Praveen Rishi
نویسندگان
چکیده
Salmonella enterica serovar typhimurium (S. typhimurium) encounters short chain fatty acids (inorganic acids containing propionate, butyrate and acetate) in the intestine as well as in food preservatives. Short chain fatty acids (SCFAs) exposed organisms have been reported to offer resistance to organic acid resulting into enhanced virulence. However, the role of hilA (hyper invasive loci) gene expression has not been assessed in this context. In the present study, S. typhimurium was grown under SCFAs stress condition simulating the in vivo environment and hilA gene expression was evaluated. The gene expression was measured by β-galactosidase (β-gal) assay using a hilA-lacZY fusion strain and calculated as Miller units. hilA gene expression was found to be significantly higher in the SCFAs exposed cells than the unexposed ones, after 2hrs and 4hrs of exposure. However, no significant difference was observed between the activities at 2hrs and 4hrs. It indicates that hilA gene gets expressed by 2 hrs and persists till 4hrs at least. The β-gal activity was also measured in the unadapted / SCFAs adapted organisms followed by acid shock for 1hr. The gene expression was also found to be higher in the SCFAs adapted – acid (pH 3) challenged as compared to the unadapated acid challenged organisms suggesting that SCFAs adaptation may induce organic acid tolerance by modulating the hilA response. This observation indicates that hilA may be the additional gene contributing to acid resistance and thereby increasing virulence of the organism after SCFAs adaptation.
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تاریخ انتشار 2007