Regulation of the acid-resistance asr gene by RcsCDB and RstBA systems in Salmonella Typhimurium

TORRES LAMBERTI, MF; FARIZANO JV; DELGADO MA,; LOPEZ, FE

Rosario, Santa Fe

Congreso; 50th Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología molecular.; 2014

SAIB

Salmonella Typhimurium uses specialized mechanisms to control the gene regulation, like the two component systems, to survive at changes in the environmental. As the RcsCDB system is induced in acidic medium, our goal was to identify genes whose expression depends on this system activation. Our results showed that the RcsCDB system controls negatively the asr transcription, an small acid shock RNA required to establish the Salmonella infection. As was reported that the RstBA system upregulated the asr expression, we also investigated if exist an RstBA/RcsCDB systems interaction to control this gene transcription, when the bacteria is growing in acid medium. The bioinformatic and gel shift analysis showed that the asr gene promoter region contains a potential binding site for RcsB and RstA, and that both regulators exert their effect by directly binding to these boxes. In addition, using the asr::lacZY chromosomal transcriptional fusions, we demonstrated that RcsB and RstA act independently to control the asr expression, indicating that no interaction between these regulators occurs. However, more advanced studies showed that the RcsB activation in an acid medium, represses expression of rstA. This observation suggests that RcsB and RstA indirectly would interact to down or upregulate the asr transcription, depending on the medium in which the bacteria is growing.