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Bean EL, McLellan LK, Grossman AD. Activation of the integrative and conjugative element Tn916 causes growth arrest and death of host bacteria. PLoS Genet 2022; 18:e1010467. [PMID: 36279314 PMCID: PMC9632896 DOI: 10.1371/journal.pgen.1010467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Revised: 11/03/2022] [Accepted: 10/10/2022] [Indexed: 11/06/2022] Open
Abstract
Integrative and conjugative elements (ICEs) serve as major drivers of bacterial evolution. These elements often confer some benefit to host cells, including antibiotic resistance, metabolic capabilities, or pathogenic determinants. ICEs can also have negative effects on host cells. Here, we investigated the effects of the ICE (conjugative transposon) Tn916 on host cells. Because Tn916 is active in a relatively small subpopulation of host cells, we developed a fluorescent reporter system for monitoring activation of Tn916 in single cells. Using this reporter, we found that cell division was arrested in cells of Bacillus subtilis and Enterococcus faecalis (a natural host for Tn916) that contained an activated (excised) Tn916. Furthermore, most of the cells with the activated Tn916 subsequently died. We also observed these phenotypes on the population level in B. subtilis utilizing a modified version of Tn916 that can be activated in the majority of cells. We identified two genes (orf17 and orf16) in Tn916 that were sufficient to cause growth defects in B. subtilis and identified a single gene, yqaR, that is in a defective phage (skin) in the B. subtilis chromosome that was required for this phenotype. These three genes were only partially responsible for the growth defect caused by Tn916, indicating that Tn916 possesses multiple mechanisms to affect growth and viability of host cells. These results highlight the complex relationships that conjugative elements have with their host cells and the interplay between mobile genetic elements.
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Affiliation(s)
- Emily L. Bean
- Department of Biology Massachusetts, Institute of Technology Cambridge, Massachusetts, United States of America
| | - Lisa K. McLellan
- Department of Biology Massachusetts, Institute of Technology Cambridge, Massachusetts, United States of America
| | - Alan D. Grossman
- Department of Biology Massachusetts, Institute of Technology Cambridge, Massachusetts, United States of America
- * E-mail:
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Serrano M, Kint N, Pereira FC, Saujet L, Boudry P, Dupuy B, Henriques AO, Martin-Verstraete I. A Recombination Directionality Factor Controls the Cell Type-Specific Activation of σK and the Fidelity of Spore Development in Clostridium difficile. PLoS Genet 2016; 12:e1006312. [PMID: 27631621 PMCID: PMC5025042 DOI: 10.1371/journal.pgen.1006312] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 08/21/2016] [Indexed: 01/05/2023] Open
Abstract
The strict anaerobe Clostridium difficile is the most common cause of nosocomial diarrhea, and the oxygen-resistant spores that it forms have a central role in the infectious cycle. The late stages of sporulation require the mother cell regulatory protein σK. In Bacillus subtilis, the onset of σK activity requires both excision of a prophage-like element (skinBs) inserted in the sigK gene and proteolytical removal of an inhibitory pro-sequence. Importantly, the rearrangement is restricted to the mother cell because the skinBs recombinase is produced specifically in this cell. In C. difficile, σK lacks a pro-sequence but a skinCd element is present. The product of the skinCd gene CD1231 shares similarity with large serine recombinases. We show that CD1231 is necessary for sporulation and skinCd excision. However, contrary to B. subtilis, expression of CD1231 is observed in vegetative cells and in both sporangial compartments. Nevertheless, we show that skinCd excision is under the control of mother cell regulatory proteins σE and SpoIIID. We then demonstrate that σE and SpoIIID control the expression of the skinCd gene CD1234, and that this gene is required for sporulation and skinCd excision. CD1231 and CD1234 appear to interact and both proteins are required for skinCd excision while only CD1231 is necessary for skinCd integration. Thus, CD1234 is a recombination directionality factor that delays and restricts skinCd excision to the terminal mother cell. Finally, while the skinCd element is not essential for sporulation, deletion of skinCd results in premature activity of σK and in spores with altered surface layers. Thus, skinCd excision is a key element controlling the onset of σK activity and the fidelity of spore development.
