Sporulation in Bacillus subtilis. Correlation of biochemical events with morphological changes in asporogenous mutants.
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ABSTRACT:
SUBMITTER: Waites WM
PROVIDER: S-EPMC1179263 | biostudies-other | 1970 Jul
REPOSITORIES: biostudies-other
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Project description:1. When Bacillus subtilis was grown in a medium in which sporulation occurred well-defined morphological changes were seen in thin sections of the cells. 2. Over a period of 7.5hr. beginning 2hr. after the initiation of sporulation the following major stages were observed: axial nuclear-filament formation, spore-septum formation, release of the fore-spore within the cell, development of the cortex around the fore-spore, the laying down of the spore coat and the completion of the corrugated spore coat before release of the spore from the mother cell. 3. The appearance of refractile bodies and 2,6-dipicolinic acid and the development of heat-resistance began between 5 and 6.5hr. after initiation of sporulation. 4. The appearance of 2,6-dipicolinic acid and the onset of refractility appeared to coincide with a diminution of electron density in the spore core and cortex. 5. Heat-resistance was associated with the terminal stage, the completion of the spore coat. 6. The spore coat was composed of an inner and an outer layer, each of which consisted of three or four electron-dense laminae. 7. Serial sections through cells at an early stage of sporulation showed that the membranes of each spore septum were always continuous with the membranes of a mesosome, which was itself in close contact with the bacterial or spore nucleoid. 8. These changes were correlated with biochemical events occurring during sporulation.
| S-EPMC1187033 | biostudies-other
Project description:1. During the course of growth and sporulation of Bacillus subtilis in chemically defined media, measurements were made of 16 different parameters, including the specific activities of nine intracellular enzymes. 2. Towards the end of exponential growth, proteolytic activity increased and reached a maximum soon after growth ceased. 3. In the presence of an excess of phosphate the specific activity of alkaline phosphatase increased fivefold at the end of exponential growth. 4. The specific activity of malate dehydrogenase remained at a high constant level throughout sporulation, but the specific activity of fumarase showed a two- to three-fold increase 5-9hr. after the end of exponential growth. 5. Aconitase activity was barely detectable during exponential growth in a glucose-glutamate medium, but increased rapidly when glutamate was replaced by citrate or when the glucose in the medium was exhausted. 6. The specific activity of alanine dehydrogenase increased threefold 1-5hr. after the end of exponential growth. 7. The specific activity of soluble NADH oxidase doubled 4-6hr. after the end of exponential growth. 8. Glucose dehydrogenase was undetectable until 4hr. after the end of exponential growth, but its specific activity increased 20-fold over the next 3-4hr. 9. The onset of refractility, the synthesis of 2,6-dipicolinic acid and the appearance of heat-resistance occurred in this order some 6-12hr. after the end of exponential growth. 10. The significance of these changes is discussed in relation to the morphological development of the spore.
| S-EPMC1187032 | biostudies-other
Project description:While vegetative Bacillus subtilis cells and mature spores are both surrounded by a thick layer of peptidoglycan (PG, a polymer of glycan strands cross-linked by peptide bridges), it has remained unclear whether PG surrounds prespores during engulfment. To clarify this issue, we generated a slender ?ponA mutant that enabled high-resolution electron cryotomographic imaging. Three-dimensional reconstructions of whole cells in near-native states revealed a thin PG-like layer extending from the lateral cell wall around the prespore throughout engulfment. Cryotomography of purified sacculi and fluorescent labelling of PG in live cells confirmed that PG surrounds the prespore. The presence of PG throughout engulfment suggests new roles for PG in sporulation, including a new model for how PG synthesis might drive engulfment, and obviates the need to synthesize a PG layer de novo during cortex formation. In addition, it reveals that B. subtilis can synthesize thin, Gram-negative-like PG layers as well as its thick, archetypal Gram-positive cell wall. The continuous transformations from thick to thin and back to thick during sporulation suggest that both forms of PG have the same basic architecture (circumferential). Endopeptidase activity may be the main switch that governs whether a thin or a thick PG layer is assembled.
| S-EPMC3893088 | biostudies-literature
Project description:This series of experiments was designed to identify the program of gene transcription for a single differentiating cell type during sporulation in Bacillus subtilis. The mother cell is one of two cell types generated by asymmetric division of sporulating cells approximately two hours after initiation of sporulation. The program is governed by a hierarchical cascade consisting of the transcription factors: sigmaE, sigmaK, GerE, GerR (YlbO) and SpoIIID. The characterization of the sigmaE regulon was reported in Eichenberger et al. (2003), J. Mol. Biol. 327, 945-972. Here we report the data for sigmaK, GerE, GerR and SpoIIID.
