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1

Advances in Genetic Manipulation of Obligate Intracellular Bacterial Pathogens  

PubMed Central

Infections by obligate intracellular bacterial pathogens result in significant morbidity and mortality worldwide. These bacteria include Chlamydia spp., which causes millions of cases of sexually transmitted disease and blinding trachoma annually, and members of the ?-proteobacterial genera Anaplasma, Ehrlichia, Orientia, and Rickettsia, agents of serious human illnesses including epidemic typhus. Coxiella burnetii, the agent of human Q fever, has also been considered a prototypical obligate intracellular bacterium, but recent host cell-free (axenic) growth has rescued it from obligatism. The historic genetic intractability of obligate intracellular bacteria has severely limited molecular dissection of their unique lifestyles and virulence factors involved in pathogenesis. Host cell restricted growth is a significant barrier to genetic transformation that can make simple procedures for free-living bacteria, such as cloning, exceedingly difficult. Low transformation efficiency requiring long-term culture in host cells to expand small transformant populations is another obstacle. Despite numerous technical limitations, the last decade has witnessed significant gains in genetic manipulation of obligate intracellular bacteria including allelic exchange. Continued development of genetic tools should soon enable routine mutation and complementation strategies for virulence factor discovery and stimulate renewed interest in these refractory pathogens. In this review, we discuss the technical challenges associated with genetic transformation of obligate intracellular bacteria and highlight advances made with individual genera.

Beare, Paul A.; Sandoz, Kelsi M.; Omsland, Anders; Rockey, Daniel D.; Heinzen, Robert A.

2011-01-01

2

Antibody-Mediated Elimination of the Obligate Intracellular Bacterial Pathogen Ehrlichia chaffeensis during Active Infection  

Microsoft Academic Search

It is generally accepted that cellular, but not humoral immunity, plays an important role in host defense against intracellular bacteria. However, studies of some of these pathogens have provided evidence that antibodies can provide immunity if present during the initiation of infection. Here, we examined immunity against infection by Ehrlichia chaffeensis, an obligate intracellular bacterium that causes human monocytic ehrlichiosis.

GARY M. WINSLOW; ERIC YAGER; KONSTANTIN SHILO; ERIN VOLK; ANDREW REILLY; FREDERICK K. CHU

2000-01-01

3

OspA, a Lipoprotein Antigen of the Obligate Intracellular Bacterial Pathogen Piscirickettsia salmonis  

Microsoft Academic Search

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

Michael A. Kuzyk; Ján Burian; Julian C. Thornton; William W. Kay

2001-01-01

4

Antibody-mediated elimination of the obligate intracellular bacterial pathogen Ehrlichia chaffeensis during active infection.  

PubMed

It is generally accepted that cellular, but not humoral immunity, plays an important role in host defense against intracellular bacteria. However, studies of some of these pathogens have provided evidence that antibodies can provide immunity if present during the initiation of infection. Here, we examined immunity against infection by Ehrlichia chaffeensis, an obligate intracellular bacterium that causes human monocytic ehrlichiosis. Studies with mice have demonstrated that immunocompetent strains are resistant to persistent infection but that SCID mice become persistently and fatally infected. Transfer of immune serum or antibodies obtained from immunocompetent C57BL/6 mice to C57BL/6 scid mice provided significant although transient protection from infection. Bacterial clearance was observed when administration occurred at the time of inoculation or well after infection was established. The effect was dose dependent, occurred within 2 days, and persisted for as long as 2 weeks. Weekly serum administration prolonged the survival of susceptible mice. Although cellular immunity is required for complete bacterial clearance, the data show that antibodies can play a significant role in the elimination of this obligate intracellular bacterium during active infection and thus challenge the paradigm that humoral responses are unimportant for immunity to such organisms. PMID:10722619

Winslow, G M; Yager, E; Shilo, K; Volk, E; Reilly, A; Chu, F K

2000-04-01

5

Pathogenic Potential of Novel Chlamydiae and Diagnostic Approaches to Infections Due to These Obligate Intracellular Bacteria  

PubMed Central

Novel chlamydiae are newly recognized members of the phylum Chlamydiales that are only distantly related to the classic Chlamydiaceae, i.e., Chlamydia and Chlamydophila species. They also exibit an obligate biphasic intracellular life cycle within eukaryote host cells. Some of these new chlamydiae are currently considered potential emerging human and/or animal pathogens. Parachlamydia acanthamoebae and Simkania negevensis are both emerging respiratory human pathogens, Waddlia chondrophila could be a novel abortigenic bovine agent, and Piscichlamydia salmonis has recently been identified as an agent of the gill epitheliocystis in the Atlantic salmon. Fritschea spp. and Rhabdochlamydia spp. seem to be confined to arthropods, but some evidence for human exposure exists. In this review, we first summarize the data supporting a pathogenic potential of the novel chlamydiae for humans and other vertebrates and the interactions that most of these chlamydiae have with free-living amoebae. We then review the diagnostic approaches to infections potentially due to the novel chlamydiae, especially focusing on the currently available PCR-based protocols, mammalian cell culture, the amoebal coculture system, and serology.

Corsaro, Daniele; Greub, Gilbert

2006-01-01

6

An optimal method of iron starvation of the obligate intracellular pathogen, Chlamydia trachomatis.  

PubMed

Iron is an essential cofactor in a number of critical biochemical reactions, and as such, its acquisition, storage, and metabolism is highly regulated in most organisms. The obligate intracellular bacterium, Chlamydia trachomatis experiences a developmental arrest when iron within the host is depleted. The nature of the iron starvation response in Chlamydia is relatively uncharacterized because of the likely inefficient method of iron depletion, which currently relies on the compound deferoxamine mesylate (DFO). Inefficient induction of the iron starvation response precludes the identification of iron-regulated genes. This report evaluated DFO with another iron chelator, 2,2'-bipyridyl (Bpdl) and presented a systematic comparison of the two across a range of criteria. We demonstrate that the membrane permeable Bpdl was superior to DFO in the inhibition of chlamydia development, the induction of aberrant morphology, and the induction of an iron starvation transcriptional response in both host and bacteria. Furthermore, iron starvation using Bpdl identified the periplasmic iron-binding protein-encoding ytgA gene as iron-responsive. Overall, the data present a compelling argument for the use of Bpdl, rather than DFO, in future iron starvation studies of chlamydia and other intracellular bacteria. PMID:21687412

Thompson, Christopher C; Carabeo, Rey A

2011-02-14

7

Innovative approach for transcriptomic analysis of obligate intracellular pathogen: selective capture of transcribed sequences of Ehrlichia ruminantium  

Microsoft Academic Search

BACKGROUND: Whole genome transcriptomic analysis is a powerful approach to elucidate the molecular mechanisms controlling the pathogenesis of obligate intracellular bacteria. However, the major hurdle resides in the low quantity of prokaryotic mRNAs extracted from host cells. Our model Ehrlichia ruminantium (ER), the causative agent of heartwater, is transmitted by tick Amblyomma variegatum. This bacterium affects wild and domestic ruminants

Loïc Emboulé; France Daigle; Damien F Meyer; Bernard Mari; Valérie Pinarello; Christian Sheikboudou; Virginie Magnone; Roger Frutos; Alain Viari; Pascal Barbry; Dominique Martinez; Thierry Lefrançois; Nathalie Vachiéry

2009-01-01

8

A MyD88-Dependent Early IL-17 Production Protects Mice against Airway Infection with the Obligate Intracellular Pathogen Chlamydia muridarum1  

PubMed Central

We found that IL-17, a signature cytokine of Th17, was produced early in the innate immunity phase after an intranasal infection with the obligate intracellular pathogen Chlamydia muridarum. The airway IL-17, which peaked at 48 h after infection, was dependent on live chlamydial organism replication and MyD88-mediated signaling pathways. Treatment with antibiotics or knockout of the MyD88 gene, but not Toll/IL receptor domain-containing adapter-inducing IFN-?, can block the early IL-17 production. Treatment of mice with an anti-IL-17-neutralizing mAb enhanced growth of chlamydial organisms in the lung, dissemination to other organs, and decreased mouse survival, whereas treatment with an isotype-matched control IgG had no effect. Although IL-17 did not directly affect chlamydial growth in cell culture, it enhanced the production of other inflammatory cytokines and chemokines by Chlamydia-infected cells and promoted neutrophil infiltration in mouse airways during chlamydial infection, which may contribute to the antichlamydial effect of IL-17. These observations suggest that an early IL-17 response as an innate immunity component plays an important role in initiating host defense against infection with intracellular bacterial pathogens in the airway.

Zhang, Xiaoyun; Gao, Lifen; Lei, Lei; Zhong, Youmin; Dube, Peter; Berton, Michael T.; Arulanandam, Bernard; Zhang, Jinshun; Zhong, Guangming

2009-01-01

9

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

10

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

11

ELECTRON MICROSCOPY IN THE STUDY OF INTRACELLULAR PATHOGENS  

Microsoft Academic Search

Chlamydia trachomatis is the causative agent of trachoma, the leading cause of infectious blind- ness worldwide, and is also the most common cause of sexually transmitted disease. Chlamydiae are obligate intracellular bacteria that replicate within a unique intracellular vacuole termed an inclusion. Although chlamydiae are clearly important pathogens, they can be difficult to study due to the lack of genetic

Elizabeth R. FISCHER; Ted HACKSTADT

12

Obligate intracellular parasites: Rickettsia prowazekii and Chlamydia trachomatis.  

PubMed

Transitions to obligate intracellular parasitism have occurred at numerous times in the evolutionary past. The genome sequences of two obligate intracellular parasites, Rickettsia prowazekii and Chlamydia trachomatis, were published last year. A comparative analysis of these two genomes has revealed examples of reductive convergent evolution, such as a massive loss of genes involved in biosynthetic functions. In addition, both genomes were found to encode transport systems for ATP and ADP, not otherwise found in bacteria. Here, we discuss adaptations to intracellular habitats by comparing the information obtained from the recently published genome sequences of R. prowazekii and C. trachomatis. PMID:10376669

Zomorodipour, A; Andersson, S G

1999-06-01

13

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

14

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

15

Metabolic Interdependence of Obligate Intracellular Bacteria and Their Insect Hosts†  

PubMed Central

Mutualistic associations of obligate intracellular bacteria and insects have attracted much interest in the past few years due to the evolutionary consequences for their genome structure. However, much less attention has been paid to the metabolic ramifications for these endosymbiotic microorganisms, which have to compete with but also to adapt to another metabolism—that of the host cell. This review attempts to provide insights into the complex physiological interactions and the evolution of metabolic pathways of several mutualistic bacteria of aphids, ants, and tsetse flies and their insect hosts.

Zientz, Evelyn; Dandekar, Thomas; Gross, Roy

2004-01-01

16

Molecular pathogenesis of the obligate intracellular bacterium Coxiella burnetii.  

PubMed

The agent of Q fever, Coxiella burnetii, is an obligate intracellular bacterium that causes acute and chronic infections. The study of C. burnetii pathogenesis has benefited from two recent fundamental advances: improved genetic tools and the ability to grow the bacterium in extracellular media. In this Review, we describe how these recent advances have improved our understanding of C. burnetii invasion and host cell modulation, including the formation of replication-permissive Coxiella-containing vacuoles. Furthermore, we describe the Dot/Icm (defect in organelle trafficking/intracellular multiplication) system, which is used by C. burnetii to secrete a range of effector proteins into the host cell, and we discuss the role of these effectors in remodelling the host cell. PMID:23797173

van Schaik, Erin J; Chen, Chen; Mertens, Katja; Weber, Mary M; Samuel, James E

2013-06-24

17

Analysis of convergent gene transcripts in the obligate intracellular bacterium Rickettsia prowazekii.  

PubMed

Termination of transcription is an important component of bacterial gene expression. However, little is known concerning this process in the obligate intracellular pathogen and model for reductive evolution, Rickettsia prowazekii. To assess transcriptional termination in this bacterium, transcripts of convergent gene pairs, some containing predicted intrinsic terminators, were analyzed. These analyses revealed that, rather than terminating at a specific site within the intervening region between the convergent genes, most of the transcripts demonstrated either a lack of termination within this region, which generated antisense RNA, or a putative non-site-specific termination that occurred throughout the intervening sequence. Transcripts terminating at predicted intrinsic terminators, as well as at a putative Rho-dependant terminator, were also examined and found to vary based on the rickettsial host environment. These results suggest that transcriptional termination, or lack thereof, plays a role in rickettsial gene regulation. PMID:21298070

Woodard, Andrew; Wood, David O

2011-01-26

18

Survival Strategy of Obligately Intracellular Ehrlichia chaffeensis: Novel Modulation of Immune Response and Host Cell Cycles  

PubMed Central

Ehrlichia chaffeensis is an obligatory intracellular bacterium which resides in an early endosome in monocytes. E. chaffeensis infection in a human monocyte cell line (THP1) significantly altered the transcriptional levels of 4.5% of host genes, including those coding for apoptosis inhibitors, proteins regulating cell differentiation, signal transduction, proinflammatory cytokines, biosynthetic and metabolic proteins, and membrane trafficking proteins. The transcriptional profile of the host cell revealed key themes in the pathogenesis of Ehrlichia. First, E. chaffeensis avoided stimulation of or repressed the transcription of cytokines involved in the early innate immune response and cell-mediated immune response to intracellular microbes, such as the interleukin-12 (IL-12), IL-15, and IL-18 genes, which might make Ehrlichia a stealth organism for the macrophage. Second, E. chaffeensis up-regulated NF-?B and apoptosis inhibitors and differentially regulated cell cyclins and CDK expression, which may enhance host cell survival. Third, E. chaffeensis also inhibited the gene transcription of RAB5A, SNAP23, and STX16, which are involved in membrane trafficking. By comparing the transcriptional response of macrophages infected with other bacteria and that of macrophages infected with E. chaffeensis, we have identified few genes that are commonly induced and no commonly repressed genes. These results illustrate the stereotyped macrophage response to other pathogens, in contrast with the novel host response to obligate intracellular Ehrlichia, whose survival depends entirely on a long evolutionary process of outmaneuvering macrophages.

Zhang, Jian-zhi; Sinha, Mala; Luxon, Bruce A.; Yu, Xue-jie

2004-01-01

19

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

20

Maspin (SERPINB5) is an obligate intracellular serpin.  

PubMed

Maspin (SERPINB5) is a tumor suppressor lost in breast and prostate cancer whose molecular function is unknown. It is a non-inhibitory member of the clade B serpins suggested to play a role in a plethora of intracellular and extracellular settings, yet its normal cellular distribution has never been clarified. Here we investigate the distribution of maspin in non-transformed human epithelial cells. By indirect immunofluorescence, maspin has a nucleocytoplasmic distribution in breast (MCF10A) and prostate (RWPE-1) cells and, by immunoblotting and pulse-chase analyses, is neither glycosylated nor secreted. Cell surface biotinylation studies also show that maspin is not present at the cell surface. Differentiation of MCF10A cells into three-dimensional acini results in the redistribution of maspin from the nucleus to the cytoplasm but does not result in secretion. Addition of an efficient conventional signal peptide to maspin directs it into the secretory pathway and results in glycosylation but not secretion. We further show that maspin in the cytoplasm of MCF10A cells is a soluble monomeric protein that is not detectably associated with the cytoskeleton or other extractable components. Taken together, these results suggest that maspin is restricted to an intracellular, possibly nuclear, role in which it influences cell-matrix interactions indirectly. It is probably released only as a consequence of cell damage or necrosis. PMID:20123984

Teoh, Sonia S Y; Whisstock, James C; Bird, Phillip I

2010-02-01

21

Heterogeneity of intracellular replication of bacterial pathogens.  

PubMed

Intracellular growth of bacterial pathogens is usually measured at the whole population level, which masks potential cell-to-cell variation. More direct measurements of replication using microscopy and Flow Cytometry have revealed extensive heterogeneity among populations of intracellular bacteria. Heterogeneity could result from differential exposure to nutritional deprivation and host cell antimicrobial activities, as well as variability in production or efficacy of virulence molecules. Furthermore, bacteria have evolved specific mechanisms to generate epigenetic variation. These include unequal partitioning of proteins during cell division, genetic phase variation and activation of toxin/antitoxin systems. An important aspect of heterogeneity concerns the generation of viable, non-replicating bacteria. These are predicted to confer tolerance to host-induced stress and antibiotics, and to be sources of persistent infection. PMID:23485258

Helaine, Sophie; Holden, David W

2013-02-26

22

A Method for Purifying Obligate Intracellular Coxiella burnetii that Employs Digitonin Lysis of Host Cells  

PubMed Central

Purification of the obligate intracellular bacterium Coxiella burnetii requires physical disruption of infected cells. Here we describe a gentle and safe digitonin lysis procedure to release C. burnetii from infected cells. The purity, yield, and infectivity of digitonin-prepped organisms are comparable to that of organisms purified using cell lysis by sonication.

Cockrell, Diane C.; Beare, Paul A.; Fischer, Elizabeth R.; Howe, Dale; Heinzen, Robert. A.

2008-01-01

23

Listeria monocytogenes -- from saprophyte to intracellular pathogen  

PubMed Central

Listeria monocytogenes is a bacterium that lives in the soil as a saprophyte but is capable of making the transition into a pathogen following its ingestion by susceptible humans or animals. Recent studies suggest that L. monocytogenes mediates its saprophyte-to-cytosolic-parasite transition through the careful modulation of the activity of a virulence regulatory protein known as PrfA, using a range of environmental cues that include available carbon sources. In this Progress article we describe the regulation of PrfA and its role in the L. monocytogenes transition from the saprophytic stage to the virulent intracellular stage.

Freitag, Nancy E.; Port, Gary C.; Miner, Maurine D.

2010-01-01

24

Autophagy as a defence against intracellular pathogens.  

PubMed

Autophagy is a membrane trafficking pathway that results in the formation of autophagosomes which deliver portions of the cytosol to lysosomes for degradation. When autophagosomes engulf intracellular pathogens, the pathway is called 'xenophagy' because it leads to the removal of foreign material. Autophagy is activated during infection by Toll-like receptors that recognize pathogen-associated molecular patterns. This allows autophagy to kill micro-organisms and present pathogen components to the innate and acquired immune systems. The targeting of pathogens by autophagy is selective and involves a growing family of autophagy receptors that bind to the autophagosome membrane protein LC3 (light-chain 3)/Atg8 (autography-related protein 8). Ubiquitination of microbes identifies them as substrates for autophagy and they are delivered to autophagosomes by autophagy receptors that bind both ubiquitin and LC3/Atg8. Bacteria can also be detected before they enter the cytosol by autophagy receptors that scan the surface of membrane compartments for evidence of damage. The observation that some pathogens survive in cells suggests they can evade complete destruction by autophagy. For some bacteria this involves proteins that shield the surface of the bacteria from recognition by autophagy receptors. Other viruses and bacteria are resistant to degradation in lysosomes and use autophagosomes and/or lysosomes as sites for replication. Most of our current understanding of the role played by autophagy during microbial infection has come from studies of bacteria and viruses in tissue culture cell lines. Future work will focus on understanding how autophagy determines the outcome of infection 'in vivo', and how autophagy pathways can be exploited therapeutically. PMID:24070478

Wileman, Tom

2013-09-27

25

Sensing intracellular pathogens-NOD-like receptors.  

PubMed

The innate immune system uses different molecules that sense pathogen associated molecular patterns. These include Toll-like receptors (TLRs), RIG-1-like receptors (RLRs) and the NOD-like receptors (NLRs). The NLRs, consisting of more than 20 related family members, are present in the cytosol and recognize intracellular ligands. Members of the NLR can be grouped into molecules that contain either a CARD or a Pyrin motif. The NOD proteins mediate NF-kappaB activation, whereas Pyrin molecules such as NALP3 regulate IL-1beta and IL-18 production. In this review, we will discuss the role of NLRs in pattern recognition of microbial components and their role in health and disease. PMID:18487086

Rietdijk, Svend T; Burwell, Timothy; Bertin, John; Coyle, Anthony J

2008-05-16

26

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

Microsoft Academic Search

Received 23 August 2004\\/Accepted 23 October 2004 We developed and applied transposon-based transformation vectors for molecular manipulation and anal- ysis 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

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

2005-01-01

27

Nanomedicine as an emerging approach against intracellular pathogens.  

PubMed

Diseases such as tuberculosis, hepatitis, and HIV/AIDS are caused by intracellular pathogens and are a major burden to the global medical community. Conventional treatments for these diseases typically consist of long-term therapy with a combination of drugs, which may lead to side effects and contribute to low patient compliance. The pathogens reside within intracellular compartments of the cell, which provide additional barriers to effective treatment. Therefore, there is a need for improved and more effective therapies for such intracellular diseases. This review will summarize, for the first time, the intracellular compartments in which pathogens can reside and discuss how nanomedicine has the potential to improve intracellular disease therapy by offering properties such as targeting, sustained drug release, and drug delivery to the pathogen's intracellular location. The characteristics of nanomedicine may prove advantageous in developing improved or alternative therapies for intracellular diseases. PMID:22228996

Armstead, Andrea L; Li, Bingyun

2011-12-09

28

Evolutionary Genomics of a Temperate Bacteriophage in an Obligate Intracellular Bacteria (Wolbachia)  

PubMed Central

Genome evolution of bacteria is usually influenced by ecology, such that bacteria with a free-living stage have large genomes and high rates of horizontal gene transfer, while obligate intracellular bacteria have small genomes with typically low amounts of gene exchange. However, recent studies indicate that obligate intracellular species that host-switch frequently harbor agents of horizontal transfer such as mobile elements. For example, the temperate double-stranded DNA bacteriophage WO in Wolbachia persistently transfers between bacterial coinfections in the same host. Here we show that despite the phage's rampant mobility between coinfections, the prophage's genome displays features of constraint related to its intracellular niche. First, there is always at least one intact prophage WO and usually several degenerate, independently-acquired WO prophages in each Wolbachia genome. Second, while the prophage genomes are modular in composition with genes of similar function grouping together, the modules are generally not interchangeable with other unrelated phages and thus do not evolve by the Modular Theory. Third, there is an unusual core genome that strictly consists of head and baseplate genes; other gene modules are frequently deleted. Fourth, the prophage recombinases are diverse and there is no conserved integration sequence. Finally, the molecular evolutionary forces acting on prophage WO are point mutation, intragenic recombination, deletion, and purifying selection. Taken together, these analyses indicate that while lateral transfer of phage WO is pervasive between Wolbachia with occasional new gene uptake, constraints of the intracellular niche obstruct extensive mixture between WO and the global phage population. Although the Modular Theory has long been considered the paradigm of temperate bacteriophage evolution in free-living bacteria, it appears irrelevant in phages of obligate intracellular bacteria.

Kent, Bethany N.; Funkhouser, Lisa J.; Setia, Shefali; Bordenstein, Seth R.

2011-01-01

29

Genome-wide screen for temperature-regulated genes of the obligate intracellular bacterium, Rickettsia typhi  

Microsoft Academic Search

BACKGROUND: The ability of rickettsiae to survive in multiple eukaryotic host environments provides a good model for studying pathogen-host molecular interactions. Rickettsia typhi, the etiologic agent of murine typhus, is a strictly intracellular gram negative ?-proteobacterium, which is transmitted to humans by its arthropod vector, the oriental rat flea, Xenopsylla cheopis. Thus, R. typhi must cycle between mammalian and flea

Sheila M Dreher-Lesnick; Shane M Ceraul; M Sayeedur Rahman; Abdu F Azad

2008-01-01

30

The Genome of the Obligately Intracellular Bacterium Ehrlichia canis Reveals Themes of Complex Membrane Structure and Immune Evasion Strategies  

SciTech Connect

Ehrlichia canis, a small obligately intracellular, tick-transmitted, gram-negative, {alpha}-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, 17 putative pseudogenes, and a substantial proportion of noncoding sequence (27%). 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. Genes associated with pathogen-host interactions were identified, including a small group encoding proteins (n = 12) with tandem repeats and another group encoding proteins with eukaryote-like ankyrin domains (n = 7).

Mavromatis, K [U.S. Department of Energy, Joint Genome Institute; Doyle, C Kuyler [Center for Biodenfense and Emerging Infectious Diseases; Lykidis, A [U.S. Department of Energy, Joint Genome Institute; Ivanova, N [U.S. Department of Energy, Joint Genome Institute; Francino, M P [U.S. Department of Energy, Joint Genome Institute; Chain, Patrick S [ORNL; Shin, M [U.S. Department of Energy, Joint Genome Institute; Malfatti, Stephanie [Lawrence Livermore National Laboratory (LLNL); Larimer, Frank W [ORNL; Copeland, A [U.S. Department of Energy, Joint Genome Institute; Detter, J C [U.S. Department of Energy, Joint Genome Institute; Land, Miriam L [ORNL; Richardson, P M [U.S. Department of Energy, Joint Genome Institute; Yu, X J [Center for Biodenfense and Emerging Infectious Diseases; Walker, D H [Center for Biodenfense and Emerging Infectious Diseases; McBride, J W [Center for Biodenfense and Emerging Infectious Diseases; Kyripides, N C [U.S. Department of Energy, Joint Genome Institute

2006-01-01

31

Apoptotic mimicry by an obligate intracellular parasite downregulates macrophage microbicidal activity.  

PubMed

Programmed cell death by apoptosis of unnecessary or potentially harmful cells is clearly beneficial to multicellular organisms. Proper functioning of such a program demands that the removal of dying cells proceed without an inflammatory reaction. Phosphatidylserine (PS) is one of the ligands displayed by apoptotic cells that participates in their noninflammatory removal when recognized by neighboring phagocytes. PS ligation induces the release of transforming growth factor-beta (TGF-beta), an antiinflammatory cytokine that mediates the suppression of macrophage-mediated inflammation. In Hydra vulgaris, an organism that stands at the base of metazoan evolution, the selective advantage provided by apoptosis lies in the fact that Hydra can survive recycling apoptotic cells by phagocytosis. In unicellular organisms, it has been proposed that altruistic death benefits clonal populations of yeasts and trypanosomatids. Now we show that advantageous features of the apoptotic process can operate without death as the necessary outcome. Leishmania spp are able to evade the killing activity of phagocytes and establish themselves as obligate intracellular parasites. Amastigotes, responsible for disease propagation, similar to apoptotic cells, inhibit macrophage activity by exposing PS. Exposed PS participates in amastigote internalization. Recognition of this moiety by macrophages induces TGF-beta secretion and IL-10 synthesis, inhibits NO production, and increases susceptibility to intracellular leishmanial growth. PMID:11728310

de Freitas Balanco, J M; Moreira, M E; Bonomo, A; Bozza, P T; Amarante-Mendes, G; Pirmez, C; Barcinski, M A

2001-11-27

32

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

33

Roles of autophagy in elimination of intracellular bacterial pathogens.  

PubMed

As a fundamental intracellular catabolic process, autophagy is important and required for the elimination of protein aggregates and damaged cytosolic organelles during a variety of stress conditions. Autophagy is now being recognized as an essential component of innate immunity; i.e., the recognition, selective targeting, and elimination of microbes. Because of its crucial roles in the innate immune system, therapeutic targeting of bacteria by means of autophagy activation may prove a useful strategy to combat intracellular infections. However, important questions remain, including which molecules are critical in bacterial targeting by autophagy, and which mechanisms are involved in autophagic clearance of intracellular microbes. In this review, we discuss the roles of antibacterial autophagy in intracellular bacterial infections (Mycobacteria, Salmonella, Shigella, Listeria, and Legionella) and present recent evidence in support of molecular mechanisms driving autophagy to target bacteria and eliminate invading pathogens. PMID:23653625

Jo, Eun-Kyeong; Yuk, Jae-Min; Shin, Dong-Min; Sasakawa, Chihiro

2013-05-06

34

Manipulation of Costimulatory Molecules by Intracellular Pathogens: Veni, Vidi, Vici!!  

PubMed Central

Some of the most successful pathogens of human, such as Mycobacterium tuberculosis (Mtb), HIV, and Leishmania donovani not only establish chronic infections but also remain a grave global threat. These pathogens have developed innovative strategies to evade immune responses such as antigenic shift and drift, interference with antigen processing/presentation, subversion of phagocytosis, induction of immune regulatory pathways, and manipulation of the costimulatory molecules. Costimulatory molecules expressed on the surface of various cells play a decisive role in the initiation and sustenance of immunity. Exploitation of the “code of conduct” of costimulation pathways provides evolutionary incentive to the pathogens and thereby abates the functioning of the immune system. Here we review how Mtb, HIV, Leishmania sp., and other pathogens manipulate costimulatory molecules to establish chronic infection. Impairment by pathogens in the signaling events delivered by costimulatory molecules may be responsible for defective T-cell responses; consequently organisms grow unhindered in the host cells. This review summarizes the convergent devices that pathogens employ to tune and tame the immune system using costimulatory molecules. Studying host-pathogen interaction in context with costimulatory signals may unveil the molecular mechanism that will help in understanding the survival/death of the pathogens. We emphasize that the very same pathways can potentially be exploited to develop immunotherapeutic strategies to eliminate intracellular pathogens.

Pahari, Susanta; Agrewala, Javed N.

2012-01-01

35

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

36

Genome-wide screen for temperature-regulated genes of the obligate intracellular bacterium, Rickettsia typhi  

PubMed Central

Background The ability of rickettsiae to survive in multiple eukaryotic host environments provides a good model for studying pathogen-host molecular interactions. Rickettsia typhi, the etiologic agent of murine typhus, is a strictly intracellular gram negative ?-proteobacterium, which is transmitted to humans by its arthropod vector, the oriental rat flea, Xenopsylla cheopis. Thus, R. typhi must cycle between mammalian and flea hosts, two drastically different environments. We hypothesize that temperature plays a role in regulating host-specific gene expression, allowing R. typhi to survive in mammalian and arthropod hosts. In this study, we used Affymetrix microarrays to screen for temperature-induced genes upon a temperature shift from 37°C to 25°C, mimicking the two different host temperatures in vitro. Results Temperature-responsive genes belonged to multiple functional categories including among others, transcription, translation, posttranslational modification/protein turnover/chaperones and intracellular trafficking and secretion. A large number of differentially expressed genes are still poorly characterized, and either have no known function or are not in the COG database. The microarray results were validated with quantitative real time RT-PCR. Conclusion This microarray screen identified various genes that were differentially expressed upon a shift in temperature from 37°C to 25°C. Further characterization of the identified genes may provide new insights into the ability of R. typhi to successfully transition between its mammalian and arthropod hosts.

Dreher-Lesnick, Sheila M; Ceraul, Shane M; Rahman, M Sayeedur; Azad, Abdu F

2008-01-01

37

The Genome of the Obligately Intracellular Bacterium Ehrlichia canis Reveals Themes of Complex Membrane Structure and Immune Evasion Strategies  

Microsoft Academic Search

Ehrlichia canis, a small obligately intracellular, tick-transmitted, gram-negative, -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, 17 putative pseudogenes, and a substantial proportion of noncoding sequence (27%). Interesting genome

K. Mavromatis; C. Kuyler Doyle; A. Lykidis; N. Ivanova; M. P. Francino; Patrick S Chain; M. Shin; Stephanie Malfatti; Frank W Larimer; A. Copeland; J. C. Detter; Miriam L Land; P. M. Richardson; X. J. Yu; D. H. Walker; J. W. McBride; N C Kyripides

2006-01-01

38

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

2013-06-14

39

The ubiquitin ligase parkin mediates resistance to intracellular pathogens.  

PubMed

Ubiquitin-mediated targeting of intracellular bacteria to the autophagy pathway is a key innate defence mechanism against invading microbes, including the important human pathogen Mycobacterium tuberculosis. However, the ubiquitin ligases responsible for catalysing ubiquitin chains that surround intracellular bacteria are poorly understood. The parkin protein is a ubiquitin ligase with a well-established role in mitophagy, and mutations in the parkin gene (PARK2) lead to increased susceptibility to Parkinson's disease. Surprisingly, genetic polymorphisms in the PARK2 regulatory region are also associated with increased susceptibility to intracellular bacterial pathogens in humans, including Mycobacterium leprae and Salmonella enterica serovar Typhi, but the function of parkin in immunity has remained unexplored. Here we show that parkin has a role in ubiquitin-mediated autophagy of M. tuberculosis. Both parkin-deficient mice and flies are sensitive to various intracellular bacterial infections, indicating parkin has a conserved role in metazoan innate defence. Moreover, our work reveals an unexpected functional link between mitophagy and infectious disease. PMID:24005326

Manzanillo, Paolo S; Ayres, Janelle S; Watson, Robert O; Collins, Angela C; Souza, Gianne; Rae, Chris S; Schneider, David S; Nakamura, Ken; Shiloh, Michael U; Cox, Jeffery S

2013-09-04

40

HIGS: host-induced gene silencing in the obligate biotrophic fungal pathogen Blumeria graminis.  

PubMed

Powdery mildew fungi are obligate biotrophic pathogens that only grow on living hosts and cause damage in thousands of plant species. Despite their agronomical importance, little direct functional evidence for genes of pathogenicity and virulence is currently available because mutagenesis and transformation protocols are lacking. Here, we show that the accumulation in barley (Hordeum vulgare) and wheat (Triticum aestivum) of double-stranded or antisense RNA targeting fungal transcripts affects the development of the powdery mildew fungus Blumeria graminis. Proof of concept for host-induced gene silencing was obtained by silencing the effector gene Avra10, which resulted in reduced fungal development in the absence, but not in the presence, of the matching resistance gene Mla10. The fungus could be rescued from the silencing of Avra10 by the transient expression of a synthetic gene that was resistant to RNA interference (RNAi) due to silent point mutations. The results suggest traffic of RNA molecules from host plants into B. graminis and may lead to an RNAi-based crop protection strategy against fungal pathogens. PMID:20884801

Nowara, Daniela; Gay, Alexandra; Lacomme, Christophe; Shaw, Jane; Ridout, Christopher; Douchkov, Dimitar; Hensel, Götz; Kumlehn, Jochen; Schweizer, Patrick

2010-09-30

41

Survival Strategy of Obligately Intracellular Ehrlichia chaffeensis: Novel Modulation of Immune Response and Host Cell Cycles  

Microsoft Academic Search

Ehrlichia chaffeensis is an obligatory intracellular bacterium which resides in an early endosome in mono- cytes. E. chaffeensis infection in a human monocyte cell line (THP1) significantly altered the transcriptional levels of 4.5% of host genes, including those coding for apoptosis inhibitors, proteins regulating cell differen- tiation, signal transduction, proinflammatory cytokines, biosynthetic and metabolic proteins, and membrane trafficking proteins. The

Jian-zhi Zhang; Mala Sinha; Bruce A. Luxon; Xue-jie Yu

2004-01-01

42

Infection of Zebrafish Embryos with Intracellular Bacterial Pathogens  

PubMed Central

Zebrafish (Danio rerio) embryos are increasingly used as a model for studying the function of the vertebrate innate immune system in host-pathogen interactions 1. The major cell types of the innate immune system, macrophages and neutrophils, develop during the first days of embryogenesis prior to the maturation of lymphocytes that are required for adaptive immune responses. The ease of obtaining large numbers of embryos, their accessibility due to external development, the optical transparency of embryonic and larval stages, a wide range of genetic tools, extensive mutant resources and collections of transgenic reporter lines, all add to the versatility of the zebrafish model. Salmonella enterica serovar Typhimurium (S. typhimurium) and Mycobacterium marinum can reside intracellularly in macrophages and are frequently used to study host-pathogen interactions in zebrafish embryos. The infection processes of these two bacterial pathogens are interesting to compare because S. typhimurium infection is acute and lethal within one day, whereas M. marinum infection is chronic and can be imaged up to the larval stage 2, 3. The site of micro-injection of bacteria into the embryo (Figure 1) determines whether the infection will rapidly become systemic or will initially remain localized. A rapid systemic infection can be established by micro-injecting bacteria directly into the blood circulation via the caudal vein at the posterior blood island or via the Duct of Cuvier, a wide circulation channel on the yolk sac connecting the heart to the trunk vasculature. At 1 dpf, when embryos at this stage have phagocytically active macrophages but neutrophils have not yet matured, injecting into the blood island is preferred. For injections at 2-3 dpf, when embryos also have developed functional (myeloperoxidase-producing) neutrophils, the Duct of Cuvier is preferred as the injection site. To study directed migration of myeloid cells towards local infections, bacteria can be injected into the tail muscle, otic vesicle, or hindbrain ventricle 4-6. In addition, the notochord, a structure that appears to be normally inaccessible to myeloid cells, is highly susceptible to local infection 7. A useful alternative for high-throughput applications is the injection of bacteria into the yolk of embryos within the first hours after fertilization 8. Combining fluorescent bacteria and transgenic zebrafish lines with fluorescent macrophages or neutrophils creates ideal circumstances for multi-color imaging of host-pathogen interactions. This video article will describe detailed protocols for intravenous and local infection of zebrafish embryos with S. typhimurium or M. marinum bacteria and for subsequent fluorescence imaging of the interaction with cells of the innate immune system.

Benard, Erica L.; van der Sar, Astrid M.; Ellett, Felix; Lieschke, Graham J.; Spaink, Herman P.; Meijer, Annemarie H.

2012-01-01

43

Actin-Based Motility of Intracellular Microbial Pathogens  

PubMed Central

A diverse group of intracellular microorganisms, including Listeria monocytogenes, Shigella spp., Rickettsia spp., and vaccinia virus, utilize actin-based motility to move within and spread between mammalian host cells. These organisms have in common a pathogenic life cycle that involves a stage within the cytoplasm of mammalian host cells. Within the cytoplasm of host cells, these organisms activate components of the cellular actin assembly machinery to induce the formation of actin tails on the microbial surface. The assembly of these actin tails provides force that propels the organisms through the cell cytoplasm to the cell periphery or into adjacent cells. Each of these organisms utilizes preexisting mammalian pathways of actin rearrangement to induce its own actin-based motility. Particularly remarkable is that while all of these microbes use the same or overlapping pathways, each intercepts the pathway at a different step. In addition, the microbial molecules involved are each distinctly different from the others. Taken together, these observations suggest that each of these microbes separately and convergently evolved a mechanism to utilize the cellular actin assembly machinery. The current understanding of the molecular mechanisms of microbial actin-based motility is the subject of this review.

Goldberg, Marcia B.

2001-01-01

44

The genome sequence of the facultative intracellular pathogen Brucella melitensis.  

PubMed

Brucella melitensis is a facultative intracellular bacterial pathogen that causes abortion in goats and sheep and Malta fever in humans. The genome of B. melitensis strain 16M was sequenced and found to contain 3,294,935 bp distributed over two circular chromosomes of 2,117,144 bp and 1,177,787 bp encoding 3,197 ORFs. By using the bioinformatics suite ERGO, 2,487 (78%) ORFs were assigned functions. The origins of replication of the two chromosomes are similar to those of other alpha-proteobacteria. Housekeeping genes, including those involved in DNA replication, transcription, translation, core metabolism, and cell wall biosynthesis, are distributed on both chromosomes. Type I, II, and III secretion systems are absent, but genes encoding sec-dependent, sec-independent, and flagella-specific type III, type IV, and type V secretion systems as well as adhesins, invasins, and hemolysins were identified. Several features of the B. melitensis genome are similar to those of the symbiotic Sinorhizobium meliloti. PMID:11756688

DelVecchio, Vito G; Kapatral, Vinayak; Redkar, Rajendra J; Patra, Guy; Mujer, Cesar; Los, Tamara; Ivanova, Natalia; Anderson, Iain; Bhattacharyya, Anamitra; Lykidis, Athanasios; Reznik, Gary; Jablonski, Lynn; Larsen, Niels; D'Souza, Mark; Bernal, Axel; Mazur, Mikhail; Goltsman, Eugene; Selkov, Eugene; Elzer, Philip H; Hagius, Sue; O'Callaghan, David; Letesson, Jean-Jacques; Haselkorn, Robert; Kyrpides, Nikos; Overbeek, Ross

2001-12-26

45

The genome sequence of the facultative intracellular pathogen Brucella melitensis  

PubMed Central

Brucella melitensis is a facultative intracellular bacterial pathogen that causes abortion in goats and sheep and Malta fever in humans. The genome of B. melitensis strain 16M was sequenced and found to contain 3,294,935 bp distributed over two circular chromosomes of 2,117,144 bp and 1,177,787 bp encoding 3,197 ORFs. By using the bioinformatics suite ERGO, 2,487 (78%) ORFs were assigned functions. The origins of replication of the two chromosomes are similar to those of other ?-proteobacteria. Housekeeping genes, including those involved in DNA replication, transcription, translation, core metabolism, and cell wall biosynthesis, are distributed on both chromosomes. Type I, II, and III secretion systems are absent, but genes encoding sec-dependent, sec-independent, and flagella-specific type III, type IV, and type V secretion systems as well as adhesins, invasins, and hemolysins were identified. Several features of the B. melitensis genome are similar to those of the symbiotic Sinorhizobium meliloti.

