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The molecular basis of the biological differences between and remains largely unknown, and relatively little is known about environmental regulation of gene expression in these bacteria. We used a proteomic approach to explore the regulatory response of each bacterium to carbon dioxide-supplemented hypoxic conditions. Both organisms responded similarly and the magnitude of their responses was similar to what was observed in low iron conditions. We also identified proteins that were expressed at different levels in and , and found that SodB is expressed more strongly at both the protein and RNA levels in than in . Enzyme activity did not directly correlate with levels of protein expression, and we propose that an amino acid change difference between these orthologous proteins has the potential to affect catalytic activity. In addition, the upstream regulatory regions of several chromosomal genes were found to exhibit specific binding with a putative transcription factor, CDS4, from the -specific pPCP1 plasmid. The potential role of this protein in modulating - specific gene regulation warrants further investigation.

In bacteria, the most rapid and efficient means of adapting gene transcription to extracellular stresses often involves sophisticated systems referred to as two-component systems (2CSs). Although highly conserved throughout the bacterial world, some of these systems may control distinct cell events and have differing contributions to virulence, depending on the species considered. This chapter summarizes the work performed by our group - from the initial PhoP-PhoQ and PmrA-PmrB studies to the most recent genome-scale preliminary analyses - in an attempt to highlight the contribution of 2CS regulon plasticity to the acquisition of some of ’ specific features.

During infections of the intestinal tract penetrates the epithelial cell layer through M-cells into the Peyeŕs patches. This early step in the infection process is primarily mediated by the outer membrane protein invasin. Expression of the invasin gene is activated by the MarR-type regulatory protein RovA in response to environmental conditions, including temperature and growth phase. In order to gain insight into the nature of the underlying control systems, mutagenesis and gene bank screens were used to identify regula components modulating the levels of invasin and RovA. We found that the and genes were both subjected to silencing by the nucleoid-associated protein H-NS. Under inducing conditions, RovA appears to disrupt the silencer complex, through displacement of H-NS from an extended AT-rich region located upstream of the and promoters. Furthermore, a LysR-type regulatory protein, RovM with homology to HexA/PecT of phytopathogenic species was shown to interact specifically with the regulatory region and represses transcription in addition to H-NS. Disruption of the gene significantly enhanced internalization of into host cells and higher numbers of the mutant bacteria were detectable in gut-associated lymphatic tissues and organs in infected mice. In addition, the histone-like protein YmoA, which has a global effect on the bacterial physiology, was found to activate expression through RovM. Together, our studies showed, that H-NS, RovM and YmoA are key regulators implicated in the environmental control of virulence factors, which are important for the initiation of a infection.

The phage-shock-protein (Psp) system of encodes a stress response that is essential for viability when the secretin component of its Ysc type III secretion system is produced. Therefore, null mutants are completely avirulent in a mouse model of infection. This article summarizes what is known about the regulation of the Psp system. gene expression is induced by the overproduction of secretins, some cytoplasmic membrane proteins, or disruption of the F0F1-ATPase. All of these may deplete the proton-motive force, which could be the inducing signal for the Psp system. None of these Psp triggers induce two other extracytoplasmic stress responses (RpoE and Cpx), which suggests that the inducing signal of the Psp system is specific. The induction of gene expression requires the cytoplasmic membrane proteins PspB and PspC, which interact and presumably work together to achieve their regulatory function. However, the regulatory role of PspBC does not completely explain why they are essential for survival during secretin-stress, suggesting that they have a second unrelated role. Finally, current ideas about how PspB/C might sense the inducing trigger(s) are briefly discussed, including a consideration of whether there might be any unidentified signal transduction components that communicate with the Psp system.

