ARS | Publication request: Comparison of real time polymerase chain reaction quantification of changes in hilA and rpoS gene expression of a Salmonella typhimurium poultry isolate grown at fast versus slow dilution rates in an anaerobic continuous

Submitted to: Food Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 31, 2012
Publication Date: August 1, 2012
Citation: Dunkley, K.D., Callaway, T.R., O Bryan, C.A., Kundinger, M.M., Dunkley, C.S., Anderson, R.C., Nisbet, D.J., Crandall, P.G., Ricke, S.C. 2012. Comparison of real time polymerase chain reaction quantification of changes in hilA and rpoS gene expression of a Salmonella typhimurium poultry isolate grown at fast versus slow dilution rates in an anaerobic continuous culture system. Food Biotechnology. 26:239-251.

Interpretive Summary: Salmonella is one of the most common foodborne bacteria; it is responsible for many human illnesses each year. The rate of bacterial growth can impact the expression of Salmonella genes including those of genes responsible for virulence. As the growth rate of Salmonella changed, the expression of two virulence genes changed. Results indicated that low sugar environments may trigger specific gene action and may be responsible for the beginning of virulence of Salmonella.

Technical Abstract: The objective of this study was to determine the genetic responses of a Salmonella enterica Typhimurium poultry isolate during low and high dilution rates (D) in steady state continuous culture (CC) incubations. Samples for genetic analyses were taken from a previous study where S. typhimurium cells had been grown in two chemostats operated concurrently, which were designated as Trials 1 and 2, with eight dilution rates sampled during steady state. Real-time PCR on two target genes (rpoS and hilA) were analyzed as changes in expression of the target gene relative to the reference gene (16S rRNA). At the lowest D (0.0125 h-1) in Trial 2, rpoS expression was more than 2-fold higher than the second highest relative expression. In Trial 1, hilA expression was 21.8- , 27.8-, and 21-fold higher in D 0.0125 h-1, 0.025 h-1, and 0.05 h-1, respectively, compared to D 0.1 h-1, 0.54 h-1, and 1.08 h-1. In Trial 2, D 0.025 h-1 and 0.27 h-1 showed no difference in hilA expression but were significantly higher compared to other D. From these results, low glucose conditions may play an essential role in triggering rpoS induction as well as contributing to potential virulence.