DelVecchio, Vito G.; Kapatral, Vinayak; Redkar, Rajendra J.; Patra, Guy; Mujer, Cesar; Los, Tamara; Ivanova, Natalia; Anderson, Iain; Bhattacharyya, Anamitra; Lykidis, Athanasios; Reznik, Gary; Jablonski, Lynn; Larsen, Niels; D'Souza, Mark; Bernal, Axel; Mazur, Mikhail; Goltsman, Eugene; Selkov, Eugene; Elzer, Philip H.; Hagius, Sue; O'Callaghan, David; Letesson, Jean-Jacques; Haselkorn, Robert; Kyrpides, Nikos; Overbeek, Ross

2002-01-01

46

Silica-Antibiotic Hybrid Nanoparticles for Targeting Intracellular Pathogens ?  

PubMed Central

We investigated the capability of biodegradable silica xerogel as a novel carrier of antibiotic and the efficacy of treatment compared to that with the same dose of free drug against murine salmonellosis. The drug molecules (31%) entrapped in the sol-gel matrix remained in biologically active form, and the bactericidal effect was retained upon drug release. The in vitro drug release profiles of the gentamicin from the xerogel and that from the xerogel-polyethylene glycol (PEG) were distinctly different at pH 7.4. A delayed release of gentamicin was observed from the silica xerogel network (57% in 33 h), and with the addition of 2% PEG, the release rate reached 90% in 33 h. Administration of two doses of the silica xerogel significantly reduced the Salmonella enterica serovar Typhimurium load in the spleens and livers of infected AJ 646 mice. The silica xerogel and xerogel-PEG achieved a 0.45-log and a 0.41-log reduction in the spleens, respectively, while for the free drug there was no reduction. On the other hand, silica xerogel and xerogel-PEG achieved statistically significant 1.13-log and 1.15-log reductions in the livers, respectively, while for the free drug the reduction was a nonsignificant value of 0.07 log. This new approach, which utilizes a room-temperature synthetic route for incorporating therapeutic drugs into the silica matrix, should improve the capability for targeting intracellular pathogens.

Seleem, Mohamed N.; Munusamy, Prabhakaran; Ranjan, Ashish; Alqublan, Hamzeh; Pickrell, Gary; Sriranganathan, Nammalwar

2009-01-01

47

Hydrodynamic Regulation of Monocyte Inflammatory Response to an Intracellular Pathogen  

PubMed Central

Systemic bacterial infections elicit inflammatory response that promotes acute or chronic complications such as sepsis, arthritis or atherosclerosis. Of interest, cells in circulation experience hydrodynamic shear forces, which have been shown to be a potent regulator of cellular function in the vasculature and play an important role in maintaining tissue homeostasis. In this study, we have examined the effect of shear forces due to blood flow in modulating the inflammatory response of cells to infection. Using an in vitro model, we analyzed the effects of physiological levels of shear stress on the inflammatory response of monocytes infected with chlamydia, an intracellular pathogen which causes bronchitis and is implicated in the development of atherosclerosis. We found that chlamydial infection alters the morphology of monocytes and trigger the release of pro-inflammatory cytokines TNF-?, IL-8, IL-1? and IL-6. We also found that the exposure of chlamydia-infected monocytes to short durations of arterial shear stress significantly enhances the secretion of cytokines in a time-dependent manner and the expression of surface adhesion molecule ICAM-1. As a functional consequence, infection and shear stress increased monocyte adhesion to endothelial cells under flow and in the activation and aggregation of platelets. Overall, our study demonstrates that shear stress enhances the inflammatory response of monocytes to infection, suggesting that mechanical forces may contribute to disease pathophysiology. These results provide a novel perspective on our understanding of systemic infection and inflammation.

Evani, Shankar J.; Murthy, Ashlesh K.; Mareedu, Naresh; Montgomery, Robbie K.; Arulanandam, Bernard P.; Ramasubramanian, Anand K.

2011-01-01

48

Gene Gain and Loss during Evolution of Obligate Parasitism in the White Rust Pathogen of Arabidopsis thaliana  

PubMed Central

Biotrophic eukaryotic plant pathogens require a living host for their growth and form an intimate haustorial interface with parasitized cells. Evolution to biotrophy occurred independently in fungal rusts and powdery mildews, and in oomycete white rusts and downy mildews. Biotroph evolution and molecular mechanisms of biotrophy are poorly understood. It has been proposed, but not shown, that obligate biotrophy results from (i) reduced selection for maintenance of biosynthetic pathways and (ii) gain of mechanisms to evade host recognition or suppress host defence. Here we use Illumina sequencing to define the genome, transcriptome, and gene models for the obligate biotroph oomycete and Arabidopsis parasite, Albugo laibachii. A. laibachii is a member of the Chromalveolata, which incorporates Heterokonts (containing the oomycetes), Apicomplexa (which includes human parasites like Plasmodium falciparum and Toxoplasma gondii), and four other taxa. From comparisons with other oomycete plant pathogens and other chromalveolates, we reveal independent loss of molybdenum-cofactor-requiring enzymes in downy mildews, white rusts, and the malaria parasite P. falciparum. Biotrophy also requires “effectors” to suppress host defence; we reveal RXLR and Crinkler effectors shared with other oomycetes, and also discover and verify a novel class of effectors, the “CHXCs”, by showing effector delivery and effector functionality. Our findings suggest that evolution to progressively more intimate association between host and parasite results in reduced selection for retention of certain biosynthetic pathways, and particularly reduced selection for retention of molybdopterin-requiring biosynthetic pathways. These mechanisms are not only relevant to plant pathogenic oomycetes but also to human pathogens within the Chromalveolata.

Kemen, Eric; Gardiner, Anastasia; Schultz-Larsen, Torsten; Kemen, Ariane C.; Balmuth, Alexi L.; Robert-Seilaniantz, Alexandre; Bailey, Kate; Holub, Eric; Studholme, David J.; MacLean, Dan; Jones, Jonathan D. G.

2011-01-01

49

The P2X 7 receptor and intracellular pathogens: a continuing struggle  

Microsoft Academic Search

The purinergic receptor, P2X7, has recently emerged as an important component of the innate immune response against microbial infections. Ligation of P2X7 by ATP can stimulate inflammasome activation and secretion of proinflammatory cytokines, but it can also lead directly to\\u000a killing of intracellular pathogens in infected macrophages and epithelial cells. Thus, while some intracellular pathogens\\u000a evade host defense responses by

Robson Coutinho-Silva; Gladys Corrêa; Ali Abdul Sater; David M. Ojcius

2009-01-01

50

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

51

Infected Dendritic Cells Facilitate Systemic Dissemination and Transplacental Passage of the Obligate Intracellular Parasite Neospora caninum in Mice  

PubMed Central

The obligate intracellular parasite Neospora caninum disseminates across the placenta and the blood-brain barrier, to reach sites where it causes severe pathology or establishes chronic persistent infections. The mechanisms used by N. caninum to breach restrictive biological barriers remain elusive. To examine the cellular basis of these processes, migration of different N. caninum isolates (Nc-1, Nc-Liverpool, Nc-SweB1 and the Spanish isolates: Nc-Spain 3H, Nc-Spain 4H, Nc-Spain 6, Nc-Spain 7 and Nc-Spain 9) was studied in an in vitro model based on a placental trophoblast-derived BeWo cell line. Here, we describe that infection of dendritic cells (DC) by N. caninum tachyzoites potentiated translocation of parasites across polarized cellular monolayers. In addition, powered by the parasite's own gliding motility, extracellular N. caninum tachyzoites were able to transmigrate across cellular monolayers. Altogether, the presented data provides evidence of two putative complementary pathways utilized by N. caninum, in an isolate-specific fashion, for passage of restrictive cellular barriers. Interestingly, adoptive transfer of tachyzoite-infected DC in mice resulted in increased parasitic loads in various organs, e.g. the central nervous system, compared to infections with free parasites. Inoculation of pregnant mice with infected DC resulted in an accentuated vertical transmission to the offspring with increased parasitic loads and neonatal mortality. These findings reveal that N. caninum exploits the natural cell trafficking pathways in the host to cross cellular barriers and disseminate to deep tissues. The findings are indicative of conserved dissemination strategies among coccidian apicomplexan parasites.

Collantes-Fernandez, Esther; Arrighi, Romanico B. G.; Alvarez-Garcia, Gema; Weidner, Jessica M.; Regidor-Cerrillo, Javier; Boothroyd, John C.; Ortega-Mora, Luis M.; Barragan, Antonio

2012-01-01

52

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

53

HIGS: Host-Induced Gene Silencing in the Obligate Biotrophic Fungal Pathogen Blumeria graminis[W][OA  

PubMed Central

Powdery mildew fungi are obligate biotrophic pathogens that only grow on living hosts and cause damage in thousands of plant species. Despite their agronomical importance, little direct functional evidence for genes of pathogenicity and virulence is currently available because mutagenesis and transformation protocols are lacking. Here, we show that the accumulation in barley (Hordeum vulgare) and wheat (Triticum aestivum) of double-stranded or antisense RNA targeting fungal transcripts affects the development of the powdery mildew fungus Blumeria graminis. Proof of concept for host-induced gene silencing was obtained by silencing the effector gene Avra10, which resulted in reduced fungal development in the absence, but not in the presence, of the matching resistance gene Mla10. The fungus could be rescued from the silencing of Avra10 by the transient expression of a synthetic gene that was resistant to RNA interference (RNAi) due to silent point mutations. The results suggest traffic of RNA molecules from host plants into B. graminis and may lead to an RNAi-based crop protection strategy against fungal pathogens.

Nowara, Daniela; Gay, Alexandra; Lacomme, Christophe; Shaw, Jane; Ridout, Christopher; Douchkov, Dimitar; Hensel, Gotz; Kumlehn, Jochen; Schweizer, Patrick

2010-01-01

54

Comparative Genomics Suggests that the Fungal Pathogen Pneumocystis Is an Obligate Parasite Scavenging Amino Acids from Its Host's Lungs  

PubMed Central

Pneumocystis jirovecii is a fungus causing severe pneumonia in immuno-compromised patients. Progress in understanding its pathogenicity and epidemiology has been hampered by the lack of a long-term in vitro culture method. Obligate parasitism of this pathogen has been suggested on the basis of various features but remains controversial. We analysed the 7.0 Mb draft genome sequence of the closely related species Pneumocystis carinii infecting rats, which is a well established experimental model of the disease. We predicted 8’085 (redundant) peptides and 14.9% of them were mapped onto the KEGG biochemical pathways. The proteome of the closely related yeast Schizosaccharomyces pombe was used as a control for the annotation procedure (4’974 genes, 14.1% mapped). About two thirds of the mapped peptides of each organism (65.7% and 73.2%, respectively) corresponded to crucial enzymes for the basal metabolism and standard cellular processes. However, the proportion of P. carinii genes relative to those of S. pombe was significantly smaller for the “amino acid metabolism” category of pathways than for all other categories taken together (40 versus 114 against 278 versus 427, P<0.002). Importantly, we identified in P. carinii only 2 enzymes specifically dedicated to the synthesis of the 20 standard amino acids. By contrast all the 54 enzymes dedicated to this synthesis reported in the KEGG atlas for S. pombe were detected upon reannotation of S. pombe proteome (2 versus 54 against 278 versus 427, P<0.0001). This finding strongly suggests that species of the genus Pneumocystis are scavenging amino acids from their host's lung environment. Consequently, they would have no form able to live independently from another organism, and these parasites would be obligate in addition to being opportunistic. These findings have implications for the management of patients susceptible to P. jirovecii infection given that the only source of infection would be other humans.

Hauser, Philippe M.; Burdet, Frederic X.; Cisse, Ousmane H.; Keller, Laurent; Taffe, Patrick; Sanglard, Dominique; Pagni, Marco

2010-01-01

55

Microsporidia: emerging pathogenic protists  

Microsoft Academic Search

Microsporidia are eukaryotic spore forming obligate intracellular protozoan parasites first recognized over 100 years ago. These organisms infect all of the major animal groups and are now recognized as opportunistic pathogens of humans. Microsporidian spores are common in the environment and microsporidia pathogenic to humans have been found in water supplies. The genera Nosema, Vittaforma, Brachiola, Pleistophora, Encephalitozoon, Enterocytozoon, Septata

Louis M. Weiss

2001-01-01

56

Delivery of host cell-directed therapeutics for intracellular pathogen clearance.  

PubMed

Intracellular pathogens present a major health risk because of their innate ability to evade clearance. Their location within host cells and ability to react to the host environment by mutation or transcriptional changes often enables survival mechanisms to resist standard therapies. Host-directed drugs do not target the pathogen, minimizing the potential development of drug resistance; however, they can be difficult to deliver efficiently to intracellular sites. Vehicle delivery of host-mediated response drugs not only improves drug distribution and toxicity profiles, but can reduce the total amount of drug necessary to clear infection. In this article, we will review some host-directed drugs and current drug delivery techniques that can be used to efficiently clear intracellular infections. PMID:24134600

Collier, Michael A; Gallovic, Matthew D; Peine, Kevin J; Duong, Anthony D; Bachelder, Eric M; Gunn, John S; Schlesinger, Larry S; Ainslie, Kristy M

2013-10-18

57

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

58

Naip5 Affects Host Susceptibility to the Intracellular Pathogen Legionella pneumophila  

Microsoft Academic Search

Background:Legionella pneumophila is a gram-negative bacterial pathogen that is the cause of Legionnaires' Disease. Legionella produces disease because it can replicate inside a specialized compartment of host macrophages. Macrophages isolated from various inbred mice exhibit large differences in permissiveness for intracellular replication of Legionella. A locus affecting this host-resistance phenotype, Lgn1, has been mapped to chromosome 13, but the responsible

Sheryl A. Goodart; Joseph D. Growney; Vey Hadinoto; Matthew G. Endrizzi; E. Michelle Long; Keyvan Sadigh; Andrew L. Abney; Isaac Bernstein-Hanley; William F. Dietrich

2003-01-01

59

Intracellular antibody-bound pathogens stimulate immune signaling via Fc-receptor TRIM21  

PubMed Central

Antibodies can be carried into the cell during pathogen infection where they are detected by the ubiquitously expressed cytosolic antibody receptor TRIM21. Here we show that TRIM21 recognition of intracellular antibodies activates immune signaling. TRIM21 catalyses K63-ubiquitin chain formation, stimulating transcription factor pathways NF-?B, AP-1 and IRF3, IRF5, IRF7. Activation results in proinflammatory cytokine production, modulation of natural killer (NK) stress ligands and the induction of an antiviral state. Intracellular antibody signaling is abrogated by genetic deletion of TRIM21 and is recovered by ectopic TRIM21 expression. Antibody sensing by TRIM21 can be stimulated upon infection by DNA or RNA non-enveloped viruses or intracellular bacteria. The antibody-TRIM21 detection system provides potent, comprehensive innate immune activation, independent of known pattern recognition receptors.

McEwan, W.A; Tam, J.C.H; Watkinson, R.E; Bidgood, S.R; Mallery, D.L; James, L.C

2013-01-01

60

Intracellular antibody-bound pathogens stimulate immune signaling via the Fc receptor TRIM21.  

PubMed

During pathogen infection, antibodies can be carried into the infected cell, where they are detected by the ubiquitously expressed cytosolic antibody receptor TRIM21. Here we found that recognition of intracellular antibodies by TRIM21 activated immune signaling. TRIM21 catalyzed the formation of Lys63 (K63)-linked ubiquitin chains and stimulated the transcription factor pathways of NF-?B, AP-1, IRF3, IRF5 and IRF7. Activation resulted in the production of proinflammatory cytokines, modulation of natural killer stress ligands and induction of an antiviral state. Intracellular antibody signaling was abrogated by genetic deletion of TRIM21 and was restored by ectopic expression of TRIM21. The sensing of antibodies by TRIM21 was stimulated after infection by DNA or RNA nonenveloped viruses or intracellular bacteria. Thus, the antibody-TRIM21 detection system provides potent, comprehensive activation of the innate immune system independently of known pattern-recognition receptors. PMID:23455675

McEwan, William A; Tam, Jerry C H; Watkinson, Ruth E; Bidgood, Susanna R; Mallery, Donna L; James, Leo C

2013-03-03

61

Molecular methods to investigate adhesion, transmigration, invasion and intracellular survival of the foodborne pathogen Campylobacter jejuni.  

PubMed

Campylobacter jejuni is a spiral-shaped Gram-negative pathogen and major agent of gastrointestinal foodborne illness in humans worldwide. This pathogen encodes numerous described pathogenicity-associated factors involved in important processes including bacterial adhesion to, transmigration across, invasion into and intracellular survival within intestinal epithelial cells. This review article highlights various molecular techniques applied in the studies of each of these individual steps of C. jejuni host cell interactions in vitro including gentamicin protection assay, chemotaxis and motility assays, transwell and intracellular survival assays, G-Lisa, siRNA knockdown, immunohistochemistry, immunofluorescence, electron microscopy and luciferase reporter assays. We discuss the strengths and limitations of the methods as well as the different cell model systems applied. Future work should employ new technologies including modern microscopic, proteomics-based and cell signaling approaches to identify and characterise novel virulence mechanisms, which are crucial to provide fresh insights into the diversity of strategies employed by this important pathogen to cause disease. PMID:23872466

Backert, Steffen; Hofreuter, Dirk

2013-07-16

62

Genome sequence of Rickettsia bellii illuminates the role of amoebae in gene exchanges between intracellular pathogens.  

PubMed

The recently sequenced Rickettsia felis genome revealed an unexpected plasmid carrying several genes usually associated with DNA transfer, suggesting that ancestral rickettsiae might have been endowed with a conjugation apparatus. Here we present the genome sequence of Rickettsia bellii, the earliest diverging species of known rickettsiae. The 1,552,076 base pair-long chromosome does not exhibit the colinearity observed between other rickettsia genomes, and encodes a complete set of putative conjugal DNA transfer genes most similar to homologues found in Protochlamydia amoebophila UWE25, an obligate symbiont of amoebae. The genome exhibits many other genes highly similar to homologues in intracellular bacteria of amoebae. We sought and observed sex pili-like cell surface appendages for R. bellii. We also found that R. bellii very efficiently multiplies in the nucleus of eukaryotic cells and survives in the phagocytic amoeba, Acanthamoeba polyphaga. These results suggest that amoeba-like ancestral protozoa could have served as a genetic "melting pot" where the ancestors of rickettsiae and other bacteria promiscuously exchanged genes, eventually leading to their adaptation to the intracellular lifestyle within eukaryotic cells. PMID:16703114

Ogata, Hiroyuki; La Scola, Bernard; Audic, Stéphane; Renesto, Patricia; Blanc, Guillaume; Robert, Catherine; Fournier, Pierre-Edouard; Claverie, Jean-Michel; Raoult, Didier

2006-05-12

63

Impact of filarial infections on coincident intracellular pathogens: Mycobacterium tuberculosis and Plasmodium falciparum  

PubMed Central

Purpose of review To examine the consequences of the immune modulation seen in chronic filarial infection on responses to intracellular pathogens (and their antigens) that are often co-endemic with filarial infections, namely Plasmodium and Mycobacterium tuberculosis. Recent findings Much of the recent data on filaria/mycobacteria or filaria/Plasmodium co-infection has focused on the modulation of mycobacteria-specific or malaria-specific responses by chronic filarial infection. As such, filarial infections very clearly alter the magnitude and quality of the mycobacteria-specific or malaria-specific cytokine responses, responses that have been typically associated with control of these intracellular pathogens. Summary Although phylogenetically distinct, mycobacteria and Plasmodium spp. often share the same geographical niche with filarial infections. The complex interplay between filarial parasites that are associated with immunomodulation and those microbial pathogens that require a proinflammatory or unmodulated response for their control is easily demonstrable ex vivo, but whether this interplay affects disease outcome in tuberculosis or malaria remains an open question.

Metenou, Simon; Babu, Subash; Nutman, Thomas B.

2012-01-01

64

Expanded functions for a family of plant intracellular immune receptors beyond specific recognition of pathogen effectors  

PubMed Central

Plants and animals deploy intracellular immune receptors that perceive specific pathogen effector proteins and microbial products delivered into the host cell. We demonstrate that the ADR1 family of Arabidopsis nucleotide-binding leucine-rich repeat (NB-LRR) receptors regulates accumulation of the defense hormone salicylic acid during three different types of immune response: (i) ADRs are required as “helper NB-LRRs” to transduce signals downstream of specific NB-LRR receptor activation during effector-triggered immunity; (ii) ADRs are required for basal defense against virulent pathogens; and (iii) ADRs regulate microbial-associated molecular pattern-dependent salicylic acid accumulation induced by infection with a disarmed pathogen. Remarkably, these functions do not require an intact P-loop motif for at least one ADR1 family member. Our results suggest that some NB-LRR proteins can serve additional functions beyond canonical, P-loop–dependent activation by specific virulence effectors, extending analogies between intracellular innate immune receptor function from plants and animals.

Bonardi, Vera; Tang, Saijun; Stallmann, Anna; Roberts, Melinda; Cherkis, Karen; Dangl, Jeffery L.

2011-01-01

65

A transcriptomic network identified in uninfected macrophages responding to inflammation controls intracellular pathogen survival.  

PubMed

Intracellular pathogens modulate host cell function to promote their survival. However, in vitro infection studies do not account for the impact of host-derived inflammatory signals. Examining the response of liver-resident macrophages (Kupffer cells) in mice infected with the parasite Leishmania donovani, we identified a transcriptomic network operating in uninfected Kupffer cells exposed to inflammation but absent from Kupffer cells from the same animal that contained intracellular Leishmania. To test the hypothesis that regulated expression of genes within this transcriptomic network might impact parasite survival, we pharmacologically perturbed the activity of retinoid X receptor alpha (RXR?), a key hub within this network, and showed that this intervention enhanced the innate resistance of Kupffer cells to Leishmania infection. Our results illustrate a broadly applicable strategy for understanding the host response to infection in vivo and identify Rxra as the hub of a gene network controlling antileishmanial resistance. PMID:24034621

Beattie, Lynette; d'El-Rei Hermida, Micely; Moore, John W J; Maroof, Asher; Brown, Najmeeyah; Lagos, Dimitris; Kaye, Paul M

2013-09-11

66

Identification of Intracellular and Plasma Membrane Calcium Channel Homologues in Pathogenic Parasites  

PubMed Central

Ca2+ channels regulate many crucial processes within cells and their abnormal activity can be damaging to cell survival, suggesting that they might represent attractive therapeutic targets in pathogenic organisms. Parasitic diseases such as malaria, leishmaniasis, trypanosomiasis and schistosomiasis are responsible for millions of deaths each year worldwide. The genomes of many pathogenic parasites have recently been sequenced, opening the way for rational design of targeted therapies. We analyzed genomes of pathogenic protozoan parasites as well as the genome of Schistosoma mansoni, and show the existence within them of genes encoding homologues of mammalian intracellular Ca2+ release channels: inositol 1,4,5-trisphosphate receptors (IP3Rs), ryanodine receptors (RyRs), two-pore Ca2+ channels (TPCs) and intracellular transient receptor potential (Trp) channels. The genomes of Trypanosoma, Leishmania and S. mansoni parasites encode IP3R/RyR and Trp channel homologues, and that of S. mansoni additionally encodes a TPC homologue. In contrast, apicomplexan parasites lack genes encoding IP3R/RyR homologues and possess only genes encoding TPC and Trp channel homologues (Toxoplasma gondii) or Trp channel homologues alone. The genomes of parasites also encode homologues of mammalian Ca2+ influx channels, including voltage-gated Ca2+ channels and plasma membrane Trp channels. The genome of S. mansoni also encodes Orai Ca2+ channel and STIM Ca2+ sensor homologues, suggesting that store-operated Ca2+ entry may occur in this parasite. Many anti-parasitic agents alter parasite Ca2+ homeostasis and some are known modulators of mammalian Ca2+ channels, suggesting that parasite Ca2+ channel homologues might be the targets of some current anti-parasitic drugs. Differences between human and parasite Ca2+ channels suggest that pathogen-specific targeting of these channels may be an attractive therapeutic prospect.

Prole, David L.; Taylor, Colin W.

2011-01-01

67

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

PubMed Central

Background Thioredoxin 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 Findings In 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 which replicate in the cytosol and the endoplasmic reticulum respectively. Our data indicate that TAMs efficiently inhibit intracellular growth of both L. monocytogenes and B. abortus. Further analysis shows that Trx80 activation prevents the escape of GFP-tagged L. monocytogenes into the cytosol, and induces accumulation of the bacteria within the lysosomes. Inhibition of the lysosomal activity by chloroquine treatment resulted in higher replication of bacteria in TAMs compared to that observed in control cells 24 h post-infection, indicating that TAMs kill bacteria by preventing their escape from the endosomal compartments, which progress into a highly degradative phagolysosome. Significance Our results show that Trx80 potentiates the bactericidal activities of professional phagocytes, and contributes to the first line of defense against intracellular bacteria.

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

2011-01-01

68

Chitin synthesis during in planta growth and asexual propagation of the cellulosic oomycete and obligate biotrophic grapevine pathogen Plasmopara viticola  

Microsoft Academic Search

PCR amplification of two CHS gene fragments of the obligate biotroph Plasmopara viticola, the causal agent of downy mildew of grapevine, is described. While one fragment shows homology to fungal class IV chitin synthases, the other fragment groups with other oomycete chitin synthases to form a novel class of chitin synthases most closely related to class I–III. RT-PCR experiments indicate

Stefan Werner; Ulrike Steiner; Rayko Becher; Andreas Kortekamp; Eva Zyprian; Holger B Deising

2002-01-01

69

d-Amino Acid Chemical Reporters Reveal Peptidoglycan Dynamics of an Intracellular Pathogen  

PubMed Central

Peptidoglycan (PG) is an essential component of the bacterial cell wall. Although experiments with organisms in vitro have yielded a wealth of information on PG synthesis and maturation, it is unclear how these studies translate to bacteria replicating within host cells. We report a chemical approach for probing PG in vivo via metabolic labeling and bioorthogonal chemistry. A wide variety of bacterial species incorporated azide and alkyne-functionalized d-alanine into their cell walls, which we visualized by covalent reaction with click chemistry probes. The d-alanine analogues were specifically incorporated into nascent PG of the intracellular pathogen Listeria monocytogenes both in vitro and during macrophage infection. Metabolic incorporation of d-alanine derivatives and click chemistry detection constitute a facile, modular platform that facilitates unprecedented spatial and temporal resolution of PG dynamics in vivo.

2012-01-01

70

Cloning to crystallization of dihydrodipicolinate synthase from the intracellular pathogen Legionella pneumophila.  

PubMed

Dihydrodipicolinate synthase (DHDPS) catalyses the rate-limiting step in the biosynthesis of meso-diaminopimelate and lysine. Here, the cloning, expression, purification and crystallization of DHDPS from the intracellular pathogen Legionella pneumophila are described. Crystals grown in the presence of high-molecular-weight PEG precipitant and magnesium chloride were found to diffract beyond 1.65?Å resolution. The crystal lattice belonged to the hexagonal space group P6122, with unit-cell parameters a = b = 89.31, c = 290.18?Å, and contained two molecules in the asymmetric unit. The crystal structure was determined by molecular replacement using a single chain of Pseudomonas aeruginosa DHDPS as the search model. PMID:24100576

Siddiqui, Tanzeela; Paxman, Jason J; Dogovski, Con; Panjikar, Santosh; Perugini, Matthew A

2013-09-30

71

Intracellular imaging of host-pathogen interactions using combined CARS and two-photon fluorescence microscopies.  

PubMed

Intracellular imaging is a key tool in the investigation of host-pathogen interactions. Advances in this area are particularly sought to understand the effect of viral infection processes on the host cell and its metabolic functions including those cases where host cell lipid metabolism is modulated as a result of infection. We demonstrate the use of combined coherent anti-Stokes Raman scattering (CARS) and two-photon fluorescence microscopies to image fibroblast cells infected by cytomegalovirus. CARS is used to image the host cell membrane, lipid droplets and morphology of the nucleus. Cell nuclei are found to expand during infection, approximately doubling in area. Some cells also show accumulations of lipid droplets at the nuclear periphery. Using a genetically modified virus strain expressing the green fluorescent protein also enables two-photon imaging of the same cells to reveal the location, nature and extent of viral protein expression. PMID:19670191

Robinson, Iain; Ochsenkühn, Michael Andreas; Campbell, Colin J; Giraud, Gerard; Hossack, William J; Arlt, Jochen; Crain, Jason

2010-03-01

72

(D)-amino acid chemical reporters reveal peptidoglycan dynamics of an intracellular pathogen.  

PubMed

Peptidoglycan (PG) is an essential component of the bacterial cell wall. Although experiments with organisms in vitro have yielded a wealth of information on PG synthesis and maturation, it is unclear how these studies translate to bacteria replicating within host cells. We report a chemical approach for probing PG in vivo via metabolic labeling and bioorthogonal chemistry. A wide variety of bacterial species incorporated azide and alkyne-functionalized d-alanine into their cell walls, which we visualized by covalent reaction with click chemistry probes. The d-alanine analogues were specifically incorporated into nascent PG of the intracellular pathogen Listeria monocytogenes both in vitro and during macrophage infection. Metabolic incorporation of d-alanine derivatives and click chemistry detection constitute a facile, modular platform that facilitates unprecedented spatial and temporal resolution of PG dynamics in vivo. PMID:23240806

Siegrist, M Sloan; Whiteside, Sarah; Jewett, John C; Aditham, Arjun; Cava, Felipe; Bertozzi, Carolyn R

2013-01-11

73

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

74

Role of the heat shock transcription factor, Hsf1, in a major fungal pathogen that is obligately associated with warm-blooded animals  

PubMed Central

All organisms have evolved mechanisms that protect them against environmental stress. The major fungal pathogen of humans, Candida albicans, has evolved robust stress responses that protect it against human immune defences and promote its pathogenicity. However, C. albicans is unlikely to be exposed to heat shock as it is obligatorily associated with warm-blooded animals. Therefore, we examined the role of the heat shock transcription factor (Hsf1) in this pathogen. We show that C. albicans expresses an evolutionarily conserved Hsf1 (orf19.4775) that is phosphorylated in response to heat shock, induces transcription via the heat shock element (HSE), contributes to the global transcriptional response to heat shock, and is essential for viability. Why has Hsf1 been conserved in this obligate animal saprophyte? We reasoned that Hsf1 might contribute to medically relevant stress responses. However, this is not the case, as an Hsf1-specific HSE-lacZ reporter is not activated by oxidative, osmotic, weak acid or pH stress. Rather, Hsf1 is required for the expression of essential chaperones in the absence of heat shock (e.g. Hsp104, Hsp90, Hsp70). Furthermore, Hsf1 regulates the expression of HSE-containing genes in response to growth temperature in C. albicans. Therefore, the main role of Hsf1 in this pathogen might be the homeostatic modulation of chaperone levels in response to growth temperature, rather than the activation of acute responses to sudden thermal transitions.

Nicholls, Susan; Leach, Michelle D; Priest, Claire L; Brown, Alistair J P

2009-01-01

75

Inducible Nitric Oxide Is Essential for Host Control of Persistent but Not Acute Infection with the Intracellular Pathogen Toxoplasma gondii  

Microsoft Academic Search

Summary The induction by IFN- g of reactive nitrogen intermediates has been postulated as a major mechanism of host resistance to intracellular pathogens. To formally test this hypothesis in vivo, the course of Toxoplasma gondii infection was assessed in nitric oxide synthase (iNOS) 2\\/2 mice. As expected, macrophages from these animals displayed defective microbicidal activity against the parasite in vitro.

Tanya M. Scharton-Kersten; George Yap; Jeanne Magram; Alan Sher

2010-01-01

76

Intracellular Growth of Legionella pneumophila in Dictyostelium discoideum, a System for Genetic Analysis of Host-Pathogen Interactions  

Microsoft Academic Search

Conditions were established in which Legionella pneumophila, an intracellular bacterial pathogen, could replicate within the unicellular organism Dictyostelium discoideum. By several criteria, L. pneumophila grew by the same mechanism within D. discoideum as it does in amoebae and macrophages. Bacteria grew within membrane-bound vesicles associated with rough endoplasmic reticulum, and L. pneumophila dot\\/icm mutants, blocked for growth in macrophages and

JONATHAN M. SOLOMON; ADAM RUPPER; JAMES A. CARDELLI; RALPH R. ISBERG

2000-01-01

77

Neutrophils Exert a Suppressive Effect on Th1 Responses to Intracellular Pathogen Brucella abortus  

PubMed Central

Polymorphonuclear neutrophils (PMNs) are the first line of defense against microbial pathogens. In addition to their role in innate immunity, PMNs may also regulate events related to adaptive immunity. To investigate the influence of PMNs in the immune response during chronic bacterial infections, we explored the course of brucellosis in antibody PMN-depleted C57BL/6 mice and in neutropenic mutant Genista mouse model. We demonstrate that at later times of infection, Brucella abortus is killed more efficiently in the absence of PMNs than in their presence. The higher bacterial removal was concomitant to the: i) comparatively reduced spleen swelling; ii) augmented infiltration of epithelioid histiocytes corresponding to macrophages/dendritic cells (DCs); iii) higher recruitment of monocytes and monocyte/DCs phenotype; iv) significant activation of B and T lymphocytes, and v) increased levels of INF-? and negligible levels of IL4 indicating a balance of Th1 over Th2 response. These results reveal that PMNs have an unexpected influence in dampening the immune response against intracellular Brucella infection and strengthen the notion that PMNs actively participate in regulatory circuits shaping both innate and adaptive immunity.

Ordonez-Rueda, Diana; Arce-Gorvel, Vilma; Alfaro-Alarcon, Alejandro; Lepidi, Hubert; Malissen, Bernard; Malissen, Marie; Gorvel, Jean-Pierre; Moreno, Edgardo

2013-01-01

78

Granzyme A Produced by ?9?2 T Cells Induces Human Macrophages to Inhibit Growth of an Intracellular Pathogen  

PubMed Central

Human ?9?2 T cells potently inhibit pathogenic microbes, including intracellular mycobacteria, but the key inhibitory mechanism(s) involved have not been identified. We report a novel mechanism involving the inhibition of intracellular mycobacteria by soluble granzyme A. ?9?2 T cells produced soluble factors that could pass through 0.45 µm membranes and inhibit intracellular mycobacteria in human monocytes cultured below transwell inserts. Neutralization of TNF-? in co-cultures of infected monocytes and ?9?2 T cells prevented inhibition, suggesting that TNF-? was the critical inhibitory factor produced by ?9?2 T cells. However, only siRNA- mediated knockdown of TNF-? in infected monocytes, but not in ?9?2 T cells, prevented mycobacterial growth inhibition. Investigations of other soluble factors produced by ?9?2 T cells identified a highly significant correlation between the levels of granzyme A produced and intracellular mycobacterial growth inhibition. Furthermore, purified granzyme A alone induced inhibition of intracellular mycobacteria, while knockdown of granzyme A in ?9?2 T cell clones blocked their inhibitory effects. The inhibitory mechanism was independent of autophagy, apoptosis, nitric oxide production, type I interferons, Fas/FasL and perforin. These results demonstrate a novel microbial defense mechanism involving granzyme A-mediated triggering of TNF-? production by monocytes leading to intracellular mycobacterial growth suppression. This pathway may provide a protective mechanism relevant for the development of new vaccines and/or immunotherapies for macrophage-resident chronic microbial infections.

Xia, Mei; Truscott, Steven M.; Eickhoff, Christopher S.; Linn, Rebecca; Blazevic, Azra; Metkar, Sunil S.; Peng, Guangyong; Froelich, Christopher J.; Hoft, Daniel F.

2013-01-01

79

A rapid genotyping method for an obligate fungal pathogen, Puccinia striiformis f.sp. tritici, based on DNA extraction from infected leaf and Multiplex PCR genotyping  

PubMed Central

Background Puccinia striiformis f.sp. tritici (PST), an obligate fungal pathogen causing wheat yellow/stripe rust, a serious disease, has been used to understand the evolution of crop pathogen using molecular markers. However, numerous questions regarding its evolutionary history and recent migration routes still remains to be addressed, which need the genotyping of a large number of isolates, a process that is limited by both DNA extraction and genotyping methods. To address the two issues, we developed here a method for direct DNA extraction from infected leaves combined with optimized SSR multiplexing. Findings We report here an efficient protocol for direct fungal DNA extraction from infected leaves, avoiding the costly and time consuming step of spore multiplication. The genotyping strategy we propose, amplified a total of 20 SSRs in three Multiplex PCR reactions, which were highly polymorphic and were able to differentiate different PST populations with high efficiency and accuracy. Conclusion These two developments enabled a genotyping strategy that could contribute to the development of molecular epidemiology of yellow rust disease, both at a regional or worldwide scale.

2011-01-01

80

Functional Characterization of the Incomplete Phosphotransferase System (PTS) of the Intracellular Pathogen Brucella melitensis  

PubMed Central

Background In many bacteria, the phosphotransferase system (PTS) is a key player in the regulation of the assimilation of alternative carbon sources notably through catabolic repression. The intracellular pathogens Brucella spp. possess four PTS proteins (EINtr, NPr, EIIANtr and an EIIA of the mannose family) but no PTS permease suggesting that this PTS might serve only regulatory functions. Methodology/Principal Findings In vitro biochemical analyses and in vivo detection of two forms of EIIANtr (phosphorylated or not) established that the four PTS proteins of Brucella melitensis form a functional phosphorelay. Moreover, in vitro the protein kinase HprK/P phosphorylates NPr on a conserved serine residue, providing an additional level of regulation to the B. melitensis PTS. This kinase activity was inhibited by inorganic phosphate and stimulated by fructose-1,6 bisphosphate. The genes encoding HprK/P, an EIIAMan-like protein and NPr are clustered in a locus conserved among ?-proteobacteria and also contain the genes for the crucial two-component system BvrR-BvrS. RT-PCR revealed a transcriptional link between these genes suggesting an interaction between PTS and BvrR-BvrS. Mutations leading to the inactivation of EINtr or NPr significantly lowered the synthesis of VirB proteins, which form a type IV secretion system. These two mutants also exhibit a small colony phenotype on solid media. Finally, interaction partners of PTS proteins were identified using a yeast two hybrid screen against the whole B. melitensis ORFeome. Both NPr and HprK/P were shown to interact with an inorganic pyrophosphatase and the EIIAMan-like protein with the E1 component (SucA) of 2-oxoglutarate dehydrogenase. Conclusions/Significance The B. melitensis can transfer the phosphoryl group from PEP to the EIIAs and a link between the PTS and the virulence of this organism could be established. Based on the protein interaction data a preliminary model is proposed in which this regulatory PTS coordinates also C and N metabolism.

Dozot, Marie; Poncet, Sandrine; Nicolas, Cecile; Copin, Richard; Bouraoui, Houda; Maze, Alain; Deutscher, Josef; De Bolle, Xavier; Letesson, Jean-Jacques

2010-01-01

81

Rapid and sensitive detection of an intracellular pathogen in human peripheral leukocytes with hybridizing magnetic relaxation nanosensors.  

