Transcriptome analysis of Bacillus subtilis salt stress adaptation
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ABSTRACT: Whole-genome microarray technology and state-of-the-art proteomic techniques were applied to provide a global and time-resolved picture of the physiological response of B. subtilis cells exposed to a severe and sudden osmotic up-shift. This combined experimental approach provided quantitative data for 3961 mRNA profiles, 590 expression profiles of proteins detected in the cytosol and 383 expression profiles of proteins detected in the membrane fraction. Our study uncovered a well-coordinated induction of gene expression subsequent to an osmotic up-shift that involves large parts of the SigB, SigW, SigM and SigX regulons and additionally osmotic up-regulation of a large number of genes that do not belong to these regulons. In total, osmotic up-regulation of about 500 B. subtilis genes was observed. Our data provide an unprecedented rich basis for further in-depth investigation on the physiological and genetic responses of B. subtilis to hyperosmotic stress.
Project description:Whole-genome microarray technology and state-of-the-art proteomic techniques were applied to provide a global and time-resolved picture of the physiological response of B. subtilis cells exposed to a severe and sudden osmotic up-shift. This combined experimental approach provided quantitative data for 3961 mRNA profiles, 590 expression profiles of proteins detected in the cytosol and 383 expression profiles of proteins detected in the membrane fraction. Our study uncovered a well-coordinated induction of gene expression subsequent to an osmotic up-shift that involves large parts of the SigB, SigW, SigM and SigX regulons and additionally osmotic up-regulation of a large number of genes that do not belong to these regulons. In total, osmotic up-regulation of about 500 B. subtilis genes was observed. Our data provide an unprecedented rich basis for further in-depth investigation on the physiological and genetic responses of B. subtilis to hyperosmotic stress. Cells were grown in a minimal medium to early exponential phase and were then exposed to a strong osmotic up-shift by the addition of 6% (w/v) NaCl. Samples were taken before and 10, 30, 60 and 120 min subsequent to the addition of NaCl. Microarray hybridizations were performed with RNA from three biological replicates. The individual samples were labeled with Cy5; a reference pool consisting of equal amounts of RNA from all 15 samples was labeled with Cy3 (common reference design). After intensity-dependent (Lowess) normalization, the ratios of duplicate spots were averaged resulting in three biologically independent expression values per gene and time point.
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)
Project description:Comprison of the transcriptome of wild type Bacillus subtilis to the mutants sigW, rasP and prsW to select all candidate sigW regulated genes. We identified 89 genes as being sigW regulated, including several non-coding RNA's. The effects of rasP and prsW mutations on sigW regulated genes were relatively mild, implying that RasP or PrsW are not strictly required for sigW activation. The rasP mutant has a peliotropic phenotype, affecting competence development, protein secretion and membrane protein production. We show that these are not mirrored in the transcriptome, suggesting that RasP exerts its effects at the post transcriptional level. RNA samples prepared from B. subtilis 168 and mutants sigW, rasP, and prsW were grown in Luria Bertani broth to O.D 600nm 1.0 were reverse transcribed, labeled and hybridized to tiling arrays. All hybridizations (except prsW which was in duplicate) were performed in triplicate using RNA isolated from independent cultures.
Project description:Comprison of the transcriptome of wild type Bacillus subtilis to the mutants sigW, rasP and prsW to select all candidate sigW regulated genes. We identified 89 genes as being sigW regulated, including several non-coding RNA's. The effects of rasP and prsW mutations on sigW regulated genes were relatively mild, implying that RasP or PrsW are not strictly required for sigW activation. The rasP mutant has a peliotropic phenotype, affecting competence development, protein secretion and membrane protein production. We show that these are not mirrored in the transcriptome, suggesting that RasP exerts its effects at the post transcriptional level.
Project description:Comparison of the transcriptome of Bacillus subtilis under going membrane protein overproduction in the wild type, sigW and cssRS deletion strains. We demonstrate that the dynamics of the stress systems involved in membrane overproduction are far more complicated than was first hypothesised and that many more systems than SigW and CssRS are involved in membrane protein overexpression stress. Interestingly the cssRS genes are repressed in the sigW deletion strain.
Project description:Background. Bacillus subtilis is a favorable host for the production of industrially relevant proteins because of its capacity of secreting proteins into the medium to high levels, its GRAS (Generally Recognized As Safe) status, its genetic accessibility and its capacity to grow in large fermentations. However, production of heterologous proteins still faces limitations. Results. This study aimed at the identification of bottlenecks in secretory protein production by analyzing the response of B. subtilis at the transcriptome level to overproduction of eight secretory proteins of endogenous and heterologous origin and with different subcellular or extracellular destination: secreted proteins (NprE and XynA of B. subtilis, Usp45 of Lactococcus lactis, TEM-1beta -lactamase of Escherichia coli), membrane proteins (LmrA of L. lactis and XylP of Lactobacillus pentosus) and lipoproteins (MntA and YcdH of B. subtilis). Responses specific for proteins with a common localization as well as more general stress responses were observed. The latter include upregulation of genes encoding intracellular stress proteins (groES/EL, CtsR regulated genes). Specific responses include upregulation of the liaIHGFSR operon under Usp45 and TEM-1 beta-lactamase overproduction; cssRS, htrA and htrB under all secreted proteins overproduction; sigW and SigW-regulated genes mainly under membrane proteins overproduction; and ykrL (encoding an HtpX homologue) specifically under membrane proteins overproduction. Conclusions. The results give better insights into B. subtilis responses to protein overproduction stress and provide potential targets for genetic engineering in order to further improve B. subtilis as a protein production host.
