CodY is required for nutritional repression of Bacillus subtilis genetic competence

Abstract

The acquisition of genetic competence by Bacillus subtilis is repressed when the growth medium contains Casamino Acids. This repression was shown to be exerted at the level of expression from the promoters of the competence-regulatory genes srfA and comK and was relieved in strains carrying a null mutation in the codY gene. DNase I footprinting experiments showed that purified CodY binds directly to the srfA and comK promoter regions.When Bacillus subtilis cells reach stationary phase, they induce several adaptive responses. Among these is the acquisition of genetic competence, a physiological state that enables cells to take up exogenous DNA. The acquisition of competence requires the expression of at least 20 "late" com genes (7), whose transcription is regulated by a variety of nutritional, growth stage-, and cell type-specific mechanisms. These regulatory mechanisms involve the products of at least 15 additional genes (13). In the primary regulatory cascade, two extracellular signal peptides, competence-stimulating factor (39) and ComX (21), are detected by the products of the oligopeptide permease (opp) operon (29, 32) and comP, respectively, and as a result, the transcription factor ComA becomes phosphorylated. Phosphorylated ComA acts as a positive regulator for the srfA operon (14,26,27,45), one of whose products, ComS, is needed for expression of comK (5,6,18). ComK, in turn, activates transcription of the late com genes (e.g., comG [1,16,42,44]). The ComK activation pathway is counterbalanced by the MecA/MecB system, which inhibits ComK activity and can prevent the acquisition of competence under inappropriate environmental conditions (10,19,20,24).During exponential growth in minimal medium, competence is repressed by the addition of Casamino acids (9), an effect that appears to be exerted before srfA expression in the regulatory cascade (15). Such a repressive effect of amino acid mixtures has been described for other operons (2), including hut, the histidine utilization operon (3), dpp (37), which encodes a dipeptide transport system (23), and gsiA (25), which codes for a regulatory protein phosphatase (28). The product of the codY gene has been shown to be required for amino acid repression of the dpp operon (36, 38), and a codY mutation partially relieves amino acid control of hut (11, 38) and gsiA (35). Moreover, purified CodY binds to a part of the dpp promoter region within which mutations relieve amino acid repression (34). Since competence is also repressed by mixtures of amino acids, we tested whether the codY gene has any role in this repression. We show that CodY is required for the effect of Casamino Acids on competence and that CodY interacts with the srfA and comK promoter regions. MATERIALS AND METHODSBacterial strains. All B. subtilis strains used in this study (Table 1) were derived from FJS107 (36), a derivative of JH642 (30).Media. S7 minimal medium for competence assays and ␤-galactosidase assays contained S7 minimal salts (46) supplemented with 1% glucose, 0.1% glutamate, and ami...

Guanine Nucleotides Guanosine 5′-Diphosphate 3′-Diphosphate and GTP Co-operatively Regulate the Production of an Antibiotic Bacilysin in Bacillus subtilis

“…Untreated culture samples (open symbols) were also examined in parallel as a reference. B, stringent TI112 (squares) and relaxed TI113 (circles) strains were grown and treated with decoyinine as in A. transcription of various stationary phase genes in B. subtilis (9,(31)(32)(33). Recently, the CodY protein was demonstrated to play a key role in the initiation of sporulation and genetic competence by detecting intracellular GTP (9, 10).…”

Induction of toxins in Clostridium difficile is associated with dramatic changes of its metabolism

“…Moreover, all PaLoc genes are induced in a codY knockout mutant (Dineen et al, 2007), and purified CodY binds to the promoter region of tcdR; this binding is enhanced by the presence of GTP and branched-chain amino acids (BCAAs). CodY is a repressor that regulates many genes in Bacillus subtilis and other Gram-positive bacteria, acting as a sensor for energy (GTP) and/or BCAAs (Guedon et al, 2001;Molle et al, 2003;Petranovic et al, 2004;Ratnayake-Lecamwasam et al, 2001;Serror & Sonenshein, 1996b;Shivers & Sonenshein, 2004). However, the control of toxin expression in C. difficile appears to be more complex, since glucose downregulates toxin production in the codY mutant also (Dineen et al, 2007).…”

A new Bacillus subtilis gene, med, encodes a positive regulator of comK

“…Another positive regulator of competence development, SinR, may be required for optimal comS expression (10,21). In addition, the Spo0A-AbrB system acts on comK regulation independently of the route involving MecA and ClpC, and CodY is also required for nutritional repression of comK (11,12,41,48). The importance of all of this regulation of comK is that ComK is the direct positive regulator of transcription of the late competence genes that encode the apparatus for processing and incorporating exogenous DNA into the cell (12,48,50,51).…”