Sulfur-limitation-regulated proteins in Bacillus subtilis: a two-dimensional gel electrophoresis study

Abstract

Little is known about the genes and enzymes involved in sulfur assimilation in Bacillus subtilis, or about the regulation of their expression or activity. To identify genes regulated by sulfur limitation, the authors used twodimensional (2D) gel electrophoresis to compare the proteome of a wild-type strain grown with either sulfate or glutathione as sole sulfur source. A total of 15 proteins whose synthesis is modified under these two conditions were identified by matrix-assisted laser desorption/ionization time of flight (MALDI TOF) mass spectrometry. In the presence of sulfate, an increased amount of proteins involved in the metabolism of C 1 units (SerA, GlyA, FolD) and in the biosynthesis of purines (PurQ, Xpt) and pyrimidines (Upp, PyrAA, PyrF) was observed. In the presence of glutathione, the synthesis of two uptake systems (DppE, SsuA), an oxygenase (SsuD), cysteine synthase (CysK) and two proteins of unknown function (YtmI, YurL) was increased. The changes in expression of the corresponding genes, in the presence of sulfate and glutathione, were monitored using slot-blot analyses and lacZ fusions. The ytmI gene is part of a locus of 12 genes which are co-regulated in response to sulfur availability. This putative operon is activated by a LysR-like regulator, YtlI. This is the first regulator involved in the control of expression in response to sulfur availability to be identified in B. subtilis.

Global Expression Profile of Bacillus subtilis Grown in the Presence of Sulfate or Methionine

“…Some genes involved in histidine biosynthesis (hisB, hisD, and hisI), pyrimidine biosynthesis (pyrAA and pyrE), one-carbon metabolism (folD), nitrogen metabolism (glnR and nrgA), NAD biosynthesis (nadA and nadB), and energy production (atpI) were upregulated in the presence of sulfate. The synthesis of proteins implicated in the metabolism of one-carbon units and in the biosynthesis of nucleotides has been shown to be repressed under sulfur-limiting conditions (3). This is consistent with our transcriptome data.…”

“…The ssu operon is expressed under the same conditions (26). However, the expression level of the ytmI and ssu operons is about 200-to 1,000-fold higher in the presence of methionine than in the presence of sulfate while the yxeK and yhcL genes are only 5-to 10-fold more strongly expressed in the presence of methionine (3,26) (this study). It is noteworthy that the ssu operon is regulated at two different levels (initiation and termination of transcription) (26), whereas a cascade of regulation modulates the expression of the ytmI operon.…”

“…The expression of the ssu operon, which encodes an ABC permease system for aliphatic sulfonates and an oxygenase, is derepressed in the presence of methionine (Table 1) (3,26). Several genes encoding transporters (yhcL, ytmJ, ytmK, ytmL, ytmM, ytmN, yxeM, and yxeO) are also expressed more strongly in the presence of methionine than in the presence of sulfate ( Table 1).…”

“…The ytlI gene is transcribed divergently from the ytmI operon. The YtlI protein controls the expression of this operon (3). Interestingly, DNA arrays showed that the expression of the ytlI gene was 1.5-fold higher in methionine than in sulfate (Table 1).…”

Transcriptome and proteome analysis of Bacillus subtilis gene expression in response to superoxide and peroxide stress

“…This operon is not regulated by the S box mechanism and is repressed by sulfate and cysteine, which also holds true for the two recently characterized operons ytmIJKLMNO-ytnI-ribR-ytnLM and yxeKLMNOPQ, encoding proteins predicted to be involved in the utilization of alternative sulfur sources (Coppee et al, 2001;Auger et al, 2002).…”