PubMed

Bacterial infections are still a major global healthcare problem. The quick and sensitive detection of pathogens responsible for these infections would facilitate correct diagnosis of the disease and expedite treatment. Of major importance are intracellular slow-growing pathogens that reside within peripheral leukocytes, evading recognition by the immune system and detection by traditional culture methods. Herein, we report the use of hybridizing magnetic nanosensors (hMRS) for the detection of an intracellular pathogen, Mycobacterium avium spp. paratuberculosis (MAP). The hMRS are designed to bind to a unique genomic sequence found in the MAP genome, causing significant changes in the sample's magnetic resonance signal. Clinically relevant samples, including tissue and blood, were screened with hMRS and results were compared with traditional PCR analysis. Within less than an hour, the hMRS identified MAP-positive samples in a library of laboratory cultures, clinical isolates, blood and homogenized tissues. Comparison of the hMRS with culture methods in terms of prediction of disease state revealed that the hMRS outperformed established culture methods, while being significantly faster (1 hour vs 12 weeks). Additionally, using a single instrument and one nanoparticle preparation we were able to detect the intracellular bacterial target in clinical samples at the genomic and epitope levels. Overall, since the nanoparticles are robust in diverse environmental settings and substantially more affordable than PCR enzymes, the potential clinical and field-based use of hMRS in the multiplexed identification of microbial pathogens and other disease-related biomarkers via a single, deployable instrument in clinical and complex environmental samples is foreseen. PMID:22496916

Kaittanis, Charalambos; Boukhriss, Hamza; Santra, Santimukul; Naser, Saleh A; Perez, J Manuel

2012-04-09

82

Rapid and Sensitive Detection of an Intracellular Pathogen in Human Peripheral Leukocytes with Hybridizing Magnetic Relaxation Nanosensors  

PubMed Central

Bacterial infections are still a major global healthcare problem. The quick and sensitive detection of pathogens responsible for these infections would facilitate correct diagnosis of the disease and expedite treatment. Of major importance are intracellular slow-growing pathogens that reside within peripheral leukocytes, evading recognition by the immune system and detection by traditional culture methods. Herein, we report the use of hybridizing magnetic nanosensors (hMRS) for the detection of an intracellular pathogen, Mycobacterium avium spp. paratuberculosis (MAP). The hMRS are designed to bind to a unique genomic sequence found in the MAP genome, causing significant changes in the sample’s magnetic resonance signal. Clinically relevant samples, including tissue and blood, were screened with hMRS and results were compared with traditional PCR analysis. Within less than an hour, the hMRS identified MAP-positive samples in a library of laboratory cultures, clinical isolates, blood and homogenized tissues. Comparison of the hMRS with culture methods in terms of prediction of disease state revealed that the hMRS outperformed established culture methods, while being significantly faster (1 hour vs 12 weeks). Additionally, using a single instrument and one nanoparticle preparation we were able to detect the intracellular bacterial target in clinical samples at the genomic and epitope levels. Overall, since the nanoparticles are robust in diverse environmental settings and substantially more affordable than PCR enzymes, the potential clinical and field-based use of hMRS in the multiplexed identification of microbial pathogens and other disease-related biomarkers via a single, deployable instrument in clinical and complex environmental samples is foreseen.

Kaittanis, Charalambos; Boukhriss, Hamza; Santra, Santimukul; Naser, Saleh A.; Perez, J. Manuel

2012-01-01

83

Evaluation of recombinant invasive, non-pathogenic Eschericia coli as a vaccine vector against the intracellular pathogen, Brucella  

Microsoft Academic Search

BACKGROUND: There is no safe, effective human vaccine against brucellosis. Live attenuated Brucella strains are widely used to vaccinate animals. However these live Brucella vaccines can cause disease and are unsafe for humans. Killed Brucella or subunit vaccines are not effective in eliciting long term protection. In this study, we evaluate an approach using a live, non-pathogenic bacteria (E. coli)

Jerome S Harms; Marina A Durward; Diogo M Magnani; Gary A Splitter

2009-01-01

84

Institutional obligation  

SciTech Connect

The institutional obligation is to act to meet primary responsibilities in the face of risks. There are risks involved in taking action, both of a quantifiable and unquantifiable nature. This paper explores weighing the risks, choosing approaches that balance primary obligations with broader ones, and presenting ethical philosophies upon which policies and strategies are based. Federal government organizations and utilities--and Bonneville Power Administration qualifies as both--have a variety of responsibilities to the public they serve. The common responsibility is that of service; for Bonneville the primary responsibility is to serve the energy related needs. It is this primary institutional obligation, as it relates to other responsibilities--and the resulting strategy for handling indoor air quality in Bonneville's new homes program--that this paper examines.

Rowan, S.S.; Berwager, S.D. (Bonneville Power Administration, Portland, OR (US))

1988-01-01

85

TmpL, a Transmembrane Protein Required for Intracellular Redox Homeostasis and Virulence in a Plant and an Animal Fungal Pathogen  

Microsoft Academic Search

The regulation of intracellular levels of reactive oxygen species (ROS) is critical for developmental differentiation and virulence of many pathogenic fungi. In this report we demonstrate that a novel transmembrane protein, TmpL, is necessary for regulation of intracellular ROS levels and tolerance to external ROS, and is required for infection of plants by the necrotroph Alternaria brassicicola and for infection

Kwang-Hyung Kim; Sven D. Willger; Sang-Wook Park; Srisombat Puttikamonkul; Nora Grahl; Yangrae Cho; Biswarup Mukhopadhyay; Robert A. Cramer; Christopher B. Lawrence

2009-01-01

86

Cryptococcus neoformans Is a Facultative Intracellular Pathogen in Murine Pulmonary Infection  

Microsoft Academic Search

To produce chronic infection, microbial pathogens must escape host immune defenses. Infection with the human pathogenic fungus Cryptococcus neoformans is typically chronic. To understand the mechanism by which C. neoformans survives in tissue after the infection of immunocompetent hosts, we systematically studied the course of pulmonary infection in mice by electron microscopy. The macrophage was the primary phagocytic cell at

MARTA FELDMESSER; YVONNE KRESS; PHYLLIS NOVIKOFF; ARTURO CASADEVALL

2000-01-01

87

Intracellular Pathogen Leishmania donovani Activates Hypoxia Inducible Factor-1 by Dual Mechanism for Survival Advantage within Macrophage  

PubMed Central

Recent evidence established a crucial role for mammalian oxygen sensing transcription factor hypoxia inducible factor-1 (HIF-1) in innate immunity against intracellular pathogens. In response to most of these pathogens host phagocytes increase transcription of HIF-1?, the regulatory component of HIF-1 to express various effector molecules against invaders. Leishmania donovani (LD), a protozoan parasite and the causative agent of fatal visceral leishmaniasis resides in macrophages within mammalian host. The mechanism of HIF-1 activation or its role in determining the fate of LD in infected macrophages is still not known. To determine that J774 macrophages were infected with LD and about four-fold increase in HIF-1 activity and HIF-1? expression were detected. A strong increase in HIF-1? expression and nuclear localization was also detected in LD-infected J774 cells, peritoneal macrophages and spleen derived macrophages of LD-infected BALB/c mice. A two-fold increase in HIF-1? mRNA was detected in LD-infected macrophages suggesting involvement of a transcriptional mechanism that was confirmed by promoter activity. We further revealed that LD also induced HIF-1? expression by depleting host cellular iron pool to affect prolyl hydroxylase activity resulting in to stabilization of HIF-1?. To determine the role of HIF-1 on intracellular LD, cells were transfected with HIF-1? siRNA to attenuate its expression and then infected with LD. Although, initial infection rate of LD in HIF-1? attenuated cells was not affected but intracellular growth of LD was significantly inhibited; while, over-expression of stabilized form of HIF-1? promoted intracellular growth of LD in host macrophage. Our results strongly suggest that LD activates HIF-1 by dual mechanism for its survival advantage within macrophage.

Singh, Amit Kumar; Mukhopadhyay, Chaitali; Biswas, Sudipta; Singh, Vandana Kumari; Mukhopadhyay, Chinmay K.

2012-01-01

88

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

89

Development of Functional and Molecular Correlates of Vaccine-Induced Protection for a Model Intracellular Pathogen, F. tularensis LVS  

PubMed Central

In contrast with common human infections for which vaccine efficacy can be evaluated directly in field studies, alternative strategies are needed to evaluate efficacy for slowly developing or sporadic diseases like tularemia. For diseases such as these caused by intracellular bacteria, serological measures of antibodies are generally not predictive. Here, we used vaccines varying in efficacy to explore development of clinically useful correlates of protection for intracellular bacteria, using Francisella tularensis as an experimental model. F. tularensis is an intracellular bacterium classified as Category A bioterrorism agent which causes tularemia. The primary vaccine candidate in the U.S., called Live Vaccine Strain (LVS), has been the subject of ongoing clinical studies; however, safety and efficacy are not well established, and LVS is not licensed by the U.S. FDA. Using a mouse model, we compared the in vivo efficacy of a panel of qualitatively different Francisella vaccine candidates, the in vitro functional activity of immune lymphocytes derived from vaccinated mice, and relative gene expression in immune lymphocytes. Integrated analyses showed that the hierarchy of protection in vivo engendered by qualitatively different vaccines was reflected by the degree of lymphocytes' in vitro activity in controlling the intramacrophage growth of Francisella. Thus, this assay may be a functional correlate. Further, the strength of protection was significantly related to the degree of up-regulation of expression of a panel of genes in cells recovered from the assay. These included IFN-?, IL-6, IL-12R?2, T-bet, SOCS-1, and IL-18bp. Taken together, the results indicate that an in vitro assay that detects control of bacterial growth, and/or a selected panel of mediators, may ultimately be developed to predict the outcome of vaccine efficacy and to complement clinical trials. The overall approach may be applicable to intracellular pathogens in general.

De Pascalis, Roberto; Chou, Alicia Y.; Bosio, Catharine M.; Huang, Chiung-Yu; Follmann, Dean A.; Elkins, Karen L.

2012-01-01

90

Intracellular Persisting Staphylococcus aureus Is the Major Pathogen in Recurrent Tonsillitis  

PubMed Central

Background The two major indications for tonsillectomy are recurrent tonsillitis (RT) and peritonsillar abscess (PTA). Unlike PTAs, which are primarily treated surgically, RT is often cured by tonsillectomy only after a series of failed drug therapy attempts. Although the bacteriological background of RT has been studied, the reason for the lack of success of conservative therapeutic approaches is not well understood. Methods In a prospective study, tonsil specimens from 130 RT patients and 124 PTA patients were examined for the presence of extra- and intracellular bacteria using antibiotic protection assays. Staphylococcus aureus isolates from RT patients were characterized by pulsed-field gel electrophoresis (PFGE), spa-typing and MSCRAMM-gene-PCR. Their ability for biofilm formation was tested and their cell invasiveness was confirmed by a flow cytometric invasion assay (FACS), fluorescent in situ hybridization (FISH) and immunohistochemistry. Findings S. aureus was the predominant species (57.7%) in RT patients, whereas Streptococcus pyogenes was most prevalent (20.2%) in PTA patients. Three different assays (FACS, FISH, antibiotic protection assay) showed that nearly all RT-associated S. aureus strains were located inside tonsillar cells. Correspondingly, the results of the MSCRAMM-gene-PCRs confirmed that 87% of these S. aureus isolates were invasive strains and not mere colonizers. Based upon PFGE analyses of genomic DNA and on spa-gene typing the vast majority of the S. aureus isolates belonged to different clonal lineages. Conclusions Our results demonstrate that intracellular residing S. aureus is the most common cause of RT and indicate that S. aureus uses this location to survive the effects of antibiotics and the host immune response. A German translation of the Abstract is provided as supplementary material (Abstract S1).

Zautner, Andreas E.; Krause, Merit; Stropahl, Gerhard; Holtfreter, Silva; Frickmann, Hagen; Maletzki, Claudia; Kreikemeyer, Bernd; Pau, Hans Wilhelm; Podbielski, Andreas

2010-01-01

91

Different host defences are required to protect mice from primary systemic vs pulmonary infection with the facultative intracellular bacterial pathogen, Francisella tularensis LVS  

Microsoft Academic Search

Francisella tularensis is a zoonotic, facultative intracellular bacterial pathogen capable of initiating infection, tularemia, via multiple routes including dermal micro-abrasions and inhalation. Mouse models of systemically-initiated infection with F. tularensis LVS have been used extensively to reveal potential host defence mechanisms against the pathogen. Such studies have demonstrated the critical need for neutrophils and interferon-gamma (IFN-?) to combat the early

J. Wayne Conlan; Rhonda KuoLee; Hua Shen; Ann Webb

2002-01-01

92

Role of PPE18 Protein in Intracellular Survival and Pathogenicity of Mycobacterium tuberculosis in Mice  

PubMed Central

Background Ever since its discovery the mycobacterial proline-proline-glutamic acid (PPE) family of proteins has generated a huge amount of interest. Understanding the role of these proteins in the pathogenesis of Mycobacterium tuberculosis (Mtb) is important. We have demonstrated earlier that the PPE18 protein of Mtb induces IL-10 production in macrophages with subsequent downregulation of pro-inflammatory cytokines like IL-12 and TNF-? and favors a T-helper (Th) 2-type of immune response. Methodology/Principal Findings Using a ppe18 genetic knock-out Mtb strain, we have now carried out infection studies in mice to understand the role of PPE18 in Mtb virulence. The studies reveal that lack of PPE18 leads to attenuation of Mtb in vivo. Mice infected with the ppe18 deleted strain have reduced infection burden in lung, liver and spleen and have better survival rates compared to mice infected with the wild-type Mtb strain. Conclusions/Significance Taken together our data suggest that PPE18 could be a crucial virulence factor for intracellular survival of Mtb.

Kumar, Santosh; Sharma, Pawan; Mukhopadhyay, Sangita

2012-01-01

93

Characterization of two pathogenic mutations in cystathionine beta-synthase: Different intracellular locations for wild-type and mutant proteins.  

PubMed

Cystathionine ?-synthase (CBS) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the condensation of homocysteine with serine to generate cystathionine. Homocystinuria is an autosomal recessive disorder commonly caused by a deficiency of CBS activity. Here, we characterized a novel CBS mutation (c.260C>A (p.T87N)) and a previously reported variant (c.700G>A (p.D234N)) found in Venezuelan homocystinuric patients, one nonresponsive and one responsive to vitamin B6. Both mutant proteins were expressed in vitro in prokaryotic and eukaryotic cells, finding lower soluble expression in HEK-293 cells (19% T87N and 23% D234N) compared to wild-type CBS. Residual activities obtained for the mutant proteins were 3.5% T87N and 43% D234N. Gel exclusion chromatography demonstrated a tendency of the T87N mutant to aggregate while the distribution of the D234N mutant was similar to wild-type enzyme. Using immunofluorescence microscopy, an unexpected difference in intracellular localization was observed between the wild-type and mutant proteins. While the T87N mutant exhibited a punctate appearance, the wild-type protein was homogeneously distributed inside the cell. Interestingly, the D234N protein showed both distributions. This study demonstrates that the pathogenic CBS mutations generate unstable proteins that are unable (T87N) or partially unable (D234N) to assemble into a functional enzyme, implying that these mutations might be responsible for the homocystinuria phenotype. PMID:23981774

Casique, L; Kabil, O; Banerjee, R; Martinez, J C; De Lucca, M

2013-08-24

94

Treatment of mice with human recombinant interleukin-2 augments resistance to the facultative intracellular pathogen Listeria monocytogenes.  

PubMed Central

The effects of exogenously administered human recombinant IL-2 (hrIL-2) on resistance to Listeria monocytogenes infection were examined. Intravenous injection of hrIL-2 significantly enhanced antibacterial resistance in both BDF1 and C3H/HeJ mice. The beneficial effect of hrIL-2 was observed with as little as 0.6 micrograms per mouse, whereas optimum protection occurred at 6 micrograms per mouse, hrIL-2 was equally protective when administered concomitant with the listeriae or up to 24 h prior to infection; it had little effect if given after the bacterial challenge. Kinetic experiments indicated that both the peak bacterial burden and the time lag before L. monocytogenes began to be cleared from the spleen and liver were reduced in hrIL-2-treated mice as compared with control mice. Histopathological examination of spleens and livers confirmed that hrIL-2-treated Listeria-infected mice experienced considerably less damage to these organs than did control mice. Spleen cells from Listeria-infected mice exhibited depressed levels of mitogen-induced proliferation coincident with the peak bacterial burden in the spleen and liver and during the subsequent recovery from the infection. Administration of hrIL-2 to uninfected mice had no effect on spleen cell proliferation in response to mitogens in vitro, nor did hrIL-2 treatment restore normal levels of splenocyte proliferative responses to Listeria-infected mice. In addition, hrIL-2 treatment resulted in attenuated levels of serum colony-stimulating activity in infected mice as compared with control infected mice. Coadministration of both hrIL-2 and human recombinant interleukin-1 alpha at various dose and time combinations had no detectable additive or synergistic effect. Although these data do not suggest an obvious mechanism of action, they clearly demonstrate that hrIL-2 can augment host defense against the facultative intracellular pathogen L. monocytogenes. Images

Haak-Frendscho, M; Young, K M; Czuprynski, C J

1989-01-01

95

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

96

HLA-B27 Modulates Intracellular Growth of Salmonella Pathogenicity Island 2 Mutants and Production of Cytokines in Infected Monocytic U937 Cells  

PubMed Central

Background Salmonella enterica serovar Enteritidis PT4 KS8822/88 replicates rapidly in HLA-B27-transfected human monocytic U937 cells. In this process, Salmonella pathogenicity island 2 (SPI-2) genes play a crucial role. Our previous study indicated that 118 Salmonella genes, including 8 SPI-2 genes were affected by HLA-B27 antigen during Salmonella infection of U937 cells. Methods/Principal Findings To further investigate Salmonella replication in HLA-B27-positive U937 monocytic cells, two SPI-2 genes, ssaS and sscA up-regulated most during Salmonella infection of HLA-B27-transfected U937 cells, were mutated by using one-step gene disruption method. Intracellular survival and replication of the mutants in the U937 cells was compared to that of the wild type strain. Surprisingly, the two mutated strains replicated significantly more than the wild type bacteria in HLA-B27-transfected cells. Secretion of tumor necrosis factor alpha (TNF-?) and interleukin 10 (IL-10) was significantly induced during the infection of HLA-B27-transfected U937 cells with the mutants. The results indicated that the certain SPI-2 genes in wild type bacteria suppress Salmonella intracellular growth and production of cytokines in infected HLA-B27-transfected cells. HLA-B27-associated modulation of Salmonella SPI-2 genes and cytokine production may have importance in the persistent infection of the bacteria and the pathogenesis of reactive arthritis. Conclusions The study provides evidence that certain virulence factors of pathogens can reduce the intracellular growth in the host cells. We suggest that the limiting intracellular growth might be a strategy for persistence of bacteria in host cells, keeping a balance between pathogenic growth and pathogenesis.

Ge, Shichao; He, Qiushui; Granfors, Kaisa

2012-01-01

97

Natural history of zoonotic Ehrlichia species in the United States and discovery of a novel ehrlichial pathogen  

Microsoft Academic Search

Ehrlichia are obligate intracellular pathogens, transmitted by ixodid ticks, of both animals and humans. Ehrlichiae are emerging diseases in the USA, and the discovery of new species proceeds more rapidly than the development of models to study these agents. Laboratory animals were evaluated as models for tick transmission with E. chaffeensis, using a quantitative real-time PCR assay we developed to

A. Loftis

2008-01-01

98

Adjuvanticity of ISCOMs incorporating a T cell-reactive lipoprotein of the facultative intracellular pathogen Francisella tularensis  

Microsoft Academic Search

Immunostimulating complexes (ISCOMs) are known to be highly effective adjuvants for envelope antigens of viral agents, but have not been evaluated for use with antigens of intracellular bacteria. Balbc mice were subcutaneously immunized with ISCOMs into which the T cell-reactive membrane protein TUL4 of Francisella tularensis had been incorporated. Spleen cells from the immunized mice responded in vitro to TUL4

I. Golovliov; M. Ericsson; L. Åkerblom; G. Sandström; A. Tärnvik; A. Sjöstedt

1995-01-01

99

Truncated Hemoglobin, HbN, Is Post-translationally Modified in Mycobacterium tuberculosis and Modulates Host-Pathogen Interactions during Intracellular Infection.  

PubMed

Mycobacterium tuberculosis (Mtb) is a phenomenally successful human pathogen having evolved mechanisms that allow it to survive within the hazardous environment of macrophages and establish long term, persistent infection in the host against the control of cell-mediated immunity. One such mechanism is mediated by the truncated hemoglobin, HbN, of Mtb that displays a potent O2-dependent nitric oxide dioxygenase activity and protects its host from the toxicity of macrophage-generated nitric oxide (NO). Here we demonstrate for the first time that HbN is post-translationally modified by glycosylation in Mtb and remains localized on the cell membrane and the cell wall. The glycan linkage in the HbN was identified as mannose. The elevated expression of HbN in Mtb and M. smegmatis facilitated their entry within the macrophages as compared with isogenic control cells, and mutation in the glycan linkage of HbN disrupted this effect. Additionally, HbN-expressing cells exhibited higher survival within the THP-1 and mouse peritoneal macrophages, simultaneously increasing the intracellular level of proinflammatory cytokines IL-6 and TNF-? and suppressing the expression of co-stimulatory surface markers CD80 and CD86. These results, thus, suggest the involvement of HbN in modulating the host-pathogen interactions and immune system of the host apart from protecting the bacilli from nitrosative stress inside the activated macrophages, consequently driving cells toward increased infectivity and intracellular survival. PMID:23983123

Arya, Swati; Sethi, Deepti; Singh, Sandeep; Hade, Mangesh Dattu; Singh, Vijender; Raju, Preeti; Chodisetti, Sathi Babu; Verma, Deepshikha; Varshney, Grish C; Agrewala, Javed N; Dikshit, Kanak L

2013-08-27

100

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

101

Type III Secretion, Contact-dependent Model for the Intracellular Development of Chlamydia  

Microsoft Academic Search

The medically significant genus Chlamydia is a class of obligate intracellular bacterial pathogens that replicate within vacuoles in host eukaryotic cells termed inclusions.\\u000a Chlamydia's developmental cycle involves two forms; an infectious extracellular form, known as an elementary body (EB), and a non-infectious\\u000a form, known as the reticulate body (RB), that replicates inside the vacuoles of the host cells. The RB

D. P. Wilson; P. Timms; D. L. S. Mcelwain; P. M. Bavoil

2006-01-01

102

Democracy and Political Obligation  

Microsoft Academic Search

The public life of political servants is characterized by other duties and obligations than private life. Conflicts can even arise between a person's public and private duties. The central point of this paper is to examine whether this difference of duties can be regarded as an effect of different forms of obligation. Can we speak of a particular form of

Herman van Erp

103

Abortion and Parental Obligation  

Microsoft Academic Search

Although it has received comparatively little attention in the literature, the question of what exactly grounds a parent's obligation to his or her offspring is of central importance to the abortion debate. This essay argues that the true ground of such obligations lies in the biological bond that exists between parents and children, a bond that is forged at conception

Andrew J. Peach

104

The Costanzo obligation  

Microsoft Academic Search

National administrative authorities are obliged to leave provisions of national law unapplied when these are incompatible with EU law. Irrespective of their position and powers under national law, national administrative authorities are supposed to comply with this so-called ‘Costanzo obligation’ as established by the Court of Justice. This raises questions of both European Union law and national constitutional law, particularly

M. J. M. Verhoeven

2011-01-01

105

Intercellular and intracellular signalling systems that globally control the expression of virulence genes in plant pathogenic bacteria.  

PubMed

Plant pathogenic bacteria utilize complex signalling systems to control the expression of virulence genes at the cellular level and within populations. Quorum sensing (QS), an important intercellular communication mechanism, is mediated by different types of small molecules, including N-acyl homoserine lactones (AHLs), fatty acids and small proteins. AHL-mediated signalling systems dependent on the LuxI and LuxR family proteins play critical roles in the virulence of a wide range of Gram-negative plant pathogenic bacteria belonging to the Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria. Xanthomonas spp. and Xylella fastidiosa, members of the Gammaproteobacteria, however, possess QS systems that are mediated by fatty acid-type diffusible signal factors (DSFs). Recent studies have demonstrated that Ax21, a 194-amino-acid protein in Xanthomonas oryzae pv. oryzae, plays dual functions in activating a rice innate immune pathway through binding to the rice XA21 pattern recognition receptor and in regulating bacterial virulence and biofilm formation as a QS signal molecule. In xanthomonads, DSF-mediated QS systems are connected with the signalling pathways mediated by cyclic diguanosine monophosphate (c-di-GMP), which functions as a second messenger for the control of virulence gene expression in these bacterial pathogens. PMID:23186372

Ham, Jong Hyun

2012-11-27

106

The immunity-related GTPases in mammals: a fast-evolving cell-autonomous resistance system against intracellular pathogens  

PubMed Central

The immunity-related GTPases (IRGs) belong to the family of large, interferon-inducible GTPases and constitute a cell-autonomous resistance system essential for the control of vacuolar pathogens like Toxoplasma gondii in mice. Recent results demonstrated that numerous IRG members accumulate collaboratively at the parasitophorous vacuole of invading T. gondii leading to the destruction of the vacuole and the parasite and subsequent necrotic host cell death. Complex regulatory interactions between different IRG proteins are necessary for these processes. Disturbance of this finely balanced system, e.g., by single genetic deficiency for the important negative regulator Irgm1 or the autophagic regulator Atg5, leads to spontaneous activation of the effector IRG proteins when induced by IFN?. This activation has cytotoxic consequences resulting in a severe lymphopenia, macrophage defects, and failure of the adaptive immune system in Irgm1-deficient mice. However, alternative functions in phagosome maturation and induction of autophagy have been proposed for Irgm1. The IRG system has been studied primarily in mice, but IRG genes are present throughout the mammalian lineage. Interestingly, the number, type, and diversity of genes present differ greatly even between closely related species, probably reflecting intimate host-pathogen coevolution driven by an armed race between the IRG resistance proteins and pathogen virulence factors. IRG proteins are targets for polymorphic T. gondii virulence factors, and genetic variation in the IRG system between different mouse strains correlates with resistance and susceptibility to virulent T. gondii strains.

Hunn, Julia P.; Feng, Carl G.; Sher, Alan

2012-01-01

107

ATP scavenging by the intracellular pathogen Porphyromonas gingivalis inhibits P2X7-mediated host-cell apoptosis  

PubMed Central

Summary The purinergic receptor P2X7 is involved in cell death, inhibition of intracellular infection and secretion of inflammatory cytokines. The role of the P2X7 receptor in bacterial infection has been primarily established in macrophages. Here we show that primary gingival epithelial cells, an important component of the oral innate immune response, also express functional P2X7 and are sensitive to ATP-induced apoptosis. Porphyromonas gingivalis, an intracellular bacterium and successful colonizer of oral tissues, can inhibit gingival epithelial cell apoptosis induced by ATP ligation of P2X7 receptors. A P. gingivalis homologue of nucleoside diphosphate kinase (NDK), an ATP-consuming enzyme, is secreted extracellularly and is required for maximal suppression of apoptosis. An ndk-deficient mutant was unable to prevent ATP-induced host-cell death nor plasma membrane permeabilization in the epithelial cells. Treatment with purified recombinant NDK inhibited ATP-mediated host-cell plasma membrane permeabilization in a dose-dependent manner. Therefore, NDK promotes survival of host cells by hydrolysing extracellular ATP and preventing apoptosis-mediated through P2X7.

Yilmaz, Ozlem; Yao, Luyu; Maeda, Kazuhiko; Rose, Timothy M.; Lewis, Emma L.; Duman, Memed; Lamont, Richard J.; Ojcius, David M.

2009-01-01

108

Molecular Pathways for Intracellular Cholesterol Accumulation: Common Pathogenic Mechanisms in Niemann-Pick Disease Type C and Cystic Fibrosis  

PubMed Central

It has been less than two decades since the underlying genetic defects in Niemann-Pick disease Type C were first identified. These defects impair function of two proteins with a direct role in lipid trafficking, resulting in deposition of free cholesterol within late endosomal compartments and a multitude of effects on cell function and clinical manifestations. The rapid pace of research in this area has vastly improved our overall understanding of intracellular cholesterol homeostasis. Excessive cholesterol buildup has also been implicated in clinical manifestations associated with a number of genetically unrelated diseases including cystic fibrosis. Applying knowledge about anomalous cell signaling behavior in cystic fibrosis opens prospects for identifying similar previously unrecognized disease pathways in Niemann-Pick disease Type C. Recognition that Niemann-Pick disease Type C and cystic fibrosis both impair cholesterol regulatory pathways also provides a rationale for identifying common therapeutic targets.

Cianciola, Nicholas L.; Carlin, Cathleen R.; Kelley, Thomas J.

2011-01-01

109

The Steroid Catabolic Pathway of the Intracellular Pathogen Rhodococcus equi Is Important for Pathogenesis and a Target for Vaccine Development  

PubMed Central

Rhodococcus equi causes fatal pyogranulomatous pneumonia in foals and immunocompromised animals and humans. Despite its importance, there is currently no effective vaccine against the disease. The actinobacteria R. equi and the human pathogen Mycobacterium tuberculosis are related, and both cause pulmonary diseases. Recently, we have shown that essential steps in the cholesterol catabolic pathway are involved in the pathogenicity of M. tuberculosis. Bioinformatic analysis revealed the presence of a similar cholesterol catabolic gene cluster in R. equi. Orthologs of predicted M. tuberculosis virulence genes located within this cluster, i.e. ipdA (rv3551), ipdB (rv3552), fadA6 and fadE30, were identified in R. equi RE1 and inactivated. The ipdA and ipdB genes of R. equi RE1 appear to constitute the ?-subunit and ?-subunit, respectively, of a heterodimeric coenzyme A transferase. Mutant strains RE1?ipdAB and RE1?fadE30, but not RE1?fadA6, were impaired in growth on the steroid catabolic pathway intermediates 4-androstene-3,17-dione (AD) and 3a?-H-4?(3?-propionic acid)-5?-hydroxy-7a?-methylhexahydro-1-indanone (5?-hydroxy-methylhexahydro-1-indanone propionate; 5OH-HIP). Interestingly, RE1?ipdAB and RE1?fadE30, but not RE1?fadA6, also displayed an attenuated phenotype in a macrophage infection assay. Gene products important for growth on 5OH-HIP, as part of the steroid catabolic pathway, thus appear to act as factors involved in the pathogenicity of R. equi. Challenge experiments showed that RE1?ipdAB could be safely administered intratracheally to 2 to 5 week-old foals and oral immunization of foals even elicited a substantial protective immunity against a virulent R. equi strain. Our data show that genes involved in steroid catabolism are promising targets for the development of a live-attenuated vaccine against R. equi infections.

van der Geize, R.; Grommen, A. W. F.; Hessels, G. I.; Jacobs, A. A. C.; Dijkhuizen, L.

2011-01-01

110

TmpL, a transmembrane protein required for intracellular redox homeostasis and virulence in a plant and an animal fungal pathogen.  

PubMed

The regulation of intracellular levels of reactive oxygen species (ROS) is critical for developmental differentiation and virulence of many pathogenic fungi. In this report we demonstrate that a novel transmembrane protein, TmpL, is necessary for regulation of intracellular ROS levels and tolerance to external ROS, and is required for infection of plants by the necrotroph Alternaria brassicicola and for infection of mammals by the human pathogen Aspergillus fumigatus. In both fungi, tmpL encodes a predicted hybrid membrane protein containing an AMP-binding domain, six putative transmembrane domains, and an experimentally-validated FAD/NAD(P)-binding domain. Localization and gene expression analyses in A. brassicicola indicated that TmpL is associated with the Woronin body, a specialized peroxisome, and strongly expressed during conidiation and initial invasive growth in planta. A. brassicicola and A. fumigatus DeltatmpL strains exhibited abnormal conidiogenesis, accelerated aging, enhanced oxidative burst during conidiation, and hypersensitivity to oxidative stress when compared to wild-type or reconstituted strains. Moreover, A. brassicicola DeltatmpL strains, although capable of initial penetration, exhibited dramatically reduced invasive growth on Brassicas and Arabidopsis. Similarly, an A. fumigatus DeltatmpL mutant was dramatically less virulent than the wild-type and reconstituted strains in a murine model of invasive aspergillosis. Constitutive expression of the A. brassicicola yap1 ortholog in an A. brassicicola DeltatmpL strain resulted in high expression levels of genes associated with oxidative stress tolerance. Overexpression of yap1 in the DeltatmpL background complemented the majority of observed developmental phenotypic changes and partially restored virulence on plants. Yap1-GFP fusion strains utilizing the native yap1 promoter exhibited constitutive nuclear localization in the A. brassicicola DeltatmpL background. Collectively, we have discovered a novel protein involved in the virulence of both plant and animal fungal pathogens. Our results strongly suggest that dysregulation of oxidative stress homeostasis in the absence of TmpL is the underpinning cause of the developmental and virulence defects observed in these studies. PMID:19893627

Kim, Kwang-Hyung; Willger, Sven D; Park, Sang-Wook; Puttikamonkul, Srisombat; Grahl, Nora; Cho, Yangrae; Mukhopadhyay, Biswarup; Cramer, Robert A; Lawrence, Christopher B

2009-11-06

111

Politics and International Legal Obligation  

Microsoft Academic Search

Why do states recognize an obligation to observe the rules of international law? Existing accounts of international legal obligation suffer from the problem of ‘interiority’. They first ground obligation in some internal feature of the international legal system — such as consent, fairness or dialogue — but when these turn out to be insufficient, they fall back on assumptions about

Christian Reus-Smit

2003-01-01

112

Up-regulation of intracellular signalling pathways may play a central pathogenic role in hypertension, atherogenesis, insulin resistance, and cancer program - the ‘PKC syndrome’  

Microsoft Academic Search

The modern diet is greatly different from that of our paleolithic forebears? in a number of respects. There is reason to believe that many of these dietary shifts can up-regulate intracellular signalling pathways mediated by free intracellular calcium and protein kinase C, particularly in vascular smooth muscle cells; this disorder of intracellular regulation is given the name ‘PKC syndrome#x02019;. PKC

M. F. McCarty

1996-01-01

113

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

114

Intracellular parasitism of macrophages by Cryptococcus neoformans  

Microsoft Academic Search

Cryptococcus neoformans, an encapsulated fungal pathogen, causes meningoencephalitis in immunocompromised patients. Recent in vivo studies have demonstrated that C. neoformans is a facultative intracellular pathogen, as was previously suggested by in vitro studies. For survival in macrophages, C. neoformans utilizes a novel strategy for intracellular parasitism that includes the accumulation of intracellular polysaccharide in cytoplasmic vesicles. Confirmation of the fact

Marta Feldmesser; Stephanie Tucker; Arturo Casadevall

2001-01-01

115

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

116

An AraC-Type Transcriptional Regulator Encoded on the Enterococcus faecalis Pathogenicity Island Contributes to Pathogenesis and Intracellular Macrophage Survival  

Microsoft Academic Search

A gene encoding a putative AraC-type transcriptional regulator was identified on the 153-kb pathogenicity island (PAI) found among virulent Enterococcus faecalis strains. In an effort to understand the function of this regulator, designated PerA (for pathogenicity island-encoded regulator), we first examined the expression of the perA gene in the original PAI strain MMH594 and in an unrelated clinical isolate E99

Phillip S. Coburn; Arto S. Baghdayan; GT Dolan; Nathan Shankar

2008-01-01

117

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

118

Microsporidia: emerging pathogenic protists.  

PubMed

Microsporidia are eukaryotic spore forming obligate intracellular protozoan parasites first recognized over 100 years ago. These organisms infect all of the major animal groups and are now recognized as opportunistic pathogens of humans. Microsporidian spores are common in the environment and microsporidia pathogenic to humans have been found in water supplies. The genera Nosema, Vittaforma, Brachiola, Pleistophora, Encephalitozoon, Enterocytozoon, Septata (reclassified to Encephalitozoon) and Trachipleistophora have been found in human infections. These organisms have the smallest known eukaryotic genomes. Microsporidian ribosomal RNA sequences have proven useful as diagnostic tools as well as for phylogenetic analysis. Recent phylogenetic analysis suggests that Microsporidia are related to the fungi. These organisms are defined by the presence of a unique invasion organelle consisting of a single polar tube that coils around the interior of the spore. All microsporidia exhibit the same response to stimuli, that is, the polar tube discharges from the anterior pole of the spore in an explosive reaction. If the polar tube is discharged next to a cell, it can pierce the cell and transfer its sporoplasm into the cell. A technique was developed for the purification of polar tube proteins (PTPs) using differential extraction followed by reverse phase HPLC. This method was used to purify the PTPs from Glugea americanus, Encephalitozoon cuniculi, Enc. hellem and Enc. intestinalis. These PTPs demonstrate conserved characteristics such as solubility, hydrophobicity, mass, proline content and immunologic epitopes. The major PTP gene from Enc. cuniculi and Enc. hellem has been cloned and expressed in vitro. The gene sequences support the importance of ER and in the formation of the polar tube as suggested by morphologic studies. Analysis of the cloned proteins also indicates that secondary structural characteristics are conserved. These characteristics are probably important in the function of this protein during the eversion/assembly of the polar tube and in providing elasticity and resiliency for sporoplasm passage. PMID:11230819

Weiss, L M

2001-02-23

119

Up-regulation of intracellular signalling pathways may play a central pathogenic role in hypertension, atherogenesis, insulin resistance, and cancer promotion--the 'PKC syndrome'.  

PubMed

The modern diet is greatly different from that of our paleolithic forebears' in a number of respects. There is reason to believe that many of these dietary shifts can up-regulate intracellular signalling pathways mediated by free intracellular calcium and protein kinase C, particularly in vascular smooth muscle cells; this disorder of intracellular regulation is given the name 'PKC syndrome'. PKC syndrome may entail either a constitutive activation of these pathways, or a sensitization to activation by various agonists. The modern dietary perturbations which tend to induce PKC syndrome may include increased dietary fat and sodium, and decreased intakes of omega-3 fats, potassium, calcium, magnesium and chromium. Insulin resistance may be both a cause and effect of PKC syndrome, and weight reduction and aerobic training should act to combat this disorder. PKC syndrome sensitizes vascular smooth muscle cells to both vasoconstrictors and growth factors, and thus promotes both hypertension and atherogenesis. In platelets, it induces hyperaggregability, while in the microvasculature it may be a mediator of diabetic microangiopathy. In vascular endothelium, intimal macrophages, and hepatocytes, increased protein kinase C activity can be expected to increase cardiovascular risk. Up-regulation of protein kinase C in stem cells may also play a role in the promotion of 'Western' fat-related cancers. Practical guidelines for combatting PKC syndrome are suggested. PMID:8676754

McCarty, M F

1996-03-01

120

Washing and Disinfecting Fish Gills: Preventing Contamination by Normal Surface Microflora of Cell Cultures Inoculated with Tissue for Isolating Intracellular Pathogens  

Microsoft Academic Search

Contamination of cell cultures by the normal microflora of water, to which fish gills are exposed, is a major obstacle to in vitro culture of the pathogenic and presumptively antibiotic-sensitive rickettsia- and chlamydia-like organisms infecting gill epithelial cells. Therefore, a protocol was developed for removal or inactivation of these potential contaminating organisms. Gills of Atlantic salmon Salmo salar were vigorously

Agnar Kvellestad; Laila G. Aune; Birgit H. Dannevig

2002-01-01

121

Interferon-gamma-activated primary enterocytes inhibit Toxoplasma gondii replication: a role for intracellular iron.  

PubMed

Toxoplasma gondii is an obligate intracellular parasite that infects a wide variety of nucleated cells in its numerous intermediate hosts including man. The oral route is the natural portal of entry of T. gondii. Ingested organisms are released from cysts or oocysts within the gastrointestinal tract and initially invade the intestinal epithelium. We show that T. gondii invades and proliferates in cultured primary rat enterocytes, obtained with an original procedure. Activation of the enterocytes with rat recombinant interferon-gamma (IFN-gamma) inhibits T. gondii replication, the inhibition being dose dependent. Neither nitrogen and oxygen derivatives nor tryptophan starvation appear to be involved in the inhibition of parasite replication by IFN-gamma. Experiments using Fe2+ salt, carrier and chelator indicate that intracellular T. gondii replication is iron dependent, suggesting that IFN-gamma-treated enterocytes inhibit T. gondii replication by limiting the availability of intracellular iron to the parasite. Our data show that enterocytes probably play a major role on mucosal surfaces as a first line of defence against this coccidia, and possibly other pathogens, through an immune mechanism. The results suggest that limiting the availability of iron could represent a broad antimicrobial mechanism through which the activated enterocytes exert control over intracellular pathogens. PMID:9767436

Dimier, I H; Bout, D T

1998-08-01

122

An AraC-Type Transcriptional Regulator Encoded on the Enterococcus faecalis Pathogenicity Island Contributes to Pathogenesis and Intracellular Macrophage Survival?  

