B. subtilis
not annotated - annotated - LINNAEUS only
20971907
Mismatch repair modulation of MutY activity drives Bacillus subtilis stationary-phase mutagenesis.
Stress-promoted mutations that occur in nondividing cells (adaptive mutations) have been implicated strongly in causing genetic variability as well as in species survival and evolutionary processes. Oxidative stress-induced DNA damage has been associated with generation of adaptive His(+) and Met(+) but not Leu(+) revertants in strain Bacillus subtilis YB955 (hisC952 metB5 leuC427). Here we report that an interplay between MutY and MutSL (mismatch repair system [MMR]) plays a pivotal role in the production of adaptive Leu(+) revertants. Essentially, the genetic disruption of MutY dramatically reduced the reversion frequency to the leu allele in this model system. Moreover, the increased rate of adaptive Leu(+) revertants produced by a MutSL knockout strain was significantly diminished following mutY disruption. Interestingly, although the expression of mutY took place during growth and stationary phase and was not under the control of RecA, PerR, or sigma(B), a null mutation in the mutSL operon increased the expression of mutY several times. Thus, in starved cells, saturation of the MMR system may induce the expression of mutY, disturbing the balance between MutY and MMR proteins and aiding in the production of types of mutations detected by reversion to leucine prototrophy. In conclusion, our results support the idea that MMR regulation of the mutagenic/antimutagenic properties of MutY promotes stationary-phase mutagenesis in B. subtilis cells.
21097612
Differential responses of Bacillus subtilis rRNA promoters to nutritional stress.
The in vivo expression levels of four rRNA promoter pairs (rrnp(1)p(2)) of Bacillus subtilis were determined by employing single-copy lacZ fusions integrated at the amyE locus. The rrnO, rrnJ, rrnD, and rrnB promoters displayed unique growth rate regulation and stringent responses. Both lacZ activity and mRNA levels were highest for rrnO under all growth conditions tested, while rrnJ, rrnB, and rrnD showed decreasing levels of activity. During amino acid starvation induced by serine hydroxamate (SHX), only the strong rrnO and rrnJ promoters demonstrated stringent responses. Under the growth conditions used, the rrn promoters showed responses similar to the responses to carbon source limitation induced by alpha-methyl glucoside (alpha-MG). The ratio of P2 to P1 transcripts, determined by primer extension analysis, was high for the strong rrnO and rrnJ promoters, while only P2 transcripts were detected for the weak rrnD and rrnB promoters. Cloned P1 or P2 promoter fragments of rrnO or rrnJ were differentially regulated. In wild-type (relA(+)) and suppressor [relA(S)] strains under the conditions tested, only P2 responded to carbon source limitation by a decrease in RNA synthesis, correlating with an increase in (p)ppGpp levels and a decrease in the GTP concentration. The weak P1 promoter elements remain relaxed in the three genetic backgrounds [relA(+), relA, relA(S)] in the presence of alpha-MG. During amino acid starvation, P2 was stringently regulated in relA(+) and relA(S) cells, while only rrnJp(1) was also regulated, but to a lesser extent. Both the relA(+) and relA(S) strains showed (p)ppGpp accumulation after alpha-MG treatment but not after SHX treatment. These data reveal the complex nature of B. subtilis rrn promoter regulation in response to stress, and they suggest that the P2 promoters may play a more prominent role in the stringent response.
21097623
Contributions of multiple binding sites and effector-independent binding to CodY-mediated regulation in Bacillus subtilis.
CodY is a branched-chain amino acid-responsive transcriptional regulator that controls, directly or indirectly, the expression of more than 100 genes and operons in Bacillus subtilis. Using DNase I footprinting and gel-shift experiments, we identified two CodY-binding regions upstream of a B. subtilis gene (bcaP, previously known as yhdG) that encodes a transporter of branched-chain amino acids. Mutational analysis revealed that both CodY-binding regions contribute to repression in vivo and do so independently of each other. Thus, a single CodY-binding site is apparently sufficient for substantial CodY-dependent regulation. By analyzing affinities of wild-type and mutant CodY-binding sites for CodY and their regulation by wild-type CodY and forms of CodY with various levels of activation by branched-chain amino acids, we concluded that unliganded CodY cannot repress transcription in vivo and that the level of endogenously produced effectors is sufficient for CodY-mediated regulation of promoters with stronger sites. Because the sites with higher affinity apparently respond to lower concentrations of CodY effectors and saturate faster as the concentrations of effectors increase, having two sites of binding with different affinities for CodY permits a promoter to respond to a wider range of intracellular concentrations of effectors.
