Research Publications (Food Safety)

Yersinia enterocolitica is a pathogen that causes gastroenteritis in humans. Because of its low temperature-dependent insecticidal activity, it can oscillate between invertebrates and mammals as host organisms. The insecticidal activity of strain W22703 is associated with a pathogenicity island of 19 kb (Tc-PAIYe), which carries regulators and genes encoding the toxin complex (Tc).

Germination of Clostridium difficile spores is a crucial early requirement for colonization of the gastrointestinal tract. Likewise, C. difficile cannot cause disease pathologies unless their spores germinate into metabolically active, toxin-producing cells. Recent advances in our understanding of C. difficile spore germination mechanisms indicate that this process is both complex and unique. This review defines unique aspects of the germination pathways of C.

Mycobacterium tuberculosis is a global pathogen of significant medical importance. A key aspect of its lifecycle is the ability to enter into an altered physiological state of non-replicating persistence during latency and resist elimination by the host immune system. One mechanism by which M. tuberculosis facilitates its survival during latency is by producing and metabolizing intracytoplasmic lipid droplets (LDs).

The biofilm growth mode is important in both the intestinal and environmental phases of Vibrio cholerae's life cycle. Regulation of biofilm formation involves several transcriptional regulators and alternative sigma factors. One such factor is the alternative sigma factor, RpoN, which positively regulates biofilm formation. RpoN requires bacterial enhancer-binding proteins (bEBPs) to initiate transcription. The V.

The electrogenic, sodium ion translocating NADH:quinone oxidoreductase (NQR) from Vibrio cholerae is frequent in pathogenic bacteria and a potential target for antibiotics. NQR couples the oxidation of NADH to the formation of a sodium motive force (SMF) and therefore drives important processes such as flagellar rotation, substrate uptake, and energy-dissipating cation-proton antiport. We performed a quantitative proteome analysis of V.

In Staphylococcus aureus, the global transcriptional regulator CodY modulates the expression of hundreds of genes in response to the availability of GTP and the branched-chain amino acids isoleucine, leucine, and valine (ILV). CodY DNA-binding activity is high when GTP and ILV are abundant. When GTP and ILV are limited, CodY's affinity for DNA drops, altering expression of CodY regulated targets. In this work, we investigated the impact of guanine nucleotides on S.

Listeria monocytogenes is a food pathogen capable of growing at a broad temperature range from 50°C to refrigerator temperatures. A key requirement for bacterial activity and growth at low temperatures is the ability to adjust membrane lipid composition to maintain cytoplasma membrane fluidity. In this study we confirmed earlier findings that the extent of fatty acid profile adaptation differed between L. monocytogenes strains.

Novel preventatives could help in efforts to limit Vibrio cholerae infection and the spread of cholera. Bacteriophage (or phage) treatment has been proposed to be an alternative intervention, given the rapid replication of virulent phages, prey specificity, and relative ease of finding new virulent phages. Phage tropism is dictated in part by the presence of phage receptors on the bacterial surface. While many phages that can kill V.

The endoribonuclease YbeY is one of the most well conserved proteins across the kingdoms of life. In the present study, we demonstrate that YbeY in Brucella abortus is linked to a variety of important activities, including proper cellular morphology, mRNA transcript levels, and virulence. Deletion of ybeY in B.

In Vibrio cholerae, high intracellular cyclic di-GMP (c-di-GMP) is associated with a biofilm lifestyle while low intracellular c-di-GMP is associated with a motile lifestyle. C-di-GMP also regulates other behaviors such as acetoin production and type II secretion; however, the extent of phenotypes regulated by c-di-GMP is not fully understood.

Vibrio cholerae is a Gram-negative bacterium with a monotrichous flagellum that causes the human disease cholera. Flagellar-mediated motility is an integral part of the bacterial lifecycle inside the host and in the aquatic environment. The V. cholerae flagellar filament is composed of five flagellin subunits (FlaA, FlaB, FlaC, FlaD, FlaE), however only FlaA is necessary and sufficient for filament synthesis.

Vibrio cholerae is a natural inhabitant of aquatic ecosystems. Some strains of V. cholerae can colonize the human host and cause cholera, a profuse watery diarrhea. The major pathogenicity factors and virulence regulators of V. cholerae are either encoded in mobile genetic elements acquired in the environment (e.g. pathogenicity islands or lysogenic phages) or in the core genome. Several lines of evidence indicate that the emergence of numerous virulence traits of V.

The Gram-negative bacterium Vibrio parahaemolyticus is an opportunistic human pathogen and the leading cause of seafood borne acute gastroenteritis worldwide. Recently, this bacterium was implicated as the etiologic agent of a severe shrimp disease with consequent devastating outcomes to shrimp farming. In both cases, acquisition of genetic material via horizontal transfer provided V. parahaemolyticus with new virulence tools to cause disease. Dissecting the molecular mechanisms of V.

