The DNA adenine methyltransferase protein participates in the regulation of LPS synthesis in Salmonella enterica serovar Enteritidis

SARNACKI SH, MAROLDA C, NOTO LLANA MA, GIACOMODONATO MN, VALVANO M, CERQUETTI MC.

Istanbul. Turkey.

Congreso; IUMS Congresses 2008: the XII. International Congress of Bacteriology and Applied Microbiology; 2008

IUMS

The DNA adenine methyltransferase (Dam) protein is a global regulator of bacterial gene expression that modulates a variety of processes including DNA replication, mismatch repair, and gene transcription. We have previously observed that a Salmonella enterica serovar Enteritidis dam mutant (SEÄdam) has a partial defect in the length distribution of O antigen polysaccharide. Since Wzz protein is implicated in the regulation of LPS O antigen chain length, we speculate that Dam modulates directly or indirectly the expression of wzz. In fact, the amount of Wzz, determined by Western blot, was 3-6-fold lower in SEÄdam than in the parental strain. It is known that RcsB and PmrA proteins regulate the expression of wzz gene; interestingly, we found that the rcsB mutant of S. Enteritidis shows an LPS pattern similar to that of the dam mutant. 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 wild type strain. We observed that the O antigen pattern in SEÄdam RcsB overproducer was similar to that shown by the parental strain. On the contrary, the overproduction of PmrA did not modify the LPS chain length in SEÄdam mutant. Altogether, our results suggest that Dam methylation modulates LPS O antigen synthesis in S. Enteritidis by the regulation of the Wzz production, probably in an RcsB-dependent fashion. Moreover, our findings would indicate that the regulation is dependent on the RcsC/YojN/RcsB two-component system and independent of PmrA/PmrB two-component system.