PubMed Central

A gene encoding a putative AraC-type transcriptional regulator was identified on the 153-kb pathogenicity island (PAI) found among virulent Enterococcus faecalis strains. In an effort to understand the function of this regulator, designated PerA (for pathogenicity island-encoded regulator), we first examined the expression of the perA gene in the original PAI strain MMH594 and in an unrelated clinical isolate E99 by reverse transcription-PCR. Interestingly, expression analysis revealed no detectable perA transcript in MMH594, whereas a transcript was observed in strain E99. Nucleotide sequence analysis revealed that this altered expression between the two strains was attributable to the differential location of an IS1191 element within the putative promoter region upstream of the perA gene. In order to determine the role of this putative regulator in E. faecalis pathogenesis, a perA-deficient mutant was created in strain E99, and the wild-type and mutant pair were compared for phenotypic differences. In in vitro biofilm assays, the mutant strain showed a significantly higher level of growth medium-specific biofilm formation compared to the wild type. However, in a murine intraperitoneal infection model, the mutant strain was significantly less pathogenic. The mutant was also attenuated for survival within macrophages in vitro. These findings highlight the importance of PerA as a regulator of biofilm formation and survival within macrophages and is likely a regulator controlling determinants important to pathogenesis.

Coburn, Phillip S.; Baghdayan, Arto S.; Dolan, GT; Shankar, Nathan

2008-01-01

123

An AraC-type transcriptional regulator encoded on the Enterococcus faecalis pathogenicity island contributes to pathogenesis and intracellular macrophage survival.  

PubMed

A gene encoding a putative AraC-type transcriptional regulator was identified on the 153-kb pathogenicity island (PAI) found among virulent Enterococcus faecalis strains. In an effort to understand the function of this regulator, designated PerA (for pathogenicity island-encoded regulator), we first examined the expression of the perA gene in the original PAI strain MMH594 and in an unrelated clinical isolate E99 by reverse transcription-PCR. Interestingly, expression analysis revealed no detectable perA transcript in MMH594, whereas a transcript was observed in strain E99. Nucleotide sequence analysis revealed that this altered expression between the two strains was attributable to the differential location of an IS1191 element within the putative promoter region upstream of the perA gene. In order to determine the role of this putative regulator in E. faecalis pathogenesis, a perA-deficient mutant was created in strain E99, and the wild-type and mutant pair were compared for phenotypic differences. In in vitro biofilm assays, the mutant strain showed a significantly higher level of growth medium-specific biofilm formation compared to the wild type. However, in a murine intraperitoneal infection model, the mutant strain was significantly less pathogenic. The mutant was also attenuated for survival within macrophages in vitro. These findings highlight the importance of PerA as a regulator of biofilm formation and survival within macrophages and is likely a regulator controlling determinants important to pathogenesis. PMID:18824537

Coburn, Phillip S; Baghdayan, Arto S; Dolan, G T; Shankar, Nathan

2008-09-29

124

Exit Mechanisms of the Intracellular Bacterium Ehrlichia  

PubMed Central

Background The obligately intracellular bacterium Ehrlichia chaffeensis that resides in mononuclear phagocytes is the causative agent of human monocytotropic ehrlichiosis. Ehrlichia muris and Ixodes ovatus Ehrlichia (IOE) are agents of mouse models of ehrlichiosis. The mechanism by which Ehrlichia are transported from an infected host cell to a non-infected cell has not been demonstrated. Methodology/Principal Findings Using fluorescence microscopy and transmission and scanning electron microscopy, we demonstrated that Ehrlichia was transported through the filopodia of macrophages during early stages of infection. If host cells were not present in the vicinity of an Ehrlichia-infected cell, the leading edge of the filopodium formed a fan-shaped structure filled with the pathogen. Formation of filopodia in the host macrophages was inhibited by cytochalasin D and ehrlichial transport were prevented due to the absence of filopodia formation. At late stages of infection the host cell membrane was ruptured, and the bacteria were released. Conclusions/Significance Ehrlichia are transported through the host cell filopodium during initial stages of infection, but are released by host cell membrane rupture during later stages of infection.

Thomas, Sunil; Popov, Vsevolod L.; Walker, David H.

2010-01-01

125

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

PubMed Central

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.

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

2012-01-01

126

47 CFR 7.5 - General Obligations.  

Code of Federal Regulations, 2012 CFR

...Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL ACCESS TO VOICEMAIL AND INTERACTIVE MENU SERVICES AND EQUIPMENT BY PEOPLE WITH DISABILITIES Obligations-What Must Covered Entities Do? § 7.5 General Obligations. (a)...

2012-10-01

127

45 CFR 83.10 - General obligations.  

Code of Federal Regulations, 2012 CFR

...false General obligations. 83.10 Section 83.10 Public Welfare DEPARTMENT OF...in Admissions Prohibited § 83.10 General obligations. (a) Eligibility...submitting such assurance fails to take whatever remedial action...

2012-10-01

128

45 CFR 83.10 - General obligations.  

Code of Federal Regulations, 2011 CFR

...false General obligations. 83.10 Section 83.10 Public Welfare DEPARTMENT OF...in Admissions Prohibited § 83.10 General obligations. (a) Eligibility...submitting such assurance fails to take whatever remedial action...

2011-10-01

129

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

130

The Small GTPase RacA Mediates Intracellular Reactive Oxygen Species Production, Polarized Growth, and Virulence in the Human Fungal Pathogen Aspergillus fumigatus ? †  

PubMed Central

Aspergillus fumigatus is the predominant mold pathogen in immunocompromised patients. In this study, we present the first characterization of the small GTPase RacA in A. fumigatus. To gain insight into the function of racA in the growth and pathogenesis of A. fumigatus, we constructed a strain that lacks a functional racA gene. The ?racA strain showed significant morphological defects, including a reduced growth rate and abnormal conidiogenesis on glucose minimal medium. In the ?racA strain, apical dominance in the leading hyphae is lost and, instead, multiple axes of polarity emerge. Intriguingly, superoxide production at the hyphal tips was reduced by 25% in the ?racA strain. Treatment of wild-type hyphae with diphenylene iodonium, an inhibitor of NADPH oxidase, resulted in phenotypes similar to that of the ?racA strain. These data suggest that ?racA strain phenotypes may be due to a reduction or alteration in the production of reactive oxygen species. Most surprisingly, despite these developmental and growth abnormalities, the ?racA strain retained at least wild-type virulence in both an insect model and two immunologically distinct murine models of invasive pulmonary aspergillosis. These results demonstrate that in vitro growth phenotypes do not always correlate with in vivo virulence and raise intriguing questions about the role of RacA in Aspergillus virulence.

Li, Haiyan; Barker, Bridget M.; Grahl, Nora; Puttikamonkul, Srisombat; Bell, Jeremey D.; Craven, Kelly D.; Cramer, Robert A.

2011-01-01

131

[Family ties and maintenance obligation].  

PubMed

Maintenance obligation is a question frequently addressed in gerontology as an elderly person prepares to enter an institution. Its implementation is a source of conflict within families as well as with professionals involved in these situations. This administrative process, generally long and complex, can shatter family ties and lengthen the time required to obtain support thereby delaying admission to the institution. To tackle these issues, professionals from the Paris Saint-Joseph hospital group have set up meetings bringing together social services, medical services and management representatives. These multi-disciplinary consultations have highlighted the need for management to work with the families of hospitalised patients to remind them of the maintenance obligation in a framework of mediation. PMID:22611896

Manteghetti, Michèle; Reznikoff, Valérie

132

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

Code of Federal Regulations, 2012 CFR

...Consolidated obligations are not obligations of the United States or guaranteed by the United States. 1270.20 Section 1270.20 Banks and...Consolidated obligations are not obligations of the United States or guaranteed by the United States....

2012-01-01

133

Caveolin-2 associates with intracellular chlamydial inclusions independently of caveolin-1  

PubMed Central

Background Lipid raft domains form in plasma membranes of eukaryotic cells by the tight packing of glycosphingolipids and cholesterol. Caveolae are invaginated structures that form in lipid raft domains when the protein caveolin-1 is expressed. The Chlamydiaceae are obligate intracellular bacterial pathogens that replicate entirely within inclusions that develop from the phagocytic vacuoles in which they enter. We recently found that host cell caveolin-1 is associated with the intracellular vacuoles and inclusions of some chlamydial strains and species, and that entry of those strains depends on intact lipid raft domains. Caveolin-2 is another member of the caveolin family of proteins that is present in caveolae, but of unknown function. Methods We utilized a caveolin-1 negative/caveolin-2 positive FRT cell line and laser confocal immunofluorescence techniques to visualize the colocalization of caveolin-2 with the chlamydial inclusions. Results We show here that in infected HeLa cells, caveolin-2, as well as caveolin-1, colocalizes with inclusions of C. pneumoniae (Cp), C. caviae (GPIC), and C. trachomatis serovars E, F and K. In addition, caveolin-2 also associates with C. trachomatis serovars A, B and C, although caveolin-1 did not colocalize with these organisms. Moreover, caveolin-2 appears to be specifically, or indirectly, associated with the pathogens at the inclusion membranes. Using caveolin-1 deficient FRT cells, we show that although caveolin-2 normally is not transported out of the Golgi in the absence of caveolin-1, it nevertheless colocalizes with chlamydial inclusions in these cells. However, our results also show that caveolin-2 did not colocalize with UV-irradiated Chlamydia in FRT cells, suggesting that in these caveolin-1 negative cells, pathogen viability and very likely pathogen gene expression are necessary for the acquisition of caveolin-2 from the Golgi. Conclusion Caveolin-2 associates with the chlamydial inclusion independently of caveolin-1. The function of caveolin-2, either in the uninfected cell or in the chlamydial developmental cycle, remains to be elucidated. Nevertheless, this second caveolin protein can now be added to the small number of host proteins that are associated with the inclusions of this obligate intracellular pathogen.

Webley, Wilmore C; Norkin, Leonard C; Stuart, Elizabeth S

2004-01-01

134

Evolution of pathogenicity in Plasmopara halstedii (sunflower downy mildew)  

Microsoft Academic Search

Comprehension of the processes of co-evolution between the pathogen and its host plant is very important, particularly in the case of obligate pathogen as Plasmopara halstedii which cannot develop only on sunflower. The influence of selection pressure exercised by qualitative resistance in sunflower plants on evolution of pathogenicity was analysed in pathogenic populations of P. halstedii. This selection pressure led

Nachaat Sakr

2011-01-01

135

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

136

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

PubMed

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 biotrophic rust fungus using a biolistic approach. Biolistic bombardment of U. fabae urediospores was used to deliver different color markers (?-glucuronidase (GUS), intron green fluorescent protein (iGFP) and red fluorescent protein (DsRed) and/or a selection marker. Endogenous regulatory elements from U. fabae plasma membrane ATPase (Uf-PMA1) were used to drive expression of the transgenes. In addition to the delivery of color markers, an in planta selection procedure using the fungicide Carboxin was established allowing the propagation of transformants. In addition to mere cytoplasmic expression of the color markers, a nuclear localization signal was fused to DsRed (pRV115-NLS) targeting the fluorescent marker protein to the nuclei. A procedure for the genetic modification of U. fabae was established. The method can be easily adapted for use with other obligate biotrophic fungi. This provides the basis for a more in depth analysis of the molecular principles governing the obligate biotrophic lifestyle. PMID:21724169

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

2011-04-09

137

Comparison of the ‘Ca. Liberibacter asiaticus’ Genome Adapted for an Intracellular Lifestyle with Other Members of the Rhizobiales  

Microsoft Academic Search

An intracellular plant pathogen ‘Candidatus Liberibacter asiaticus,’ a member of the Rhizobiales, is related to Sinorhizobium meliloti, Bradyrhizobium japonicum, nitrogen fixing endosymbionts, Agrobacterium tumefaciens, a plant pathogen, and Bartonella henselae, an intracellular mammalian pathogen. Whole chromosome comparisons identified at least 50 clusters of conserved orthologous genes found on the chromosomes of all five metabolically diverse species. The intracellular pathogens ‘Ca.

John S. Hartung; Jonathan Shao; L. David Kuykendall

2011-01-01

138

Functional genomics of intracellular bacteria.  

PubMed

During the genomic era, a large amount of whole-genome sequences accumulated, which identified many hypothetical proteins of unknown function. Rapidly, functional genomics, which is the research domain that assign a function to a given gene product, has thus been developed. Functional genomics of intracellular pathogenic bacteria exhibit specific peculiarities due to the fastidious growth of most of these intracellular micro-organisms, due to the close interaction with the host cell, due to the risk of contamination of experiments with host cell proteins and, for some strict intracellular bacteria such as Chlamydia, due to the absence of simple genetic system to manipulate the bacterial genome. To identify virulence factors of intracellular pathogenic bacteria, functional genomics often rely on bioinformatic analyses compared with model organisms such as Escherichia coli and Bacillus subtilis. The use of heterologous expression is another common approach. Given the intracellular lifestyle and the many effectors that are used by the intracellular bacteria to corrupt host cell functions, functional genomics is also often targeting the identification of new effectors such as those of the T4SS of Brucella and Legionella. PMID:23564838

de Barsy, Marie; Greub, Gilbert

2013-04-05

139

Brucella abortus intracellular survival and intercellular trafficking  

Microsoft Academic Search

Brucella spp. are host specific facultative intracellular pathogens. Brucella abortus is responsible for causing abortions in cattle and is also able to cause disease in humans. Brucella internalization and intracellular trafficking varies depending on whether the bacterium was opsonized or non-opsonized with serum immunoglobulin. Interferon-gamma has been shown to be critical for the control of B. abortus infection in vivo

Jennifer Ann Ritchie

2011-01-01

140

Rickettsia as obligate and mycetomic bacteria.  

PubMed

Rickettsiae are well known as intracellular pathogens of animals, humans, and plants and facultative and unorganized symbionts of invertebrates. No close relative of mitochondria has yet been associated with nutritional or developmental dependency of its host cell or organism. We have found a mycetomic Rickettsia that is a strict obligatory symbiont of the parthenogenetic booklouse Liposcelis bostrychophila (Psocoptera). These rickettsiae show an evolutionary transition from a solitary to a primary mycetomic bacterium adapted to the development of its host. These intracellular and intranuclear bacteria reside in specialized cells in several tissues. Their distribution changes markedly with the development of their host. The most advanced phenotype is a paired mycetome in the abdomen, described for the first time for Rickettsia and this host order. The mycetomic rickettsiae of two parthenogenetic book lice species are in the spotted fever group and in the basal limoniae group. While mycetomic bacteria are well known for their metabolic or light-emitting functions, these rickettsiae have an essential role in the early development of the oocyte. Removal of the Rickettsia stops egg production and reproduction in the book louse. In two phylogenetically distant psocopteran species, Rickettsia are shown to be associated with four transitional stages from free bacteria, infected cells, through single mycetocytes to organ-forming mycetomes. PMID:17012243

Perotti, M Alejandra; Clarke, Heather K; Turner, Bryan D; Braig, Henk R

2006-09-28

141

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

142

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

143

Intracellular Bacteria Encode Inhibitory SNARE-Like Proteins  

Microsoft Academic Search

Pathogens use diverse molecular machines to penetrate host cells and manipulate intracellular vesicular trafficking. Viruses employ glycoproteins, functionally and structurally similar to the SNARE proteins, to induce eukaryotic membrane fusion. Intracellular pathogens, on the other hand, need to block fusion of their infectious phagosomes with various endocytic compartments to escape from the degradative pathway. The molecular details concerning the mechanisms

Fabienne Paumet; Jordan Wesolowski; Alejandro Garcia-Diaz; Cedric Delevoye; Nathalie Aulner; Howard A. Shuman; Agathe Subtil; James E. Rothman

2009-01-01

144

Autophagy in intracellular bacterial infection.  

PubMed

Numerous pathogens have developed the capacity to invade host cells to be protected from components of the systemic immune system. However, once in the host cells they utilize sophisticated strategies to avoid the powerful machinery built by the cells to kill invading pathogens. In the last few years cumulative evidence indicates that autophagy is one of the most remarkable tools of the intracellular host cell defense machinery that bacteria must confront upon cell invasion. However, several pathogens subvert the autophagic pathway and, manipulate this process at the molecular level, as a strategy to establish a persistent infection. In this review we have summarized the interaction between autophagy and different bacterial pathogens including those that take advantage of the host cell autophagy, allowing successful colonization, as well as those microorganisms which are controlled by autophagy as part of the innate surveillance mechanism. PMID:19303905

Campoy, Emanuel; Colombo, María I

2009-03-19

145

The cell-penetrating peptide, Pep-1, has activity against intracellular chlamydial growth but not extracellular forms of Chlamydia trachomatis  

PubMed Central

Objectives In the course of studies to identify novel treatment strategies against the pathogenic bacterium, Chlamydia, we tested the carrier peptide, Pep-1, for activity against an intracellular infection. Methods Using a cell culture model of Chlamydia trachomatis infection, the effect of Pep-1 was measured by incubating the peptide with extracellular chlamydiae prior to infection, or by adding Pep-1 to the medium at varying times after infection, and assaying for inhibition of inclusion formation. Results Pep-1 had a concentration-dependent effect on chlamydial growth with 100% inhibition of inclusion formation at 8 mg/L peptide. There was a window of susceptibility during the chlamydial developmental cycle with a maximal effect when treatment was begun within 12 h of infection. Pep-1 treatment caused a severe reduction in the production of infectious progeny even when started later, when the effect on inclusion formation was minimal. Furthermore, electron micrographs showed a paucity of progeny elementary bodies (EBs) in the inclusion. In contrast, pre-incubation of EBs with Pep-1 prior to infection did not affect inclusion formation. Taken together, these findings indicate that the antichlamydial effect was specific for the intracellular stage of chlamydial infection. By comparison, Pep-1 had no antimicrobial activity against Escherichia coli and Staphylococcus aureus or the obligate intracellular parasite, Toxoplasma gondii. Conclusions Pep-1 has antichlamydial activity by preventing intracellular chlamydial growth and replication but has no effect on extracellular chlamydiae.

Park, Narae; Yamanaka, Kinrin; Tran, Dat; Chandrangsu, Pete; Akers, Johnny C.; de Leon, Jessica C.; Morrissette, Naomi S.; Selsted, Michael E.; Tan, Ming

2009-01-01

146

Comparison of the 'Ca Liberibacter asiaticus' genome adapted for an intracellular lifestyle with other members of the rhizobiales  

Technology Transfer Automated Retrieval System (TEKTRAN)

An intracellular plant pathogen ‘Ca. Liberibacter asiaticus,’ a member of the Rhizobiales, is related to Sinorhizobium meliloti, Bradyrhizobium japonicum, Agrobacterium tumefaciens and Bartonella henselae, an intracellular mammalian pathogen. Whole chromosome comparisons identified at least 52 clust...

147

45 CFR 63.21 - Obligation and liquidation by grantee.  

Code of Federal Regulations, 2012 CFR

...false Obligation and liquidation by grantee. 63.21 Section 63.21 Public...21 Obligation and liquidation by grantee. Obligations will be considered to have been incurred by a grantee on the basis of documentary evidence...

2012-10-01

148

45 CFR 1226.13 - Obligations of sponsors.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Obligations of sponsors. 1226.13 Section 1226.13 Public...ON ELECTORAL AND LOBBYING ACTIVITIES Sponsor Employee Activities § 1226.13 Obligations of sponsors. (a) It shall be the obligation...

2012-10-01

149

31 CFR 225.5 - Pledge of definitive Government obligations.  

Code of Federal Regulations, 2013 CFR

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

2013-07-01

150

11 CFR 9034.5 - Net outstanding campaign obligations.  

Code of Federal Regulations, 2013 CFR

...ENTITLEMENTS § 9034.5 Net outstanding campaign obligations...shall submit a statement of net outstanding campaign obligations. The candidate's net outstanding campaign obligations...currency; balances on deposit in banks; savings and loan...

2013-01-01

151

24 CFR 891.755 - Obligations of the family.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Obligations of the family. 891.755 Section 891.755...Projects for the Nonelderly Handicapped Families and Individuals-Section 162 Assistance § 891.755 Obligations of the family. The obligations of the...

2013-04-01

152

Caring work, personal obligation and collective responsibility.  

PubMed

Studies of workers in health care and the care of older people disclose tensions that emerge partly from their conflicting obligations. They incur some obligations from the personal relationships they have with clients, but these can be at odds with organizational demands and resource constraints. One implication is the need for policies to recognize the importance of allowing workers some discretion in decison making. Another implication may be that sometimes care workers can meet their obligations to clients only by taking collective action. PMID:14763646

Provis, Chris; Stack, Sue

2004-01-01

153

Genetic transformation of an obligate anaerobe, P. gingivalis for FMN-green fluorescent protein expression in studying host-microbe interaction.  

PubMed

The recent introduction of "oxygen-independent" flavin mononucleotide (FMN)-based fluorescent proteins (FbFPs) is of major interest to both eukaryotic and prokaryotic microbial biologists. Accordingly, we demonstrate for the first time that an obligate anaerobe, the successful opportunistic pathogen of the oral cavity, Porphyromonas gingivalis, can be genetically engineered for expression of the non-toxic green FbFP. The resulting transformants are functional for studying dynamic bacterial processes in living host cells. The visualization of the transformed P. gingivalis (PgFbFP) revealed strong fluorescence that reached a maximum emission at 495 nm as determined by fluorescence microscopy and spectrofluorometry. Human primary gingival epithelial cells (GECs) were infected with PgFbFP and the bacterial invasion of host cells was analyzed by a quantitative fluorescence microscopy and antibiotic protection assays. The results showed similar levels of intracellular bacteria for both wild type and PgFbFP strains. In conjunction with organelle specific fluorescent dyes, utilization of the transformed strain provided direct and accurate determination of the live/metabolically active P. gingivalis' trafficking in the GECs over time. Furthermore, the GECs were co-infected with PgFbFP and the ATP-dependent Clp serine protease-deficient mutant (ClpP-) to study the differential fates of the two strains within the same host cells. Quantitative co-localization analyses displayed the intracellular PgFbFP significantly associated with the endoplasmic reticulum network, whereas the majority of ClpP- organisms trafficked into the lysosomes. Hence, we have developed a novel and reliable method to characterize live host cell-microbe interactions and demonstrated the adaptability of FMN-green fluorescent protein for studying persistent host infections induced by obligate anaerobic organisms. PMID:21525983

Choi, Chul Hee; DeGuzman, Jefferson V; Lamont, Richard J; Yilmaz, Özlem

2011-04-15

154

Genetic Transformation of an Obligate Anaerobe, P. gingivalis for FMN-Green Fluorescent Protein Expression in Studying Host-Microbe Interaction  

PubMed Central

The recent introduction of “oxygen-independent” flavin mononucleotide (FMN)-based fluorescent proteins (FbFPs) is of major interest to both eukaryotic and prokaryotic microbial biologists. Accordingly, we demonstrate for the first time that an obligate anaerobe, the successful opportunistic pathogen of the oral cavity, Porphyromonas gingivalis, can be genetically engineered for expression of the non-toxic green FbFP. The resulting transformants are functional for studying dynamic bacterial processes in living host cells. The visualization of the transformed P. gingivalis (PgFbFP) revealed strong fluorescence that reached a maximum emission at 495 nm as determined by fluorescence microscopy and spectrofluorometry. Human primary gingival epithelial cells (GECs) were infected with PgFbFP and the bacterial invasion of host cells was analyzed by a quantitative fluorescence microscopy and antibiotic protection assays. The results showed similar levels of intracellular bacteria for both wild type and PgFbFP strains. In conjunction with organelle specific fluorescent dyes, utilization of the transformed strain provided direct and accurate determination of the live/metabolically active P. gingivalis' trafficking in the GECs over time. Furthermore, the GECs were co-infected with PgFbFP and the ATP-dependent Clp serine protease-deficient mutant (ClpP-) to study the differential fates of the two strains within the same host cells. Quantitative co-localization analyses displayed the intracellular PgFbFP significantly associated with the endoplasmic reticulum network, whereas the majority of ClpP- organisms trafficked into the lysosomes. Hence, we have developed a novel and reliable method to characterize live host cell-microbe interactions and demonstrated the adaptability of FMN-green fluorescent protein for studying persistent host infections induced by obligate anaerobic organisms.

Choi, Chul Hee; DeGuzman, Jefferson V.; Lamont, Richard J.; Yilmaz, Ozlem

2011-01-01

155

19 CFR 10.412 - 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-Chile Free Trade Agreement Import Requirements § 10.412 Importer obligations. (a) General. An importer...

2013-04-01

156

7 CFR 982.50 - Restricted obligation.  

Code of Federal Regulations, 2013 CFR

...Order Regulating Handling Control of Distribution § 982.50 Restricted obligation...withheld from handling a quantity, by weight, of certified merchantable hazelnuts...section, the equivalent quantity, by weight as determined under that...

2013-01-01

157

46 CFR Sec. 11 - Guarantee obligations.  

Code of Federal Regulations, 2012 CFR

...REPAIRS UNDER NATIONAL SHIPPING AUTHORITY MASTER LUMP SUM REPAIR CONTRACT-NSA-LUMPSUMREP Sec. 11 Guarantee obligations. (a) Under the provisions of Article 10 of the NSA-LUMPSUMREP Contract the Contractor's guarantee liability...

2012-10-01

158

Real-Time Molecular Monitoring of Chemical Environment in ObligateAnaerobes during Oxygen Adaptive Response  

SciTech Connect

Determining the transient chemical properties of the intracellular environment canelucidate the paths through which a biological system adapts to changes in its environment, for example, the mechanisms which enable some obligate anaerobic bacteria to survive a sudden exposure to oxygen. Here we used high-resolution Fourier Transform Infrared (FTIR) spectromicroscopy to continuously follow cellular chemistry within living obligate anaerobes by monitoring hydrogen bonding in their cellular water. We observed a sequence of wellorchestrated molecular events that correspond to changes in cellular processes in those cells that survive, but only accumulation of radicals in those that do not. We thereby can interpret the adaptive response in terms of transient intracellular chemistry and link it to oxygen stress and survival. This ability to monitor chemical changes at the molecular level can yield important insights into a wide range of adaptive responses.

Holman, Hoi-Ying N.; Wozei, Eleanor; Lin, Zhang; Comolli, Luis R.; Ball, David. A.; Borglin, Sharon; Fields, Matthew W.; Hazen, Terry C.; Downing, Kenneth H.

2009-02-25

159

Studies of polyamine metabolism in obligately alkalophilic Bacillus alcalophilus that grow at pH 11  

Microsoft Academic Search

Bacillus alcalophilus, an obligately alkalophilic bacterium, grow at pH 11 with an intracellular pH greater than 9.5. Polyamines are positively charged at physiological pH, but less than 50% of polyamines will be charged at pH 9.5 and above. In view of the importance of polycationic nature of polyamines in their physiological functions, it is of interest to study the polyamine

S. Cheng; K. Y. Chen

1987-01-01

160

Ehrlichia chaffeensis: a Prototypical Emerging Pathogen  

PubMed Central

Ehrlichia chaffeensis is an obligately intracellular, tick-transmitted bacterium that is maintained in nature in a cycle involving at least one and perhaps several vertebrate reservoir hosts. The moderate to severe disease caused by E. chaffeensis in humans, first identified in 1986 and reported for more than 1,000 patients through 2000, represents a prototypical “emerging infection.” Knowledge of the biology and natural history of E. chaffeensis, and of the epidemiology, clinical features, and laboratory diagnosis of the zoonotic disease it causes (commonly referred to as human monocytic ehrlichiosis [HME]) has expanded considerably in the period since its discovery. In this review, we summarize briefly the current understanding of the microbiology, pathogenesis, and clinical manifestations associated with this pathogen but focus primarily on discussing various ecological factors responsible for the recent recognition of this important and potentially life-threatening tick-borne disease. Perhaps the most pivotal element in the emergence of HME has been the staggering increases in white-tailed deer populations in the eastern United States during the 20th century. This animal serves as a keystone host for all life stages of the principal tick vector (Amblyomma americanum) and is perhaps the most important vertebrate reservoir host for E. chaffeensis. The contributions of other components, including expansion of susceptible human populations, growth and broadening geographical distributions of other potential reservoir species and A. americanum, and improvements in confirmatory diagnostic methods, are also explored.

Paddock, Christopher D.; Childs, James E.

2003-01-01

161

Autophagy in Immunity Against Intracellular Bacteria  

Microsoft Academic Search

\\u000a Autophagy is an innate immune defense mechanism against various intracellular bacterial pathogens, such as Salmonella enterica serovar Typhimurium (S. typhimurium), Listeria monocytogenes and Shigella flexneri. S. typhimurium uses type three secretion systems (T3SSs) to invade mammalian cells and replicate in Salmonella-containing vacuoles (SCVs). A small population of intracellular S. typhimurium is targeted by autophagy shortly after infection. Evidence suggests that

Ju Huang; John H. Brumell

162

REGULATION OF PRIMARY T CELL RESPONSES TO INTRACELLULAR INFECTION IN THE LUNG  

Microsoft Academic Search

Pulmonary infections caused by viruses, bacteria, mycobacteria and fungi, are a leading cause of death world-wide. Intracellular pathogens such as influenza virus and M.tb live inside host cells, making it difficult for the host to eliminate the pathogen. Adaptive T cell immune responses are required to clear intracellular pathogens. Rapid T cell priming and recruitment of effector T cells to

Sarah M McCormick

2011-01-01

163

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

164

Patients' ethical obligation for their health.  

PubMed Central

In contemporary medical ethics health is rarely acknowledged to be an ethical obligation. This oversight is due to the preoccupation of most bioethicists with a rationalist, contract model for ethics in which moral obligation is limited to truth-telling and promise-keeping. Such an ethics is poorly suited to medicine because it fails to appreciate that medicine's basis as a moral enterprise is oriented towards health values. A naturalistic model for medical ethics is proposed which builds upon biological and medical values. This perspective clarifies ethical obligations to ourselves and to others for life and health. It provides a normative framework for the doctor-patient relationship within which to formulate medical advice and by which to evaluate patient choice.

Sider, R C; Clements, C D

1984-01-01

165

The Francisella Intracellular Life Cycle: Toward Molecular Mechanisms of Intracellular Survival and Proliferation  

PubMed Central

The tularemia-causing bacterium Francisella tularensis is a facultative intracellular organism with a complex intracellular lifecycle that ensures its survival and proliferation in a variety of mammalian cell types, including professional phagocytes. Because this cycle is essential to Francisella pathogenesis and virulence, much research has focused on deciphering the mechanisms of its intracellular survival and replication and characterizing both bacterial and host determinants of the bacterium's intracellular cycle. Studies of various strains and host cell models have led to the consensual paradigm of Francisella as a cytosolic pathogen, but also to some controversy about its intracellular cycle. In this review, we will detail major findings that have advanced our knowledge of Francisella intracellular survival strategies and also attempt to reconcile discrepancies that exist in our molecular understanding of the Francisella–phagocyte interactions.

Chong, Audrey; Celli, Jean

2010-01-01

166

Chlamydiae Assemble a Pathogen Synapse to Hijack the Host Endoplasmic Reticulum  

PubMed Central

Chlamydiae are obligate intracellular bacterial pathogens that replicate within a specialized membrane-bound compartment, termed an ‘inclusion’. The inclusion membrane is a critical host–pathogen interface, yet the extent of its interaction with cellular organelles and the origin of this membrane remain poorly defined. Here we show that the host endoplasmic reticulum (ER) is specifically recruited to the inclusion, and that key rough ER (rER) proteins are enriched on and translocated into the inclusion. rER recruitment is a Chlamydia-orchestrated process that occurs independently of host trafficking. Generation of infectious progeny requires an intact ER, since ER vacuolation early during infection stalls inclusion development, whereas disruption post ER recruitment bursts the inclusion. Electron tomography and immunolabelling of Chlamydia-infected cells reveal ‘pathogen synapses’ at which ordered arrays of chlamydial type III secretion complexes connect to the inclusion membrane only at rER contact sites. Our data show a supramolecular assembly involved in pathogen hijack of a key host organelle.

Dumoux, Maud; Clare, Daniel K; Saibil, Helen R; Hayward, Richard D

2012-01-01

167

Plasmodiophorids: The Challenge to Understand Soil-Borne, Obligate Biotrophs with a Multiphasic Life Cycle  

Microsoft Academic Search

\\u000a Plasmodiophorids are an enigmatic group of obligate biotrophic pathogens of higher plants. Together with their sister group\\u000a phagomyxids, which infect stramenopiles, they form the monophyletic eukaryote clade phytomyxids. They have long been treated\\u000a as a basal group of fungi, but recent molecular phylogenies point to a close affiliation with the protozoan phylum Cercozoa.\\u000a The soil-borne and plant-associated nature of plasmodiophorids

Sigrid Neuhauser; Simon Bulman; Martin Kirchmair

168

Host-cell interactions with pathogenic Rickettsia species  

PubMed Central

Pathogenic Rickettsia species are Gram-negative, obligate intracellular bacteria responsible for the spotted fever and typhus groups of diseases around the world. It is now well established that a majority of sequelae associated with human rickettsioses are the outcome of the pathogen's affinity for endothelium lining the blood vessels, the consequences of which are vascular inflammation, insult to vascular integrity and compromised vascular permeability, collectively termed ‘Rickettsial vasculitis’. Signaling mechanisms leading to transcriptional activation of target cells in response to Rickettsial adhesion and/or invasion, differential activation of host-cell signaling due to infection with spotted fever versus typhus subgroups of Rickettsiae, and their contributions to the host's immune responses and determination of cell fate are the major subtopics of this review. Also included is a succinct analysis of established in vivo models and their use for understanding Rickettsial interactions with host cells and pathogenesis of vasculotropic rickettsioses. Continued progress in these important but relatively under-explored areas of bacterial pathogenesis research should further highlight unique aspects of Rickettsial interactions with host cells, elucidate the biological basis of endothelial tropism and reveal novel chemotherapeutic and vaccination strategies for debilitating Rickettsial diseases.

Sahni, Sanjeev K; Rydkina, Elena

2009-01-01

169

Inhibition of intracellular replication by pyridinylimidazoles  

US Patent & Trademark Office Database

Substituted pyridinylimidazoles SB203580 and SB202190 strongly inhibit replication and cause stage conversion from active tachyzoites to relatively dormant bradyzoites of the medically important, obligate intracellular parasite Toxoplasma gondii. The pyridinylimidazoles probably mediate these effects by acting on a presently unidentified homologue(s) of human p38-mitogen activated protein kinase present in the tachyzoites. SB203580 also significantly enhanced in vitro inhibition of T. gondii replication by the approved anti-Toxoplasma drug pyrimethamine. The pyridinylimidazoles and related compounds disclosed herein could thus be significant adjuncts to currently available therapies.

2003-11-18

170

48 CFR 519.7013 - Obligation.  

Code of Federal Regulations, 2011 CFR

...gé Program 519.7013 Obligation. (a) The mentor or protégé may terminate the Agreement in accordance with 519.7010. The mentor will notify the Mentor-Protégé Program Manager and the contracting officer, in writing, at least 30...

2011-10-01

171

48 CFR 519.7013 - Obligation.  

Code of Federal Regulations, 2012 CFR

...gé Program 519.7013 Obligation. (a) The mentor or protégé may terminate the Agreement in accordance with 519.7010. The mentor will notify the Mentor-Protégé Program Manager and the contracting officer, in writing, at least 30...

2012-10-01

172

Ethical obligations of computing center personnel  

Microsoft Academic Search

Ethical issues often arise between computing center personnel and other university members concerning the appropriate use of computer resources, the safeguarding of information, the ownership of software, the giving of credit for computer-related work, and many other areas. These issues take the form of ethical obligations, which are the just and fair dealings that people have with other people, dealings

Gary Abshire

1981-01-01

173

40 CFR 1043.30 - General obligations.  

Code of Federal Regulations, 2013 CFR

...EMISSIONS FROM MARINE ENGINES AND VESSELS SUBJECT TO THE MARPOL PROTOCOL § 1043.30 General obligations. (a) 33 U.S.C. 1907 prohibits any person from violating any provisions of the MARPOL Protocol, whether or not they are a manufacturer,...

2013-07-01

174

Communities, obligations and health-care  

Microsoft Academic Search

This paper examines the notion that, in the modern world, a just community will find it necessary to supply a decent minimum of health-care as well as a decent minimum of other basic needs to its members. The argument that health-care is an obligation of the just community is made by examining concepts of health, and the natural lottery as

Erich H. Loewy

1987-01-01

175

What makes pathogens pathogenic  

PubMed Central

Metazoans contain multiple complex microbial ecosystems in which the balance between host and microbe can be tipped from commensalism to pathogenicity. This transition is likely to depend both on the prevailing environmental conditions and on specific gene-gene interactions placed within the context of the entire ecosystem.

Ehrlich, Garth D; Hiller, N Luisa; Hu, Fen Ze

2008-01-01

176

Fluorescence labeling of bacteria for studies of intracellular pathogenesis  

Microsoft Academic Search

Interactions between intracellular bacterial pathogens and their eukaryotic cellular hosts or targets are often studied with fluorescence-based techniques such as fluorescence microscopy and flow cytometry. We tested whether the intracellular bacterial pathogens L. monocytogenes, M. avium, M. tuberculosis, and S. typhimurium could be labeled by growth in broth containing the fluorochromes carboxy-X-rhodamine (CR), a hydrazine derivative of fluorescein (FH), and

Douglas A Drevets; Alison M Elliott

1995-01-01

177

18 CFR 367.22 - Accounting for asset retirement obligations.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Accounting for asset retirement obligations...General Instructions § 367.22 Accounting for asset retirement obligations...retirement cost must be stated at the fair value of the asset retirement...

2013-04-01

178

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

179

13 CFR 400.213 - Termination of obligations.  

Code of Federal Regulations, 2013 CFR

...obligations. 400.213 Section 400.213 Business Credit and Assistance EMERGENCY STEEL GUARANTEE LOAN BOARD EMERGENCY STEEL GUARANTEE LOAN PROGRAM Steel Guarantee Loans § 400.213 Termination of obligations. The Board shall...

2013-01-01

180

13 CFR 400.213 - Termination of obligations.  

Code of Federal Regulations, 2012 CFR

...obligations. 400.213 Section 400.213 Business Credit and Assistance EMERGENCY STEEL GUARANTEE LOAN BOARD EMERGENCY STEEL GUARANTEE LOAN PROGRAM Steel Guarantee Loans § 400.213 Termination of obligations. The Board shall...

2012-01-01

181

22 CFR 62.9 - General obligations of sponsors.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false General obligations of sponsors. 62.9 Section 62.9 Foreign... § 62.9 General obligations of sponsors. (a) Adherence to Department of State regulations. Sponsors are required to adhere to all...

2013-04-01

182

29 CFR 102.164 - Review of the obligation.  

Code of Federal Regulations, 2013 CFR

... false Review of the obligation. 102...Relating to Labor NATIONAL LABOR RELATIONS BOARD...REGULATIONS, SERIES 8 Debt-Collection Procedures...164 Review of the obligation. (a...existence or amount of the debt as set forth in...

2013-07-01

183

29 CFR 102.175 - Agency review of the obligation.  

Code of Federal Regulations, 2013 CFR

... Agency review of the obligation. 102...Relating to Labor NATIONAL LABOR RELATIONS BOARD...REGULATIONS, SERIES 8 Debt Collection Procedures... Agency review of the obligation. (a...for collection of the debt will consider...

2013-07-01

184

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

185

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

186

Obligate vertebrate scavengers must be large soaring fliers  

Microsoft Academic Search

Among extant vertebrates, only the 23 species of vulture are obligate scavengers. We use an energetic modelling approach to explore the constraints imposed by an obligate scavenging lifestyle, and to ask whether obligate scavengers must always be avian and generally large-bodied users of soaring flight. Our model found that aerial scavengers always out-competed postulated terrestrial ones, mainly because flight allows

Graeme D. Ruxton; David C. Houston

2004-01-01

187

Informed consent: Enforcing pharmaceutical companies' obligations abroad.  

PubMed

The past several years have seen an evolution in the obligations of pharmaceutical companies conducting clinical trials abroad. Key players, such as international human rights organizations, multinational pharmaceutical companies, the United States government and courts, and the media, have played a significant role in defining these obligations. This article examines how such obligations have developed through the lens of past, present, and future recommendations for informed consent protections. In doing so, this article suggests that, no matter how robust obligations appear, they will continue to fall short of providing meaningful protection until they are accompanied by a substantive enforcement mechanism that holds multinational pharmaceutical companies accountable for their conduct. Issues of national sovereignty, particularly in the United States, will continue to prevent meaningful enforcement by an international tribunal or through one universally adopted code of ethics. This article argues that, rather than continuing to pursue an untenable international approach, the Alien Torts Statute (ATS) offers a viable enforcement mechanism, at least for US-based pharmaceutical companies. Recent federal appellate court precedent interpreting the ATS provides the mechanism for granting victims redress and enforcing accountability of sponsors (usually pharmaceutical companies and research and academic institutions) for informed consent misconduct. Substantive human rights protections are vital in order to ensure that every person can realize the "right to health." This article concludes that by building on the federal appellate court's ATS analysis, which grants foreign trial participants the right to pursue claims of human rights violations in US courts, a mechanism can be created for enforcing not only substantive informed consent, but also human rights protections. PMID:20930251

Lee, Stacey B

2010-06-15

188

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

189

Acquisition of polyamines by the obligate intracytoplasmic bacterium Rickettsia prowazekii.  

