Global Gene Expression and the Role of Sigma Factors in
            <i>Neisseria gonorrhoeae</i>
            in Interactions with Epithelial Cells

Du, Ying; Lenz, Jonathan D.; Arvidson, Cindy Grove

doi:10.1128/iai.73.8.4834-4845.2005

Cited by 39 publications

(60 citation statements)

References 81 publications

(85 reference statements)

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“…In addition, when comparing the transcriptional profiles of RNA samples isolated before and after incubation in saponin, we found that these incubation conditions caused no appreciable change in bacterial gene expression (expression of ϳ0.1% of all genes changed by a statistically significant measure [data not shown]). This is consistent with studies of other bacterial pathogens, where saponin has also been used to specifically lyse host cells and has been shown to have no noticeable effect on bacterial gene expression (18).…”

supporting

confidence: 77%

Transcriptional Profiling of Bacillus anthracis during Infection of Host Macrophages

Bergman

Anderson²,

Swenson³

et al. 2007

Infect Immun

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The interaction between Bacillus anthracis and the mammalian phagocyte is one of the central stages in the progression of inhalational anthrax, and it is commonly believed that the host cell plays a key role in facilitating germination and dissemination of inhaled B. anthracis spores. Given this, a detailed definition of the survival strategies used by B. anthracis within the phagocyte is critical for our understanding of anthrax. In this study, we report the first genome-wide analysis of B. anthracis gene expression during infection of host phagocytes. We developed a technique for specific isolation of bacterial RNA from within infected murine macrophages, and we used custom B. anthracis microarrays to characterize the expression patterns occurring within intracellular bacteria throughout infection of the host phagocyte. We found that B. anthracis adapts very quickly to the intracellular environment, and our analyses identified metabolic pathways that appear to be important to the bacterium during intracellular growth, as well as individual genes that show significant induction in vivo. We used quantitative reverse transcription-PCR to verify that the expression trends that we observed by microarray analysis were valid, and we chose one gene (GBAA1941, encoding a putative transcriptional regulator) for further characterization. A deletion strain missing this gene showed no phenotype in vitro but was significantly attenuated in a mouse model of inhalational anthrax, suggesting that the microarray data described here provide not only the first comprehensive view of how B. anthracis survives within the host cell but also a number of promising leads for further research in anthrax.Bacillus anthracis, the causative agent of anthrax, has come under increased scrutiny in recent years because of its potential role as a bioweapon (35). In the environment, B. anthracis exists primarily as a metabolically dormant endospore, and in this morphology the bacterium is both highly infectious and resistant to a wide range of harsh conditions (42). When the spores are inhaled, they reach the alveolar spaces of the lung, where they are efficiently taken up by resident phagocytes (5, 9, 48). It is commonly believed that the host cells then migrate across the alveolocapillary barrier, transporting the intracellular bacteria into the lymphatic system (26,40). During this time, the bacteria germinate, transforming from spores into vegetative bacilli, which begin to replicate within the phagocytes (15, 50). Eventually, the bacteria kill the phagocytes and escape into the extracellular environment, and the resulting sepsis ultimately leads to death of the host (23,24,43,52,57).Since the progression of anthrax is typically quite rapid once the systemic phase of the infection begins (16, 24), successful intervention depends on early diagnosis and treatment. Given this fact, it is particularly important from a therapeutic standpoint that the early events in anthrax are well understood. Most of these events occur within the context of the h...

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supporting

confidence: 77%

Transcriptional Profiling of Bacillus anthracis during Infection of Host Macrophages

Bergman

Anderson²,

Swenson³

et al. 2007

Infect Immun

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“…In particular, we noted that expression of rpoH, which encodes the stress-related sigma factor RpoH, and some RpoH-regulated genes (grpE, clpB, and marR [8,29]) were increased in strain JF1 relative to the MtrR-positive parental strain FA19, suggesting that they are MtrR repressed. Since RpoH expression in gonococci is increased during exposure to certain environmental stresses (8) when gonococci bind to cervical epithelial cells (2,3) and is essential for viability (3,8), we studied the ability of MtrR to regulate rpoH expression in N. gonorrhoeae.…”

Section: Resultsmentioning

confidence: 99%

“…H 2 O 2 assays were performed because loss of RpoH production was found to enhance the susceptibility of Brucella melitensis (1) to the oxidizing agent. Since we (unpublished observations) and others (3,8,14) have been unsuccessful in obtaining an rpoH null mutant, we hypothesized that under conditions where rpoH expression is dampened due to the repressive action of MtrR, gonococcal susceptibility to H 2 O 2 would increase. Indeed, we found that inducible expression of mtrR increased gonococcal susceptibility to H 2 O 2 (Fig.…”

Section: Vol 191 2009mentioning

confidence: 99%

“…An MtrR-repressed gene of particular interest, which was the subject of this investigation, was rpoH. rpoH encodes the alternative stress response sigma factor RpoH (sigma 32), which appears to be essential for gonococcal viability even under normal growth conditions (3,8). Earlier studies showed that rpoH expression is increased during exposure of gonococci to certain stress conditions, such as growth at elevated temperatures (8), and during bacterial contact with cultured epithelial cells (2,3).…”

