Research Publications (Food Safety)

FadR is a master regulator of fatty acid (FA) metabolism that coordinates the pathways of FA degradation and biosynthesis in enteric bacteria. We show here that a fadR mutation in the El Tor biotype of Vibrio cholerae prevents the expression of the virulence cascade by influencing both the transcription and post-translational regulation of the master virulence regulator ToxT.

Brucella abortus E1 is an EcfG-family sigma factor that regulates transcription of dozens of genes in response to diverse stress conditions, and is required for maintenance of chronic infection in a mouse model. A putative ATP-binding cassette transporter operon, bab1_0223-bab1_0226, is among the most highly activated gene sets in the E1 regulon.

Galactitol degradation by salmonellae remains underinvestigated, although this metabolic capability contributes to growth in animals (1). The genes responsible for this metabolic capability are part of a 9.6-kb gene cluster that spans from gatY to gatR (STM3253 to STM3262) and encodes a phosphotransferase system, four enzymes, and a transporter of the major facilitator superfamily. Genome comparison revealed the presence of this genetic determinant in nearly all Salmonella strains.

Salmonella enterica serovars causes gastroenteritis or typhoid fever in humans, with virulence depending on the action of two type III secretion systems (SPI-1 and SPI-2). SptP is a Salmonella SPI-1 effector, involved in mediating recovery of the host cytoskeleton post-infection. SptP requires a chaperone, SicP, for stability and secretion. SptP has 94% identity between S. Typhimurium and S. Typhi; direct comparison of the protein sequences revealed that S.

Ribonuclease Y (RNase Y) is a major endoribonuclease that plays a crucial role in mRNA degradation and processing. We study the role of RNase Y in the Gram-positive anaerobic pathogen Clostridium perfringens, which has until now not been well understood. Our study implies an important role for RNase Y-mediated RNA degradation and processing in virulence gene expression and the physiological development of the organism.

The cell division protein GpsB is a regulator of the penicillin binding protein A1 (PBP A1) in the Gram-positive human pathogen Listeria monocytogenes. Penicillin binding proteins mediate the last two steps of peptidoglycan biosynthesis as they polymerize and crosslink peptidoglycan strands, the main components of the bacterial cell wall. It is not known what other processes are controlled by GpsB. L.

The type III secretion system (T3SS) is a supramolecular machine used by many bacterial pathogens to translocate effector proteins directly into the eukaryotic host cell cytoplasm. Enteropathogenic Escherichia coli (EPEC) is an important cause of infantile diarrheal disease in underdeveloped countries. EPEC virulence relies on a T3SS encoded within a chromosomal pathogenicity island known as the locus of enterocyte effacement (LEE).

Since adhesion fimbriae are a major virulence factor for many pathogenic Gram-negative bacteria, they are potential targets for antibodies. Fimbriae are commonly required to initiate colonization leading to disease, and their success as adhesion organelles lies in their ability to both initiate and sustain bacterial attachment to epithelial cells.

The Phage shock protein (Psp) system is a widely conserved cell envelope stress response that is essential for the virulence of some bacteria, including Yersinia enterocolitica. Recruitment of PspA by the inner membrane PspB•PspC complex characterizes the activated state of this response. The PspB•PspC complex has been proposed to be a stress-responsive switch, changing from an OFF to an ON state in response to an inducing stimulus.

The riboflavin analogs roseoflavin (RoF) and 8-demethyl-8-aminoriboflavin (AF) are produced by the bacteria Streptomyces davawensis and Streptomyces cinnabarinus. Riboflavin analogs have the potential to be used as broad-spectrum antibiotics and we therefore studied the metabolism of riboflavin (vitamin B2), RoF and AF in the human pathogen Listeria monocytogenes, a bacterium which is a riboflavin auxotroph. We show that the L.

Bacterial genomes commonly contain prophage sequences as a result of past infections with lysogenic phages. Many of these integrated viral sequences are believed to be cryptic, but prophage genes are sometimes co-opted by the host, and some prophages may be re-activated to form infectious particles when cells are stressed or mutate. We found that a previously uncharacterized filamentous phage emerged from the genome of Acinetobacter baylyi ADP1 during a laboratory evolution experiment.

Klebsiella pneumoniae, one of the most important nosocomial pathogens, is becoming a major problem in health care because of its resistance to multiple antibiotics including cephalosporins of the latest generation and more recently even carbapenems. This is largely due to the spread of plasmid-coded extended spectrum β-lactamases.

Horizontal acquisition of novel chromosomal genes is considered to be a key process in the evolution of bacterial pathogens. However, identification of gene presence or absence could be hindered by the inconsistencies in bacterial genome annotations. Here, we perform a cross-annotation of omnipresent core and mosaic accessory genes in the chromosome of Salmonella enterica serovar Typhimurium, across a total of 20 fully-assembled genomes deposited into GenBank.

