Research Publications (Food Safety)

Virulence traits are essential for pathogen fitness but whether they affect microbial performance in the environment, where they are not needed, remains experimentally unconfirmed. We investigated this question with the facultative pathogen Listeria monocytogenes and its PrfA virulence regulon. PrfA-regulated genes are activated intracellularly (PrfA “ON”) but shut down outside the host (PrfA “OFF”).

The parasite Toxoplasma gondii is an environmentally persistent pathogen that can cause fatal disease in humans, terrestrial warm-blooded animals, and aquatic mammals. While an association between T. gondii exposure and prey specialization on marine snails was identified in threatened California sea otters, the ability of kelp-dwelling snails to transmit terrestrially derived pathogens has not been previously investigated.

Due to climate change, sea ice experiences changes in terms of extent and physical properties. In order to understand how sea ice microbial communities are affected by changes in physiochemical properties of the ice, we used 454-sequencing of 16S and 18S rRNA genes to examine environmental control of microbial diversity and composition in Antarctic sea ice.

In order to elucidate the main predictors of Vibrio cholerae dynamics and to estimate the risk of V.cholerae related diseases, a recently developed direct detection approach based on FISH and solid phase cytometry (CARD-FISH/SPC) was applied in comparison to cultivation for water samples from the lake Neusiedler See, Austria and three shallow alkaline lakes over a period of 20 months. V.cholerae attached to crustacean zooplankton was quantified via FISH and epifluorescence microscopy.

Vibrio vulnificus is a marine bacterium associated with human and fish (mainly farmed eels) diseases globally known as vibriosis. The ability to infect and overcome eel innate immunity relies on a virulence plasmid (pVvbt2) specific for biotype 2 (Bt2) strains. In the present study, we demonstrated that pVvbt2 encodes a host-specific iron acquisition system that depends on an outer membrane receptor for eel transferrin called Vep20.

The CRISPR/Cas system is used by bacteria and archaea against invading conjugative plasmids or bacteriophages. Central to this immunity system are genomic CRISPR loci that contain fragments of invading DNA. These are maintained as spacers in the CRISPR loci between direct repeats and the spacer composition in any bacterium reflects its evolutionary history. We analyzed the CRISPR locus sequences of 335 Yersinia pseudotuberculosis complex strains.

Biofilm formation is crucial to the environmental survival and transmission of Vibrio cholerae, the facultative human pathogen responsible for the disease cholera. During its infectious cycle V. cholerae experiences fluctuations in temperature within the aquatic environment and during the transition between human host and aquatic reservoirs.

We report the population structure and dynamics of one E. coli population of wild mallard ducks in their natural environment over four winter seasons, following the characterization of 100 isolates each consecutive season.

The biological roles of low molecular weight penicillin-binding proteins (LMW PBP) have been difficult to discern in Gram-negative organisms. In E. coli, mutants lacking these proteins often have no phenotype, and cells lacking all 7 LMW PBPs remain viable. In contrast, we report here that Vibrio cholerae lacking DacA-1, a PBP5 homolog, displays slow growth, aberrant morphology, and altered peptidoglycan (PG) homeostasis in LB medium, as well as a profound plating defect.