Gram-negative bacteria predominantly use two types of quorum sensing (QS) systems - LuxI-LuxR, responsible for synthesis of N-acylhomoserine lactones (AHL or AI-1 signal molecule), and LuxS, which makes furanones (AI-2 signal molecule). We showed that LuxS and two LuxI-LuxR (YtbIR and YpsIR) systems are functional in . Four different AHL molecules were detected in extracts using TLC bioassays. Our data suggest that YtbIR is responsible for the production of long chain AHLs. Confocal laser scanning microscopy showed that biofilm formation is decreased in an mutant. Twodimensional gel electrophoresis revealed altered levels of protein expression in a triple QS mutant at 26°C and 37°C.

is the causative agent of plague. Unlike the other pathogenic species, has evolved an arthropod-borne route of transmission, alternately infecting flea and mammalian hosts. Distinct subsets of genes are hypothesized to be differentially expressed during infection of the arthropod vector and mammalian host. Genes crucial for mammalian infection are referred to as virulence factors whilst genes playing a role in the flea vector are termed transmission factors. This article serves as a review of known factors involved in flea-borne transmission and introduces an ‘’ microarray approach to elucidating the genetic basis of infection of- and transmission by the flea.

Plague biofilm development is controlled by positive (HmsT) and negative (HmsP) regulators. The GGDEF-domain protein HmsT appears to have diguanylate cyclase activity to synthesize bis-(3’-5’)-cyclic dimeric guanosine monophosphate (c-di-GMP) from 2 GTP molecules. The EAL domain of HmsP has phosphodiesterase activity and likely degrades c-di- GMP. This second messenger molecule probably influences biofilm development by activating the glycosyl transferase activity of HmsR. Here we demonstrate the in vitro pH optimum for phosphodiesterase activity of HmsP and that an alanine substitution in residue L508, D626, or E686 within the EAL domain affects this enzymatic activity and the biological function of the protein. Finally, protein-protein interactions and the cytoplasmic location of the enzymatic domains of HmsT and HmsP are evaluated.

has two type III secretion systems (TTSS): The well characterized Ysc-Yop system and the relatively uncharacterized Ysa-Ysp system. Detection of Ysps in culture supernatants has only been observed when cultures are grown at low temperature (26°C) and in high salt (290mM NaCl). Previous reports demonstrated that expression from the promoter was activated by high salt. In this study, we report a new environmental stimulus for gene expression; in the presence of high salt, growth on solid surface stimulates expression 7-fold compared to growth in high salt broth. These new data indicate that, in the presence of salt, solid surface is an extremely robust signal for the Ysa system.

Low temperatures as well as encounters with host phagocytes are two stresses that have been relatively well studied in many species of bacteria. The exoribonuclease polynucleotide phosphorylase (PNPase) has previously been shown to be required by several species of bacteria, including , for low-temperature growth. We have shown that PNPase also enhances the ability of to withstand the killing activities of murine macrophages. We have gone on to show that PNPase is required for the optimal functioning of ’s type three secretion system (T3SS), an organelle that injects effector proteins directly into host cells. Surprisingly, the PNPase-mediated effect on T3SS activity is independent of PNPase’s ribonuclease activity and instead requires only its S1 RNA-binding domain. In stark contrast, the catalytic activity of PNPase is strictly required for enhanced growth at low temperature. Preliminary experiments suggest that the RNA-binding interface of the S1 domain is critical for its T3SS-enhancing activity. Our findings indicate that PNPase plays versatile roles in promoting ’s survival in response to stressful conditions.

Control of Yops secretion in pathogenic Yersinia is achieved at several levels. These levels likely include transcriptional, post-transcriptional, translational and secretional controls. Secretion control appears to be mediated by two pathways. One pathway involves YopN and proteins that interact with YopN. The second pathway consists of LcrG and its interaction with LcrV. LcrV is a postive regulator of Yops secretion that exerts control over Yops secretion by negating the secretion blocking role of LcrG. However, the intersection of these two control pathways is not understood. Recent work has allowed the development of a speculative model that brings YopN-mediated and LcrG-LcrV-mediated control together in the context of the ability of the needle complex to respond to Ca2+.