[show abstract][hide abstract] ABSTRACT: Bacillus subtilis produces and exports a peptide sporulation killing factor (SkfA) that induces lysis of sibling cells. skfA is part of the skf operon (skfA-H), which is responsible for immunity to SkfA, as well as for production and export of SkfA. Here we report that transcription of skfA is markedly induced when cells of B. subtilis are subjected to phosphate starvation. The role of PhoP in regulation of the skf operon was confirmed by in vitro gel shift assays, which showed that this operon is a new member of the PhoP regulon. A putative stem-loop structure in the skfA-skfB intergenic region is proposed to act as a stabilizer of an skfA-specific transcript.
Journal of Bacteriology 08/2006; 188(14):5299-303. · 3.19 Impact Factor
[show abstract][hide abstract] ABSTRACT: Bacillus subtilis responds to phosphate starvation stress by inducing the PhoP and SigB regulons. While the PhoP regulon provides a specific response to phosphate starvation stress, maximizing the acquisition of phosphate (P(i)) from the environment and reducing the cellular requirement for this essential nutrient, the SigB regulon provides nonspecific resistance to stress by protecting essential cellular components, such as DNA and membranes. We have characterized the phosphate starvation stress response of B. subtilis at a genome-wide level using DNA macroarrays. A combination of outlier and cluster analyses identified putative new members of the PhoP regulon, namely, yfkN (2',3' cyclic nucleotide 2'-phosphodiesterase), yurI (RNase), yjdB (unknown), and vpr (extracellular serine protease). YurI is thought to be responsible for the nonspecific degradation of RNA, while the activity of YfkN on various nucleotide phosphates suggests that it could act on substrates liberated by YurI, which produces 3' or 5' phosphoribonucleotides. The putative new PhoP regulon members are either known or predicted to be secreted and are likely to be important for the recovery of inorganic phosphate from a variety of organic sources of phosphate in the environment.
Journal of Bacteriology 01/2006; 187(23):8063-80. · 3.19 Impact Factor
[show abstract][hide abstract] ABSTRACT: During phosphate starvation, Bacillus subtilis regulates genes in the PhoP regulon to reduce the cell's requirement for this essential substrate and to facilitate the recovery of inorganic phosphate from organic sources such as teichoic and nucleic acids. Among the proteins that are highly induced under these conditions is PstS, the phosphate-binding lipoprotein component of a high-affinity ABC-type phosphate transporter. PstS is encoded by the first gene in the pst operon, the other four members of which encode the integral membrane and cytoplasmic components of the transporter. The transcription of the pst operon was analysed using a combination of methods, including transcriptional reporter gene technology, Northern blotting and DNA arrays. It is shown that the primary transcript of the pst operon is processed differentially to maintain higher concentrations of PstS relative to other components of the transporter. The comparative studies have revealed limitations in the use of reporter gene technology for analysing the transcription of operons in which the messenger RNA transcript is differentially processed.
[show abstract][hide abstract] ABSTRACT: When Bacillus subtilis is subjected to phosphate starvation, the Pho regulon is activated by the PhoP-PhoR two-component signal transduction system to elicit specific responses to this nutrient limitation. The response regulator, PhoP, and its cognate histidine sensor kinase, PhoR, are encoded by the phoPR operon that is transcribed as a 2.7-kb bicistronic mRNA. The phoPR operon is transcribed from two sigma(A)-dependent promoters, P(1) and P(2). Under conditions where the Pho regulon was not induced (i.e., phosphate-replete conditions or phoR-null mutant), a low level of phoPR transcription was detected only from promoter P(1). During phosphate starvation-induced transition from exponential to stationary phase, the expression of the phoPR operon was up-regulated in a phosphorylated PhoP (PhoP approximately P)-dependent manner; in addition to P(1), the P(2) promoter becomes active. In vitro gel shift assays and DNase I footprinting experiments showed that both PhoP and PhoP approximately P could bind to the control region of the phoPR operon. The data indicate that while low-level constitutive expression of phoPR is required under phosphate-replete conditions for signal perception and transduction, autoinduction is required to provide sufficient PhoP approximately P to induce other members of the Pho regulon. The extent to which promoters P(1) and P(2) are activated appears to be influenced by the presence of other sigma factors, possibly the result of sigma factor competition. For example, phoPR is hyperinduced in a sigB mutant and, later in stationary phase, in sigH, sigF, and sigE mutants. The data point to a complex regulatory network in which other stress responses and post-exponential-phase processes influence the expression of phoPR and, thereby, the magnitude of the Pho regulon response.
Journal of Bacteriology 03/2004; 186(4):1182-90. · 3.19 Impact Factor