse pregnancy outcomes in humans and/or animals. Moreover, newly discovered Chlamydia-like organisms have recently emerged as new pathogens of both animals and humans. For example, Waddlia chondrophila, a Chlamydia-related bacterium isolated from aborted bovine fetuses, has also been implicated in human miscarriages. Future research should help us to better understand the pathophysiology of adverse pregnancy outcomes caused by intracellular bacteria and to determine the precise mode of transmission of newly identified bacteria, such as Waddlia and Parachlamydia. These emerging pathogens may represent the tip of the iceberg of a large number of as yet unknown intracellular pathogenic agents. PMID:21884294

Baud, D; Greub, G

2011-09-01

446

Staphylococcus aureus promotes autophagy by decreasing intracellular cAMP levels.  

PubMed

Staphylococcus aureus is an intracellular bacterium responsible for serious infectious processes. This pathogen escapes fr