Global expression profile of Bacillus subtilis grown in the presence of sulfate or methionine

Abstract

DNA arrays were used to investigate the global transcriptional profile of Bacillus subtilis grown in the presence of sulfate or methionine as the sole sulfur source. The expression of at least 56 genes differed significantly under the two growth conditions. The expression of several genes belonging to the S-box regulon was repressed in the presence of methionine probably in response to S-adenosylmethionine availability. The expression of genes encoding transporters (yhcL, ytmJKLMN, and yxeMO) was high when the sulfur source was methionine or taurine and reduced when it was sulfate.

FIG. 1.

Cysteine and methionine biosynthesis pathways in B. subtilis. The different genes encoding proteins involved in sulfate assimilation, cysteine biosynthesis, and methionine biosynthesis are indicated. The functions of some genes are indicated in Table 1. ylnB, ATP sulfurylase; ylnC, adenosine phosphosulfate kinase; cysE, serine acetyltransferase; cysH, 3′-phosphoadenosine 5′-phosphosulfate sulfotransferase; metA, homoserine acetyltransferase; metI, cystathionine γ-synthase/O-acetylhomoserine sulfhydrylase; metC, cystathionine β-lyase; metK, S-adenosylmethionine synthetase; speD, S-adenosylmethionine decarboxylase; mtnK, methylthioribose kinase. The arrow between S-adenosylmethionine and methionine represents several enzymatic steps. Asterisks indicate genes that contain an S box in the leader region.

FIG. 2.

Comparison of the signal intensities of duplicate dots and independent hybridizations. The reproducibility of the DNA arrayresults obtained with 1 μg of total RNA extracted from B. subtilis 168 grown in minimal medium in the presence of sulfate as the sole sulfur source was assessed before subtraction of the background. In all experiments, the results showed a high degree of correlation (>0.94). (A) Comparison of signal intensities of pairs of dots corresponding to each gene. (B) Comparison of signal intensities of each gene in two independent hybridizations obtained from the same RNA sample but reverse transcribed and hybridized independently.(C) Comparison of signal intensities of each gene in two independent hybridizations of RNAs isolated from different cultures grown under the same conditions. Similar results were obtained with B. subtilis 168 grown in minimal medium in the presence of methionine as the sole sulfur source.