The Twin-arginine translocation (Tat) system mediates secretion of folded proteins that in bacteria, plants and archaea are identified via an N-terminal signal peptide. Tat systems are associated with virulence in many bacterial pathogens and our previous studies revealed that Tat deficient Yersinia pseudotuberculosis was severely attenuated for virulence.

The sialic acids (N-acylneuraminates) are a group of nine-carbon keto-sugars existing mainly as terminal residues on animal glycoprotein and glycolipid carbohydrate chains. Bacterial commensals and pathogens exploit host sialic acids for nutrition, adhesion, or anti-recognition, where N-acetyl- or N-glycolylneuraminic acids are the two predominant chemical forms of sialic acids.

Manganese plays an important role in the cellular physiology and metabolism of bacterial species, including the human pathogen, Vibrio cholerae. The intracellular level of manganese ions is controlled through coordinated regulation of the import and export of this element. We have identified a putative manganese exporter (VC0022), named mneA (manganese exporter A), which is highly conserved among Vibrio spp. An mneA mutant exhibited sensitivity to manganese, but not to other cations.

Vibrio cholerae is the etiological agent of the acute intestinal disorder cholera. The toxin-coregulated pilus (TCP), a type IVb pilus, is an essential virulence factor of V. cholerae. Recent work has shown TcpB is a large minor pilin encoded within the tcp operon. TcpB contributes to efficient pilus formation and is essential for all TCP functions. Here we have initiated a detailed, targeted mutagenesis approach to further characterize this salient TCP component.

Despite the importance of lipooligosaccharides (LOS) in the pathogenicity of campylobacteriosis, little is known about the genetic and phenotypic diversity of LOS in C. coli. In this study, we investigated the distribution of LOS locus classes among a large collection of unrelated C. coli isolates sampled from several different host species. Furthermore, we paired C.

Listeria monocytogenes is a significant foodborne human pathogen that can cause severe disease in certain high-risk individuals. L. monocytogenes is known to produce high molecular weight, phage tail-like bacteriocins, "monocins", upon induction of the SOS system. In this work we purified and characterized monocins and found them to be a new class of F-type bacteriocins. The L.

We searched for a source of reactive oxygen species (ROS) in the cytoplasm of the human pathogen Vibrio cholerae and addressed the mechanism of ROS formation using the dye 2’, 7’ -dichlorofluoresceine diacetate (DCFH-DA) in respiring cells. By comparing V. cholerae strains with or without active Na+ -translocating NADH:quinone oxidoreductase (Na+ -NQR), this respiratory sodium ion redox pump was identified as producer of ROS in vivo. The amount of cytoplasmic ROS detected in V.

The unique Escherichia coli GTPase Der (Double Era-like GTPase), which contains tandemly repeated GTP-binding domains, has been shown to play an essential role in 50S ribosomal subunit biogenesis. The depletion of Der results in the accumulation of precursors of 50S ribosomal subunits that are structurally unstable at low Mg2+ concentrations. Der homologs are ubiquitously found in eubacteria. Conversely, very few are conserved in eukaryotes and none is conserved in archaea.

The tetrachloroethene (PCE)-respiring Sulfurospirillum multivorans produces a unique cobamide, namely norpseudo-B12, which in comparison to other cobamides, e.g., cobalamin or pseudo-B12, lacks the methyl group in the linker moiety of the nucleotide loop. In this study, the protein SMUL_1544 was shown to be responsible for the formation of the unusual linker moiety, which is most probably derived from ethanolamine-phosphate (EA-P) as precursor.

Using the squid-vibrio association, we aimed to characterize the mechanism through which Vibrio fischeri cells signal morphogenesis of the symbiotic light-emitting organ. The symbiont releases two cell-envelope molecules, peptidoglycan (PG) and lipopolysaccharide (LPS) that, within 12 h of light-organ colonization, act in synergy to trigger normal tissue development. Recent work has shown that outer membrane vesicles (OMVs) produced by V.

The iprA gene (formerly known as yaiV or STM0374) is located in a two-gene operon in the Salmonella enterica serovar Typhimurium genome and is associated with altered expression during spaceflight and rotating wall vessel culture conditions that increase virulence. However, iprA is uncharacterized in the literature. In this report, we present the first targeted characterization of this gene which reveals that iprA is highly conserved across Enterobacteriaceae. We found that S.

Listeria monocytogenes is a food-borne Gram-positive bacterial pathogen and many of its virulence factors are either secreted proteins, or proteins covalently or non-covalently-attached to the cell wall. Previous work has indicated that non-covalently-attached proteins with GW domains are retained in the cell wall by binding to the cell wall polymer lipoteichoic acid (LTA). LTA is a glycerolphosphate polymer, which is modified in L. monocytogenes with galactose and D-alanine residues.