PubMed Central

Both the polyamine content and the route of acquisition of polyamines by Rickettsia prowazekii, an obligate intracellular parasitic bacterium, were determined. The rickettsiae grew normally in an ornithine decarboxylase mutant of the Chinese hamster ovary (C55.7) cell line whether or not putrescine, which this host cell required in order to grow, was present. The rickettsiae contained approximately 6 mM putrescine, 5 mM spermidine, and 3 mM spermine when cultured in the presence or absence of putrescine. Neither the transport of putrescine and spermidine by the rickettsiae nor a measurable rickettsial ornithine decarboxylase activity could be demonstrated. However, we demonstrated the de novo synthesis of polyamines from arginine by the rickettsiae. Arginine decarboxylase activity (29 pmol of 14CO2 released per h per 10(8) rickettsiae) was measured in the rickettsiae growing within their host cell. A markedly lower level of this enzymatic activity was observed in cell extracts of R. prowazekii and could be completely inhibited with 1 mM difluoromethylarginine, an irreversible inhibitor of the enzyme. R. prowazekii failed to grow in C55.7 cells that had been cultured in the presence of 1 mM difluoromethylarginine. After rickettsiae were grown in C55.7 in the presence of labeled arginine, the specific activities of arginine in the host cell cytoplasm and polyamines in the rickettsiae were measured; these measurements indicated that 100% of the total polyamine content of R. prowazekii was derived from arginine.

Speed, R R; Winkler, H H

1990-01-01

190

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

191

Host metabolism regulates intracellular growth of Trypanosoma cruzi.  

PubMed

Metabolic coupling of intracellular pathogens with host cells is essential for successful colonization of the host. Establishment of intracellular infection by the protozoan Trypanosoma cruzi leads to the development of human Chagas' disease, yet the functional contributions of the host cell toward the infection process remain poorly characterized. Here, a genome-scale functional screen identified interconnected metabolic networks centered around host energy production, nucleotide metabolism, pteridine biosynthesis, and fatty acid oxidation as key processes that fuel intracellular T. cruzi growth. Additionally, the host kinase Akt, which plays essential roles in various cellular processes, was critical for parasite replication. Targeted perturbations in these host metabolic pathways or Akt-dependent signaling pathways modulated the parasite's replicative capacity, highlighting the adaptability of this intracellular pathogen to changing conditions in the host. These findings identify key cellular process regulating intracellular T. cruzi growth and illuminate the potential to leverage host pathways to limit T. cruzi infection. PMID:23332160

Caradonna, Kacey L; Engel, Juan C; Jacobi, David; Lee, Chih-Hao; Burleigh, Barbara A

2013-01-16

192

Pathogenic trickery: deception of host cell processes  

Microsoft Academic Search

Microbial pathogens cause a spectrum of diseases in humans. Although the disease mechanisms vary considerably, most pathogens have developed virulence factors that interact with host molecules, often usurping normal cellular processes, including cytoskeletal dynamics and vesicle targeting. These virulence factors often mimic host molecules, and mediate events as diverse as bacterial invasion, antiphagocytosis, and intracellular parastism.

Leigh A. Knodler; Jean Celli; B. Brett Finlay

2001-01-01

193

Intracellular infections in Drosophila melanogaster: Host defense and mechanisms of pathogenesis.  

PubMed

The fruit-fly Drosophila melanogaster has emerged as a powerful model to study innate immunity against intracellular pathogens. To combat infection, the fly relies on multiple lines of defense, many of which are shared with mammals and arthropod vectors of human diseases. In addition to conserved immune pathways, the ease of performing sophisticated genetic screens has allowed the identification of novel host immune factors and novel pathogen virulence factors. Recently, some groups have exploited this to simultaneously analyze the host and pathogen genetics of intracellular infection. This review aims to unravel the Drosophila immune response against intracellular pathogens, highlighting recent discoveries. PMID:23648644

Péan, Claire B; Dionne, Marc S

2013-05-03

194

Apoptotic mimicry by an obligate intracellular parasite downregulates macrophage microbicidal activity  

Microsoft Academic Search

Programmed cell death by apoptosis of unnecessary or potentially harmful cells is clearly beneficial to multicellular organisms [1]. Proper functioning of such a program demands that the removal of dying cells proceed without an inflammatory reaction [2]. Phosphatidylserine (PS) is one of the ligands displayed by apoptotic cells that participates in their noninflammatory removal when recognized by neighboring phagocytes [3].

José Mario de Freitas Balanco; Maria Elisabete Costa Moreira; Adriana Bonomo; Patricia Torres Bozza; Gustavo Amarante-Mendes; Claude Pirmez; Marcello André Barcinski

2001-01-01

195

"Obligated aliens": recognizing sperm donors' ethical obligation to disclose genetic information.  

PubMed

Sperm donors' obligations are typically constrained to the immediate circumstances surrounding the donation and to its time frame. This paper makes the case for recognizing an ongoing ethical obligation that binds sperm donors to disclose, in a timely manner, meaningful genetic information to recipients and donor-conceived children. The paper delineates and conceptualizes the suggested (potentially reciprocal) duty and argues that it is not the genetic link between the donor and the donor-conceived child that binds donors by said duty, but rather social responsibility. Accordingly, an original perception of the donor as an obligated alien is suggested and developed. The main thesis of the paper is supported inter alia by a comparison between transmitting infectious diseases and passing faulty genes on to donor-conceived children. The paper also provides an in-depth analysis of the conflicting interests of the parties generated by such an obligation and proposes a model for embedding this ethical duty in a (legal) contractual framework. PMID:23678628

Tamir, Sivan

2013-03-01

196

Verifying nonproliferation treaties: Obligation, process, and sovereignty  

SciTech Connect

The foregoing chapters examine what verification is and why states would bother with so difficult and politically sensitive an issue when negotiating agreements on arms control and disarmament issues. Now it is necessary to confront the question of whether there are any meaningful conclusions to be drawn from this exercise. Are the patterns discerned in the history of these treaties meaningful for understanding how other treaties have evolved or will evolve. Are there lessons here which might benefit future negotiators. This final chapter seeks to provide some answers, albeit partial ones, to these questions. There are in fact several interesting and potentially important conclusions to be drawn. Verification of multilateral treaty obligations contains its own intrinsic structure and logic, independent of the obligations undertaken by the parties and the political context in which those undertakings are negotiated and made. The many significant similarities in the verification processes for the CFE Treaty, the NPT, and the CWC demonstrate the degree to which there is such an underlying structure regardless of whether the behavior or activity is strictly military or has essentially civilian dimensions, whether all relevant states participate or only some of the most important states agree from the beginning to participate, and whether the agreement is global or regional in scope.

Kessler, J.C.

1995-10-01

197

Axenic culture of fastidious and intracellular bacteria.  

PubMed

The culture of microorganisms has been the basis of microbiology. However, revolutionary tools such as metagenomics have made it possible to describe uncultivated bacteria, but several breakthroughs have occurred in culture leading to a revival of these techniques. In this review we focus on new applications that have successfully cultivated previously uncultivated bacteria. We also review the axenic cultivation of intracellular bacteria such as Tropheryma whipplei and Coxiella burnetii. These successes provide new tools for the design of axenic media for intracellular bacteria, such as Rickettsiae and Chlamydiae, or historically uncultivable pathogens, such as Mycobacterium leprae and Treponema pallidum. The future axenic culture of these microorganisms will facilitate antibiotic susceptibility testing and will provide insight into their microbial ecology and pathogenicity. PMID:23182864

Singh, Sudhir; Eldin, Carole; Kowalczewska, Malgorzata; Raoult, Didier

2012-11-23

198

The Obligation to Participate in Biomedical Research  

PubMed Central

The prevailing view is that participation in biomedical research is above and beyond the call of duty. While some commentators have offered reasons against this, we propose a novel public goods argument for an obligation to participate in biomedical research. Biomedical knowledge is a public good, available to any individual even if that individual does not contribute to it. Participation in research is a critical way to support that important public good. Consequently, we all have a duty to participate. The current social norm is that people participate only if they have a good reason to do so. The public goods argument implies that people should participate unless they have a good reason not to. Such a shift would be of great aid to the progress of biomedical research, eventually making our society significantly healthier and longer-lived.

Schaefer, G. Owen; Emanuel, Ezekiel J.; Wertheimer, Alan

2009-01-01

199

Intracellular aquaporins: clues for intracellular water transport?  

Microsoft Academic Search

Aquaporins (AQPs) are usually present at the plasma membrane to regulate influx and outflow of water and small molecules.\\u000a They are important for the regulation of water homeostasis for the cells and organisms. AQPs are also present inside the cell,\\u000a at the membranes of intracellular organelles. The roles of such AQPs have not yet been established. They will be clues

Kenma Nozaki; Daishi Ishii; Kenichi Ishibashi

2008-01-01

200

Obligate biotrophy features unraveled by the genomic analysis of the rust fungi, Melampsora larici-populina and Puccinia graminis f. sp. tritici  

Technology Transfer Automated Retrieval System (TEKTRAN)

Rust fungi are some of the most devastating pathogens of crop plants. They are obligate biotrophs, which extract nutrients only from living plant tissues and cannot grow apart from their hosts. Their lifestyle has slowed the dissection of molecular mechanisms underlying host invasion and avoidance...

201

Obligate Biotrophy Features Unraveled by the Genomic Analysis of the Rust Fungi, Melampsora larici-populina and Puccinia graminis f. sp. tritici  

Microsoft Academic Search

Rust fungi are some of the most devastating pathogens of crop plants. They are obligate biotrophs, which extract nutrients only from living plant tissues and cannot grow apart from their hosts. Their lifestyle has slowed the dissection of molecular mechanisms underlying host invasion and avoidance or suppression of plant innate immunity. We sequenced the 101 mega base pair genome of

Sebastien Duplessis; Christina A. Cuomo; Yao-Cheng Lin; Andrea Aerts; Emilie Tisserant; Claire Veneault-Fourrey; David L. Joly; Stephane Hacquard; Joelle Amselem; Brandi Cantarel; Readman Chiu; Pedro Couthinho; Nicolas Feau; Matthew Field; Pascal Frey; Eric Gelhaye; Jonathan Goldberg; Manfred Grabherr; Chinnappa Kodira; Annegret Kohler; Ursula Kues; Erika Lindquist; Susan Lucas; Rohit Mago; Evan Mauceli; Emmanuelle Morin; Claude Murat; Jasmyn L. Pangilinan; Robert Park; Matthew Pearson; Hadi Quesneville; Nicolas Rouhier; Sharadha Sakthikumar; Asaf A. Salamov; Jeremy Schmutz; Benjamin Selles; Harris Shapiro; Philippe Tangay; Gerald A. Tuskan; Yves Van de Peer; Bernard Henrissat; Pierre Rouze; Jeffrey G. Ellis; Peter N. Dodds; Jacqueline E. Schein; Shaobin Zhong; Richard C. Hamelin; Igor V. Grigoriev; Les J. Szabo

2011-01-01

202

CD11c Expression Identifies a Population of Extrafollicular Antigen-Specific Splenic Plasmablasts Responsible for CD4 T-Independent Antibody Responses during Intracellular Bacterial Infection1  

PubMed Central

Although T-independent immunity is known to be generated against bacterial capsular and cell wall polysaccharides expressed by a number of bacterial pathogens, it has not been studied in depth during intracellular bacterial infections. Our previous study demonstrated that Ehrlichia muris, an obligate intracellular tick-borne pathogen, generates protective classical TI responses in CD4 T cell-deficient C57BL/6 mice. We found that E. muris T-independent immunity is accompanied by the expansion of a very large extrafollicular spleen population of CD11clow-expressing plasmablasts that exhibit characteristics of both B-1 and marginal zone B cells. The plasmablasts comprised up to 15% of the total spleen lymphocytes and ?70% of total spleen IgMhighIgDlow cells during peak infection in both wild-type and MHC class II-deficient mice. The CD11clow cells exhibited low surface expression of B220, CD19, and CD1d, high expression of CD11b, CD43, but did not express CD5. Approximately 50% of the CD11clow cells also expressed CD138. In addition to CD11b and CD11c, the plasmablasts expressed the ?1 (CD29) and ?4 (CD49d) integrins, as well as the chemokine receptor CXCR4, molecules which may play roles in localizing the B cells extrafollicular region of the spleen. During peak infection, the CD11clow cells accounted for the majority of the IgM-producing splenic B cells and nearly all of the E. muris outer membrane protein-specific IgM-secreting cells. Thus, during this intracellular bacterial infection, CD11c expression identifies a population of Ag-specific spleen plasmablasts responsible for T-independent Ab production.

Racine, Rachael; Chatterjee, Madhumouli; Winslow, Gary M.

2008-01-01

203

The Chlamydia protease CPAF regulates host and bacterial proteins to maintain pathogen vacuole integrity and promote virulence  

PubMed Central

SUMMARY The obligate intracellular bacterial pathogen Chlamydia trachomatis injects numerous effector proteins into the epithelial cell cytoplasm to manipulate host functions important for bacterial survival. In addition, the bacterium secretes a serine protease, chlamydial protease-like activity factor (CPAF). Although several CPAF targets are reported, the significance of CPAF-mediated proteolysis is unclear due to the lack of specific CPAF inhibitors and the diversity of host targets. We report that CPAF also targets chlamydial effectors secreted early during the establishment of the pathogen-containing vacuole (“inclusion”). We designed a cell-permeable CPAF-specific inhibitory peptide and used it to determine that CPAF prevents superinfection by degrading early Chlamydia effectors translocated during entry into a pre-infected cell. Prolonged CPAF inhibition leads to loss of inclusion integrity and caspase-1-dependent death of infected epithelial cells. Thus, CPAF functions in niche protection, inclusion integrity and pathogen survival, making the development of CPAF-specific protease inhibitors an attractive anti-chlamydial therapeutic strategy.

Jorgensen, Ine; Bednar, Maria; Amin, Vishar; Davies, Beckley K.; Ting, Jenny P.Y.; McCafferty, Dewey; Valdivia, Raphael H.

2011-01-01

204

Deconfounding Distance Effects in Judgments of Moral Obligation  

ERIC Educational Resources Information Center

A heavily disputed question of moral philosophy is whether spatial distance between agent and victim is normatively relevant for the degree of obligation to help strangers in need. In this research, we focus on the associated descriptive question whether increased distance does in fact reduce individuals' sense of helping obligation. One problem…

Nagel, Jonas; Waldmann, Michael R.

2013-01-01

205

18 CFR 37.8 - Obligations of OASIS users.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Obligations of OASIS users. 37.8 Section 37.8 Conservation...SAME-TIME INFORMATION SYSTEMS § 37.8 Obligations of OASIS users. Each OASIS user must notify the Responsible Party one...

2009-04-01

206

18 CFR 37.8 - Obligations of OASIS users.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Obligations of OASIS users. 37.8 Section 37.8 Conservation...SAME-TIME INFORMATION SYSTEMS § 37.8 Obligations of OASIS users. Each OASIS user must notify the Responsible Party one...

2010-04-01

207

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

208

High Noon and the Problems of American Political Obligation  

Microsoft Academic Search

The Western drama High Noon introduces political considerations deeper than the maelstrom of American anticommunism of the 1950s against which it is most often viewed. It presents the central problems of modern political obligation as arising out of an encounter between Aristotelian and Lockean ideas about marriage, friendship, consent and coercion, and religious obligation. The marshal Kane, representing the altered

J. Jeffrey Tillman

2007-01-01

209

Intracellular functions of galectins  

Microsoft Academic Search

Many galectin family members are detected primarily intracellularly in most of the systems studied, although certain members can be found both inside and outside of cells. Specific functions that are consistent with their intracellular localization have now been documented for some of the galectins. Galectin-1 and -3 have been identified as redundant pre-mRNA splicing factors. Galectin-3, -7, and -12 have

Fu-Tong Liu; Ronald J Patterson; John L Wang

2002-01-01

210

Rickettsia as obligate and mycetomic bacteria  

Microsoft Academic Search

Rickettsiae are well known as intracellu- lar pathogens of animals, humans, and plants and facultative and unorganized symbionts of invertebrates. No close relative of mitochondria has yet been associ- ated with nutritional or developmental dependency of its host cell or organism. We have found a mycetomic Rickettsia that is a strict obligatory symbiont of the parthenogenetic booklouse Liposcelis bostrychophila (Psocoptera).

M. Alejandra Perotti; Heather K. Clarke; Bryan D. Turner; Henk R. Braig

2006-01-01

211

Intracellular cryptococci suppress Fc-mediated cyclin D1 elevation  

PubMed Central

Cryptococcus neoformans (Cn) is the only encapsulated fungal pathogen pathogenic to humans and macrophages play a vital role in the Cn infection pathway. Previously we documented that phagocytosis or crosslinking of Fc?R on macrophage cell surface promoted macrophage cell cycle progression via the activation of MAPK pathway. However, we seldom observed sustained macrophage growth after they phagocytosed live Cn. In fact, many macrophages were finally observed to undergo apoptotic changes after phagocytosis of live Cn. Here we report that cyclin D1 elevation in macrophages promoted by phagocytosis was suppressed by intracellular Cn cells. This suggests a novel cytotoxic mechanism for host cells of intracellular cryptococci.

Luo, Yong

2010-01-01

212

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

213

Obligate oil-degrading marine bacteria.  

PubMed

Over the past few years, a new and ecophysiologically unusual group of marine hydrocarbon-degrading bacteria - the obligate hydrocarbonoclastic bacteria (OHCB) - has been recognized and shown to play a significant role in the biological removal of petroleum hydrocarbons from polluted marine waters. The introduction of oil or oil constituents into seawater leads to successive blooms of a relatively limited number of indigenous marine bacterial genera--Alcanivorax, Marinobacter, Thallassolituus, Cycloclasticus, Oleispira and a few others (the OHCB)--which are present at low or undetectable levels before the polluting event. The types of OHCB that bloom depend on the latitude/temperature, salinity, redox and other prevailing physical-chemical factors. These blooms result in the rapid degradation of many oil constituents, a process that can be accelerated further by supplementation with limiting nutrients. Genome sequencing and functional genomic analysis of Alcanivorax borkumensis, the paradigm of OHCB, has provided significant insights into the genomic basis of the efficiency and versatility of its hydrocarbon utilization, the metabolic routes underlying its special hydrocarbon diet, and its ecological success. These and other studies have revealed the potential of OHCB for multiple biotechnological applications that include not only oil pollution mitigation, but also biopolymer production and biocatalysis. PMID:17493798

Yakimov, Michail M; Timmis, Kenneth N; Golyshin, Peter N

2007-05-09

214

Neurofilaments are obligate heteropolymers in vivo  

PubMed Central

Neurofilaments (NFs), composed of three distinct subunits NF-L, NF-M, and NF-H, are neuron-specific intermediate filaments present in most mature neurons. Using DNA transfection and mice expressing NF transgenes, we find that despite the ability of NF-L alone to assemble into short filaments in vitro NF-L cannot form filament arrays in vivo after expression either in cultured cells or in transgenic oligodendrocytes that otherwise do not contain a cytoplasmic intermediate filament (IF) array. Instead, NF-L aggregates into punctate or sheet like structures. Similar nonfilamentous structures are also formed when NF-M or NF-H is expressed alone. The competence of NF-L to assemble into filaments is fully restored by coexpression of NF- M or NF-H to a level approximately 10% of that of NF-L. Deletion of the head or tail domain of NF-M or substitution of the NF-H tail onto an NF- L subunit reveals that restoration of in vivo NF-L assembly competence requires an interaction provided by the NF-M or NF-H head domains. We conclude that, contrary to the expectation drawn from earlier in vitro assembly studies, NF-L is not sufficient to assemble an extended filament network in an in vivo context and that neurofilaments are obligate heteropolymers requiring NF-L and NF-M or NF-H.

1993-01-01

215

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

Code of Federal Regulations, 2011 CFR

...period for obligation and expenditure of grant funds. 96.14 Section 96.14 Public...SERVICES GENERAL ADMINISTRATION BLOCK GRANTS General Procedures § 96.14 Time period for obligation and expenditure of grant funds. (a) Obligations....

2011-10-01

216

31 CFR 225.9 - Return of Government obligations to obligor.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Return of Government obligations to obligor. 225... ACCEPTANCE OF BONDS SECURED BY GOVERNMENT OBLIGATIONS IN LIEU OF BONDS WITH SURETIES § 225.9 Return of Government obligations to obligor....

2013-07-01

217

69 FR 20845 - Rules and Regulations Implementing Minimum Customer Account Record Exchange Obligations on All...  

Federal Register 2010, 2011, 2012, 2013

...Customer Account Record Exchange Obligations on All Local and Interexchange Carriers AGENCY...Record Exchange (CARE) obligations on all local and interexchange carriers and, in...Customer Account Record Exchange Obligations on All Local and Interexchange Carriers, CG...

2004-04-19

218

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

219

COMPARATIVE ANALYSIS OF EXPRESSED SEQUENCES IN THE SOYBEAN RUST PATHOGEN PHAKOPSORA PACHYRHIZI  

Technology Transfer Automated Retrieval System (TEKTRAN)

Phakopsora pachyrhizi Sydow is an obligate fungal pathogen that causes the soybean rust disease. Unidirectional cDNA libraries were constructed in the plasmid pSPORT1, using mRNA isolated from three different stages of the life cycle of the pathogen. mRNA was isolated from P. pachyrhizi urediniospor...

220

29 CFR 500.60 - Farm labor contractors' recruitment, contractual and general obligations.  

Code of Federal Regulations, 2013 CFR

...false Farm labor contractors' recruitment, contractual and general obligations...60 Farm labor contractors' recruitment, contractual and general obligations...Act imposes certain specific recruitment, contractual and...

2013-07-01

221

7 CFR 1942.316 - Grant approval, fund obligation and third party financial assistance.  

Code of Federal Regulations, 2013 CFR

...Grant approval, fund obligation and third party financial assistance. 1942...approval, fund obligation and third party financial assistance. (a...1942 of this chapter. (c) Third party financial assistance....

2013-01-01

222

7 CFR 1942.316 - Grant approval, fund obligation and third party financial assistance.  

Code of Federal Regulations, 2012 CFR

...Grant approval, fund obligation and third party financial assistance. 1942...approval, fund obligation and third party financial assistance. (a...1942 of this chapter. (c) Third party financial assistance....

2012-01-01

223

34 CFR 686.40 - Documenting the service obligation.  

Code of Federal Regulations, 2010 CFR

...Department of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION TEACHER EDUCATION ASSISTANCE FOR COLLEGE AND HIGHER EDUCATION (TEACH) GRANT PROGRAM Service and Repayment Obligations § 686.40...

2009-07-01

224

48 CFR 2933.213 - Obligation to continue performance.  

Code of Federal Regulations, 2011 CFR

...Appeals 2933.213 Obligation to continue performance. The contracting officer must include the clause at FAR 52.233-1, Disputes (Alternate I), in contracts where continued performance is necessary pending resolution of any claim...

2011-10-01

225

48 CFR 333.213 - Obligation to continue performance.  

Code of Federal Regulations, 2012 CFR

...213 Obligation to continue performance. (a) The Contracting Officer shall use the Disputes clause at FAR 52.233-1 without the use of Alternate I. However, if the Contracting Officer determines that the Government's interest...

2012-10-01

226

48 CFR 2933.213 - Obligation to continue performance.  

Code of Federal Regulations, 2012 CFR

...Appeals 2933.213 Obligation to continue performance. The contracting officer must include the clause at FAR 52.233-1, Disputes (Alternate I), in contracts where continued performance is necessary pending resolution of any claim...

2012-10-01

227

48 CFR 333.213 - Obligation to continue performance.  

Code of Federal Regulations, 2011 CFR

...213 Obligation to continue performance. (a) The Contracting Officer shall use the Disputes clause at FAR 52.233-1 without the use of Alternate I. However, if the Contracting Officer determines that the Government's interest...

2011-10-01

228

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

229

29 CFR 1986.102 - Obligations and prohibited acts.  

Code of Federal Regulations, 2013 CFR

...PROCEDURES FOR THE HANDLING OF RETALIATION COMPLAINTS UNDER THE EMPLOYEE PROTECTION PROVISION OF THE SEAMAN'S PROTECTION ACT (SPA), AS AMENDED Complaints, Investigations, Findings, and Preliminary Orders § 1986.102 Obligations and...

2013-07-01

230

7 CFR 760.507 - Obligations of a participant.  

Code of Federal Regulations, 2013 CFR

...PROGRAMS INDEMNITY PAYMENT PROGRAMS Tree Assistance Program § 760.507 Obligations... (a) Eligible orchardists and nursery tree growers must execute all required documents... (b) Eligible orchardist or nursery tree growers must allow representatives...

2013-01-01

231

7 CFR 1450.105 - Obligations of participant.  

Code of Federal Regulations, 2013 CFR

...Agriculture (Continued) COMMODITY CREDIT CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS BIOMASS CROP ASSISTANCE PROGRAM (BCAP) Matching Payments § 1450.105 Obligations of participant. (a) All...

2013-01-01

232

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

233

34 CFR 686.43 - Obligation to repay the grant.  

Code of Federal Regulations, 2013 CFR

...of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION (CONTINUED) TEACHER EDUCATION ASSISTANCE FOR COLLEGE AND HIGHER EDUCATION (TEACH) GRANT PROGRAM Service and Repayment Obligations § 686.43...

2013-07-01

234

28 CFR 0.147 - Certification of obligations.  

Code of Federal Regulations, 2013 CFR

...147 Certification of obligations. The...200(c): For the Federal Bureau of Investigation, the Assistant Director...Services Division; for the Bureau of Prisons, the Assistant...and Development; for Federal Prison...

2013-07-01

235

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

236

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

237

15 CFR 711.4 - Assistance in determining your obligations.  

Code of Federal Regulations, 2013 CFR

...SECURITY, DEPARTMENT OF COMMERCE CHEMICAL WEAPONS CONVENTION REGULATIONS GENERAL...obligations. (a) Determining if your chemical is subject to declaration, reporting...assistance in determining if your chemical is classified as a Schedule...

2013-01-01

238

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

239

25 CFR 226.9 - Rental and drilling obligations.  

Code of Federal Regulations, 2011 CFR

...MINERALS LEASING OF OSAGE RESERVATION LANDS FOR OIL AND GAS MINING Leasing Procedure, Rental and Royalty...Rental and drilling obligations. (a) Oil leases, gas leases, and combination oil and gas leases. Unless Lessee shall complete...

2011-04-01

240

13 CFR 500.213 - Termination of obligations.  

Code of Federal Regulations, 2012 CFR

... 500.213 Section 500.213 Business Credit and Assistance EMERGENCY OIL AND GAS GUARANTEED LOAN BOARD EMERGENCY OIL AND GAS GUARANTEED LOAN PROGRAM Oil and Gas Guaranteed Loans § 500.213 Termination of obligations....

2012-01-01

241

47 CFR 64.3001 - Obligation to transmit 911 calls.  

Code of Federal Regulations, 2011 CFR

...CONTINUED) COMMON CARRIER SERVICES (CONTINUED) MISCELLANEOUS RULES RELATING TO COMMON CARRIERS Universal Emergency Telephone Number § 64.3001 Obligation to transmit 911 calls. All telecommunications carriers shall transmit all 911 calls...

2011-10-01

242

Mechanisms of Francisella tularensis intracellular pathogenesis.  

PubMed

Francisella tularensis is a zoonotic intracellular pathogen and the causative agent of the debilitating febrile illness tularemia. Although natural infections by F. tularensis are sporadic and generally localized, the low infectious dose, with the ability to be transmitted to humans via multiple routes and the potential to cause life-threatening infections, has led to concerns that this bacterium could be used as an agent of bioterror and released intentionally into the environment. Recent studies of F. tularensis and other closely related Francisella species have greatly increased our understanding of mechanisms used by this organism to infect and cause disease within the host. Here, we review the intracellular life cycle of Francisella and highlight key genetic determinants and/or pathways that contribute to the survival and proliferation of this bacterium within host cells. PMID:23545572

Celli, Jean; Zahrt, Thomas C

2013-04-01

243

A Logical Analysis of the Relationship between Commitment and Obligation  

Microsoft Academic Search

In this paper, we analyze the relationship between commitment and obligation from a logical viewpoint. The principle of commitment\\u000a implying obligation is proven in a specific logic of action preference which is a generalization of Meyer's dynamic deontic\\u000a logic. In the proposed formalism, an agent's commitment to goals is considered as a special kind of action which can change\\u000a one's

Churn-Jung Liau

2001-01-01

244

The evolution of genomic instability in the obligate endosymbionts of whiteflies.  

PubMed

Many insects depend on ancient associations with intracellular bacteria to perform essential metabolic functions. These endosymbionts exhibit striking examples of convergence in genome architecture, including a high degree of structural stability that is not typical of their free-living counterparts. However, the recently sequenced genome of the obligate whitefly endosymbiont Portiera revealed features that distinguish it from other ancient insect associates, such as a low gene density and the presence of perfectly duplicated sequences. Here, we report the comparative analysis of Portiera genome sequences both within and between host species. In one whitefly lineage (Bemisia tabaci), we identify large-scale structural polymorphisms in the Portiera genome that exist even within individual insects. This variation is likely mediated by recombination across identical repeats that are maintained by gene conversion. The complete Portiera genome sequence from a distantly related whitefly host (Trialeurodes vaporarium) confirms a history of extensive genome rearrangement in this ancient endosymbiont. Using gene-order-based phylogenetic analysis, we show that the majority of rearrangements have occurred in the B. tabaci lineage, coinciding with an increase in the rate of nucleotide substitutions, a proliferation of short tandem repeats (microsatellites) in intergenic regions, and the loss of many widely conserved genes involved in DNA replication, recombination, and repair. These results indicate that the loss of recombinational machinery is unlikely to be the cause of the extreme structural conservation that is generally observed in obligate endosymbiont genomes and that large, repetitive intergenic regions are an important substrate for genomic rearrangements. PMID:23542079

Sloan, Daniel B; Moran, Nancy A

2013-01-01

245

The Evolution of Genomic Instability in the Obligate Endosymbionts of Whiteflies  

PubMed Central

Many insects depend on ancient associations with intracellular bacteria to perform essential metabolic functions. These endosymbionts exhibit striking examples of convergence in genome architecture, including a high degree of structural stability that is not typical of their free-living counterparts. However, the recently sequenced genome of the obligate whitefly endosymbiont Portiera revealed features that distinguish it from other ancient insect associates, such as a low gene density and the presence of perfectly duplicated sequences. Here, we report the comparative analysis of Portiera genome sequences both within and between host species. In one whitefly lineage (Bemisia tabaci), we identify large-scale structural polymorphisms in the Portiera genome that exist even within individual insects. This variation is likely mediated by recombination across identical repeats that are maintained by gene conversion. The complete Portiera genome sequence from a distantly related whitefly host (Trialeurodes vaporarium) confirms a history of extensive genome rearrangement in this ancient endosymbiont. Using gene-order-based phylogenetic analysis, we show that the majority of rearrangements have occurred in the B. tabaci lineage, coinciding with an increase in the rate of nucleotide substitutions, a proliferation of short tandem repeats (microsatellites) in intergenic regions, and the loss of many widely conserved genes involved in DNA replication, recombination, and repair. These results indicate that the loss of recombinational machinery is unlikely to be the cause of the extreme structural conservation that is generally observed in obligate endosymbiont genomes and that large, repetitive intergenic regions are an important substrate for genomic rearrangements.

Sloan, Daniel B.; Moran, Nancy A.

2013-01-01

246

Intracellular biology and virulence determinants of Francisella tularensis revealed by transcriptional profiling inside macrophages  

PubMed Central

Summary The highly infectious bacterium Francisella tularensis is a facultative intracellular pathogen, whose virulence requires proliferation inside host cells, including macrophages. Here we have performed a global transcriptional profiling of the highly virulent F. tularensis subsp. tularensis Schu S4 strain during its intracellular cycle within primary murine macrophages, to characterize its intracellular biology and identify pathogenic determinants based on their intracellular expression profiles. Phagocytosed bacteria rapidly responded to their intracellular environment and subsequently altered their transcriptional profile. Differential gene expression profiles were revealed that correlated with specific intracellular locale of the bacteria. Upregulation of general and oxidative stress response genes was a hallmark of the early phagosomal and late endosomal stages, while induction of transport and metabolic genes characterized the cytosolic replication stage. Expression of the Francisella Pathogenicity Island (FPI) genes, which are required for intracellular proliferation, increased during the intracellular cycle. Similarly, 27 chromosomal loci encoding putative hypothetical, secreted, outer membrane proteins or transcriptional regulators were identified as upregulated. Among these, deletion of FTT0383, FTT0369c or FTT1676 abolished the ability of Schu S4 to survive or proliferate intracellularly and cause lethality in mice, therefore identifying novel determinants of Francisella virulence from their intracellular expression profile.

Wehrly, Tara D.; Chong, Audrey; Virtaneva, Kimmo; Sturdevant, Dan E.; Child, Robert; Edwards, Jessica A.; Brouwer, Dedeke; Nair, Vinod; Fischer, Elizabeth R.; Wicke, Luke; Curda, Alissa J.; Kupko, John J.; Martens, Craig; Crane, Deborah D.; Bosio, Catharine M.; Porcella, Stephen F.; Celli, Jean

2009-01-01

247

Proteomics of Plant Pathogenic Fungi  

PubMed Central

Plant pathogenic fungi cause important yield losses in crops. In order to develop efficient and environmental friendly crop protection strategies, molecular studies of the fungal biological cycle, virulence factors, and interaction with its host are necessary. For that reason, several approaches have been performed using both classical genetic, cell biology, and biochemistry and the modern, holistic, and high-throughput, omic techniques. This work briefly overviews the tools available for studying Plant Pathogenic Fungi and is amply focused on MS-based Proteomics analysis, based on original papers published up to December 2009. At a methodological level, different steps in a proteomic workflow experiment are discussed. Separate sections are devoted to fungal descriptive (intracellular, subcellular, extracellular) and differential expression proteomics and interactomics. From the work published we can conclude that Proteomics, in combination with other techniques, constitutes a powerful tool for providing important information about pathogenicity and virulence factors, thus opening up new possibilities for crop disease diagnosis and crop protection.

Gonzalez-Fernandez, Raquel; Prats, Elena; Jorrin-Novo, Jesus V.

2010-01-01

248

Intracellular Symbiosis in Insects  

Microsoft Academic Search

Many eukaryotic cells constitute the sole habitat for a vast and varied array of prokaryotic lineages (xcBuchner, 1965). These\\u000a intracellular associations have evolved repeatedly and have had major consequences for the diversification of both bacteria\\u000a and host. The magnitude of these consequences is immediately evident if one considers the examples of mitochondria and chloroplasts,\\u000a now widely acknowledged to be descended

Hajime Ishikawa

249

Intracellular infection and the carrier state.  

PubMed

The evidence summarized in this article is sufficient to support conclusions as follows. 1) Antibiotics penetrate rapidly into mammalian cells and inhibit multiplication of susceptible microbes within the cell as promptly and effectively as they inhibit multiplication of such microbes outside the cell. This is consistent with clinical experience. 2) Death of individual organisms inside mammalian cells bathed in medium containing antibiotics continues over several weeks but may not proceed pari passu with time. This observation supports the as yet meager clinical data, which suggest that eradication of the typhoid carrier state may be accomplished through antibiotic therapy, provided (i) the proper antibiotic is selected; (ii) it is administered in amounts sufficient to obtain continuous suppression of growth of intracellular organisms; and (iii) the regimen is maintained for 2 or 3 weeks. 3) The actual cause of death and destruction of intracellular microbes in treated cells remains an enigma. To attribute this to inanition or senescence of the organisms, without describing mechanisms, is to avoid the issue. The hypotheses dealing with inactivation of intracellular microbes by intracellular antimicrobial substances and antibodies deserve to be explored. 4) Evidence from the ward and laboratory suggests that infected cells can clear themselves of invading pathogens and recover. Although antibiotics have played the major role in demonstrating this in the laboratory, it is possible that they do nothing more than hold the intruders in abeyance while natural defense mechanisms of the cell gain the upper hand. Certainly such cellular mechanisms must provide a potent force for survival; otherwise, why would 98 percent of typhoid patients fail to become chronic carriers? 5) The continued study of infections, including the carrier state, with a view to understanding the abnormalities created by the multiplying intracellular microbe and the means by which the cell corrects these and eliminates the intruder, should open new vistas in chemotherapy and immunology. PMID:13989296

SMADEL, J E

1963-04-12

250

Novel bioactive hydrophobic gentamicin carriers for the treatment of intracellular bacterial infections  

Microsoft Academic Search

Gentamicin (GEN) is an aminoglycoside antibiotic with a potent antibacterial activity against a wide variety of bacteria. However, its poor cellular penetration limits its use in the treatment of infections caused by intracellular pathogens. One potential strategy to overcome this problem is the use of particulate carriers that can target the intracellular sites of infection. In this study GEN was

Edurne Imbuluzqueta; Elisa Elizondo; Carlos Gamazo; Evelyn Moreno-Calvo; Jaume Veciana; Nora Ventosa; María J. Blanco-Prieto

2011-01-01

251

Unravelling the biology of macrophage infection by gene expression profiling of intracellular Salmonella enterica  

Microsoft Academic Search

Summary For intracellular pathogens such as Salmonellae , Mycobacteriae and Brucellae , infection requires adaptation to the intracellular environment of the phagocytic cell . The transition from extracellular to intravacuolar environment has been expected to involve a global modulation of bacterial gene expres- sion, but the precise events have been difficult to determine. We now report the complete transcrip- tional

Sofia Eriksson; Sacha Lucchini; Arthur Thompson; Mikael Rhen; Jay C. D. Hinton

2003-01-01

252

Chlamydia trachomatis co-opts GBF1 and CERT to acquire host sphingomyelin for distinct roles during intracellular development.  

PubMed

The obligate intracellular pathogen Chlamydia trachomatis replicates within a membrane-bound inclusion that acquires host sphingomyelin (SM), a process that is essential for replication as well as inclusion biogenesis. Previous studies demonstrate that SM is acquired by a Brefeldin A (BFA)-sensitive vesicular trafficking pathway, although paradoxically, this pathway is dispensable for bacterial replication. This finding suggests that other lipid transport mechanisms are involved in the acquisition of host SM. In this work, we interrogated the role of specific components of BFA-sensitive and BFA-insensitive lipid trafficking pathways to define their contribution in SM acquisition during infection. We found that C. trachomatis hijacks components of both vesicular and non-vesicular lipid trafficking pathways for SM acquisition but that the SM obtained from these separate pathways is being utilized by the pathogen in different ways. We show that C. trachomatis selectively co-opts only one of the three known BFA targets, GBF1, a regulator of Arf1-dependent vesicular trafficking within the early secretory pathway for vesicle-mediated SM acquisition. The Arf1/GBF1-dependent pathway of SM acquisition is essential for inclusion membrane growth and stability but is not required for bacterial replication. In contrast, we show that C. trachomatis co-opts CERT, a lipid transfer protein that is a key component in non-vesicular ER to trans-Golgi trafficking of ceramide (the precursor for SM), for C. trachomatis replication. We demonstrate that C. trachomatis recruits CERT, its ER binding partner, VAP-A, and SM synthases, SMS1 and SMS2, to the inclusion and propose that these proteins establish an on-site SM biosynthetic factory at or near the inclusion. We hypothesize that SM acquired by CERT-dependent transport of ceramide and subsequent conversion to SM is necessary for C. trachomatis replication whereas SM acquired by the GBF1-dependent pathway is essential for inclusion growth and stability. Our results reveal a novel mechanism by which an intracellular pathogen redirects SM biosynthesis to its replicative niche. PMID:21909260

Elwell, Cherilyn A; Jiang, Shaobo; Kim, Jung Hwa; Lee, Albert; Wittmann, Torsten; Hanada, Kentaro; Melancon, Paul; Engel, Joanne N

2011-09-01

253

Obligate biotrophy features unraveled by the genomic analysis of rust fungi  

PubMed Central

Rust fungi are some of the most devastating pathogens of crop plants. They are obligate biotrophs, which extract nutrients only from living plant tissues and cannot grow apart from their hosts. Their lifestyle has slowed the dissection of molecular mechanisms underlying host invasion and avoidance or suppression of plant innate immunity. We sequenced the 101-Mb genome of Melampsora larici-populina, the causal agent of poplar leaf rust, and the 89-Mb genome of Puccinia graminis f. sp. tritici, the causal agent of wheat and barley stem rust. We then compared the 16,399 predicted proteins of M. larici-populina with the 17,773 predicted proteins of P. graminis f. sp tritici. Genomic features related to their obligate biotrophic lifestyle include expanded lineage-specific gene families, a large repertoire of effector-like small secreted proteins, impaired nitrogen and sulfur assimilation pathways, and expanded families of amino acid and oligopeptide membrane transporters. The dramatic up-regulation of transcripts coding for small secreted proteins, secreted hydrolytic enzymes, and transporters in planta suggests that they play a role in host infection and nutrient acquisition. Some of these genomic hallmarks are mirrored in the genomes of other microbial eukaryotes that have independently evolved to infect plants, indicating convergent adaptation to a biotrophic existence inside plant cells.