2004-09-01 | GSE1620 | GEO
Project description:Endospore (hereafter called spore) is a dormant, tough, and non-reproductive structure produced in a lack of nutrients by certain species of bacteria from the Firmicute phylum. Sporulation is tightly linked to cell cycle and involving by temporal and spatial regulation of hundreds genes. It has been suggested more than 500 genes are contributed to sporulation in B. subtilis, and there are certainly more. In our study, we identified four new sporulation genes and their mutants exhibited sporulation abnormal. RNA-seq of mutants compared to wild type during sporulation will reveal the regulation of sporulation related genes in the four mutants, and therefore shed the light to the functional role of the four new sporulation genes.
2020-03-18 | E-MTAB-8124 | biostudies-arrayexpress
Project description:1. Antisera, prepared against extracts of cells and spores of Bacillus subtilis, were used in immunoelectrophoretic studies of the changes occurring in cell extracts during the course of spore formation. 2. At least 15 antigens could be detected in vegetative-cell extracts by the antiserum prepared against cell extracts and at least seven could be demonstrated in spore extracts by the homologous antiserum. 3. Cross-absorption studies showed that two of these antigens were probably completely specific for vegetative-cell extracts and that one was probably completely specific for spore extracts. The remainder were probably present in very small quantities in the heterologous extract. 4. In extracts of cells sporulating in an ;exhaustion medium' those antigens characteristic of the spore began to appear about 1hr. after the end of exponential growth. 5. In cells sporulating in a resuspension medium, spore antigens were detected at 4hr., and by 7hr. a decrease in vegetative-cell antigens was observed. 6. In an asporogenous mutant blocked early in sporulation there was neither an increase in spore antigens nor a decrease in vegetative-cell antigens. 7. In an asporogenous mutant blocked later in sporulation, there was an increase in spore antigens similar to that which occurred in the sporogenous strain.
| S-EPMC1187031 | biostudies-other
Project description:Biofilms are structured multicellular communities of bacteria that form through a developmental process. In standing culture, undomesticated strains of Bacillus subtilis produce a floating biofilm, called a pellicle, with a distinct macroscopic architecture. Here we report on a comprehensive analysis of B. subtilis pellicle formation, with a focus on transcriptional regulators and morphological changes. To date, 288 known or putative transcriptional regulators encoded by the B. subtilis genome have been identified or assigned based on similarity to other known proteins. The genes encoding these regulators were systematically disrupted, and the effects of the mutations on pellicle formation were examined, resulting in the identification of 19 regulators involved in pellicle formation. In addition, morphological analysis revealed that pellicle formation begins with the formation of cell chains, which is followed by clustering and degradation of cell chains. Genetic and morphological evidence showed that each stage of morphological change can be defined genetically, based on mutants of transcriptional regulators, each of which blocks pellicle formation at a specific morphological stage. Formation and degradation of cell chains are controlled by down- and up-regulation of sigma(D)- and sigma(H)-dependent autolysins expressed at specific stages during pellicle formation. Transcriptional analysis revealed that the transcriptional activation of sigH depends on the formation of cell clusters, which in turn activates transcription of sigma(H)-dependent autolysin in cell clusters. Taken together, our results reveal relationships between transcriptional regulators and morphological development during pellicle formation by B. subtilis.