21131488
Bacillus anthracis sin locus and regulation of secreted proteases.
Bacillus anthracis shares many regulatory loci with the nonpathogenic Bacillus species Bacillus subtilis. One such locus is sinIR, which in B. subtilis controls sporulation, biofilm formation, motility, and competency. As B. anthracis is not known to be motile, to be naturally competent, or to readily form biofilms, we hypothesized that the B. anthracis sinIR regulon is distinct from that of B. subtilis. A genome-wide expression microarray analysis of B. anthracis parental and sinR mutant strains indicated limited convergence of the B. anthracis and B. subtilis SinR regulons. The B. anthracis regulon includes homologues of some B. subtilis SinR-regulated genes, including the signal peptidase gene sipW near the sinIR locus and the sporulation gene spoIIE. The B. anthracis SinR protein also negatively regulates transcription of genes adjacent to the sinIR locus that are unique to the Bacillus cereus group species. These include calY and inhA1, structural genes for the metalloproteases camelysin and immune inhibitor A1 (InhA1), which have been suggested to be associated with virulence in B. cereus and B. anthracis, respectively. Electrophoretic mobility shift assays revealed direct binding of B. anthracis SinR to promoter DNA from strongly regulated genes, such as calY and sipW, but not to the weakly regulated inhA1 gene. Assessment of camelysin and InhA1 levels in culture supernates from sinR-, inhA1-, and calY-null mutants showed that the concentration of InhA1 in the culture supernatant is inversely proportional to the concentration of camelysin. Our data are consistent with a model in which InhA1 protease levels are controlled at the transcriptional level by SinR and at the posttranslational level by camelysin.
21529147
Growth inhibition of Beauveria bassiana by bacteria isolated from the cuticular surface of the corn leafhopper, Dalbulus maidis and the planthopper, Delphacodes kuscheli, two important vectors of maize pathogens.
The phytosanitary importance of the corn leafhopper, Dalbulus maidis (De Long and Wolcott) (Hemiptera: Cicadellidae) and the planthopper, Delphacodes kuscheli Fennah (Hemiptera: Delphacidae) lies in their ability to transmit phloem-associated plant pathogens, mainly viruses and mollicutes, and to cause considerable mechanical damage to corn plants during feeding and oviposition. Fungi, particularly some members of the Ascomycota, are likely candidates for biocontrol agents against these insect pests, but several studies revealed their failure to invade the insect cuticle possibly because of the presence of inhibitory compounds such as phenols, quinones, and lipids and also by the antibiosis effect of the microbiota living on the cuticular surface of the host. The present work aims to understand interactions between the entomopathogenic fungus Beauveria bassiana (Balsamao-Crivelli) Vuillemin (Hypocreales: Cordycipitaceae) and bacterial antagonists isolated from the cuticular surface of D. maidis and D. kuscheli. A total of 155 bacterial isolates were recovered from the insect's cuticle and tested against B. bassiana. Ninety-one out of 155 strains inhibited the growth of B. bassiana. Bacterial strains isolated from D. maidis were significantly more antagonistic against B. bassiana than those isolates from D. kuscheli. Among the most effective antagonistic strains, six isolates of Bacillus thuringiensis Berliner (Bacillales: Bacillaeae (after B. subtilis)), one isolate of B. mycoides Flugge, eight isolates of B. megaterium de Bary, five isolates of B.pumilus Meyer and Gottheil, one isolate of B. licheniformis (Weigmann) Chester, and four isolates of B. subtilis (Ehrenberg) Cohn were identified.