Duplessis, Sebastien; Cuomo, Christina A.; Lin, Yao-Cheng; Aerts, Andrea; Tisserant, Emilie; Veneault-Fourrey, Claire; Joly, David L.; Hacquard, Stephane; Amselem, Joelle; Cantarel, Brandi L.; Chiu, Readman; Coutinho, Pedro M.; Feau, Nicolas; Field, Matthew; Frey, Pascal; Gelhaye, Eric; Goldberg, Jonathan; Grabherr, Manfred G.; Kodira, Chinnappa D.; Kohler, Annegret; Kues, Ursula; Lindquist, Erika A.; Lucas, Susan M.; Mago, Rohit; Mauceli, Evan; Morin, Emmanuelle; Murat, Claude; Pangilinan, Jasmyn L.; Park, Robert; Pearson, Matthew; Quesneville, Hadi; Rouhier, Nicolas; Sakthikumar, Sharadha; Salamov, Asaf A.; Schmutz, Jeremy; Selles, Benjamin; Shapiro, Harris; Tanguay, Philippe; Tuskan, Gerald A.; Henrissat, Bernard; Van de Peer, Yves; Rouze, Pierre; Ellis, Jeffrey G.; Dodds, Peter N.; Schein, Jacqueline E.; Zhong, Shaobin; Hamelin, Richard C.; Grigoriev, Igor V.; Szabo, Les J.; Martin, Francis

2011-01-01

254

The obligately lichenicolous genus Lichenoconium represents a novel lineage in the Dothideomycetes.  

PubMed

Lichenicolous fungi are obligately lichen-associated organisms that have evolved many times throughout the Ascomycota and Basidiomycota. Approximately 20% of lichenicolous ascomycetes are recognized only from asexual (anamorphic) characteristics, so the phylogenetic position of many groups has never been resolved. Here we present the first molecular phylogeny of Lichenoconium, a genus of strictly asexual, obligately lichenicolous species with broad geographic distributions and diverse host ecologies. We obtained nuclear and mitochondrial rDNA sequences from fungal cultures isolated from four species in the genus, including a new species, Lichenoconium aeruginosum sp. nov., collected in France, Luxembourg and Netherlands. Our multilocus phylogeny supports the monophyly of fungi in the genus Lichenoconium, and places the genus in the Dothideomycetes, an ascomycete class made up mainly of saprobes and plant-associated endophytes and pathogens. There are only a few recognized groups of lichen-formers in the Dothideomycetes, but Lichenoconium is not supported as being closely related to any of these, nor to any other recognized order within the Dothideomycetes. Given that Lichenoconium is but one of over 100 genera of anamorphic lichenicolous fungi, most of which have never been studied phylogenetically, we suggest that asexual lichenicolous fungi may represent novel and evolutionarily significant phylogenetic groups in the Kingdom Fungi. PMID:21315315

Lawrey, James D; Diederich, Paul; Nelsen, Matthew P; Sikaroodi, Masoumeh; Gillevet, Patrick M; Brand, A Maarten; van den Boom, Pieter

2010-12-10

255

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

256

LOW PATHOGENIC POTENTIAL IN HETEROTROPHIC BACTERIA FROM POTABLE WATER  

EPA Science Inventory

Forty-five isolates of HPC bacteria, most of which express virulence-related characteristics are being tested for pathogenicity in immunocompromised mice. All forty-five were negative for facultative intracellular pathogenicity. All twenty-three isolates tested thus far were a...

257

Temperature dependent virulence of obligate and facultative fungal pathogens of honeybee brood  

Technology Transfer Automated Retrieval System (TEKTRAN)

Chalkbrood (Ascosphaera apis) and stonebrood (Aspergillus flavus) are well known fungal brood diseases of honeybees (Apis mellifera), but they have hardly been systematically studied because the difficulty of rearing larvae in vitro has precluded controlled experimentation. Chalkbrood is a chronic h...

258

Invasion and Intracellular Survival by Protozoan Parasites  

PubMed Central

Summary Intracellular parasitism has arisen only a few times during the long ancestry of protozoan parasites including in diverse groups such as microsporidians, kinetoplastids, and apicomplexans. Strategies used to gain entry differ widely from injection (e.g. microsporidians), active penetration of the host cell (e.g. Toxoplasma), recruitment of lysosomes to a plasma membrane wound (e.g. Trypanosoma cruzi), to host cell-mediated phagocytosis (e.g. Leishmania). The resulting range of intracellular niches is equally diverse ranging from cytosolic (e.g. T. cruzi) to residing within a nonfusigenic vacuole (e.g. Toxoplasma, Encephalitizoon) or a modified phagolysosome (e.g. Leishmania). These lifestyle choices influence access to nutrients, interaction with host cell signaling pathways, and detection by pathogen recognition systems. As such, intracellular life requires a repertoire of adaptations to assure entry-exit from the cell, as well as to thwart innate immune mechanisms and prevent clearance. Elucidating these pathways at the cellular and molecular level may identify key steps that can be targeted to reduce parasite survival or augment immunological responses and thereby prevent disease.

Sibley, L. David

2013-01-01

259

Endosymbiosis In Statu Nascendi: Close Phylogenetic RelationshipBetween Obligately Endosymbiotic and Obligately Free-LivingPolynucleobacter Strains (Betaproteobacteria)  

SciTech Connect

Bacterial strains affiliated to the phylogenetically shallowsubcluster C (PnecC) of the 28 Polynucleobacter cluster, which ischaracterized by a minimal 16S rRNA gene sequence similarity of approx.98.5 percent, have been reported to occur as obligate endosymbionts of 30ciliates (Euplotes spp.), as well as to occur as free-living cells in thepelagic zone of freshwater habitats. We investigated if these two groupsof closely related bacteria represent 32 strains fundamentally differingin lifestyle, or if they simply represent different stages of afacultative endosymbiotic lifestyle. The phylogenetic analysis of 16SrRNA gene and 16S34 23S ITS sequences of five endosymbiont strains fromtwo different Euplotes species and 40 pure culture strains demonstratedhost-species-specific clustering of the endosymbiont 36 sequences withinthe PnecC subcluster. The sequences of the endosymbionts showedcharacteristics indicating an obligate endosymbiotic lifestyle.Cultivation experiments 38 revealed fundamental differences inphysiological adaptations, and determination of the genome sizesindicated a slight size reduction in endosymbiotic strains. We concludethat the 40 two groups of PnecC bacteria represent obligately free-livingand obligately endosymbiotic strains, respectively, and do not representdifferent stages of the same complex lifecycle. 42 These closely relatedstrains occupy completely separated ecological niches. To our bestknowledge, this is the closest phylogenetic relationship between obligateendosymbionts and 44 obligately free-living bacteria everrevealed.

Vannini, Claudia; Pockl, Matthias; Petroni, Giulio; Wu, Qinglong; Lang, Elke; Stackebrandt, Erko; Schrallhammer, Martina; Richardson, PaulM.; Hahn, Martin W.

2006-07-21

260

Environmental and safety obligations of the Chemical Weapons Convention  

SciTech Connect

Among its many unique and precedent-setting provisions, the Chemical Weapons Convention (CWC) includes important requirements for States Parties to protect the public safety and the environment in the course of carrying out the treaty. These obligations will apply to the destruction of chemical weapons, of former chemical weapons production facilities, and to other activities under the Convention such as the verification scheme. This morning, I will briefly discuss the Convention`s safety and environmental obligations, concentrating on their effects in this country as the United States chemical weapons stockpile is destroyed.

Tanzman, E.A.

1994-04-07

261

Real-time PCR and spore trap-based detection of the downy mildew pathogen, Peronospora effusa  

Technology Transfer Automated Retrieval System (TEKTRAN)

Peronospora effusa is an obligate pathogen and the causal agent of downy mildew on spinach. The pathogen can be dispersed by splashing rain and wind, and may overwinter as oospores. Outbreaks of downy mildew on spinach are common in the cool climate of central coastal California, including the Sal...

262

Nanovehicular Intracellular Delivery Systems  

PubMed Central

This article provides an overview of principles and barriers relevant to intracellular drug and gene transport, accumulation and retention (collectively called as drug delivery) by means of nanovehicles (NV). The aim is to deliver a cargo to a particular intracellular site, if possible, to exert a local action. Some of the principles discussed in this article apply to noncolloidal drugs that are not permeable to the plasma membrane or to the blood–brain barrier. NV are defined as a wide range of nanosized particles leading to colloidal objects which are capable of entering cells and tissues and delivering a cargo intracelullarly. Different localization and targeting means are discussed. Limited discussion on pharmacokinetics and pharmacodynamics is also presented. NVs are contrasted to micro-delivery and current nanotechnologies which are already in commercial use. Newer developments in NV technologies are outlined and future applications are stressed. We also briefly review the existing modeling tools and approaches to quantitatively describe the behavior of targeted NV within the vascular and tumor compartments, an area of particular importance. While we list “elementary” phenomena related to different level of complexity of delivery to cancer, we also stress importance of multi-scale modeling and bottom-up systems biology approach.

PROKOP, ALES; DAVIDSON, JEFFREY M.

2013-01-01

263

Application of the theory of adaptive polymorphism to the ecology and epidemiology of pathogenic yeasts.  

PubMed Central

The theory of adaptive polymorphism predicts that species occupying broad ecological niches will be phenotypically and genotypically more varied than those occupying narrow niches. It is suggested that this theory has direct relevance to the epidemiology of microbial pathogens in that environmental pathogens inhabit a broader niche and should be expected to exhibit greater variation than pathogens that are obligate commensals. This proved to be the case when one obligate commensal, the pathogenic yeast Candida albicans, was compared with other Candida spp. and an environmental pathogen, Cryptococcus neoformans. Further evidence of this relationship is derived from the literature. This observation adds further support to the theory of adaptive polymorphism, although the mechanisms of maintenance of polymorphism is asexually reproducing populations must be different from those in sexually reproducing populations. This observation may give important clues to the epidemiology of those infections for which it is not already known.

Hunter, P R; Fraser, C A

1990-01-01

264

Back from the Dormant Stage: Second Messenger Cyclic ADP-Ribose Essential for Toxoplasma gondii Pathogenicity  

NSDL National Science Digital Library

Cyclic adenosine diphosphoribose (cADPR) is an endogenous Ca2+-mobilizing second messenger found in cells of animals, plants, and protozoans. It is formed by a specific class of enzymes, the ADP-ribosyl cyclases. cADPR stimulates Ca2+ release by means of ryanodine receptors located in the sarcoplasmic and endoplasmic reticulum. Recently, a role for cADPR has been demonstrated in the obligate intracellular protozoan pathogen Toxoplasma gondii. In T. gondii, stress conditions evoked synthesis of the plant hormone abscisic acid by the apicoplast, a remnant organelle of an algal endosymbiont of T. gondii. Abscisic acid in turn activated formation of cADPR within T. gondii, resulting in Ca2+ release and secretion of proteins involved in egress of T. gondii from its host cell. Evidence for a synthetic pathway of plant origin was obtained with the ABA synthesis inhibitor fluridone, which antagonized cellular egress and induced differentiation of long-lived semidormant cystic forms of T. gondii. Moreover, fluridone protected mice from toxoplasmosis.

Andreas H. Guse (University Medical Centre Hamburg-Eppendorf;Institute of Biochemistry and Molecular Biology and Centre of Experimental Medicine REV)

2008-04-29

265

A Toxoplasma gondii mutant defective in responding to calcium fluxes shows reduced in vivo pathogenicity  

PubMed Central

Toxoplasma gondii is an important opportunistic pathogen in immunocompromised individuals. Successful propagation in an infected host by this obligate intracellular parasite depends on its ability to enter and exit host cells. Egress from the cell can be artificially induced by causing fluxes of calcium within the parasite with the use of calcium ionophores. While this ionophore-induced egress (IIE) has been characterized in detail, it is not known whether it mimics a normal physiological process of the parasite. This is underscored by the fact that mutants in IIE do not exhibit strong defects in any of the normal growth characteristics of the parasite in tissue culture. We have isolated and characterized a T. gondii mutant that along with a delay in IIE exhibits a severe defect in establishing a successful infection in vivo. In tissue culture this mutant displays normal ability to invade, divide within cells and convert into the latent encysted bradyzoite form. Nevertheless, mice infected with this mutant are less likely to die and carry less brain cysts than those infected with wild type parasites. Thus, our results suggest that normal response to calcium fluxes plays an important role during in vivo development of T. gondii.

Lavine, Mark D.; Knoll, Laura J.; Rooney, Peggy J.; Arrizabalaga, Gustavo

2007-01-01

266

Exploring Anti-Bacterial Compounds against Intracellular Legionella.  

PubMed

Legionella pneumophila is a ubiquitous fresh-water bacterium which reproduces within its erstwhile predators, environmental amoeba, by subverting the normal pathway of phagocytosis and degradation. The molecular mechanisms which confer resistance to amoeba are apparently conserved and also allow replication within macrophages. Thus, L. pneumophila can act as an 'accidental' human pathogen and cause a severe pneumonia known as Legionnaires' disease. The intracellular localisation of L. pneumophila protects it from some antibiotics, and this fact must be taken into account to develop new anti-bacterial compounds. In addition, the intracellular lifestyle of L. pneumophila may render the bacteria susceptible to compounds diminishing bacterial virulence and decreasing intracellular survival and replication of this pathogen. The development of a single infection cycle intracellular replication assay using GFP-producing L. pneumophila and Acanthamoebacastellanii amoeba is reported here. This fluorescence-based assay allows for continuous monitoring of intracellular replication rates, revealing the effect of bacterial gene deletions or drug treatment. To examine how perturbations of the host cell affect L. pneumophila replication, several known host-targeting compounds were tested, including modulators of cytoskeletal dynamics, vesicle scission and Ras GTPase localisation. Our results reveal a hitherto unrealized potential antibiotic property of the ?-lactone-based Ras depalmitoylation inhibitor palmostatin M, but not the closely related inhibitor palmostatin B. Further characterisation indicated that this compound caused specific growth inhibition of Legionella and Mycobacterium species, suggesting that it may act on a common bacterial target. PMID:24058631

Harrison, Christopher F; Kicka, Sébastien; Trofimov, Valentin; Berschl, Kathrin; Ouertatani-Sakouhi, Hajer; Ackermann, Nikolaus; Hedberg, Christian; Cosson, Pierre; Soldati, Thierry; Hilbi, Hubert

2013-09-13

267

Exploring Anti-Bacterial Compounds against Intracellular Legionella  

PubMed Central

Legionella pneumophila is a ubiquitous fresh-water bacterium which reproduces within its erstwhile predators, environmental amoeba, by subverting the normal pathway of phagocytosis and degradation. The molecular mechanisms which confer resistance to amoeba are apparently conserved and also allow replication within macrophages. Thus, L. pneumophila can act as an ‘accidental’ human pathogen and cause a severe pneumonia known as Legionnaires’ disease. The intracellular localisation of L. pneumophila protects it from some antibiotics, and this fact must be taken into account to develop new anti-bacterial compounds. In addition, the intracellular lifestyle of L. pneumophila may render the bacteria susceptible to compounds diminishing bacterial virulence and decreasing intracellular survival and replication of this pathogen. The development of a single infection cycle intracellular replication assay using GFP-producing L. pneumophila and Acanthamoebacastellanii amoeba is reported here. This fluorescence-based assay allows for continuous monitoring of intracellular replication rates, revealing the effect of bacterial gene deletions or drug treatment. To examine how perturbations of the host cell affect L. pneumophila replication, several known host-targeting compounds were tested, including modulators of cytoskeletal dynamics, vesicle scission and Ras GTPase localisation. Our results reveal a hitherto unrealized potential antibiotic property of the ?-lactone-based Ras depalmitoylation inhibitor palmostatin M, but not the closely related inhibitor palmostatin B. Further characterisation indicated that this compound caused specific growth inhibition of Legionella and Mycobacterium species, suggesting that it may act on a common bacterial target.

Harrison, Christopher F.; Kicka, Sebastien; Trofimov, Valentin; Berschl, Kathrin; Ouertatani-Sakouhi, Hajer; Ackermann, Nikolaus; Hedberg, Christian; Cosson, Pierre; Soldati, Thierry; Hilbi, Hubert

2013-01-01

268

Facultative monogamy in obligate coral-dwelling hawkfishes (Cirrh tidae)  

Microsoft Academic Search

Obligate coral-dwelling hawkfishes have been hypothesized to be monogamous. This hypothesized mating system is at odds with what is known of those of other cirrhitids. Neocirrhites armatus, which inhabits Pocillopora spp. corals, and Oxycirrhites typus, which inhabits gorgonians and antipatharian corals, were examined for evidence of a monogamous mating system. Life history criteria that favor monogamy in reef fishes (Barlow

Terry J. Donaldson

1989-01-01

269

TAKING DUE CARE: MORAL OBLIGATIONS IN DUAL USE RESEARCH  

Microsoft Academic Search

ABSTRACTIn the past decade, the perception of a bioterrorist threat has increased and created a demand on life scientists to consider the potential security implications of dual use research. This article examines a selection of proposed moral obligations for life scientists that have emerged to meet these concerns and the extent to which they can be considered reasonable. It also

FRIDA KUHLAU; STEFAN ERIKSSON; KATHINKA EVERS; ANNA T. HÖGLUND

2008-01-01

270

18 CFR 367.2300 - Account 230, Asset retirement obligations.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Account 230, Asset retirement obligations...AND NATURAL GAS ACT UNIFORM SYSTEM OF ACCOUNTS FOR CENTRALIZED SERVICE COMPANIES SUBJECT...NATURAL GAS ACT Balance Sheet Chart of Accounts Other Noncurrent Liabilities §...

2013-04-01

271

45 CFR 1386.2 - Obligation of funds.  

Code of Federal Regulations, 2011 CFR

...property. (c) (1) The Protection and Advocacy System may elect to treat entry of...salaries of employees of the Protection and Advocacy agency. All funds made available for...Disabilities Councils and to the Protection and Advocacy System obligated under this...

2011-10-01

272

45 CFR 1386.2 - Obligation of funds.  

Code of Federal Regulations, 2012 CFR

...property. (c) (1) The Protection and Advocacy System may elect to treat entry of...salaries of employees of the Protection and Advocacy agency. All funds made available for...Disabilities Councils and to the Protection and Advocacy System obligated under this...

2012-10-01

273

Civic Engagement in Teacher Education: Activities or Obligation?  

ERIC Educational Resources Information Center

Some might question whether teacher education programs have an obligation to promote or enhance the teaching of civic responsibility and engagement, especially if they believe that the primary purpose of education is to prepare students to enter the workforce or be successful as individuals. However, others have a more encompassing view of…

Erickson, Lynnette B.

2011-01-01

274

30 CFR 582.20 - Obligations and responsibilities of lessees.  

Code of Federal Regulations, 2013 CFR

...CONTINENTAL SHELF FOR MINERALS OTHER THAN OIL, GAS, AND SULPHUR Obligations and Responsibilities...precautions to prevent waste and damage to oil, gas, sulphur, and other OCS mineral-bearing...cause harm or damage to life (including fish and other aquatic life); to...

2013-07-01

275

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

276

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.

277

76 FR 72645 - Calculation of Maximum Obligation Limitation  

Federal Register 2010, 2011, 2012, 2013

...Act. The Maximum Obligation Limitation (``MOL''), as set forth...amount that is equal to 10 percent of the total consolidated assets...amount that is equal to 90 percent of the fair value of the...amount that is equal to 10 percent of the total consolidated...

2011-11-25

278

77 FR 37554 - Calculation of Maximum Obligation Limitation  

Federal Register 2010, 2011, 2012, 2013

...Act. The Maximum Obligation Limitation (``MOL''), as set forth...amount that is equal to 10 percent of the total consolidated assets...amount that is equal to 90 percent of the fair value of the total...amount that is equal to 10 percent of the total consolidated...

2012-06-22

279

CHANGING OBLIGATIONS AND THE PSYCHOLOGICAL CONTRACT: A LONGITUDINAL STUDY  

Microsoft Academic Search

In an exploratory longitudinal study of business school alumni, we investigated changes in employment obligations as perceived by em- ployees. During the first two years of employment, employees came to perceive that they owed less to their employers while seeing tbeir em- ployers as owing them more. An employer's failure to fulfill its com- mitments was found to be significantly

SANDRA L. ROBINSON; MATTHEW S. KRAATZ; DENISE M. ROUSSEAU

1994-01-01

280

Of community, organs and obligations: Routine salvage with a twist  

Microsoft Academic Search

This paper makes the assumption that organ transplantation is, under some conditions at least, a proper use of communal medical resources. Proceeding from this assumption, the author: (1) sketches the history of the problem; (2) briefly examines the prevalent models of communal structure and offers an alternate version; (3) discusses notions of justice and obligation derived from these different models;

Erich H. Loewy

1996-01-01

281

Specifying and monitoring economic environments using rights and obligations  

Microsoft Academic Search

We provide a formal scripting language to capture the semantics of economic environments. The language is based on a set of well-defined design principles and makes explicit an agent's rights, as derived from property, and an agent's obligations, as derived from restrictions placed on its actions either voluntarily or as a consequence of other actions. Coupled with the language is

Loizos Michael; David C. Parkes; Avi Pfeffer

2010-01-01

282

Developer's Concerns about Staff Retreat Create Opportunity and Obligation  

ERIC Educational Resources Information Center

This article deals with a staff developer's concerns about Bill Stewart's staff retreat, and how these concerns create opportunity and obligation. The author presents views from a superintendent and two staff developers on the staff retreat. Aside from these, the author talks about a superintendent named Darlene Preston, and her course of action.…

Killion, Joellen

2004-01-01

283

Ethical Obligations in a Tragedy of the Commons  

Microsoft Academic Search

When people use a resource without a co-ordinated plan the result is often a tragedy of the commons in which the resource is depleted. Many environmental resources display the characteristics of a developing tragedy of the commons. Many believe that each person is ethically obligated to reduce use of the commons to the sustainable level. I argue that this is

Baylor L. Johnson

2003-01-01

284

Oxidation of Inorganic Sulfur Compounds by Obligately Organotrophic Bacteria  

Microsoft Academic Search

New data obtained by the author and other researchers on two different groups of obligately heterotrophic bacteria capable of inorganic sulfur oxidation are reviewed. Among culturable marine and (halo)alkaliphilic heterotrophs oxidizing sulfur compounds (thiosulfate and, much less actively, elemental sulfur and sulfide) incompletely to tetrathionate, representatives of the gammaproteobacteria, especially from the Halomonas group, dominate. Some denitrifying species from this

D. Yu. Sorokin

2003-01-01

285

Simulation methods for risk analysis of collateralized debt obligations  

Microsoft Academic Search

Collateralized debt obligations (CDOs) are sophisticated financial products that offer a range of investments, known as tranches, at varying risk levels backed by a collateral pool typically consisting of corporate debt (bonds, loans, default swaps, etc.). The analysis of the risk-return properties of CDO tranches is complicated by the highly non-linear and time dependent relationship between the cash flows to

William J. Morokoff

2003-01-01

286

28 CFR 811.3 - Notice of obligation to register.  

Code of Federal Regulations, 2013 CFR

...sex offenders have an independent obligation to register. Persons who have been convicted or found not guilty by reason of insanity of a sex offense or who have been determined to be a sexual psychopath should report to CSOSA in order to ascertain...

2013-07-01

287

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.

288

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

289

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

290

Main Flaws of The Collateralized Debt Obligation‘s: Valuation Before And During The 2008\\/2009 Global Turmoil  

Microsoft Academic Search

As a result of the 2008 financial crisis, the world credit markets stalled significantly and raised the doubts of market participants and policymakers about the proper and fair valuation of financial derivatives and structured products such as collateralized debt obligations (CDOs). The aim of the paper is to contribute to the understanding of CDOs and shed light on CDO valuation

Petra Benešová; Petr Teply

2010-01-01

291

Phenotypic variation and intracellular parasitism by Histoplasma capsulatum  

PubMed Central

The success of Histoplasma capsulatum as an intracellular pathogen depends completely on successful conversion of the saprophytic mycelial (mold) form of this fungus to a parasitic yeast form. It is therefore not surprising that yeast phase-specific genes and gene products are proving to be important for survival and proliferation of H. capsulatum within macrophages. In this study, we have focused on the role and regulation of two yeast-specific characteristics: ?-(1,3)-glucan, a cell wall polysaccharide modulated by cell-density (quorum) sensing, and a secreted calcium-binding protein (CBP) that is essential for pathogenicity.

Kugler, Silke; Sebghati, Tricia Schurtz; Eissenberg, Linda Groppe; Goldman, William E.

2000-01-01

292

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

293

18 CFR 292.310 - Procedures for utilities requesting termination of obligation to purchase from qualifying...  

Code of Federal Regulations, 2013 CFR

...obligation to purchase from qualifying facilities. 292.310 Section 292.310 ...Cogeneration and Small Power Production Facilities Under Section 210 of the Public Utility...obligation to purchase from qualifying facilities. (a) An electric utility...

2013-04-01

294

40 CFR 152.97 - Rights and obligations of data submitters.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Rights and obligations of data submitters. 152.97 Section 152...PROCEDURES Procedures To Ensure Protection of Data Submitters' Rights § 152.97 Rights and obligations of data submitters. (a) Right to be...

2013-07-01

295

Drug Control: Status of Obligations for Fiscal Year 1990 DOD Counternarcotics Funds.  

National Technical Information Service (NTIS)

This fact sheet responds to your request for information on the status of obligations for the fiscal year 1990 Department of Defense (DOD) counternarcotics appropriation of $450 million. Specifically, we (1) compared the obligation rates for counternarcot...

1990-01-01

296

2 CFR 376.370 - What are the obligations of Medicare carriers and intermediaries?  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false What are the obligations of Medicare carriers and intermediaries? 376.370...376.370 What are the obligations of Medicare carriers and intermediaries? Because Medicare carriers, intermediaries and other...

2013-01-01

297

75 FR 62634 - Proposed Information Collection (Obligation to Report Factors Affecting Entitlement) Activity...  

Federal Register 2010, 2011, 2012, 2013

...Information Collection (Obligation to Report Factors Affecting Entitlement) Activity: Comment...technology. Title: Obligation to Report Factors Affecting Entitlement (38 CFR 3.204...must report changes in their entitlement factors. Individual factors such as...

2010-10-12

298

78 FR 46418 - Proposed Information Collection (Obligation To Report Factors Affecting Entitlement) Activity...  

Federal Register 2010, 2011, 2012, 2013

...Information Collection (Obligation To Report Factors Affecting Entitlement) Activity; Comment...technology. Title: Obligation to Report Factors Affecting Entitlement (38 CFR 3.204...must report changes in their entitlement factors. Individual factors such as...

2013-07-31

299

75 FR 80114 - Agency Information Collection (Obligation To Report Factors Affecting Entitlement) Activity Under...  

Federal Register 2010, 2011, 2012, 2013

...Information Collection (Obligation To Report Factors Affecting Entitlement) Activity Under...INFORMATION: Title: Obligation to Report Factors Affecting Entitlement (38 CFR 3.204...must report changes in their entitlement factors. Individual factors such as...

2010-12-21

300

40 CFR 80.1407 - How are the Renewable Volume Obligations calculated?  

Code of Federal Regulations, 2013 CFR

...following formulas: (1) Cellulosic biofuel. RVOCB,i = (RFStdCB,i ...Renewable Volume Obligation for cellulosic biofuel for an obligated party for calendar year...RFStdCB,i = The standard for cellulosic biofuel for calendar year i, determined by...

2013-07-01

301

24 CFR 982.633 - Homeownership option: Continued assistance requirements; Family obligations.  

Code of Federal Regulations, 2013 CFR

...option: Continued assistance requirements; Family obligations. 982.633 Section 982...option: Continued assistance requirements; Family obligations. (a) Occupancy of home...Homeownership assistance may only be paid while the family is residing in the home. If the...

2013-04-01

302

18 CFR 367.2270 - Account 227, Obligations under capital lease-Non-current.  

Code of Federal Regulations, 2013 CFR

... Account 227, Obligations under capital lease-Non-current. 367.2270...ACT OF 2005, FEDERAL POWER ACT AND NATURAL GAS ACT UNIFORM SYSTEM OF ACCOUNTS... Account 227, Obligations under capital leaseâNon-current....

2013-04-01

303

18 CFR 367.2430 - Account 243, Obligations under capital leases-Current.  

Code of Federal Regulations, 2013 CFR

... Account 243, Obligations under capital leases-Current. 367.2430...ACT OF 2005, FEDERAL POWER ACT AND NATURAL GAS ACT UNIFORM SYSTEM OF ACCOUNTS... Account 243, Obligations under capital leasesâCurrent. This...

2013-04-01

304

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

Code of Federal Regulations, 2010 CFR

...false Statutory obligation of third party payer to pay. 220.2 Section...MISCELLANEOUS COLLECTION FROM THIRD PARTY PAYERS OF REASONABLE CHARGES FOR...220.2 Statutory obligation of third party payer to pay. (a) Basic...

2009-07-01

305

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

Code of Federal Regulations, 2010 CFR

...false Statutory obligation of third party payer to pay. 220.2 Section...MISCELLANEOUS COLLECTION FROM THIRD PARTY PAYERS OF REASONABLE CHARGES FOR...220.2 Statutory obligation of third party payer to pay. (a) Basic...

2010-07-01

306

45 CFR 303.31 - Securing and enforcing medical support obligations.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Securing and enforcing medical support obligations. 303.31...303.31 Securing and enforcing medical support obligations. (a) For purposes of this section: (1) Cash medical support means an amount...

2012-10-01

307

18 CFR 292.303 - Electric utility obligations under this subpart.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Electric utility obligations under this subpart...AND COGENERATION Arrangements Between Electric Utilities and Qualifying Cogeneration...Policies Act of 1978 § 292.303 Electric utility obligations under this...

2013-04-01

308

10 CFR 40.56 - Restrictions on the use of Australian-obligated source material.  

Code of Federal Regulations, 2013 CFR

...Australian-obligated source material. 40.56 Section 40.56 Energy NUCLEAR REGULATORY...DOMESTIC LICENSING OF SOURCE MATERIAL Transfer...Peaceful Uses of Nuclear Energy, dated 2010, Australian-obligated source material...

2013-01-01

309

12 CFR 1511.5 - Obligations of Funding Corporation; no adverse claims.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Obligations of Funding Corporation; no adverse claims. ...DEPARTMENT OF THE TREASURY RESOLUTION FUNDING CORPORATION BOOK-ENTRY PROCEDURE § 1511.5 Obligations of Funding Corporation; no adverse...

2013-01-01

310

18 CFR 37.5 - Obligations of Transmission Providers and Responsible Parties.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Obligations of Transmission Providers and Responsible Parties...SYSTEMS § 37.5 Obligations of Transmission Providers and Responsible Parties. (a) Each Transmission Provider is required to provide...

2013-04-01

311

78 FR 63276 - Interim Policy, FAA Review of Solar Energy System Projects on Federally Obligated Airports  

Federal Register 2010, 2011, 2012, 2013

...Interim Policy, FAA Review of Solar Energy System Projects on Federally Obligated...obligated airports to construct solar energy systems on airport property. FAA...measuring ocular impact of proposed solar energy systems which are effective...

2013-10-23

312

Moral obligations of nurses and physicians in neonatal end-of-life care  

PubMed Central

The aim of this study was to explore the obligations of nurses and physicians in providing end-of-life care. Nineteen nurses and 11 physicians from a single newborn intensive care unit participated. Using content analysis, an overarching obligation of creating the best possible experience for infants and parents was identified, within which two categories of obligations (decision making and the end of life itself) emerged. Obligations in decision making included talking to parents and timing withdrawal. End-of-life obligations included providing options, preparing parents, being with, advocating, creating peace and normalcy, and providing comfort. Nurses and physicians perceived obligations in both categories, although nurse obligations centered on the end of life while physician obligations focused on decision making. The findings demonstrate that, although the ultimate goal is shared by both disciplines, the paths to achieving that goal are often different. This has important implications for collaboration, communication, and improving the end of life.

Epstein, Elizabeth Gingell

2013-01-01

313

31 CFR 1010.940 - Photographic or other reproductions of Government obligations.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Photographic or other reproductions of Government obligations. 1010...1010.940 Photographic or other reproductions of Government obligations. Nothing...authorize the microfilming or other reproduction of: (a) Currency or other...

2013-07-01

314

43 CFR 9.11 - What are the Secretary's obligations in interstate situations?  

Code of Federal Regulations, 2010 CFR

...Secretary's obligations in interstate situations? 9.11 Section 9.11 Public Lands: Interior Office of the Secretary...DEPARTMENT OF THE INTERIOR PROGRAMS AND ACTIVITIES § 9.11 What are the Secretary's obligations in...

2009-10-01

315

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

316

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

Code of Federal Regulations, 2013 CFR

...obligations of small recipients regarding Equal Opportunity Officers? 37.27 Section 37...IMPLEMENTATION OF THE NONDISCRIMINATION AND EQUAL OPPORTUNITY PROVISIONS OF THE WORKFORCE INVESTMENT...obligations of small recipients regarding Equal Opportunity Officers? Although small...

2013-07-01

317

29 CFR 37.29 - What are a recipient's obligations to disseminate its equal opportunity policy?  

Code of Federal Regulations, 2013 CFR

...obligations to disseminate its equal opportunity policy? 37.29 Section 37.29...IMPLEMENTATION OF THE NONDISCRIMINATION AND EQUAL OPPORTUNITY PROVISIONS OF THE WORKFORCE INVESTMENT...obligations to disseminate its equal opportunity policy? (a) A recipient...

2013-07-01

318

29 CFR 37.26 - What are a recipient's obligations relating to the Equal Opportunity Officer?  

Code of Federal Regulations, 2013 CFR

...recipient's obligations relating to the Equal Opportunity Officer? 37.26 Section 37.26...IMPLEMENTATION OF THE NONDISCRIMINATION AND EQUAL OPPORTUNITY PROVISIONS OF THE WORKFORCE INVESTMENT...recipient's obligations relating to the Equal Opportunity Officer? A recipient has the...

2013-07-01

319

43 CFR 9.5 - What is the Secretary's obligation with respect to Federal interagency coordination?  

Code of Federal Regulations, 2012 CFR

...Secretary's obligation with respect to Federal interagency coordination? 9.5 Section 9.5 Public Lands: Interior...PROGRAMS AND ACTIVITIES § 9.5 What is the Secretary's obligation with respect to Federal interagency...

2012-10-01

320

43 CFR 9.5 - What is the Secretary's obligation with respect to Federal interagency coordination?  

Code of Federal Regulations, 2011 CFR

...Secretary's obligation with respect to Federal interagency coordination? 9.5 Section 9.5 Public Lands: Interior...PROGRAMS AND ACTIVITIES § 9.5 What is the Secretary's obligation with respect to Federal interagency...

2011-10-01

321

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

Federal Register 2010, 2011, 2012, 2013

...3133-AEOO Loan Participations; Purchase, Sale and Pledge of Eligible Obligations; Purchase...titled Loan Participations; Purchase, Sale and Pledge of Eligible Obligations; Purchase...FURTHER INFORMATION CONTACT: Pamela Yu, Staff Attorney, Office of General...

2013-07-09

322

26 CFR 15a.453-2 - Installment obligations received as liquidating distribution. [Reserved  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Installment obligations received as liquidating distribution...TEMPORARY INCOME TAX REGULATIONS UNDER THE INSTALLMENT SALES REVISION ACT § 15a.453-2 Installment obligations received as liquidating...

2010-04-01

323

26 CFR 15a.453-2 - Installment obligations received as liquidating distribution. [Reserved  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Installment obligations received as liquidating distribution...TEMPORARY INCOME TAX REGULATIONS UNDER THE INSTALLMENT SALES REVISION ACT § 15a.453-2 Installment obligations received as liquidating...

2009-04-01

324

Revisiting intracellular calcium signaling semantics  

Microsoft Academic Search

Cells use intracellular free calcium concentration changes for signaling. Signal encoding occurs through both spatial and temporal modulation of the free calcium concentration. The encoded message is detected by an ensemble of intracellular sensors forming the family of calcium-binding proteins (CaBPs) which must faithfully translate the message using a new syntax that is recognized by the cell. The cell is

Jacques Haiech; Emilie Audran; Marie Fève; Raoul Ranjeva; Marie-Claude Kilhoffer

2011-01-01

325

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

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Pledge of book-entry Government obligations. 225.4 Section 225...SERVICE ACCEPTANCE OF BONDS SECURED BY GOVERNMENT OBLIGATIONS IN LIEU OF BONDS WITH SURETIES § 225.4 Pledge of book-entry Government obligations. (a)...

2013-07-01

326

Embedded cosmopolitanism and the politics of obligation: the Ghanaian diaspora and development  

Microsoft Academic Search

The author analyses how identities and obligations operate within the spaces of transnational communities and how this affects development. Within spatially diffuse communities, identities are fluid and overlapping, as are the obligations to multiple others—be that kin, ethnic group, or nation—in different localities. The author is concerned with the institutions through which these identities are formed and obligations are fulfilled.

Giles Mohan

2006-01-01

327

31 CFR 223.13 - Full penalty of the obligation regarded as the liability; exceptions.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Full penalty of the obligation regarded as...BUSINESS WITH THE UNITED STATES § 223.13 Full penalty of the obligation regarded as the...limitation prescribed in this part, the full penalty of the obligation will be...

2013-07-01

328

Implementing Collective Obligations in Human-Agent Teams Using KAoS Policies  

Microsoft Academic Search

Obligations can apply to individuals, either severally or collectively. When applied severally, each individual or member of a team is independently responsible to fulfill the obligation. When applied collectively, it is the group as a whole that becomes responsible, with individual members sharing the obligation. In this paper, we present several variations of teamwork models involving the performance of collective

Jurriaan van Diggelen; Jeffrey M. Bradshaw; Matthew Johnson; Andrzej Uszok; Paul J. Feltovich

2009-01-01

329

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

330

Deconfounding distance effects in judgments of moral obligation.  

PubMed

A heavily disputed question of moral philosophy is whether spatial distance between agent and victim is normatively relevant for the degree of obligation to help strangers in need. In this research, we focus on the associated descriptive question whether increased distance does in fact reduce individuals' sense of helping obligation. One problem with empirically answering this question is that physical proximity is typically confounded with other factors, such as informational directness, shared group membership, or increased efficaciousness. In a series of 5 experiments, we show that distance per se does not influence people's moral intuitions when it is isolated from such confounds. We support our claims with both frequentist and Bayesian statistics. We relate these findings to philosophical arguments concerning the normative relevance of distance and to psychological theories linking distance cues to higher level social cognition. The effects of joint versus separate evaluation paradigms on moral judgments are also discussed. PMID:22686846

Nagel, Jonas; Waldmann, Michael R

2012-06-11

331

Evolution of obligate pollination mutualism in New Caledonian Phyllanthus (Euphorbiaceae)  

Microsoft Academic Search

About half a dozen obligate pollination mutualisms between plants and their seed-consuming pollinators are currently recognized, including fig-fig wasp, yucca-yucca moth, and the recently discoveredGlochidion tree-Epicephala moth mutualisms. A common principle among these interactions is that the pollinators consume only a limited amount of the seed crop within a developing fruit (or fig in the case of fig-fig wasp mutualism),

ATSUSHI KAWAKITA; MAKOTO KATO

2004-01-01

332

Losing the desire: selection can promote obligate asexuality.  

