Scatter plot of the microarray analysis of the S. meliloti rpoH1 mutant versus wild type at pH 7.0. The plot shows the log2 ratio (M-value) versus the mean signal intensity (A-value) obtained by comparison of the transcriptomes of S. meliloti rpoH1 mutant versus S. meliloti wild type strain 1021. Genes with the greatest changes in expression values (-1 ≤ M-value ≥ 1) are indicated. On the low right corner is an illustration of the genetic map for the operon coding for proteins involved in rhizobactin 1021 biosynthesis and uptake. The numbers below the genes indicate the log2 expression ratios of the genes obtained through the transcriptome analysis.