Project description:Here, the role of σM and its regulon in stress response and survival of B. cereus ATCC 14579 was assessed by comparative transciptome and phenotypic analysis of this strain and its sigM deletion strain. Exposure of B. cereus ATCC 14579 to a wide range of stresses revealed expression of sigM, encoding σM, to be up-regulated mainly in the presence of ethanol and after alkaline pH-shock. Next to this, disc diffusion tests showed the sigM deletion strain to be more sensitive to oxidizing agents and to be more resistant to cell-wall targeting antibiotics than the wild-type strain. The σM regulon was subsequently determined by comparative transcriptional analyses of the wild-type and its sigM-deletion strain after exposure to ethanol. The putative σM-regulon was shown to consist of 29 genes, several of these genes are predicted to be involved in counteracting oxidative stress, such as an NADH oxidase, a ferredoxin, and a lysine decarboxylase or could encode enzymes involved in methionine metabolism, leading toward L-cysteine production, including luxS. Screening of promoter upstream regions allowed for the assessment of a B. cereus consensus promoter binding site for σM. Since the consensus promoter binding site for B. cereus ATCC 14579 σM, its regulon and the predicted functionalities are different from the corresponding features in B. subtilis, it can be concluded that σM plays a unique role in B. cereus stress response and survival. Keywords: Stress response, comparative transcriptome study
Project description:Background. Bacillus subtilis is a favorable host for the production of industrially relevant proteins because of its capacity of secreting proteins into the medium to high levels, its GRAS (Generally Recognized As Safe) status, its genetic accessibility and its capacity to grow in large fermentations. However, production of heterologous proteins still faces limitations. Results. This study aimed at the identification of bottlenecks in secretory protein production by analyzing the response of B. subtilis at the transcriptome level to overproduction of eight secretory proteins of endogenous and heterologous origin and with different subcellular or extracellular destination: secreted proteins (NprE and XynA of B. subtilis, Usp45 of Lactococcus lactis, TEM-1beta -lactamase of Escherichia coli), membrane proteins (LmrA of L. lactis and XylP of Lactobacillus pentosus) and lipoproteins (MntA and YcdH of B. subtilis). Responses specific for proteins with a common localization as well as more general stress responses were observed. The latter include upregulation of genes encoding intracellular stress proteins (groES/EL, CtsR regulated genes). Specific responses include upregulation of the liaIHGFSR operon under Usp45 and TEM-1 beta-lactamase overproduction; cssRS, htrA and htrB under all secreted proteins overproduction; sigW and SigW-regulated genes mainly under membrane proteins overproduction; and ykrL (encoding an HtpX homologue) specifically under membrane proteins overproduction. Conclusions. The results give better insights into B. subtilis responses to protein overproduction stress and provide potential targets for genetic engineering in order to further improve B. subtilis as a protein production host. Samples for transcriptome analyses were induced at the exponential-growth phase (OD600 = 0.7) with 0.1% subtilin (subtilin containing supernatant of subtilin producing B. subtilis strain ATCC 6633). Cells were harvested 30 min after induction. Three or four independent cultures of each strain (target strains and controls) were used, and cells were sampled for microarray experiment.
Project description:Here, the role of σM and its regulon in stress response and survival of B. cereus ATCC 14579 was assessed by comparative transciptome and phenotypic analysis of this strain and its sigM deletion strain. Exposure of B. cereus ATCC 14579 to a wide range of stresses revealed expression of sigM, encoding σM, to be up-regulated mainly in the presence of ethanol and after alkaline pH-shock. Next to this, disc diffusion tests showed the sigM deletion strain to be more sensitive to oxidizing agents and to be more resistant to cell-wall targeting antibiotics than the wild-type strain. The σM regulon was subsequently determined by comparative transcriptional analyses of the wild-type and its sigM-deletion strain after exposure to ethanol. The putative σM-regulon was shown to consist of 29 genes, several of these genes are predicted to be involved in counteracting oxidative stress, such as an NADH oxidase, a ferredoxin, and a lysine decarboxylase or could encode enzymes involved in methionine metabolism, leading toward L-cysteine production, including luxS. Screening of promoter upstream regions allowed for the assessment of a B. cereus consensus promoter binding site for σM. Since the consensus promoter binding site for B. cereus ATCC 14579 σM, its regulon and the predicted functionalities are different from the corresponding features in B. subtilis, it can be concluded that σM plays a unique role in B. cereus stress response and survival. The sigM deletion strain of B. cereus ATCC 14579 was cultured to an OD600 of ~0.6. Here the first RNA sample was taken, 0 min. After sampling 4% of ethanol was added (v/v), and samples were taken after 10, 30 and 60 minutes of exposure. Comparisons performed were 0 min - 10 min, 0 min - 30 min, and 0 min - 60 min.