| S-EPMC1913431 | biostudies-literature
Project description:Starving Bacillus subtilis cells execute a gene expression program resulting in the formation of stress-resistant spores. Sporulation master regulator, Spo0A, is activated by a phosphorelay and controls the expression of a multitude of genes, including the forespore-specific sigma factor σ(F) and the mother cell-specific sigma factor σ(E). Identification of the system-level mechanism of the sporulation decision is hindered by a lack of direct control over Spo0A activity. This limitation can be overcome by using a synthetic system in which Spo0A activation is controlled by inducing expression of phosphorelay kinase KinA. This induction results in a switch-like increase in the number of sporulating cells at a threshold of KinA. Using a combination of mathematical modeling and single-cell microscopy, we investigate the origin and physiological significance of this ultrasensitive threshold. The results indicate that the phosphorelay is unable to achieve a sufficiently fast and ultrasensitive response via its positive feedback architecture, suggesting that the sporulation decision is made downstream. In contrast, activation of σ(F) in the forespore and of σ(E) in the mother cell compartments occurs via a cascade of coherent feed-forward loops, and thereby can produce fast and ultrasensitive responses as a result of KinA induction. Unlike σ(F) activation, σ(E) activation in the mother cell compartment only occurs above the KinA threshold, resulting in completion of sporulation. Thus, ultrasensitive σ(E) activation explains the KinA threshold for sporulation induction. We therefore infer that under uncertain conditions, cells initiate sporulation but postpone making the sporulation decision to average stochastic fluctuations and to achieve a robust population response.
| S-EPMC3528541 | biostudies-literature
Project description:In microbial communities, bacteria chemically and physically interact with one another. Some of these interactions are mediated by secreted specialized metabolites that act as either intraspecies or interspecies signals to alter gene expression and to change cell physiology. Bacillus subtilis is a well-characterized soil microbe that can differentiate into multiple cell types, including metabolically dormant endospores. We were interested in identifying microbial interactions that affected sporulation in B. subtilis Using a fluorescent transcriptional reporter, we observed that coculturing B. subtilis with Escherichia coli promoted sporulation gene expression via a secreted metabolite. To identify the active compound, we screened the E. coli Keio Collection and identified the sporulation-accelerating cue as the siderophore enterobactin. B. subtilis has multiple iron acquisition systems that are used to take up the B. subtilis-produced siderophore bacillibactin, as well as to pirate exogenous siderophores such as enterobactin. While B. subtilis uses a single substrate binding protein (FeuA) to take up both bacillibactin and enterobactin, we discovered that it requires two distinct genes to sporulate in response to these siderophores (the esterase gene besA for bacillibactin and a putative esterase gene, ybbA, for enterobactin). In addition, we found that siderophores from a variety of other microbial species also promote sporulation in B. subtilis Our results thus demonstrate that siderophores can act not only as bacterial iron acquisition systems but also as interspecies cues that alter cellular development and accelerate sporulation in B. subtilisIMPORTANCE While much is known about the genetic regulation of Bacillus subtilis sporulation, little is understood about how other bacteria influence this process. This work describes an interaction between Escherichia coli and B. subtilis that accelerates sporulation in B. subtilis The interaction is mediated by the E. coli siderophore enterobactin; we show that other species' siderophores also promote sporulation gene expression in B. subtilis These results suggest that siderophores not only may supply bacteria with the mineral nutrient iron but also may play a role in bacterial interspecies signaling, providing a cue for sporulation. Siderophores are produced by many bacterial species and thus potentially play important roles in altering bacterial cell physiology in diverse environments.
| S-EPMC5411514 | biostudies-literature
Project description:During sporulation in Bacillus subtilis, germinant receptors assemble in the inner membrane of the developing spore. In response to specific nutrients, these receptors trigger germination and outgrowth. In a transposon-sequencing screen, we serendipitously discovered that loss of function mutations in the gerA receptor partially suppress the phenotypes of > 25 sporulation mutants. Most of these mutants have modest defects in the assembly of the spore protective layers that are exacerbated in the presence of a functional GerA receptor. Several lines of evidence indicate that these mutants inappropriately trigger the activation of GerA during sporulation resulting in premature germination. These findings led us to discover that up to 8% of wild-type sporulating cells trigger premature germination during differentiation in a GerA-dependent manner. This phenomenon was observed in domesticated and undomesticated wild-type strains sporulating in liquid and on solid media. Our data indicate that the GerA receptor is poised on a knife's edge during spore development. We propose that this sensitized state ensures a rapid response to nutrient availability and also elicits premature germination of spores with improperly assembled protective layers resulting in the elimination of even mildly defective individuals from the population.
| S-EPMC5570633 | biostudies-literature