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Affiliation(s)
- Mónica Serrano
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Nicolas Kint
- Laboratoire Pathogénese des Bactéries Anaérobies, Institut Pasteur, Paris, France
- University Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Fátima C. Pereira
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Laure Saujet
- Laboratoire Pathogénese des Bactéries Anaérobies, Institut Pasteur, Paris, France
- University Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Pierre Boudry
- Laboratoire Pathogénese des Bactéries Anaérobies, Institut Pasteur, Paris, France
- University Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Bruno Dupuy
- Laboratoire Pathogénese des Bactéries Anaérobies, Institut Pasteur, Paris, France
- University Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Adriano O. Henriques
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
- * E-mail: (AOH); (IMV)
| | - Isabelle Martin-Verstraete
- Laboratoire Pathogénese des Bactéries Anaérobies, Institut Pasteur, Paris, France
- University Paris Diderot, Sorbonne Paris Cité, Paris, France
- * E-mail: (AOH); (IMV)
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Updates on the sporulation process in Clostridium species. Res Microbiol 2015; 166:225-35. [DOI: 10.1016/j.resmic.2014.12.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 12/07/2014] [Accepted: 12/09/2014] [Indexed: 12/19/2022]
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Abstract
My career in science was launched when I was an undergraduate at Princeton University and reinforced by graduate training at the Massachusetts Institute of Technology. However, it was only after I moved to Harvard University as a junior fellow that my affections were captured by a seemingly mundane soil bacterium. What Bacillus subtilis offered was endless fascinating biological problems (alternative sigma factors, sporulation, swarming, biofilm formation, stochastic cell fate switching) embedded in a uniquely powerful genetic system. Along the way, my career in science became inseparably interwoven with teaching and mentoring, which proved to be as rewarding as the thrill of discovery.
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Affiliation(s)
- Richard Losick
- From the Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 01238
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Alternative sigma factors SigF, SigE, and SigG are essential for sporulation in Clostridium botulinum ATCC 3502. Appl Environ Microbiol 2014; 80:5141-50. [PMID: 24928875 DOI: 10.1128/aem.01015-14] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clostridium botulinum produces heat-resistant endospores that may germinate and outgrow into neurotoxic cultures in foods. Sporulation is regulated by the transcription factor Spo0A and the alternative sigma factors SigF, SigE, SigG, and SigK in most spore formers studied to date. We constructed mutants of sigF, sigE, and sigG in C. botulinum ATCC 3502 and used quantitative reverse transcriptase PCR and electron microscopy to assess their expression of the sporulation pathway on transcriptional and morphological levels. In all three mutants the expression of spo0A was disrupted. The sigF and sigE mutants failed to induce sigG and sigK beyond exponential-phase levels and halted sporulation during asymmetric cell division. In the sigG mutant, peak transcription of sigE was delayed and sigK levels remained lower than that in the parent strain. The sigG mutant forespore was engulfed by the mother cell and possessed a spore coat but no peptidoglycan cortex. The findings suggest that SigF and SigE of C. botulinum ATCC 3502 are essential for early sporulation and late-stage induction of sigK, whereas SigG is essential for spore cortex formation but not for coat formation, as opposed to previous observations in B. subtilis sigG mutants. Our findings add to a growing body of evidence that regulation of sporulation in C. botulinum ATCC 3502, and among the clostridia, differs from the B. subtilis model.
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Kirk DG, Palonen E, Korkeala H, Lindström M. Evaluation of normalization reference genes for RT-qPCR analysis of spo0A and four sporulation sigma factor genes in Clostridium botulinum Group I strain ATCC 3502. Anaerobe 2014; 26:14-9. [PMID: 24389585 DOI: 10.1016/j.anaerobe.2013.12.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 12/21/2013] [Accepted: 12/24/2013] [Indexed: 11/17/2022]
Abstract
Heat-resistant spores of Clostridium botulinum can withstand the pasteurization processes in modern food processing. This poses a risk to food safety as spores may germinate into botulinum neurotoxin-producing vegetative cells. Sporulation in Bacillus subtilis, the model organism for sporulation, is regulated by the transcription factor Spo0A and four alternative sigma factors, SigF, SigE, SigG, and SigK. While the corresponding regulators are found in available genomes of C. botulinum, little is known about their expression. To accurately measure the expression of these genes using quantitative reverse-transcriptase PCR (RT-qPCR) during the exponential and stationary growth phases, a suitable normalization reference gene is required. 16S rrn, adK, alaS, era, gluD, gyrA, rpoC, and rpsJ were selected as the candidate reference genes. The most stable candidate reference gene was 16S ribosomal RNA gene (rrn), based on its low coefficient of variation (1.81%) measured during the 18-h study time. Using 16S rrn as the normalization reference gene, the relative expression levels of spo0A, sigF, sigE, sigG, and sigK were measured over 18h. The pattern of expression showed spo0A expression during the logarithmic growth phase, followed by a drop in expression upon entry to the stationary phase. Expression levels of sigF, sigE, and sigG peaked simultaneously at the end of the exponential growth phase. Peak expression of sigK occurred at 18h, however low levels of expression were detected during the exponential phase. These findings suggest these sigma factors play a role in C. botulinum sporulation that is similar, but not equal, to their role in the B. subtilis model.
