Research Publications (Food Safety)

The Yersinia genus comprises pathogens that are able to adapt to an environmental life cycle stage as well as to mammals. Yersinia enterocolitica strain W22703 exhibits both insecticidal and nematocidal activity conferred by the tripartite toxin complex (Tc) that is encoded on the 19 kb pathogenicity island Tc-PAIYe. All tc genes follow a strict temperature regulation in that they are silenced at 37°C, but activated at lower temperatures.

Cohesion of biofilms made by Yersinia pestis and Yersinia pseudotuberculosis (Yptb) has been attributed solely to an extracellular polysaccharide matrix encoded by the hms genes (Hms-ECM). However, mutations in the Yptb BarA/UvrY/CsrB regulatory cascade enhance biofilm stability without dramatically increasing Hms-ECM production.

While alternating between insects and mammals during its lifecycle, Yersinia pestis, the flea transmitted bacterium that causes plague, regulates its gene expression appropriately to adapt to these two physiologically disparate host environments. In fleas competent to transmit Y. pestis, low GC content genes y3555, y3551 and y3550 are highly transcribed, suggesting that these genes have a highly prioritized role in flea infection.

The phage shock protein (Psp) system is a stress response pathway that senses and responds to inner membrane damage. The genetic components of the Psp system are present in several clinically relevant Gram-negative bacteria, including Vibrio cholerae. However, most of the current knowledge about the Psp response stems from in vitro studies in Escherichia coli and Yersinia enterocolitica. In fact, the Psp response in V. cholerae has remained completely uncharacterized.

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).

The second messenger cyclic di-GMP is almost ubiquitous among bacteria and so are the cyclic di-GMP turnover proteins, which mediate the transition between motility and sessility. EAL domain proteins have been characterized as cyclic di-GMP-specific phosphodiesterases.

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 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 Yersinia enterocolitica Ysa type III secretion system (T3SS) is associated with intracellular survival, and, like other characterized T3SSs, it is tightly controlled. Expression of the ysa genes is only detected following growth at low temperatures (26°C) and in high concentrations of sodium chloride (290 mM) in the media. The YsrSTR phosphorelay (PR) system is required for ysa expression and likely responds to NaCl.

Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) catalyzes electron transfer from NADH to ubiquinone in the bacterial respiratory chain, coupled with Na+ translocation across the membrane. Na+-NQR maturation involves covalent attachment of FMN residues, catalyzed by flavin transferase encoded by the nqr-associated apbE gene.