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Bacillus subtilis 168, WT vs. ΔMWX, WT vs. Δ7ECF, Δ7ECF vs. ΔMWX.

ABSTRACT: Bacillus subtilis encodes seven extracytoplasmic function (ECF) sigma factors. Three (sigma M, sigma W and simga X) mediate responses to cell envelope active antibiotics. The functions of sigma Y, sigma Z, sigma V, and YlaC remain largely unknown, and strong inducers of these sigma factors and their regulons have yet to be defined. Here, we define transcriptomic and phenotypic differences under non-stress conditions between strains carrying deletions in all seven ECF sigma factor genes (Δ7ECF), a sigMWX triple mutant (∆MWX), and the parental 168 strain. Our results identify >80 genes as at least partially dependent on ECF sigma factors and, as expected, most of these are dependent on sigma M, sigma W or sigma X which are active at a significant basal level during growth. Several genes, including the eps operon encoding enzymes for exopolysaccharide (EPS) production, were decreased in expression in Δ7ECF but affected little if at all in ΔMWX. Consistent with this observation, Δ7ECF (but not ∆MWX) showed reduced biofilm formation. Extending previous observations, we also note that ∆MWX is sensitive to a variety of antibiotics and Δ7ECF is either as sensitive as, or slightly more sensitive than, the ΔMWX strain to these stressors. These findings emphasize the overlapping nature of the seven ECF s factor regulons in B. subtilis, confirm that three of these (sigma M, W or X) play the dominant role in conferring intrinsic resistance to antibiotics, and provide initial insights into the roles of the remaining ECF sigma factors.

ORGANISM(S): Bacillus subtilis Bacillus subtilis subsp. subtilis str. 168

PROVIDER: GSE22930 | GEO | 2010/07/21

SECONDARY ACCESSION(S): PRJNA127933

REPOSITORIES: GEO

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Project description:To define the ECF sigma sigV - regulated genes during log growth phase in LB media under induction conditions for sigV The seven extracytoplasmic function (ECF) sigma (σ) factors of Bacillus subtilis are broadly implicated in resistance to antibiotics and other cell envelope stressors mediated, in part, by regulation of cell envelope synthesis and modification enzymes. We here define the regulon of σV as including at least 20 operons many of which are also regulated by σM, σX, or σW. The σV regulon is strongly and specifically induced by lysozyme and this induction is key to the intrinsic resistance of B. subtilis to lysozyme. Strains with null mutations in either sigV or in all seven ECF σ factor genes (Δ7ECF) have essentially equal increases in sensitivity to lysozyme. Induction of σV in the Δ7ECF background restores lysozyme resistance, whereas induction of σM, σX or σW does not. Lysozyme resistance results from the ability of σV to activate the transcription of two operons: the autoregulated sigV-rsiV-oatA-yrhK operon and dltABCDE. Genetic analyses reveal that oatA and dlt are largely redundant with respect to lysozyme sensitivity: single mutants are not affected in lysozyme sensitivity whereas a double oatA dltA mutant is as sensitive as a sigV null strain. Moreover, the triple sigV oatA dltA mutant is no more sensitive than the oatA dltA double mutant, indicating that there are no other σV-dependent genes necessary for lysozyme resistance. Thus, σV confers lysozyme resistance by activation of two cell wall modification pathways: O-acetylation of peptidoglycan catalyzed by OatA and D-alanylation of teichoic acids by DltABCDE. Strains Δ7Pxyl-sigV + xylose vs. Δ7Pxyl-sigV - xylose, 168 + lysozyme vs. 168 - lysozyme. Each experiment was conducted 6 times using three independent total RNA preparations (biologlical triplicates). For each paired comparison, one sample was labeled with Alexa Fluor 555 and the other was with Alexa Fluor 647. For each comparison, three replicates were performed with dyeswap with the same RNA preparation.

Project description:Abstract of associated manuscript: The Bacillus subtilis extracytoplasmic function (ECF) sigma(M) factor is activated by cell envelope stress elicited by antibiotics, and by acid, heat, ethanol and superoxide stresses. Here, we have used several complementary approaches to identify genes controlled by sigma(M). In many cases, expression is only partially dependent on sigma(M) because of both overlapping promoter recognition with other ECF sigma factors and the presence of additional promoter elements. Genes regulated by sigma(M) have a characteristic pattern of induction in response to cell envelope-acting antibiotics as evidenced by hierarchical clustering analysis. sigma(M) also contributes to the expression of the Spx transcription factor and thereby indirectly regulates genes of the Spx regulon. Cell envelope stress responses also include regulons controlled by sigma(W), sigma(B) and several two-component regulatory systems (e.g. LiaRS, YycFG, BceRS). Activation of the sigma(M) regulon increases expression of proteins functioning in transcriptional control, cell wall synthesis and shape determination, cell division, DNA damage monitoring, recombinational repair and detoxification. WT (-van) vs. WT (+van), sigM (-van) vs. sigM (+van), WT (-van) vs. sigM (-van), WT (+van) vs. sigM (+van), WT (-van) vs. spx (-van), WT (+van) vs. spx (+van). Each experiment was conducted at least twice using two independent total RNA preparations. For vancomycin untreated and treated experiments, untreated samples were labeled with Alexa Fluor 555 and treated samples with Alexa Fluor 647. For WT vs. mutant experiments, wild type was labeled with Alexa Fluor 555 and mutants with Alexa Fluor 647. For dye swap experiment, wild-type was labeled with Alexa Fluor 647 and mutant with Alexa Fluor 555. Bacillus subtilis CU1065, WT (-van) vs. WT (+van), sigM (-van) vs. sigM (+van), WT (-van) vs. sigM (-van), WT (+van) vs. sigM (+van), WT (-van) vs. spx (-van), WT (+van) vs. spx (+van)

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Bacillus subtilis 168, WT vs. ΔMWX, WT vs. Δ7ECF, Δ7ECF vs. ΔMWX.

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