Overexpression of Sinorhizobium meliloti ECF sigma factors.

We characterized transcriptomes for strains overexpressing each of the Sinorhizobium meliloti ECF sigma factors the via a plasmid-borne, melibiose-inducible promoter plasmid (PmelA; pCAP11: Pinedo et al. 2008 J Bacteriol 190:2947-2956) compared to control strains carrying the empty vector. To identify genes whose expression was dependent on each of the 11 ECF sigma factors (RpoE1-RpoE10 and FecI), we used strains overexpressing ECF sigma factors via the melibiose-inducible promoter (PmelA) plasmids. Each plasmid was conjugated into S. meliloti wild type strain, CL150, an Rm1021-derived strain corrected for mutations in pstC and ecfR1 (Schlüter et al. 2013 BMC Genomics 14:156). We employed three different control strains: CL150 pCAP11; CL101 pCAP11 (corrected only for ecfR1); and Rm1021 pCAP11.