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confidence: 99%

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MtrR Modulates rpoH Expression and Levels of Antimicrobial Resistance in Neisseria gonorrhoeae

et al. 2009

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The MtrR transcriptional-regulatory protein is known to repress transcription of the mtrCDE operon, which encodes a multidrug efflux pump possessed by Neisseria gonorrhoeae that is important in the ability of gonococci to resist certain hydrophobic antibiotics, detergents, dyes, and host-derived antimicrobials. In order to determine whether MtrR can exert regulatory action on other gonococcal genes, we performed a whole-genome microarray analysis using total RNA extracted from actively growing broth cultures of isogenic MtrR-positive and MtrR-negative gonococci. We determined that, at a minimum, 69 genes are directly or indirectly subject to MtrR control, with 47 being MtrR repressed and 22 being MtrR activated. rpoH, which encodes the general stress response sigma factor RpoH (sigma 32), was found by DNA-binding studies to be directly repressed by MtrR, as it was found to bind to a DNA sequence upstream of rpoH that included sites within the rpoH promoter. MtrR also repressed the expression of certain RpoH-regulated genes, but this regulation was likely indirect and a reflection of MtrR control of rpoH expression. Inducible expression of MtrR was found to repress rpoH expression and to increase gonococcal susceptibility to hydrogen peroxide (H 2 O 2 ) and an antibiotic (erythromycin) recognized by the MtrC-MtrD-MtrE efflux pump system. We propose that, apart from its ability to control the expression of the mtrCDE-encoded efflux pump operon and, as a consequence, levels of gonococcal resistance to host antimicrobials (e.g., antimicrobial peptides) recognized by the efflux pump, the ability of MtrR to regulate the expression levels of rpoH and RpoH-regulated genes also modulates levels of gonococcal susceptibility to H 2 O 2 .

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“…It has also been proposed that the intestine is relatively nutrient poor (28), and some of the 32 -regulated genes listed in Table 2 may promote growth under nutrientlimiting conditions. Adherence of V. cholerae to the intestinal epithelium may promote 32 activation, as has been observed following adherence of Neisseria gonorrhoeae to host epithelial cells (11). Adherence could stimulate changes in the cell membrane that activate E , which appears to be a regulator of rpoH in V. cholerae.…”

Section: Discussionmentioning

confidence: 99%

Global Gene Expression and Phenotypic Analysis of a Vibrio cholerae rpoH Deletion Mutant

2007

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Vibrio cholerae, the cause of cholera, can grow in a variety of environments outside of human hosts. During infection, this pathogen must adapt to significant environmental alterations, including the elevated temperature of the human gastrointestinal tract. 32 , an alternative sigma factor encoded by rpoH, activates transcription of genes involved in the heat shock response in several bacterial species. Here, we assessed the role of 32 in V. cholerae physiology. In aggregate, our findings suggest that 32 promotes V. cholerae growth at temperatures ranging at least from 15°C to 42°C. Growth of the rpoH mutant was severely attenuated within the suckling mouse intestine, suggesting that 32 -regulated genes are critical for V. cholerae adaptation to conditions within the gastrointestinal tract. We defined the V. cholerae RpoH regulon by comparing the whole-genome transcription profiles of the wild-type and rpoH mutant strains after a temperature up-shift. Most of the V. cholerae genes expressed in an RpoH-dependent manner after heat shock encode proteins that influence protein fate, such as proteases and chaperones, or are of unknown function. Bioinformatic analyses of the microarray data were used to define a putative 32 consensus binding sequence and subsequently to identify genes that are likely to be directly regulated by RpoH in the whole V. cholerae genome.Vibrio cholerae, the cause of the diarrheal disease cholera, is a facultative pathogen. This curved gram-negative rod grows well in a variety of aquatic ecosystems (37). In addition, when humans ingest food or water contaminated with V. cholerae, this microorganism can multiply in the small bowel. During the transition from aquatic habitats to the human gastrointestinal tract, and vice-versa, V. cholerae cells confront significant alterations in their environment. The molecular factors that enable V. cholerae to adapt to the abrupt changes in the environment, such as the elevated temperature and acidity that the organism encounters in the human host, are largely unknown. However, alterations in the patterns of total cellular transcription, mediated by a variety of alternative sigma factors and other transcriptional regulators, often constitute an important part of the cellular response to environmental stress.Sigma factors interact with the core components of the RNA polymerase to generate a holoenzyme complex that is capable of initiating transcription at promoters. While 70 , the major sigma factor, activates transcription of most genes in growing cells, alternative sigma factors enable the RNA polymerase to transcribe genes important for cellular adaptation to various stresses (14). In Escherichia coli, the alternative sigma factor 32 activates transcription of genes involved in the heat shock response (52). This sigma factor, also referred to as RpoH, has also been implicated in the E. coli response to other stresses, including elevated hydrostatic pressure (1), hyperosmolar shock (3), and nutrient limitation (21).A variety of mechanisms govern 32 levels...

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Global Gene Expression and the Role of Sigma Factors in Neisseria gonorrhoeae in Interactions with Epithelial Cells

Cited by 39 publications

References 81 publications

Transcriptional Profiling of Bacillus anthracis during Infection of Host Macrophages

Transcriptional Profiling of Bacillus anthracis during Infection of Host Macrophages

MtrR Modulates rpoH Expression and Levels of Antimicrobial Resistance in Neisseria gonorrhoeae

Global Gene Expression and Phenotypic Analysis of a Vibrio cholerae rpoH Deletion Mutant

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