Dam controls O-Ag chain length in Salmonella enterica by regulating the expression of Wzz protein.

SARNACKI SH, MAROLDA CL, NOTO LLANA M, GIACOMODONATO MN, VALDANO MA, CERQUETTI MC

Argentina

Congreso; SAIB 2009. Reunion Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.; 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.

Dam protein is a global regulator of bacterial gene expression. We have previously observed that a S. Enteritidis dam mutant (Ädam) has a partial defect in the length distribution of O Ag polysaccharide. Since Wzz protein is implicated in the regulation of LPS O Ag chain length, we speculate that Dam modulates wzz expression. The amount of Wzz, determined by Western blot, was 3-fold lower in Ädam than in the wt. Ädam wzz promoter activity showed a reduction compared to the wt (results further confirmed by RT-PCR). RcsB and PmrA proteins regulate the expression of wzz gene. The rcsB mutant of S. Enteritidis shows an LPS pattern similar to that of the Ädam. For that reason we investigated whether LPS pattern is affected in a SEÄdam mutant with an RcsB and PmrA overproducing background. To this purpose, rcsB and pmrA genes were cloned into pUC18 and electroporated in SEÄdam mutant and wt. We observed that the O Ag pattern in Ädam RcsB overproducer was similar to that shown by the wt. On the contrary, the overproduction of PmrA did not modify the LPS chain length in Ädam. The expression of both pmrA and rcsB genes measured by RT-PCR was reduced in the dam mutant background. Altogether, our results suggest that Dam methylation modulates LPS O Ag synthesis in S. Enteritidis by the regulation of the Wzz production, probably in an RcsB-dependent fashion.