Expression analysis of Sinorhizobium meliloti 1021rpoH1 rpoH2 mutant during heat shock

Investigation of whole genome gene expression level changes in a Sinorhizobium meliloti 1021 rpoH1 rpoH2 double mutant, compared to the wild-type strain. The mutations engineered into this strain render it deficient in symbiotic nitrogen fixation. The mutants analyzed in this study are further described in Mitsui, H, T. Sato, Y. Sato, and K. Minamisawa. 2004. Sinorhizobium meliloti RpoH1 is required for effective nitrogen-fixing symbiosis with alfalfa. Mol Gen Genomics 271:416-425. A twenty chip study using total RNA recovered from four separate cultures of a wild-type strain grown at 25°C, four separate cultures of a wild-type strain with heat shock at 37°C for 10 min after a shift from 25°C, four separate cultures of a wild-type strain with heat shock at 37°C for 40 min after a shift from 25°C, four separate cultures of a rpoH1 rpoH2 double mutant strain with heat shock at 37°C for 10 min after a shift from 25°C, and four separate cultures of a rpoH rpoH2 double mutant strain with heat shock at 37°C for 40 min after a shift from 25°C. Each chip measures the expression level of 6,197 genes from Sinorhizobium meliloti 1021 with four 60-mer perfect-match probes per gene, with two-fold technical redundancy.