PubMed

Whilst parthenogenesis has evolved multiple times from sexual invertebrate and vertebrate lineages, the drivers and consequences of the sex-asex transition remain mostly uncertain. A model by Stouthamer et al. recently published in BMC Evolutionary Biology shows a pathway by which obligate asexuality could be selected for following endosymbiont infection. See research article http://www.biomedcentral.com/1471-2148/10/229. PMID:20687906

King, Kayla C; Hurst, Gregory D D

2010-07-28

333

An Empirical Analysis of the Pricing of Collateralized Debt Obligations  

Microsoft Academic Search

We use the information in collateralized debt obligations (CDO) prices to study market expectations about how corporate defaults cluster. A three-factor portfolio credit model explains virtually all of the time-series and cross-sectional variation in an extensive data set of CDX index tranche prices. Tranches are priced as if losses of 0.4%, 6%, and 35% of the portfolio occur with expected

FRANCIS A. LONGSTAFF; ARVIND RAJAN

2008-01-01

334

Genetic variability in obligate apomicts of the genus Taraxacum  

Microsoft Academic Search

To test whether obligate apomicts can generate genetic variability, the only valid procedure is to investigate heritable variation\\u000a amongst the offspring of fully agamospermous mothers. Among plants, most reports have been forTaraxacum, and this review concentrates on this genus, although there are many analogous reports for animals. InTaraxacum, within-family variation is commonly found at the levels of ploidy, aneuploidy, recombination

A. John Richards

1996-01-01

335

Automating the Extraction of Rights and Obligations for Regulatory Compliance  

Microsoft Academic Search

Government regulations are increasingly affecting the security, privacy and governance of information systems in the United\\u000a States, Europe and elsewhere. Consequently, companies and software developers are required to ensure that their software systems\\u000a comply with relevant regulations, either through design or re-engineering. We previously proposed a methodology for extracting\\u000a stakeholder requirements, called rights and obligations, from regulations. In this paper,

Nadzeya Kiyavitskaya; Nicola Zeni; Travis D. Breaux; Annie I. Antón; James R. Cordy; Luisa Mich; John Mylopoulos

2008-01-01

336

Clinical findings in obligate carriers of type I Usher syndrome  

SciTech Connect

Seventeen obligate carriers from nine families with autosomal recessive Usher syndrome type I underwent otological, audiological, vestibular, and ophthalmological examination in order to identify possible manifestations of heterozygosity. Linkage studies were performed and six families showed linkage to chromosome region 11q13.5 while 3 families have so far failed to show linkage to the candidate regions. Eight obligate carriers had an abnormal puretone audiogram. Two different audiometric patterns could be distinguished when hearing loss was corrected for age and sex. Four carriers (24%) had significant sensorineural hearing loss (SNHL) which increased at higher frequencies. The other 13 carriers had SNHL of about 10 dB at 0.25 and 0.5 kHz, but less at higher frequencies. Vestibular findings were generally normal. Electrooculography demonstrated a significant lower mean light peak/dark trough ratio in Usher type I carriers compared to normal control individuals. The methods used in this study were found not to be specific enough to clinically identify carriers of Usher type I syndrome. Nevertheless it is remarkable that a number of obligate carriers showed significant audiological and ophthalmological abnormalities. 29 refs., 1 fig., 3 tabs.

Wagenaar, M.; Rahe, B. ter; Aarem, A. van; Huygen, P.; Admiraal, R. [University Hospital Nijmegen (Netherlands)] [and others

1995-11-20

337

A novel obligate cultivation mutualism between damselfish and Polysiphonia algae.  

PubMed

In cultivation mutualisms, farming animals prepare fields for cultivars, enhance their growth and harvest them. For example, in terrestrial ecosystems, plant-herbivore cultivation mutualisms arose between humans and their crops only relatively recently. We discovered an obligate cultivation mutualism between a damselfish and an alga in a coral reef ecosystem. The damselfish, Stegastes nigricans, manages algal farms through territorial defence against the invading grazers and through weeding of unpalatable algae. As a result, the algal farms of S. nigricans are dominated by one species, Polysiphonia sp. We performed an exhaustive survey of algal assemblages inside and outside the territories of five damselfish species around the Ryukyu Islands, Japan, using molecular and morphological characteristics. Polysiphonia sp. 1 grew exclusively inside the farms of S. nigricans, and never elsewhere. Since only Polysiphonia sp. 1 is harvested and consumed by the damselfish as a staple food, this interdependent relationship is an obligate cultivation mutualism. This is the first record of an obligate plant-herbivore cultivation mutualism in a marine ecosystem. Our data also suggest that three other Polysiphonia species are facultatively mutual with, commensal with, or parasitic on other damselfish species. PMID:17148297

Hata, Hiroki; Kato, Makoto

2006-12-22

338

Floral scents repel facultative flower visitors, but attract obligate ones  

PubMed Central

Background and Aims Biological mutualisms rely on communication between partners, but also require protective measures against exploitation. Animal-pollinated flowers need to attract pollinators but also to avoid conflicts with antagonistic consumers. The view of flower visitors as mutualistic and antagonistic agents considers primarily the plants' interest. A classification emphasizing the consumer's point of view, however, may be more useful when considering animal's adaptations to flower visits which may include a tolerance against defensive floral scent compounds. Methods In a meta-analysis covering 18 studies on the responses of animals to floral scents, the animals were assigned to the categories of obligate and facultative flower visitors which considers their dependency on floral resources. Their responses on floral scents were compared. Key Results On average, obligate flower visitors, often corresponding to pollinators, were attracted to floral scent compounds. In contrast, facultative and mainly antagonistic visitors were strongly repelled by floral scents. The findings confirm that floral scents have a dual function both as attractive and defensive cues. Conclusions Whether an animal depends on floral resources determines its response to these signals, suggesting that obligate flower visitors evolved a tolerance against primarily defensive compounds. Therefore, floral scent bouquets in conjunction with nutritious rewards may solve the conflicting tasks of attracting mutualists while repelling antagonists.

Junker, Robert R.; Bluthgen, Nico

2010-01-01

339

A novel obligate cultivation mutualism between damselfish and Polysiphonia algae  

PubMed Central

In cultivation mutualisms, farming animals prepare fields for cultivars, enhance their growth and harvest them. For example, in terrestrial ecosystems, plant–herbivore cultivation mutualisms arose between humans and their crops only relatively recently. We discovered an obligate cultivation mutualism between a damselfish and an alga in a coral reef ecosystem. The damselfish, Stegastes nigricans, manages algal farms through territorial defence against the invading grazers and through weeding of unpalatable algae. As a result, the algal farms of S. nigricans are dominated by one species, Polysiphonia sp. We performed an exhaustive survey of algal assemblages inside and outside the territories of five damselfish species around the Ryukyu Islands, Japan, using molecular and morphological characteristics. Polysiphonia sp. 1 grew exclusively inside the farms of S. nigricans, and never elsewhere. Since only Polysiphonia sp. 1 is harvested and consumed by the damselfish as a staple food, this interdependent relationship is an obligate cultivation mutualism. This is the first record of an obligate plant–herbivore cultivation mutualism in a marine ecosystem. Our data also suggest that three other Polysiphonia species are facultatively mutual with, commensal with, or parasitic on other damselfish species.

Hata, Hiroki; Kato, Makoto

2006-01-01

340

Rapid Identification and Detection of Intracellular Survival Testing of Mycobacterium smegmatis mc 2 155 that Contains eis Gene from Mycobacterium tuberculosis by Flow Cytometry  

Microsoft Academic Search

Mycobacterium tuberculosis is a facultative intracellular pathogen that has evolved the ability to survive and multiply within human macrophages. The\\u000a enhanced intracellular survival (eis) gene (Rv2416c) from M. tuberculosis has been identified as a potential factor that can enhance the intracellular survival of Mycobacterium smegmatis in the macrophage cell line. However, the time requirements for intracellular survival testing of Mycobacterium

Zichun He; Shengjin Li; Xiangdong Zhou

341

The Type IV Secretion System of Sinorhizobium meliloti Strain 1021 Is Required for Conjugation but Not for Intracellular Symbiosis?  

PubMed Central

The type IV secretion system (T4SS) of the plant intracellular symbiont Sinorhizobium meliloti 1021 is required for conjugal transfer of DNA. However, it is not required for host invasion and persistence, unlike the T4SSs of closely related mammalian intracellular pathogens. A comparison of the requirement for a bacterial T4SS in plant versus animal host invasion suggests an important difference in the intracellular niches occupied by these bacteria.

Jones, Kathryn M.; Lloret, Javier; Daniele, Joseph R.; Walker, Graham C.

2007-01-01

342

EXPRESSED SEQUENCE TAG ANALYSIS OF THE SOYBEAN RUST PATHOGEN PHAKOPSORA PACHYRHIZI  

Technology Transfer Automated Retrieval System (TEKTRAN)

Soybean rust, caused by the obligate fungal pathogen Phakopsora pachyrhizi, is a devastating disease in most soybean growing regions throughout the world except North America and Europe. No soybean cultivars have been identified that are resistant to all rust isolates. In order to develop novel m...

343

Efficient Procedure for Purification of Obligate Intracellular Wolbachia pipientis and Representative Amplification of Its Genome by Multiple-Displacement Amplification  

PubMed Central

Bacteria belonging to the genus Wolbachia are obligatorymicroendocytobionts that infect a variety of arthropods and a majority of filarial nematode species, where they induce reproductive alterations or establish a mutualistic symbiosis. Although two whole genome sequences of Wolbachia pipientis, for strain wMel from Drosophila melanogaster and strain wBm from Brugia malayi, have been fully completed and six other genome sequencing projects are ongoing (http://www.genomesonline.org/index.cgi?want=Prokaryotic+Ongoin), genetic analyses of these bacteria are still scarce, mainly due to the inability to cultivate them outside of eukaryotic cells. Usually, a large amount of host tissue (a thousand individuals, or about 10 g) is required in order to purify Wolbachia and extract its DNA, which is often recovered in small amounts and contaminated by host cell DNA, thus hindering genomic studies. In this report, we describe an efficient and reliable procedure to representatively amplify the Wolbachia genome by multiple-displacement amplification from limited infected host tissue (0.2 g or 2 × 107 cells). We obtained sufficient amounts (8 to 10 ?g) of DNA of suitable quality for genomic studies, and we demonstrated that the amplified DNA contained all of the Wolbachia loci targeted. In addition, our data indicated that the genome of strain wRi, an obligatory endosymbiont of Drosophila simulans, shares a similar overall architecture with its relative strain wMel.

Mavingui, Patrick; Tran Van, Van; Labeyrie, Estelle; Rances, Edwige; Vavre, Fabrice; Simonet, Pascal

2005-01-01

344

Coxiella subversion of intracellular host signaling.  

PubMed

Coxiella burnetii is a highly infectious bacterial pathogen that replicates in a specialized vacuole inside eukaryotic cells. Due to a prolonged growth cycle, Coxiella continuously manipulates cellular processes to generate this parasitophorous vacuole (PV) and promote host cell viability. Here, we discuss recent findings that indicate Coxiella modulates several host signaling pathways to influence survival and ensure intracellular replication. The pathogen actively inhibits apoptotic cell death and activates the pro-survival kinases Akt and Erk1/2 to promote host viability. Coxiella's anti-apoptotic activity also involves the interface between autophagy and apoptosis, which is regulated by the interaction of autophagy-related Beclin-1 and anti-apoptotic Bcl-2. Additionally, Coxiella requires host kinase activity for PV biogenesis and maintenance. Thus, signaling modulation by Coxiella is critical for multiple aspects of host cell parasitism. Collectively, recent signaling studies have enhanced our understanding of the unique Coxiella-host cell interaction. Identification of bacterial factors that regulate signaling events will further our ability to model this intriguing infectious process. PMID:22711630

Hussain, S Kauser; Voth, Daniel E

2012-01-01

345

Studies of polyamine metabolism in obligately alkalophilic Bacillus alcalophilus that grow at pH 11  

SciTech Connect

Bacillus alcalophilus, an obligately alkalophilic bacterium, grow at pH 11 with an intracellular pH greater than 9.5. Polyamines are positively charged at physiological pH, but less than 50% of polyamines will be charged at pH 9.5 and above. In view of the importance of polycationic nature of polyamines in their physiological functions, it is of interest to study the polyamine metabolism in B. alcalophilus, an unusual organism that grow at very high pH. Spermidine is the major polyamine in this organism, accounts for more than 90% of total polyamine. The level of spermidine fluctuates between 10 to 30 nmol per mg protein during growth. In contrast, putrescine and spermine levels stay constant during entire period of growth. No ornithine decarboxylase (DC) activity can be detected in B. alcalophilus under all conditions examined. When (/sup 3/H)arginine was added to the bacterial culture, the distribution of radioactivity in polyamine pool was 3% for putrescine, 94% for spermidine, and 3% for spermine, suggesting the presence of arginine pathway for polyamine biosynthesis. B. alcalophilus appears to possess a polyamine transport system that is Na/sup +/-dependent. Putrescine uptake in B. alcalophilus is sensitive to the inhibition of gramicidine S (10 ..mu..M) and valinomycin (2..mu..M).

Cheng, S.; Chen, K.Y.

1987-05-01

346

For better or worse: genomic consequences of intracellular mutualism and parasitism.  

PubMed

Bacteria that replicate within eukaryotic host cells include a variety of pathogenic and mutualistic species. Early genome data for these intracellular associates suggested they experience continual gene loss, little if any gene acquisition, and minimal recombination in small, isolated populations. This view of reductive evolution is itself evolving as new genome sequences clarify mechanisms and outcomes of diverse intracellular associations. Recently sequenced genomes have confirmed a trajectory of gene loss and exceptional genome stability in long-term, nutritional mutualists and certain pathogens. However, new genome data for the Rickettsiales and Chlamydiales indicate more repeated DNA, a greater abundance of mobile DNA elements, and more labile genome dynamics than previously suspected for ancient intracellular lineages. Surprising discoveries of conjugation machinery in the parasite Rickettsia felis and the amoebae symbiont Parachlamydia sp. suggest that DNA transfer might play key roles in some intracellular taxa. PMID:16230003

Wernegreen, Jennifer J

2005-10-17

347

Autophagic control of Listeria through intracellular innate immune recognition in drosophila  

PubMed Central

Autophagy, an evolutionally conserved homeostatic process for catabolizing cytoplasmic components, has been implicated in the elimination of intracellular pathogens during mammalian innate immune responses. However, the mechanisms underlying cytoplasmic infection-induced autophagy, and the role of autophagy in host survival against intracellular pathogens are unknown. Here we report that in drosophila, recognition of diaminopimelic acid-type peptidoglycans by the pattern recognition receptor PGRP-LE is crucial for the induction of autophagy, and that autophagy prevents the intracellular growth of Listeria monocytogenes and promotes host survival against this infection. Autophagy induction occurs independently of the Toll and IMD innate signaling pathways. These findings define a clear pathway leading from the intracellular pattern recognition receptors to the induction of autophagy to host defense.

Yano, Tamaki; Mita, Shizuka; Ohmori, Hiroko; Oshima, Yoshiteru; Fujimoto, Yukari; Ueda, Ryu; Takada, Haruhiko; Goldman, William E.; Fukase, Koichi; Silverman, Neal; Yoshimori, Tamotsu; Kurata, Shoichiro

2008-01-01

348

INTRACELLULAR SIGNALING AND DEVELOPMENTAL NEUROTOXICITY.  

EPA Science Inventory

A book chapter in ?Molecular Toxicology: Transcriptional Targets? reviewed the role of intracellular signaling in the developmental neurotoxicity of environmental chemicals. This chapter covered a number of aspects including the development of the nervous system, role of intrace...

349

Polyamine metabolism in an obligately alkalophilic Bacillus alcalophilus that grows at pH 11.0.  

PubMed

Bacillus alcalophilus, an obligately alkalophilic bacterium that grows at pH 11.0, has an intracellular pH of 9.5 or less. Unlike all other living organisms, polyamines (putrescine, spermidine and spermine) in B. alcalophilus, if present, will be largely unprotonated. HPLC analysis indicated that spermidine is the major polyamine in B. alcalophilus, accounting for more than 90% of total polyamines, and the level of spermidine varies during growth. Ornithine decarboxylase activity was not detectable in B. alcalophilus under all conditions examined. When [3H]arginine was added to the culture medium, the radioactivity can be recovered from polyamine pool; the distribution is 3% for putrescine, 94% for spermidine, and 3% for spermine, suggesting the presence of arginine pathway for polyamine biosynthesis. The polyamine transport system in B. alcalphilus appears to be Na+-dependent and is highly sensitive to the inhibition of gramicidin S and valinomycin. PMID:2447890

Chen, K Y; Cheng, S

1988-01-15

350

Intracellular Adaptation of Brucella abortus  

PubMed Central

Macrophages were infected with virulent B. abortus strain 2308 or attenuated strain 19. Intracellular bacteria were recovered at different times after infection and their proteomes compared. The virulent strain initially reduced most biosynthesis and altered its respiration, adaptations reversed later in infection. The attenuated strain was unable to match the magnitude of the virulent strain’s adjustments. The results provide insight into mechanisms utilized by Brucella to establish intracellular infections.

Lamontagne, Julie; Forest, Anik; Marazzo, Elena; Denis, Francois; Butler, Heather; Michaud, Jean-Francois; Boucher, Lyne; Pedro, Ida; Villeneuve, Annie; Sitnikov, Dmitri; Trudel, Karine; Nassif, Najib; Boudjelti, Djamila; Tomaki, Fadi; Chaves-Olarte, Esteban; Guzman-Verri, Caterina; Brunet, Sylvain; Cote-Martin, Alexandra; Hunter, Joanna; Moreno, Edgardo; Paramithiotis, Eustache

2009-01-01

351

The Obligate Mutualist Wigglesworthia glossinidia Influences Reproduction, Digestion, and Immunity Processes of Its Host, the Tsetse Fly?  

PubMed Central

Tsetse flies (Diptera: Glossinidae) are vectors for trypanosome parasites, the agents of the deadly sleeping sickness disease in Africa. Tsetse also harbor two maternally transmitted enteric mutualist endosymbionts: the primary intracellular obligate Wigglesworthia glossinidia and the secondary commensal Sodalis glossinidius. Both endosymbionts are transmitted to the intrauterine progeny through the milk gland secretions of the viviparous female. We administered various antibiotics either continuously by per os supplementation of the host blood meal diet or discretely by hemocoelic injections into fertile females in an effort to selectively eliminate the symbionts to study their individual functions. A symbiont-specific PCR amplification assay and fluorescence in situ hybridization analysis were used to evaluate symbiont infection outcomes. Tetracycline and rifampin treatments eliminated all tsetse symbionts but reduced the fecundity of the treated females. Ampicillin treatments did not affect the intracellular Wigglesworthia localized in the bacteriome organ and retained female fecundity. The resulting progeny of ampicillin-treated females, however, lacked Wigglesworthia but still harbored the commensal Sodalis. Our results confirm the presence of two physiologically distinct Wigglesworthia populations: the bacteriome-localized Wigglesworthia involved with nutritional symbiosis and free-living Wigglesworthia in the milk gland organ responsible for maternal transmission to the progeny. We evaluated the reproductive fitness, longevity, digestion, and vectorial competence of flies that were devoid of Wigglesworthia. The absence of Wigglesworthia completely abolished the fertility of females but not that of males. Both the male and female Wigglesworthia-free adult progeny displayed longevity costs and were significantly compromised in their blood meal digestion ability. Finally, while the vectorial competence of the young newly hatched adults without Wigglesworthia was comparable to that of their wild-type counterparts, older flies displayed higher susceptibility to trypanosome infections, indicating a role for the mutualistic symbiosis in host immunobiology. The ability to rear adult tsetse that lack the obligate Wigglesworthia endosymbionts will now enable functional investigations into this ancient symbiosis.

Pais, Roshan; Lohs, Claudia; Wu, Yineng; Wang, Jingwen; Aksoy, Serap

2008-01-01

352

Depression, SSRIs, and the supposed obligation to suffer mentally.  

PubMed

Within both popular and academic literature, concerns have been expressed about the implications of antidepressant use on character development. In this paper, I identify specific versions of these worries and argue that they are misguided. I begin by arguing that the obligation to suffer if it will bring about a noble character is imagined. Legitimate concerns about character enhancement remain, but they do not count against most antidepressant use. Thus there is no moral prohibition against antidepressant use. Furthermore, some of the calls for caution about antidepressant use, such as those expressed by the President's Council on Bioethics, are overstated. PMID:17091563

Olsen, J Mark

2006-09-01

353

Role of the Clp System in Stress Tolerance, Biofilm Formation, and Intracellular Invasion in Porphyromonas gingivalis  

Microsoft Academic Search

Clp proteases and chaperones are ubiquitous among prokaryotes and eukaryotes, and in many pathogenic bacteria the Clp stress response system is also involved in regulation of virulence properties. In this study, the roles of ClpB, ClpC, and ClpXP in stress resistance, homotypic and heterotypic biofilm formation, and intracellular invasion in the oral opportunistic pathogen Porphyromonas gingivalis were investigated. Absence of

Cindy A. Capestany; Gena D. Tribble; Kazuhiko Maeda; Donald R Demuth; Richard J. Lamont

2008-01-01

354

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

355

Comparative analysis of Chlamydia psittaci genomes reveals the recent emergence of a pathogenic lineage with a broad host range.  

PubMed

Chlamydia psittaci is an obligate intracellular bacterium. Interest in Chlamydia stems from its high degree of virulence as an intestinal and pulmonary pathogen across a broad range of animals, including humans. C. psittaci human pulmonary infections, referred to as psittacosis, can be life-threatening, which is why the organism was developed as a bioweapon in the 20th century and is listed as a CDC biothreat agent. One remarkable recent result from comparative genomics is the finding of frequent homologous recombination across the genome of the sexually transmitted and trachoma pathogen Chlamydia trachomatis. We sought to determine if similar evolutionary dynamics occurred in C. psittaci. We analyzed 20 C. psittaci genomes from diverse strains representing the nine known serotypes of the organism as well as infections in a range of birds and mammals, including humans. Genome annotation revealed a core genome in all strains of 911 genes. Our analyses showed that C. psittaci has a history of frequently switching hosts and undergoing recombination more often than C. trachomatis. Evolutionary history reconstructions showed genome-wide homologous recombination and evidence of whole-plasmid exchange. Tracking the origins of recombinant segments revealed that some strains have imported DNA from as-yet-unsampled or -unsequenced C. psittaci lineages or other Chlamydiaceae species. Three ancestral populations of C. psittaci were predicted, explaining the current population structure. Molecular clock analysis found that certain strains are part of a clonal epidemic expansion likely introduced into North America by South American bird traders, suggesting that psittacosis is a recently emerged disease originating in New World parrots. PMID:23532978

Read, Timothy D; Joseph, Sandeep J; Didelot, Xavier; Liang, Brooke; Patel, Lisa; Dean, Deborah

2013-03-26

356

Functional Transfer of Salmonella Pathogenicity Island 2 to Salmonella bongori and Escherichia coli  

Microsoft Academic Search

The type III secretion system (T3SS) encoded by the Salmonella pathogenicity island 2 (SPI2) has a central role in systemic infections by Salmonella enterica and for the intracellular phenotype. Intracellular S. enterica uses the SPI2-encoded T3SS to translocate a set of effector proteins into the host cell, which modify host cell functions, enabling intracellular survival and replication of the bacteria.

Imke Hansen-Wester; Dipshikha Chakravortty; Michael Hensel

2004-01-01

357

Pathogen life-history trade-offs revealed in allopatry.  

PubMed

Trade-offs in life-history traits is a central tenet in evolutionary biology, yet their ubiquity and relevance to realized fitness in natural populations remains questioned. Trade-offs in pathogens are of particular interest because they may constrain the evolution and epidemiology of diseases. Here, we studied life-history traits determining transmission in the obligate fungal pathogen, Podosphaera plantaginis, infecting Plantago lanceolata. We find that although traits are positively associated on sympatric host genotypes, on allopatric host genotypes relationships between infectivity and subsequent transmission traits change shape, becoming even negative. The epidemiological prediction of this change in life-history relationships in allopatry is lower disease prevalence in newly established pathogen populations. An analysis of the natural pathogen metapopulation confirms that disease prevalence is lower in newly established pathogen populations and they are more prone to go extinct during winter than older pathogen populations. Hence, life-history trade-offs mediated by pathogen local adaptation may influence epidemiological dynamics at both population and metapopulation levels. PMID:24152013

Susi, Hanna; Laine, Anna-Liisa

2013-07-11

358

Intracellular Bacteria Encode Inhibitory SNARE-Like Proteins  

PubMed Central

Pathogens use diverse molecular machines to penetrate host cells and manipulate intracellular vesicular trafficking. Viruses employ glycoproteins, functionally and structurally similar to the SNARE proteins, to induce eukaryotic membrane fusion. Intracellular pathogens, on the other hand, need to block fusion of their infectious phagosomes with various endocytic compartments to escape from the degradative pathway. The molecular details concerning the mechanisms underlying this process are lacking. Using both an in vitro liposome fusion assay and a cellular assay, we showed that SNARE-like bacterial proteins block membrane fusion in eukaryotic cells by directly inhibiting SNARE-mediated membrane fusion. More specifically, we showed that IncA and IcmG/DotF, two SNARE-like proteins respectively expressed by Chlamydia and Legionella, inhibit the endocytic SNARE machinery. Furthermore, we identified that the SNARE-like motif present in these bacterial proteins encodes the inhibitory function. This finding suggests that SNARE-like motifs are capable of specifically manipulating membrane fusion in a wide variety of biological environments. Ultimately, this motif may have been selected during evolution because it is an efficient structural motif for modifying eukaryotic membrane fusion and thus contribute to pathogen survival.

Paumet, Fabienne; Wesolowski, Jordan; Garcia-Diaz, Alejandro; Delevoye, Cedric; Aulner, Nathalie; Shuman, Howard A.; Subtil, Agathe; Rothman, James E.

2009-01-01

359

Facultative and obligate slavery in formicine ants: frequency of slavery, and proportion and size of slaves  

Microsoft Academic Search

Slave-making ants raid nests of other ant species, capture the developing offspring and rear them to slave workers. Here we compare slave-making of three formicine slave-making ants: the facultativeFormica subnuda, the obligatePolyergus breviceps, andF. subintegrawhich previously has been considered facultative but appears to be an obligate slave-making ant. IfF. subintegrais an obligate slavemaker, slave-making ofF. subintegrashould differ from that ofF.

RIITTA SAVOLAINEN; RICHARD J. DESLIPPE

1996-01-01

360

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

2013-01-31

361

Mycobacterium intracellulare Reference Precipitation System  

Microsoft Academic Search

Characteristics of a Mycobacterium intracellulare reference precipitation system for immunodiffusion and immunoelectrophoresis analyses are presented. The system was produced by the initiative of the International Working Group on Mycobacterial Taxonomy, and the purpose is to permit comparisons of precipitinogenic patterns of mycobacteria obtained in different laboratories. The reference material, consisting of an antigen preparation and a corresponding antiserum, is available

MALIN RIDELL; SOTIROS D. CHAPARAS; PHILIPPE DESMETTRE; ARNE LIND; ORJAN OUCHTERLONY; MARIE-FRANCOISE THOREL; LAWRENCE G. WAYNE

362

Mechanisms of intracellular protein transport  

Microsoft Academic Search

Recent advances have uncovered the general protein apparatus used by all eukaryotes for intracellular transport, including secretion and endocytosis, and for triggered exocytosis of hormones and neurotransmitters. Membranes are shaped into vesicles by cytoplasmic coats which then dissociate upon GTP hydrolysis. Both vesicles and their acceptor membranes carry targeting proteins which interact specifically to initiate docking. A general apparatus then

James E. Rothman

1994-01-01

363

Emerging Role of Lipid Droplets in Host/Pathogen Interactions*  

PubMed Central

Lipid droplets (LDs) are highly dynamic cell organelles involved in energy homeostasis and membrane trafficking. Here, we review how select pathogens interact with LDs. Several RNA viruses use host LDs at different steps of their life cycle. Some intracellular bacteria and parasites usurp host LDs or encode their own lipid biosynthesis machinery, thus allowing production of LDs independently of their host. Although many mechanistic details of host/pathogen LD interactions are unknown, a picture emerges in which the unique cellular architecture and energy stored in LDs are important in the replication of diverse pathogens.

Herker, Eva; Ott, Melanie

2012-01-01

364

Pathogens and polymers: Microbe-host interactions illuminate the cytoskeleton  

PubMed Central

Intracellular pathogens subvert the host cell cytoskeleton to promote their own survival, replication, and dissemination. Study of these microbes has led to many discoveries about host cell biology, including the identification of cytoskeletal proteins, regulatory pathways, and mechanisms of cytoskeletal function. Actin is a common target of bacterial pathogens, but recent work also highlights the use of microtubules, cytoskeletal motors, intermediate filaments, and septins. The study of pathogen interactions with the cytoskeleton has illuminated key cellular processes such as phagocytosis, macropinocytosis, membrane trafficking, motility, autophagy, and signal transduction.

Haglund, Cat M.

2011-01-01

365

Brucella microti: the genome sequence of an emerging pathogen  

Microsoft Academic Search

BACKGROUND: Using a combination of pyrosequencing and conventional Sanger sequencing, the complete genome sequence of the recently described novel Brucella species, Brucella microti, was determined. B. microti is a member of the genus Brucella within the Alphaproteobacteria, which consists of medically important highly pathogenic facultative intracellular bacteria. In contrast to all other Brucella species, B. microti is a fast growing

Stéphane Audic; Magali Lescot; Jean-Michel Claverie; Holger C Scholz

2009-01-01

366

Digest this! A role for autophagy in controlling pathogens.  

PubMed

Autophagy provides a mechanism for cells to conserve nutrients, but was recently associated with immunity to intracellular pathogens. Here, Zhao et al. (2008) present direct in vivo evidence that autophagy is linked to macrophage control of Toxoplasma gondii and Listeria monocytogenes and highlights that this process intersects with cytokine-mediated antimicrobial responses. PMID:18996340

Whitmarsh, Ryan J; Hunter, Christopher A

2008-11-13

367

Molecular Characterization and Evolution of Arthropod-Pathogenic Rickettsiella Bacteria  

Microsoft Academic Search

Members of the genus Rickettsiella are intracellular bacterial pathogens of arthropods (13). They are found in a wide range of hosts including insects, crustaceans, and arachnids, and they exhibit a worldwide geographic distribution (11-13). In natu- rally infected hosts, the Rickettsiella-mediated disease affects both larvae and adults and develops very slowly (13). In its crustacean hosts, \\

Richard Cordaux; Melanie Paces-Fessy; Maryline Raimond; Alice Michel-Salzat; Martin Zimmer; Didier Bouchon

2007-01-01

368

Obligate versus rich patch opportunism: evolution and endocrine mechanisms.  

PubMed

Opportunistic breeding has been hypothesized to evolve in response to rare or unpredictable resource pulses. In this traditional view of opportunism, individuals invest heavily in reproduction whenever conditions are permissive for breeding, perhaps at the expense of investment in survival. We term this strategy 'obligate opportunism' (OBO). We also present an additional strategy that could account for the evolution of opportunism. High mobility may allow individuals to move between rich patches of resources that are spatially or temporally unpredictable, reducing exposure to food scarcity and taking advantage of breeding opportunities. This strategy, which we term 'rich patch exploiter' (RPE), predicts that investment in survival-enhancing processes may occur at the expense of reproduction despite high resource availability. We review examples to determine which opportunists better match predictions from the OBO strategy or the RPE strategy and then review endocrine profiles in the context of the two strategies. PMID:23612018

Cornelius, J M; Watts, H E; Dingle, H; Hahn, T P

2013-04-20

369

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

370

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

Microsoft Academic Search

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

Kyle H. Rohde; Diogo F. T. Veiga; Shannon Caldwell; Gábor Balázsi; David G. Russell

2012-01-01

371

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

372

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

373

Intracellular localization of Crimean-Congo Hemorrhagic Fever (CCHF) virus glycoproteins  

Microsoft Academic Search

BACKGROUND: Crimean-Congo Hemorrhagic Fever virus (CCHFV), a member of the genus Nairovirus, family Bunyaviridae, is a tick-borne pathogen causing severe disease in humans. To better understand the CCHFV life cycle and explore potential intervention strategies, we studied the biosynthesis and intracellular targeting of the glycoproteins, which are encoded by the M genome segment. RESULTS: Following determination of the complete genome

Sebastian Haferkamp; Lisa Fernando; Tino F Schwarz; Heinz Feldmann; Ramon Flick

2005-01-01

374

Identification of Linked Legionella pneumophila Genes Essential for Intracellular Growth and Evasion of the Endocytic Pathway  

Microsoft Academic Search

Legionella pneumophila replicates within a specialized phagosome in cultured cells, a function necessary for its pathogenicity. The replicative phagosome lacks membrane marker proteins, such as the glycoprotein LAMP-1, that are indicators of the normal endocytic pathway. We describe the isolation of several Legionella genes essential for intracellular growth and evasion of the endocytic pathway, using a genetic and cell biological

HELENE L. ANDREWS; JOSEPH P. VOGEL; RALPH R. ISBERG

375

Innate and adaptive immune responses to an intracellular bacterium, Francisella tularensis live vaccine strain  

Microsoft Academic Search

The immune response to intracellular bacterium, Francisella tularensis, which causes tularemia and is proposed to be a potential bioterrorism pathogen, has been studied in mice using the attenuated live vaccine strain (LVS). Here we review this infection model, which provides a convenient means of studying protective immune mechanisms not only for Francisella, but also for the large and important class

Karen L. Elkins

2003-01-01

376

Inhibitory effect of the natural product betulin and its derivatives against the intracellular bacterium Chlamydia pneumoniae  

Microsoft Academic Search

Chlamydia pneumoniae is a universal pathogen that has been indicated to play a part in the development of asthma, atherosclerosis and lung cancer. The complete eradication of this intracellular bacterium is in practice impossible with the antibiotics that are currently in use and studies on new antichlamydial compounds is challenging because Chlamydia research lacks the tools required for the genetic

Olli Salin; Sami Alakurtti; Leena Pohjala; Antti Siiskonen; Viola Maass; Matthias Maass; Jari Yli-Kauhaluoma; Pia Vuorela

2010-01-01

377

Pathogen Phytosensing: Plants to Report Plant Pathogens  

PubMed Central

Real-time systems that provide evidence of pathogen contamination in crops can be an important new line of early defense in agricultural centers. Plants possess defense mechanisms to protect against pathogen attack. Inducible plant defense is controlled by signal transduction pathways, inducible promoters and cis-regulatory elements corresponding to key genes involved in defense, and pathogen-specific responses. Identified inducible promoters and cis-acting elements could be utilized in plant sentinels, or ‘phytosensors’, by fusing these to reporter genes to produce plants with altered phenotypes in response to the presence of pathogens. Here, we have employed cis-acting elements from promoter regions of pathogen inducible genes as well as those responsive to the plant defense signal molecules salicylic acid, jasmonic acid, and ethylene. Synthetic promoters were constructed by combining various regulatory elements supplemented with the enhancer elements from the Cauliflower mosaic virus (CaMV) 35S promoter to increase basal level of the GUS expression. The inducibility of each synthetic promoter was first assessed in transient expression assays using Arabidopsis thaliana protoplasts and then examined for efficacy in stably transgenic Arabidopsis and tobacco plants. Histochemical and fluorometric GUS expression analyses showed that both transgenic Arabidopsis and tobacco plants responded to elicitor and phytohormone treatments with increased GUS expression when compared to untreated plants. Pathogen-inducible phytosensor studies were initiated by analyzing the sensitivity of the synthetic promoters against virus infection. Transgenic tobacco plants infected with Alfalfa mosaic virus showed an increase in GUS expression when compared to mock-inoculated control plants, whereas Tobacco mosaic virus infection caused no changes in GUS expression. Further research, using these transgenic plants against a range of different pathogens with the regulation of detectable reporter gene could provide biological evidence to define the functional differences between pathogens, and provide new technology and applications for transgenic plants as phytosensors.

Mazarei, Mitra; Teplova, Irina; Hajimorad, M. Reza; Stewart, C. Neal

2008-01-01

378

Intracellular staphylococcus aureus: Live-in and let die  

PubMed Central

Staphylococcus aureus uses a plethora of virulence factors to accommodate a diversity of niches in its human host. Aside from the classical manifestations of S. aureus-induced diseases, the pathogen also invades and survives within mammalian host cells.The survival strategies of the pathogen are as diverse as strains or host cell types used. S. aureus is able to replicate in the phagosome or freely in the cytoplasm of its host cells. It escapes the phagosome of professional and non-professional phagocytes, subverts autophagy, induces cell death mechanisms such as apoptosis and pyronecrosis, and even can induce anti-apoptotic programs in phagocytes. The focus of this review is to present a guide to recent research outlining the variety of intracellular fates of S. aureus.

Fraunholz, Martin; Sinha, Bhanu

2012-01-01

379

Opposing Biological Functions of Tryptophan Catabolizing Enzymes During Intracellular Infection  

PubMed Central

Recent studies have underscored physiological and pathophysiological roles for the tryptophan-degrading enzyme indolamine 2,3-dioxygenase (IDO) in immune counterregulation. However, IDO was first recognized as an antimicrobial effector, restricting tryptophan availability to Toxoplasma gondii and other pathogens in vitro. The biological relevance of these findings came under question when infectious phenotypes were not forthcoming in IDO-deficient mice. The recent discovery of an IDO homolog, IDO-2, suggested that the issue deserved reexamination. IDO inhibition during murine toxoplasmosis led to 100% mortality, with increased parasite burdens and no evident effects on the immune response. Similar studies revealed a counterregulatory role for IDO during leishmaniasis (restraining effector immune responses and parasite clearance), and no evident role for IDO in herpes simplex virus type 1 (HSV-1) infection. Thus, IDO plays biologically important roles in the host response to diverse intracellular infections, but the dominant nature of this role—antimicrobial or immunoregulatory—is pathogen-specific.

Divanovic, Senad; Sawtell, Nancy M.; Trompette, Aurelien; Warning, Jamie I.; Dias, Alexandra; Cooper, Andrea M.; Yap, George S.; Arditi, Moshe; Shimada, Kenichi; DuHadaway, James B.; Prendergast, George C.; Basaraba, Randall J.; Mellor, Andrew L.; Munn, David H.; Aliberti, Julio

2012-01-01

380

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

381

Intracellularly induced cyclophilins play an important role in stress adaptation and virulence of Brucella abortus.  

PubMed

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. PMID:23230297

Roset, Mara S; García Fernández, Lucía; DelVecchio, Vito G; Briones, Gabriel

2012-12-10

382

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

383

Attitudes Toward Family Obligation Among Adolescents in Contemporary Urban and Rural China  

ERIC Educational Resources Information Center

|A sense of obligation to support, assist, and respect the family was examined among approximately 700 urban and rural 10th- (M=16.6 years) and 12th- (M=18.9 years) grade students in the People's Republic of China. Urban male adolescents reported a weaker sense of family obligation than did rural male adolescents and both urban and rural female…

Fuligni, Andrew J.; Zhang, Wenxin

2004-01-01

384

47 CFR 51.603 - Resale obligation of all local exchange carriers.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Resale obligation of all local exchange carriers. 51.603 Section... § 51.603 Resale obligation of all local exchange carriers. (a) A LEC shall...terms and conditions that are reasonable and non-discriminatory. (b) A LEC...

2011-10-01

385

Allocating and Funding Universal Service Obligations in a Competitive Network Market  

Microsoft Academic Search

We examine, in a network market open to competition, various mechanisms of allocating and funding ''universal service obligations'' among agents (rival operators and consumers). The obligations we consider are geographic ubiquity and non discrimination. We analyze, from both the efficiency and equity point of views, the respective advantages of a ''restricted-entry'' system (where the entrant is not allowed to serve

Philippe Choné; Laurent Flochel; Anne Perrot

1999-01-01

386

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

Federal Register 2010, 2011, 2012, 2013

...Roaming Obligations of Commercial Mobile Radio Service Providers and Other Providers...Commission, at (202) 418-0214 or via the Internet at Judith-B.Herman@fcc.gov. SUPPLEMENTARY...Roaming Obligations of Commercial Mobile Radio Service Providers and Other...

2011-10-13

387

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

388

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

389

Pebbles in a Pond: Learner, Teacher, and Policy Perspectives on Mutual Obligation.  

ERIC Educational Resources Information Center

|This book contains nine chapters, by various authors, containing research and policy perspectives on issues of mutual obligation between teachers and students, especially in Australia. The following are included: (1) "Researching Literacy, Language, and Numeracy and Mutual Obligation: An Introduction to Some Issues" (Sheilagh Kelly and Liz…

Adult Literacy and Numeracy Australian Research Consortium, Melbourne (Victoria). Victorian Centre.