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Affiliation(s)
- David G Kirk
- Department of Food Hygiene and Environmental Health, Centre of Excellence in Microbial Food Safety Research, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014 Helsinki University, Finland
| | - Eveliina Palonen
- Department of Food Hygiene and Environmental Health, Centre of Excellence in Microbial Food Safety Research, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014 Helsinki University, Finland
| | - Hannu Korkeala
- Department of Food Hygiene and Environmental Health, Centre of Excellence in Microbial Food Safety Research, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014 Helsinki University, Finland
| | - Miia Lindström
- Department of Food Hygiene and Environmental Health, Centre of Excellence in Microbial Food Safety Research, Faculty of Veterinary Medicine, University of Helsinki, P.O. Box 66, 00014 Helsinki University, Finland.
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Saujet L, Pereira FC, Serrano M, Soutourina O, Monot M, Shelyakin PV, Gelfand MS, Dupuy B, Henriques AO, Martin-Verstraete I. Genome-wide analysis of cell type-specific gene transcription during spore formation in Clostridium difficile. PLoS Genet 2013; 9:e1003756. [PMID: 24098137 PMCID: PMC3789822 DOI: 10.1371/journal.pgen.1003756] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2013] [Accepted: 07/12/2013] [Indexed: 01/05/2023] Open
Abstract
Clostridium difficile, a Gram positive, anaerobic, spore-forming bacterium is an emergent pathogen and the most common cause of nosocomial diarrhea. Although transmission of C. difficile is mediated by contamination of the gut by spores, the regulatory cascade controlling spore formation remains poorly characterized. During Bacillus subtilis sporulation, a cascade of four sigma factors, σ(F) and σ(G) in the forespore and σ(E) and σ(K) in the mother cell governs compartment-specific gene expression. In this work, we combined genome wide transcriptional analyses and promoter mapping to define the C. difficile σ(F), σ(E), σ(G) and σ(K) regulons. We identified about 225 genes under the control of these sigma factors: 25 in the σ(F) regulon, 97 σ(E)-dependent genes, 50 σ(G)-governed genes and 56 genes under σ(K) control. A significant fraction of genes in each regulon is of unknown function but new candidates for spore coat proteins could be proposed as being synthesized under σ(E) or σ(K) control and detected in a previously published spore proteome. SpoIIID of C. difficile also plays a pivotal role in the mother cell line of expression repressing the transcription of many members of the σ(E) regulon and activating sigK expression. Global analysis of developmental gene expression under the control of these sigma factors revealed deviations from the B. subtilis model regarding the communication between mother cell and forespore in C. difficile. We showed that the expression of the σ(E) regulon in the mother cell was not strictly under the control of σ(F) despite the fact that the forespore product SpoIIR was required for the processing of pro-σ(E). In addition, the σ(K) regulon was not controlled by σ(G) in C. difficile in agreement with the lack of pro-σ(K) processing. This work is one key step to obtain new insights about the diversity and evolution of the sporulation process among Firmicutes.
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Affiliation(s)
- Laure Saujet
- Laboratoire Pathogenèse des Bactéries Anaérobies, Institut Pasteur, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Cellule Pasteur, Paris, France
| | - Fátima C. Pereira
- Microbial Development Laboratory, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Monica Serrano
- Microbial Development Laboratory, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Olga Soutourina
- Laboratoire Pathogenèse des Bactéries Anaérobies, Institut Pasteur, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Cellule Pasteur, Paris, France
| | - Marc Monot
- Laboratoire Pathogenèse des Bactéries Anaérobies, Institut Pasteur, Paris, France
| | - Pavel V. Shelyakin
- Institute for Information Transmission Problems, RAS, Bolshoi Karetny per, 19, Moscow, Russia
| | - Mikhail S. Gelfand
- Institute for Information Transmission Problems, RAS, Bolshoi Karetny per, 19, Moscow, Russia
- M.V. Lomonosov Moscow State University, Faculty of Biengineering and Bioinformatics, Vorobievy Gory 1-73, Moscow, Russia
| | - Bruno Dupuy
- Laboratoire Pathogenèse des Bactéries Anaérobies, Institut Pasteur, Paris, France
| | - Adriano O. Henriques
- Microbial Development Laboratory, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Isabelle Martin-Verstraete
- Laboratoire Pathogenèse des Bactéries Anaérobies, Institut Pasteur, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Cellule Pasteur, Paris, France
- * E-mail:
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Pleiotropic functions of catabolite control protein CcpA in Butanol-producing Clostridium acetobutylicum. BMC Genomics 2012; 13:349. [PMID: 22846451 PMCID: PMC3507653 DOI: 10.1186/1471-2164-13-349] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 06/28/2012] [Indexed: 12/24/2022] Open
