Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/12/2006
Publication Date: 5/12/2006
Citation: Bearson, S.M., Bearson, B.L., Rasmussen, M.A. 2006. Genetic analysis of the survival of Salmonella enterica serovar Typhimurium within rumen protozoa. Proceedings of 13S International Symposium Salmonella and Salmonellosis. p.279-282. Interpretive Summary:
Technical Abstract: As revealed by recent investigations, Salmonella enterica serovar Typhimurium is not only capable of surviving within the intracellular environment of rumen protozoa, but Salmonella recovered from rumen protozoa can be more invasive (tissue culture invasion assay) and more virulent (calf infection model). These findings suggest that the intracellular environment of the protozoa triggers the expression of Salmonella genes important for pathogenesis and survival in the host. To identify genes that are critical for Salmonella survival within the protozoal environment, the functional genomic technique, signature-tagged mutagenesis (STM) was used. This insertional mutagenesis system employs transposons containing unique DNA sequences that are easily identified in a complex pool of mutants. Screening of ~ 1,600 STM mutants in a 24-hour rumen protozoa engulfment assay identified six genes important for Salmonella survival within the protozoal environment, rfaI (lipopolysaccharide 1,3-galactosyltransferase), pitA (putative low-affinity phosphate transporter), trkH (potassium uptake protein), hemL (glutamate-1-semialdehyde-2, 1-aminomutase), parA (plasmid partition protein A), rfbU (mannosyl transferase). Characterization of Salmonella in rumen protozoa may reveal an unappreciated reservoir for the pathogen that influences the carrier status of the host as well as enhances virulence of the microorganism.