Mycobacterium marinum is a non-tuberculous pathogen of poikilothermic fish and an opportunistic human pathogen. Like tuberculous mycobacteria, the M. marinum M strain requires the ESX-1 (ESAT-6 System 1) secretion system for virulence in host cells. EsxB and EsxA, two major virulence factors exported by the ESX-1 system, are encoded by the esxBA genes within the ESX-1 locus. Deletion of the esxBA genes abrogates ESX-1 export and attenuates M.

The Type VI Secretion System (T6SS) inhibits growth of neighboring bacterial cells through a contact-mediated mechanism. We describe a detailed characterization of the protein localization dynamics in the Pseudomonas aeruginosa T6SS. It has been proposed that Type VI secretion process is driven by a conformational-change induced contraction of the T6SS sheath.

Most motile bacteria are able to bias their movement towards more favorable environments or to escape from obnoxious substances by a process called chemotaxis. Chemotaxis depends on a chemosensory system that is able to sense specific environmental signals and generate a behavioral response. Typically, the signal is transmitted to the bacterial flagellum, ultimately regulating the swimming behavior of individual cells.

Diarrhea is the most common infection in children under the age of five worldwide. In spite of this, only a few vaccines to treat infectious diarrhea exist, and many of the available vaccines are sparingly and sporadically administered. Major obstacles to the development and widespread implementation of vaccination include the ease and cost of production, distribution, and delivery.

Reactive enamine stress caused by intracellular 2-aminoacrylate accumulation leads to pleiotropic growth defects in a variety of organisms. Members of the well-conserved RidA/YER057c/UK114 protein family prevent enamine stress by enhancing the breakdown of 2-aminoacrylate to pyruvate.

Yersinia pestis, the causative agent of plague, evolved from the closely related pathogen Yersinia pseudotuberculosis. During its emergence, Y. pestis is believed to have acquired its unique pathogenic characteristics through numerous gene gains/losses, genomic rearrangements and single nucleotide polymorphism (SNP) changes. One such SNP creates a single amino acid variation in the DNA binding domain of PhoP, the response regulator in the PhoP/PhoQ two-component system. Y.

Vibrio parahaemolyticus is a marine bacterium that is globally associated as the leading cause of seafood-borne gastroenteritis. V. parahaemolyticus uses various toxins and two type 3 secretion systems (T3SS-1 and T3SS-2) to subvert host cells during infection. We previously determined that V. parahaemolyticus T3SS-1 activity is upregulated by increasing the expression level of the master regulator ExsA under specific growth conditions. In this study, we set out to identify V.

The RidA protein (PF01042) from Salmonella enterica is a deaminase that quenches 2-aminoacrylate (2AA), and other reactive metabolites. In the absence of RidA, 2AA accumulates, damages cellular enzymes and compromises the metabolic network. In vitro, RidA homologs from all domains of life deaminate 2-aminoacrylate and RidA proteins from plants, bacteria, yeast, and humans complement the mutant phenotypes of a ridA mutant strain of S. enterica.

Septicemia-causing Vibrio vulnificus produces at least three exoproteases, VvpE, VvpS and VvpM, all of which participate in interactions with human cells. Expression of VvpE and VvpS is induced in the stationary phase by multiple transcription factors including Sigma S, SmcR, and cAMP-CRP complex. Distinct roles of VvpM, such as induction of apoptosis, lead us to hypothesize VvpM expression is different from that of the other exoproteases.

Cyclic di-GMP (c-di-GMP) is a bacterial second messenger molecule that is a key global regulator in Vibrio cholerae, but the molecular mechanisms by which this molecule regulates downstream phenotypes have not been fully characterized. One such regulatory factor that may respond to c-di-GMP is the Vc2 c-di-GMP-binding riboswitch that is hypothesized to control the expression of the downstream putative transcription factor TfoY.

Elevated levels of the second messenger c-di-GMP suppress virulence in diverse pathogenic bacteria, yet mechanisms are poorly characterized. In the food-borne pathogen Listeria monocytogenes, high c-di-GMP levels inhibit mammalian cell invasion. Here, we show that invasion is impaired because of the decreased expression of internalin genes whose products are involved in invasion.

The β-barrel assembly machinery (BAM) complex is the core machinery for the assembly of β-barrel membrane proteins, and inhibition of BAM complex activity is lethal to bacteria. Discovery of integral membrane proteins that are key to pathogenesis yet do not require assistance from the BAM complex raises the question of how these proteins assemble into bacterial outer membranes.