390

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

391

28 CFR 811.4 - Determination of the obligation to register and the length of registration.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Determination of the obligation...DISTRICT OF COLUMBIA SEX OFFENDER REGISTRATION § 811.4 Determination of the obligation...that a person is a sex offender and that...CSOSA makes those determinations. CSOSA also...

2009-07-01

392

28 CFR 811.4 - Determination of the obligation to register and the length of registration.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Determination of the obligation...DISTRICT OF COLUMBIA SEX OFFENDER REGISTRATION § 811.4 Determination of the obligation...that a person is a sex offender and that...CSOSA makes those determinations. CSOSA also...

2013-07-01

393

28 CFR 811.4 - Determination of the obligation to register and the length of registration.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Determination of the obligation...DISTRICT OF COLUMBIA SEX OFFENDER REGISTRATION § 811.4 Determination of the obligation...that a person is a sex offender and that...CSOSA makes those determinations. CSOSA also...

2010-07-01

394

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

Code of Federal Regulations, 2013 CFR

...for obligations transmitted at death, but contains no requirement...transmitted, the date of his death, and the internal revenue district...the election is made under the penalties of perjury. (2) Filing...obligation was transmitted at A's death to B who filed a...

2013-04-01

395

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

396

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

Code of Federal Regulations, 2011 CFR

NEPA and NHPA obligations are typically enforced by interested parties who may file lawsuits against Federal agencies alleging that the agencies have not complied with their legal obligations under NEPA and NHPA. These lawsuits may only be filed in Federal court under the provisions of the APA, 5...

2011-10-01

397

The obligately lichenicolous genus Lichenoconium represents a novel lineage in the Dothideomycetes  

Microsoft Academic Search

Lichenicolous fungi are obligately lichen-associated organisms that have evolved many times throughout the Ascomycota and Basidiomycota. Approximately 20% of lichenicolous ascomycetes are recognized only from asexual (anamorphic) characteristics, so the phylogenetic position of many groups has never been resolved. Here we present the first molecular phylogeny of Lichenoconium, a genus of strictly asexual, obligately lichenicolous species with broad geographic distributions

James D. Lawrey; Paul Diederich; Matthew P. Nelsen; Masoumeh Sikaroodi; Patrick M. Gillevet; A. Maarten Brand; Pieter van den Boom

2011-01-01

398

26 CFR 1.1037-1 - Certain exchanges of United States obligations.  

Code of Federal Regulations, 2010 CFR

...States of obligations of the United States issued under the Second Liberty Bond Act (31...exchange obligations of the United States issued under the Second Liberty Bond Act for other...registered in the name of C, who is B's son. Each $5,000...

2010-04-01

399

26 CFR 1.1037-1 - Certain exchanges of United States obligations.  

Code of Federal Regulations, 2010 CFR

...States of obligations of the United States issued under the Second Liberty Bond Act (31...exchange obligations of the United States issued under the Second Liberty Bond Act for other...registered in the name of C, who is B's son. Each $5,000...

2009-04-01

400

77 FR 50544 - Notice of Release From Federal Surplus Property and Grant Assurance Obligations at Porterville...  

Federal Register 2010, 2011, 2012, 2013

...Administration Notice of Release From Federal Surplus Property and Grant Assurance Obligations...California from all conditions contained in the Surplus Property Deed and Grant Assurances because...imposed on a federally obligated airport by surplus property conveyance deeds or grant...

2012-08-21

401

76 FR 49477 - Termination of Federal Home Loan Bank Resolution Funding Corporation Obligation  

Federal Register 2010, 2011, 2012, 2013

...satisfied their statutory obligation to contribute a percentage of their annual net earnings...enacted, the law required the Banks to contribute $300 million annually toward the RefCorp...Banks would satisfy their obligation to contribute to the RefCorp debt service...

2011-08-10

402

Goods with embedded software: Obligations under Section 12 of the Sale of Goods Act 1979  

Microsoft Academic Search

The Sale of Goods Act 1979, section 12 imposes obligations on sellers. Sellers must have the right to sell the goods, and they impliedly warranty that the buyer will enjoy quiet possession. Actions by intellectual property rights holders can lead to liability for sellers for breach of the section 12 obligations. Recent technological change has brought about the development of

Sean Thomas

2012-01-01

403

Energy Saving Obligations and White Certificates: Ideas and Considerations for the Transport Sector  

Microsoft Academic Search

A lot of policy interest and analysis has been focused on energy saving obligations on energy distributors or suppliers (mainly electricity and gas) coupled with trading of certified energy savings via tradable white certificates. While in the European Union the Energy Services Directive (2006\\/32\\/EC) also applies to transport fuels and some of the existing energy saving obligations allow certification of

Paolo Bertoldi; Silvia Rezessy; Jillian Anable; Patrick Jochem; Vlasis Oikonomou

2011-01-01

404

26 CFR 1.453-11 - Installment obligations received from a liquidating corporation.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Installment obligations received from a liquidating...Gross Income Included § 1.453-11 Installment obligations received from a liquidating...section 453(h)(1)(C) (relating to installment sales of depreciable property...

2010-04-01

405

26 CFR 1.453-11 - Installment obligations received from a liquidating corporation.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Installment obligations received from a liquidating...Gross Income Included § 1.453-11 Installment obligations received from a liquidating...section 453(h)(1)(C) (relating to installment sales of depreciable property...

2009-04-01

406

11 CFR 104.11 - Continuous reporting of debts and obligations.  

Code of Federal Regulations, 2010 CFR

...date on which the debt or obligation is incurred, except that any obligation incurred for rent, salary or other regularly reoccurring administrative expense shall not be reported as a debt before the payment due date. See 11 CFR 116.6. If the...

2009-01-01

407

11 CFR 104.11 - Continuous reporting of debts and obligations.  

Code of Federal Regulations, 2010 CFR

...date on which the debt or obligation is incurred, except that any obligation incurred for rent, salary or other regularly reoccurring administrative expense shall not be reported as a debt before the payment due date. See 11 CFR 116.6. If the...

2010-01-01

408

Lipid Body–Phagosome Interaction in Macrophages during Infectious Diseases: Host Defense or Pathogen Survival Strategy?  

Microsoft Academic Search

Phagocytosis of invading microorganisms by specialized cells such as macrophages and neutrophils is a key component of the innate immune response. These cells capture and engulf pathogens and subsequently destroy them in intracellular vacuoles—the phagosomes. Pathogen phagocytosis and progression and maturation of pathogen-containing phagosomes, a crucial event to acquire microbicidal features, occurs in parallel with accentuated formation of lipid-rich organelles,

Rossana C. N. Melo; Ann M. Dvorak

2012-01-01

409

Intracellular magnesium and magnesium buffering  

Microsoft Academic Search

The development of new techniques for measuring intracellular free Mg2+ during the 1980s has provided investigators with the tools needed to produce new insights into the regulation of cellular magnesium. Within the limits of this technology, it appears that all mammalian cells maintain free cytosolic Mg2+ levels within the fairly narrow range of 0.25–1 mM. While transport mechanisms and sequestration within

Robert D. Grubbs

2002-01-01

410

Mechanisms of intracellular protein transport  

NASA Astrophysics Data System (ADS)

Recent advances have uncovered the general protein apparatus used by all eukaryotes for intracellular transport, including secretion and endocytosis, and for triggered exocytosis of hormones and neurotransmitters. Membranes are shaped into vesicles by cytoplasmic coats which then dissociate upon GTP hydrolysis. Both vesicles and their acceptor membranes carry targeting proteins which interact specifically to initiate docking. A general apparatus then assembles at the docking site and fuses the vesicle with its target.

Rothman, James E.

1994-11-01

411

Intracellular localization of Borrelia burgdorferi within human endothelial cells.  

PubMed Central

The later stages of infection by the Lyme disease pathogen, Borrelia burgdorferi, are characterized by the persistence of the organism in individuals possessing a strong anti-Borrelia immune response. This suggests that the organism is sequestered in a tissue protected from the immune system of the host or there is a reservoir of the organism residing within the cells of the host. In this report, the ability of B. burgdorferi to gain entrance into human umbilical vein endothelial cells was explored as a model for invasion. Incubation of B. burgdorferi with human umbilical vein endothelial cells at ratios ranging from 200:1 to 5,000:1 resulted in the intracellular localization of 10 to 25% of B. burgdorferi in 24 h. The intracellular location of the spirochetes was demonstrated by the incorporation of radiolabeled B. burgdorferi into a trypsin-resistant compartment and was confirmed by double-immunofluorescence staining which differentiated intracellular from extracellular organisms. Actin-containing microfilaments were required for the intracellular localization, indicating that the host cell participates in the internalization process. Activation of endothelial cells by agents known to increase the expression of several adhesion molecules had no effect on the interaction of B. burgdorferi with the endothelial monolayer. This indicates that the endothelial receptor for B. burgdorferi is constitutively expressed and that internalization is not dependent upon adhesion molecules whose expression is induced by inflammatory mediators. The demonstration of B. burgdorferi within endothelial cells suggest that intracellular localization may be a potential mechanism by which the organism escapes from the immune response of the host and may contribute to persistence of the organism during the later stages of Lyme disease. Images

Ma, Y; Sturrock, A; Weis, J J

1991-01-01

412

Murine Salmonellosis Studied by Confocal Microscopy: Salmonella typhimurium Resides Intracellularly Inside Macrophages and Exerts a Cytotoxic Effect on Phagocytes In Vivo  

Microsoft Academic Search

Summary Salmonella typhimurium is considered a facultative intracellular pathogen, but its intracellular lo- cation in vivo has not been demonstrated conclusively. Here we describe the development of a new method to study the course of the histopathological processes associated with murine sal- monellosis using confocal laser scanning microscopy of immunostained sections of mouse liver. Confocal microscopy of 30- m m-thick

Agneta Richter-Dahlfors; Alison M. J. Buchan; B. Brett Finlay

413

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

414

Citizens' obligation to obey the law: an empirical study of Guangzhou, China.  

PubMed

For thousands of years, China primarily used morality for its social control. Since its economic reform starting in 1978, China has moved toward legal control. Two fundamental questions, however, remain understudied in China: (a) the degree to which citizens feel obligated to obey the law and (b) the sources of citizens' perceived obligation to obey the law. This study was intended to answer these questions based on random surveys of 1,196 residents from Guangzhou, China. The study revealed that the vast majority of citizens in Guangzhou felt obligated to obey the law irrespective of their personal feelings. Normative and instrumental perspectives were important sources of Guangzhou citizens' perceived obligation to obey the law. In addition, Guangzhou citizens' perception of obligation to obey the law was related to not only individual-level variables but also neighborhood contextual factors. PMID:22222495

Jiang, Shanhe; Wu, Yuning; Wang, Jin

2012-01-05

415

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

2012-03-16

416

Intracellular trafficking of nonviral vectors  

Microsoft Academic Search

Nonviral vectors continue to be attractive alternatives to viruses due to their low toxicity and immunogenicity, lack of pathogenicity, and ease of pharmacologic production. However, nonviral vectors also continue to suffer from relatively low levels of gene transfer compared to viruses, thus the drive to improve these vectors continues. Many studies on vector–cell interactions have reported that nonviral vectors bind

L K Medina-Kauwe; J Xie; S Hamm-Alvarez

2005-01-01

417

High Consequence Plant Pathogens  

Microsoft Academic Search

Threatening pathogens present a great concern since they can impact agriculture, economy, international trade and environmental\\u000a diversity. Among the pathogens which cause increased agricultural and social concern are new or re-emerging pathogens. Most\\u000a of the important agricultural crops have spread during the last two centuries outside their original environment all over\\u000a the world. An immediate and parallel trend is the

Abraham Gamliel

418

42 CFR 137.251. - What obligation does the retroceding Self-Governance Tribe have with respect to returning...  

Code of Federal Regulations, 2011 CFR

...obligation does the retroceding Self-Governance Tribe have with respect to...HUMAN SERVICES TRIBAL SELF-GOVERNANCE Retrocession § 137.251...obligation does the retroceding Self-Governance Tribe have with respect...

2011-10-01

419

20 CFR 1002.261 - Who is responsible for funding any plan obligation to provide the employee with pension benefits?  

Code of Federal Regulations, 2013 CFR

...plan obligation to provide the employee with pension benefits? 1002.261 Section 1002.261 Employees' Benefits OFFICE OF THE...VETERANS' EMPLOYMENT AND TRAINING SERVICE, DEPARTMENT OF LABOR...obligation to provide the employee with pension...

2013-04-01

420

45 CFR 309.135 - What requirements apply to funding, obligating and liquidating Federal title IV-D grant funds?  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false What requirements apply to funding, obligating and liquidating Federal title...IV-D) PROGRAM Tribal IV-D Program Funding § 309.135 What requirements apply to funding, obligating and liquidating Federal...

2012-10-01

421

45 CFR 309.135 - What requirements apply to funding, obligating and liquidating Federal title IV-D grant funds?  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false What requirements apply to funding, obligating and liquidating Federal title...IV-D) PROGRAM Tribal IV-D Program Funding § 309.135 What requirements apply to funding, obligating and liquidating Federal...

2011-10-01

422

41 CFR 101-6.2105 - What is the Administrator's obligation with respect to Federal interagency coordination?  

Code of Federal Regulations, 2012 CFR

...2012-07-01 false What is the Administrator's obligation with respect...Property Management Regulations System FEDERAL PROPERTY MANAGEMENT...101-6.2105 What is the Administrator's obligation with respect...interagency coordination? The Administrator, to the extent...

2012-07-01

423

25 CFR 162.239 - How will payment rights and obligations relating to agricultural land be allocated between the...  

Code of Federal Regulations, 2010 CFR

...How will payment rights and obligations relating to agricultural land be allocated between the Indian landowners and the...How will payment rights and obligations relating to agricultural land be allocated between the Indian landowners and...

2010-04-01

424

25 CFR 162.239 - How will payment rights and obligations relating to agricultural land be allocated between the...  

Code of Federal Regulations, 2010 CFR

...How will payment rights and obligations relating to agricultural land be allocated between the Indian landowners and the...How will payment rights and obligations relating to agricultural land be allocated between the Indian landowners and...

2009-04-01

425

26 CFR 1.6049-3 - Statements to recipients of interest payments and holders of obligations to which there is...  

Code of Federal Regulations, 2011 CFR

...obligations to which there is attributed original issue discount in calendar years before 1983...obligations to which there is attributed original issue discount in calendar years before 1983...or 1087-OID with respect to original issue discount includible in gross...

2011-04-01

426

26 CFR 1.6049-3 - Statements to recipients of interest payments and holders of obligations to which there is...  

Code of Federal Regulations, 2013 CFR

...obligations to which there is attributed original issue discount in calendar years before 1983...obligations to which there is attributed original issue discount in calendar years before 1983...or 1087-OID with respect to original issue discount includible in gross...

2013-04-01

427

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

Code of Federal Regulations, 2013 CFR

...holders of obligations for attributed original issue discount. 1.6049-6 Section 1...holders of obligations for attributed original issue discount. (a) Requirement of furnishing...payments of interest (other than original issue discount) to any person during a...

2013-04-01

428

Pathogenic Microorganisms in Water  

NSDL National Science Digital Library

Pathogenic Microorganisms in Water: Traditionally, groundwater has been used without treatment because the soil acts as a filter, removing pathogenic microorganisms. Some potential sources of pathogens (or disease causing organisms) in groundwater include septic tanks, leaking sewer lines, sewage sludge, intentional groundwater recharge with sewage, irrigation with sewage, direct injection of sewage, domestic solid waste disposal (landfills) and sewage oxidation ponds. The objective of the session is to introduce hydrogeologist to the types of microorganisms, sources of pathogens, and a simple exercise that can be incorporated into a hydrogeology class.

Lenczewski, Melissa

429

Realizing benefit sharing - the case of post-study obligations.  

PubMed

In 2006, the Indonesian government decided to withhold avian flu samples from the World Health Organization. They argued that even though Indonesian samples were crucial to the development of vaccines, the results of vaccine research would be unaffordable for its citizens. Commentaries on the case varied from alleging blackmail to welcoming this strong stance against alleged exploitation. What is clear is that the concern expressed is related to benefit sharing. Benefit sharing requires resource users to return benefits to resource providers in order to achieve justice. One benefit sharing tool within health research is the duty to provide a health care intervention which has been proven to be beneficial (or alternative benefits) to research participants after a study has been concluded. This duty is generally known as a post-study obligation. It was enshrined in the Declaration of Helsinki in 2000 and re-emphasized in 2008. Yet, there are few, if any, examples of good practice. In this article, we analyse the obstacles to giving more bite to benefit sharing provisions in health research through ethical review. We conclude that the provision of post-study access to healthcare interventions is not a promising mechanism when monitored through research ethics committees. Alternative benefit provision is preferable if one focuses on achieving compliance. However, even the latter faces challenges, which we address in specific recommendations. PMID:21241344

Schroeder, Doris; Gefenas, Eugenijus

2011-01-17

430

Ethical obligations and counseling challenges in cancer genetics.  

PubMed

Cancer genetics is creating new practice opportunities in medical genetics, oncology, and primary care. The ethical and counseling challenges of this new area of practice are not unique but sometimes take new form in the context of genetic risk. This article uses cases to explore the issues associated with shared family risk, including competing concerns of family members, duty to warn relatives of genetic risk, and testing of children and other relatives. The ethical obligations of clinicians start with the need to maintain competence in the face of rapidly evolving science. Clinicians should be able to identify patients within their practice who are candidates for genetic testing. When genetic susceptibility to cancer is identified, patients should be offered counseling and follow-up, with referral as appropriate, to ensure delivery of care consistent with current standards. When patients experience barriers to needed health care, clinicians should advocate for their needs. Clinicians must ensure the autonomy and informed decision-making of all members of cancer-prone families. Clinicians must also provide emotional support and accurate information about cancer risks and cancer risk reduction measures, including uncertainties. Teamwork among different specialties is important in addressing these challenges. PMID:16451774

Burke, Wylie; Press, Nancy

2006-02-01

431

Prestin in HEK cells is an obligate tetramer  

PubMed Central

The unusual membrane motor protein prestin is essential for mammalian hearing and for the survival of cochlear outer hair cells. While prestin has been demonstrated to be a homooligomer, by Western blot and FRET analyses, the stoichiometry of self association is unclear. Prestin, coupled to the enhanced green fluorescent protein, was synthesized and membrane targeted in human embryonic kidney cells by plasmid transfection. Fragments of membrane containing immobilized fluorescent molecules were isolated by osmotic lysis. Diffraction-limited fluorescent spots consistent in size with single molecules were observed. Under continuous excitation, the spots bleached to background in sequential and approximately equal-amplitude steps. The average step count to background levels was 2.7. A binomial model of prestin oligomerization indicated that prestin was most likely a tetramer, and that a fraction of the green fluorescent protein molecules was dark. As a positive control, the same procedure was applied to cells transfected with plasmids coding for the human cyclic nucleotide-gated ion channel A3 subunit (again coupled to the enhanced green fluorescent protein), which is an obligate tetramer. The average step count for this molecule was also 2.7. This result implies that in cell membranes prestin oligomerizes to a tetramer.

Nichols, Michael G.

2012-01-01

432

Methylophilus quaylei sp. nov., a new aerobic obligately methylotrophic bacterium.  

PubMed

A new obligately methylotrophic bacterium (strain MTT) with the ribulose monophosphate pathway of carbon assimilation is described. The isolate, utilizing only methanol, is an aerobic, Gram-negative, asporogenous, non-motile short rod multiplying by binary fission. Its cellular fatty acids profile consists primarily of straight-chain saturated C16:0 and unsaturated C16:l acids. The major ubiquinone is Q-8. The dominant phospholipids are phosphatidylethanolamine and phosphatidylglycerol. Diphosphatidylglycerol (cardiolipin) is absent. Optimal growth conditions are 25-29 degree C, pH 6.5 - 7.5, 0.5% CH3OH and 0.05% NaCl. Strain MTT lacks alpha-ketoglutarate dehydrogenase, the glyoxylate shunt enzymes, and glutamate dehydrogenase. Ammonium is assimilated by the operation of the glutamate cycle enzymes: glutamine synthetase and glutamate synthase. An exopolysaccharide consisting of rhamnose, glucose and galactose is formed under nitrogen limitation. The G + C content of the DNA is 54.0 mol%. Based on 16S rDNA sequence analysis and DNA-DNA relatedness (29-34%) with type strains of the genus Methylophilus, the novel isolate was classified as a new species of this genus and named Methylophilus quaylei MTT (VKM B-2338T, DSMZ, etc.). PMID:15997702

Doronina, Nina; Ivanova, Ekaterina; Trotsenko, Yuri; Pshenichnikova, Anna; Kalinina, Ekaterina; Shvets, Vitaly

2005-06-01

433

Comparative Proteomics Analyses Reveal the virB of B. melitensis Affects Expression of Intracellular Survival Related Proteins  

Microsoft Academic Search

BackgoundBrucella melitensis is a facultative, intracellular, pathogenic bacterium that replicates within macrophages. The type IV secretion system encoded by the virB operon (virB) is involved in Brucella intracellular survival. However, the underlying molecular mechanisms, especially the target proteins affected by the virB, remain largely unclear.Methodology\\/Principal FindingsIn order to define the proteins affected by virB, the proteomes of wild-type and the

Yufei Wang; Zeliang Chen; Feng Qiao; Tianyi Ying; Jing Yuan; Zhijun Zhong; Lei Zhou; Xinying Du; Zhoujia Wang; Jin Zhao; Shicun Dong; Leili Jia; Xitong Yuan; Ruifu Yang; Yansong Sun; Liuyu Huang; David M. Ojcius

2009-01-01

434

Comparative Proteomics Analyses Reveal the virB of B. melitensis Affects Expression of Intracellular Survival Related Proteins  

Microsoft Academic Search

Backgound: Brucella melitensis is a facultative, intracellular, pathogenic bacterium that replicates within macrophages. The type IV secretion system encoded by the virB operon (virB) is involved in Brucella intracellular survival. However, the underlying molecular mechanisms, especially the target proteins affected by the virB, remain largely unclear. Methodology\\/Principal Findings: In order to define the proteins affected by virB, the proteomes of

Yufei Wang; Zeliang Chen; Feng Qiao; Tianyi Ying; Jing Yuan; Zhijun Zhong; Lei Zhou; Xinying Du; Zhoujia Wang; Jin Zhao; Shicun Dong; Leili Jia; Xitong Yuan; Ruifu Yang; Yansong Sun; Liuyu Huang

2009-01-01

435

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

436

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

437

50 CFR 80.91 - What is a Federal obligation of funds and how does it occur?  

Code of Federal Regulations, 2011 CFR

...Federal obligation of funds and how does it occur? 80.91 Section 80.91 Wildlife...Federal obligation of funds and how does it occur? An obligation of funds is...assistance to use the funds available to it under the Acts and commits to provide...

2011-10-01

438

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

Microsoft Academic Search

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

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

2004-01-01

439

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

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Pledge of Government obligations in lieu of a bond with... ACCEPTANCE OF BONDS SECURED BY GOVERNMENT OBLIGATIONS IN LIEU OF BONDS WITH SURETIES § 225.3 Pledge of Government obligations in lieu of a bond...

2013-07-01

440

[Granulomatous diseases and pathogenic microorganism].  

PubMed

Granuloma formation is a chronic inflammatory reaction where macrophage system and other inflammatory cells are involved. After some antigen exposure and processing, T cells, macrophages, epithelioid cells, and giant cell are activated, and granulomas are formed. Granuloma is considered as a defense mechanism against antigens, which stay in the organs without inactivation. Granulomas including fibroblasts extra-cellular matrix surround and isolate the antigens. Granulomas are classified to noninfectious granulomas and infectious granulomas. However recent studies revealed pathogenic microorganism are suspected to be a cause of granuloma in non-inflammatory diseases. Balance between pathogenic microorganisms and defense mechanisms of the host might be important in the special immunologic reaction. In some cases, it is hard to clearly classify infectious and noninfectious granulomas. Recently, Eishi et al. reported that latent infection of Propionibacterium acnes might be cause of sarcoidosis. Several hypersensitivity pneumonias are considered to be caused by exogenous microorganisms. The symposium was organized to know and clarify the new mechanisms of non-infectious granulomatous lung diseases and pathogenic microorganisms. This report is a summary of a symposium entitled "Granulomatous Diseases and Pathogenic Microorganism", organized in the 82nd Japanese Society for Tuberculosis (president Dr. Mitsunori Sakatani, M.D.). 1. Imaging of Granulomatous Lung Diseases: Masanori AKIRA (Department of Radiology, National Hospital Organization Kinki-chuo Chest Medical Center) High-resolution computed tomography (HRCT) is a useful tool in the evaluation of parenchymal changes in patients with a granulomatous lung disease. In sarcoidosis, the HRCT findings include small, well-defined nodules in relation to lymphatic roots, lymph node enlargement, and middle or upper lobe predominance. The appearances of subacute hypersensitivity pneumonitis include ill-defined centrilobular nodules, ground-glass opacity, and air trapping especially on expiratory CT scan. Those of Langerhans cell histiocytosis include bizarre thin-walled lung cysts, centrilobular nodules and upper lobe predominance. Each of granulomatous lung disease has some characteristic HRCT appearances, but they all are non-specific for diagnosis. HRCT is also useful for grading of parenchymal changes in granulomatous lung diseases. 2. Histopathology of granulomatous lung diseases with special reference to differential diagnosis of infectious disease: Tamiko TAKEMURA (Department of Pathology, Japanese Red Cross Medical Center) The lung is commonly involved by various granulomatous diseases of various etiology. It is difficult to pathologically differentiate these granuloumatous diseases to conduct appropriate therapy, because of morphological similarity of epithelioid cell granuloma, variable etiology, and difficulty of identification of causative agents. Granulomatous diseases generally are divided into infectious and non-infectious ones for treatment. Although infectious granulomas usually reveal necrosis and abscess, non-infectious ones occasionally also reveal necrosis. In cases with granulomas in the lung, it is necessary to explore the etiologic agents including environmental ones. 3. Sarcoidosis and Propionibacterium acnes: Yoshinobu EISHI (Department of Pathology, Tokyo Medical and Dental University) P. acnes can cause latent infection in peripheral lung tissue and the mediastinal lymph nodes and persist intracellularly in a cell-wall-deficient form. This dormant form of P. acnes can be activated endogenously under certain environmental conditions (hormones, stress, living habits, etc.) and proliferate in cells at the sites of latent infection. Granulomatous inflammation occurs in sarcoidosis patients with hypersensitivity to intracellular proliferation of the cell-wall-deficient bacteria, which can infect other cells or organs when spread via the lymphatic or blood streams. The timely use of antibiotics may not only kill the bacteria proliferating at the site

Inoue, Yoshikazu; Suga, Moritaka

2008-02-01

441

Emerging Escherichia pathogen.  

PubMed

Escherichia hermannii was first identified as a new species in 1982. It has rarely been reported as a human pathogen. We report the first case of E. hermannii as the sole pathogen in a catheter-related bloodstream infection. PMID:23740732

Kaewpoowat, Quanhathai; Permpalung, Nitipong; Sentochnik, Deborah E

2013-06-05

442

Plant pathogen resistance  

SciTech Connect

Azelaic acid or its derivatives or analogs induce a robust and a speedier defense response against pathogens in plants. Azelaic acid treatment alone does not induce many of the known defense-related genes but activates a plant's defense signaling upon pathogen exposure.

Greenberg, Jean T; Jung, Ho Won; Tschaplinski, Timothy

2012-11-27

443

Pathogens: raft hijackers  

Microsoft Academic Search

Throughout evolution, organisms have developed immune-surveillance networks to protect themselves from potential pathogens. At the cellular level, the signalling events that regulate these defensive responses take place in membrane rafts — dynamic microdomains that are enriched in cholesterol and glycosphingolipids — that facilitate many protein–protein and lipid–protein interactions at the cell surface. Pathogens have evolved many strategies to ensure their

Santos Mañes; Gustavo del Real; Carlos Martínez-A

2003-01-01

444

Plant pathogenic Pseudomonas species  

Microsoft Academic Search

In the current taxonomy, plant pathogenic Pseudomonas species are restricted to rRNA group I organisms belonging to the Gamma subclass of Proteobacteria. Currently, about 21 validly described plant pathogenic Pseudomonas species are known. The most important species is P. syringae with more than 50 described pathovars. The pathovar concept is confusing and the taxonomy of P. syringae needs revision. P.

Monica Höfte; PAUL DE VOS

445

Novel bioactive hydrophobic gentamicin carriers for the treatment of intracellular bacterial infections.  

PubMed

Gentamicin (GEN) is an aminoglycoside antibiotic with a potent antibacterial activity against a wide variety of bacteria. However, its poor cellular penetration limits its use in the treatment of infections caused by intracellular pathogens. One potential strategy to overcome this problem is the use of particulate carriers that can target the intracellular sites of infection. In this study GEN was ion-paired with the anionic AOT surfactant to obtain a hydrophobic complex (GEN-AOT) that was formulated as a particulated material either by the precipitation with a compressed antisolvent (PCA) method or by encapsulation into poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs). The micronization of GEN-AOT by PCA yielded a particulated material with a higher surface area than the non-precipitated complex, while PLGA NPs within a size range of 250-330 nm and a sustained release of the drug over 70 days were obtained by preparing the NPs using the emulsion solvent evaporation method. For the first time, GEN encapsulation efficiency values of ?100% were achieved for the different NP formulations with no signs of interaction between the drug and the polymer. Finally, in vitro studies against the intracellular bacteria Brucella melitensis, used as a model of intracellular pathogen, demonstrated that the bactericidal activity of GEN was unmodified after ion-pairing, precipitation or encapsulation into NPs. These results encourage their use for treatment for infections caused by GEN-sensitive intracellular bacteria. PMID:21115143

Imbuluzqueta, Edurne; Elizondo, Elisa; Gamazo, Carlos; Moreno-Calvo, Evelyn; Veciana, Jaume; Ventosa, Nora; Blanco-Prieto, María J

2010-11-27

446

Francisella tularensis harvests nutrients derived via ATG5-independent autophagy to support intracellular growth.  

PubMed

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. PMID:23966861

Steele, Shaun; Brunton, Jason; Ziehr, Benjamin; Taft-Benz, Sharon; Moorman, Nathaniel; Kawula, Thomas

2013-08-15

447

Processes for managing pathogens.  

PubMed

Wastewater contains human, animal, and plant pathogens capable of causing viral, bacterial, or parasitic infections. There are several routes whereby sewage pathogens may affect human health, including direct contact, contamination of food crops, zoonoses, and vectors. The range and numbers of pathogens in municipal wastewater vary with the level of endemic disease in the community, discharges from commercial activities, and seasonal factors. Regulations to control pathogen risk in the United States and Europe arising from land application of biosolids are based on the concept of multiple barriers to the prevention of transmission. The barriers are (i) treatment to reduce pathogen content and vector attraction, (ii) restrictions on crops grown on land to which biosolids have been applied, and (iii) minimum intervals following application and grazing or harvesting. Wastewater treatment reduces number of pathogens in the wastewater by concentrating them with the solids in the sludge. Although some treatment processes are designed specifically to inactivate pathogens, many are not, and the actual mechanisms of microbial inactivation are not fully understood for all processes. Vector attraction is reduced by stabilization (reduction of readily biodegradable material) and/or incorporation immediately following application. Concerns about health risks have renewed interest in the effects of treatment (on pathogens) and advanced treatment methods, and work performed in the United States suggests that Class A pathogen reduction can be achieved less expensively than previously thought. Effective pathogen risk management requires control to the complete chain of sludge treatment, biosolids handling and application, and post-application activities. This may be achieved by adherence to quality management systems based on hazard analysis critical control point (HACCP) principles. PMID:15647539

Godfree, Alan; Farrell, Joseph

448

Gene Expression Profiles of Blumeria graminis Indicate Dynamic Changes to Primary Metabolism during Development of an Obligate Biotrophic Pathogen  

Microsoft Academic Search

cDNA microarrays of Blumeria graminis fs phordei transcript profiles during the asexual development cycle reveal the dynamics of global gene expression as the fungus germinates, penetrates, feeds on its host, and produces masses of conidia for dispersal. The expression profiles of genes encoding enzymes involved in primary metabolism show that there is a striking degree of coordinate regulation of some

Michael Csukai; Michael P. H. Stumpf; Pietro D. Spanua

2005-01-01

449

Autophagy in Innate Recognition of Pathogens and Adaptive Immunity  

PubMed Central

Autophagy is a specialized cellular pathway involved in maintaining homeostasis by degrading long-lived cellular proteins and organelles. Recent studies have demonstrated that autophagy is utilized by immune systems to protect host cells from invading pathogens and regulate uncontrolled immune responses. During pathogen recognition, induction of autophagy by pattern recognition receptors leads to the promotion or inhibition of consequent signaling pathways. Furthermore, autophagy plays a role in the delivery of pathogen signatures in order to promote the recognition thereof by pattern recognition receptors. In addition to innate recognition, autophagy has been shown to facilitate MHC class II presentation of intracellular antigens to activate CD4 T cells. In this review, we describe the roles of autophagy in innate recognition of pathogens and adaptive immunity, such as antigen presentation, as well as the clinical relevance of autophagy in the treatment of human diseases.

Oh, Ji Eun

2012-01-01

450

Baculovirus genes modulating intracellular innate antiviral immunity of lepidopteran insect cells.  

PubMed

Innate immunity is essential for insects to survive infectious pathogens. In baculovirus-infected lepidopteran cells, apoptosis and global protein synthesis shutdown are major mechanisms of intracellular innate immunity that inhibit viral replication. In contrast, baculoviruses have evolved diverse genes and mechanisms to counter the antiviral immunity activated in infected cells. In this review, we summarize the current knowledge of the cellular antiviral pathways and the baculovirus genes that modulate antiviral immunity. The studies highlighted illustrate a high degree of diversity in both the cellular responses against viral infections and viral responses against intracellular antiviral immunity, providing an important basis of further studies in this field. PMID:23217611

Ikeda, Motoko; Yamada, Hayato; Hamajima, Rina; Kobayashi, Michihiro

2013-01-01

451

[Pathogenicity of bacteria and the actin cytoskeleton].  

PubMed

Actin system of eukaryotic cells creates the driving force for alteration of the phagocytic cytoplasmatic membrane shape, which is needed for cell movement in the space and for microorganism capturing. Manipulation by actin cytoskeleton mediated through specialized bacterial products can promote proliferation of bacteria in the host. Published reports indicate that bacterial regulation of the actin system activity can be carried out by two modes: 1) by bacterial interactions with surface receptors regulating the cytoskeleton status and 2) by introduction of bacterial products targeted to the cytoskeleton components into the cells. Intracellular pathogens (Legionella) possess ligands which interact with eukaryotic receptors and type IV secretion system fit for translocation of heretofore unknown effector molecules into the cytoplasm. This can result in stimulation of actin polymerization activity and accelerated phagocytosis of the bacteria with rapid multiplication in tissues. By contrast, representatives of extracellular pathogens (Clostridium) produce substances penetrating inside the eukaryotic cells and destroying the actin network, thus making capturing and intracellular digestion of these microorganisms impossible. PMID:11816117

Bely?, Iu F

2001-01-01

452

Chrysosporium anamorph Nannizziopsis vriesii: an emerging fungal pathogen of captive and wild reptiles.  

PubMed

Chrysosporium anamorph Nannizziopsis vriesii is a recent pathogen associated with infections in lizards, snakes, and crocodilians. It seems to be an obligate pathogen. It has been isolated from wild reptiles in addition to captive animals. Affected animals often present with aggressive, pyogranulomatous lesions that can affect the integument and musculoskeletal systems. Diagnosis can be done using culture, histopathology, and polymerase chain reaction assay. Ancillary diagnostic tests can be useful in characterizing the health status of the affected reptile and aid in planning supportive care and therapy. Treatment using antifungals has shown mixed results. PMID:24018030

Mitchell, Mark A; Walden, Michael R

2013-07-17

453

How complex are intracellular immune receptor signaling complexes?  

PubMed Central

Nucleotide binding leucine-rich repeat proteins (NLRs) are the major class of intracellular immune receptors in plants. NLRs typically function to specifically recognize pathogen effectors and to initiate and control defense responses that severely limit pathogen growth in plants (termed effector-triggered immunity, or ETI). Despite numerous reports supporting a central role in innate immunity, the molecular mechanisms driving NLR activation and downstream signaling remain largely elusive. Recent reports shed light on the pre- and post-activation dynamics of a few NLR-containing protein complexes. Recent technological advances in the use of proteomics may enable high-resolution definition of immune protein complexes and possible activation-relevant post-translational modifications of the components in these complexes. In this review, we focus on research aimed at characterizing pre- and post-activation NLR protein complexes and the molecular events that follow activation. We discuss the use of new or improved technologies as tools to unveil the molecular mechanisms that define NLR-mediated pathogen recognition.

Bonardi, Vera; Dangl, Jeffery L.

2012-01-01

454

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

Code of Federal Regulations, 2013 CFR

...contract that expires by its own terms is a ânew contract or obligationâ without a continuing obligation...PJM Interconnection, L.L.C. (PJM), ISO New England, Inc. (ISO-NE), and New York Independent System Operator (NYISO)...

2013-04-01

455

25 CFR 163.42 - Obligated service and breach of contract.  

Code of Federal Regulations, 2013 CFR

...Forestry Education, Education Assistance, Recruitment and Training § 163.42 Obligated...scholarship program. (4) Postgraduation recruitment program âAmount plus interest equal...the Secretary under the postgraduation recruitment program. (5) Postgraduate...

2013-04-01

456

25 CFR 163.42 - Obligated service and breach of contract.  

Code of Federal Regulations, 2011 CFR

...Forestry Education, Education Assistance, Recruitment and Training § 163.42 Obligated...scholarship program. (4) Postgraduation recruitment program âAmount plus interest equal...the Secretary under the postgraduation recruitment program. (5) Postgraduate...

2011-04-01

457

12 CFR 366.13 - What is my obligation regarding confidential information?  

Code of Federal Regulations, 2013 CFR

... FEDERAL DEPOSIT INSURANCE CORPORATION REGULATIONS AND STATEMENTS OF GENERAL POLICY MINIMUM STANDARDS OF INTEGRITY AND FITNESS FOR AN FDIC CONTRACTOR § 366.13 What is my obligation regarding confidential information? (a) Neither you...

2013-01-01

458

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

Code of Federal Regulations, 2012 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...

2012-10-01

459

47 CFR 1.21004 - Winning bidder's obligation to apply for support  

Code of Federal Regulations, 2012 CFR

...21004 Section 1.21004 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL PRACTICE AND PROCEDURE Grants by Random Selection Competitive Bidding for Universal Service Support § 1.21004 Winning bidder's obligation to apply for...

2012-10-01

460

31 CFR 535.438 - Standby letters of credit, performance or payment bonds and similar obligations.  

Code of Federal Regulations, 2013 CFR

...performance or payment bonds and similar obligations. 535.438 Section 535.438 Money and Finance: Treasury Regulations Relating...ASSETS CONTROL REGULATIONS Interpretations § 535.438 Standby letters of credit, performance or...

2013-07-01

461

Parks and Recreation: Obligations and Outlays from the Land and Water Conservation Fund.  

National Technical Information Service (NTIS)

The fact sheet presents Land and Water Conservation Fund (LWCF) obligations and outlays for fiscal years 1976 through 1985. A description of the legislative authorities, restrictions, and prohibitions governing recreational fees charged by federal agencie...

1986-01-01

462

12 CFR 1510.5 - How does the Funding Corporation make interest payments on its obligations?  

Code of Federal Regulations, 2012 CFR

...2012-01-01 2012-01-01 false How does the Funding Corporation make interest payments on its obligations...Banking DEPARTMENT OF THE TREASURY RESOLUTION FUNDING CORPORATION RESOLUTION FUNDING CORPORATION OPERATIONS § 1510.5 How...

2012-01-01

463

12 CFR 1510.5 - How does the Funding Corporation make interest payments on its obligations?  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false How does the Funding Corporation make interest payments on its obligations...Banking DEPARTMENT OF THE TREASURY RESOLUTION FUNDING CORPORATION RESOLUTION FUNDING CORPORATION OPERATIONS § 1510.5 How...

2010-01-01

464

12 CFR 1510.5 - How does the Funding Corporation make interest payments on its obligations?  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false How does the Funding Corporation make interest payments on its obligations...Banking DEPARTMENT OF THE TREASURY RESOLUTION FUNDING CORPORATION RESOLUTION FUNDING CORPORATION OPERATIONS § 1510.5 How...

2009-01-01