Abstract
Background Clostridium acetobutylicum has been used to produce butanol in industry. Catabolite control protein A (CcpA), known to mediate carbon catabolite repression (CCR) in low GC gram-positive bacteria, has been identified and characterized in C. acetobutylicum by our previous work (Ren, C. et al. 2010, Metab Eng 12:446–54). To further dissect its regulatory function in C. acetobutylicum, CcpA was investigated using DNA microarray followed by phenotypic, genetic and biochemical validation. Results CcpA controls not only genes in carbon metabolism, but also those genes in solvent production and sporulation of the life cycle in C. acetobutylicum: i) CcpA directly repressed transcription of genes related to transport and metabolism of non-preferred carbon sources such as d-xylose and l-arabinose, and activated expression of genes responsible for d-glucose PTS system; ii) CcpA is involved in positive regulation of the key solventogenic operon sol (adhE1-ctfA-ctfB) and negative regulation of acidogenic gene bukII; and iii) transcriptional alterations were observed for several sporulation-related genes upon ccpA inactivation, which may account for the lower sporulation efficiency in the mutant, suggesting CcpA may be necessary for efficient sporulation of C. acetobutylicum, an important trait adversely affecting the solvent productivity. Conclusions This study provided insights to the pleiotropic functions that CcpA displayed in butanol-producing C. acetobutylicum. The information could be valuable for further dissecting its pleiotropic regulatory mechanism in C. acetobutylicum, and for genetic modification in order to obtain more effective butanol-producing Clostridium strains.
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Involvement of Clostridium botulinum ATCC 3502 sigma factor K in early-stage sporulation. Appl Environ Microbiol 2012; 78:4590-6. [PMID: 22544236 DOI: 10.1128/aem.00304-12] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A key survival mechanism of Clostridium botulinum, the notorious neurotoxic food pathogen, is the ability to form heat-resistant spores. While the genetic mechanisms of sporulation are well understood in the model organism Bacillus subtilis, nothing is known about these mechanisms in C. botulinum. Using the ClosTron gene-knockout tool, sigK, encoding late-stage (stage IV) sporulation sigma factor K in B. subtilis, was disrupted in C. botulinum ATCC 3502 to produce two different mutants with distinct insertion sites and orientations. Both mutants were unable to form spores, and their elongated cell morphology suggested that the sporulation pathway was blocked at an early stage. In contrast, sigK-complemented mutants sporulated successfully. Quantitative real-time PCR analysis of sigK in the parent strain revealed expression at the late log growth phase in the parent strain. Analysis of spo0A, encoding the sporulation master switch, in the sigK mutant and the parent showed significantly reduced relative levels of spo0A expression in the sigK mutant compared to the parent strain. Similarly, sigF showed significantly lower relative transcription levels in the sigK mutant than the parent strain, suggesting that the sporulation pathway was blocked in the sigK mutant at an early stage. We conclude that σ(K) is essential for early-stage sporulation in C. botulinum ATCC 3502, rather than being involved in late-stage sporulation, as reported for the sporulation model organism B. subtilis. Understanding the sporulation mechanism of C. botulinum provides keys to control the public health risks that the spores of this dangerous pathogen cause through foods.
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Sporulation and enterotoxin (CPE) synthesis are controlled by the sporulation-specific sigma factors SigE and SigK in Clostridium perfringens. J Bacteriol 2009; 191:2728-42. [PMID: 19201796 DOI: 10.1128/jb.01839-08] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Clostridium perfringens is the third most frequent cause of bacterial food poisoning annually in the United States. Ingested C. perfringens vegetative cells sporulate in the intestinal tract and produce an enterotoxin (CPE) that is responsible for the symptoms of acute food poisoning. Studies of Bacillus subtilis have shown that gene expression during sporulation is compartmentalized, with different genes expressed in the mother cell and the forespore. The cell-specific RNA polymerase sigma factors sigma(F), sigma(E), sigma(G), and sigma(K) coordinate much of the developmental process. The C. perfringens cpe gene, encoding CPE, is transcribed from three promoters, where P1 was proposed to be sigma(K) dependent, while P2 and P3 were proposed to be sigma(E) dependent based on consensus promoter recognition sequences. In this study, mutations were introduced into the sigE and sigK genes of C. perfringens. With the sigE and sigK mutants, gusA fusion assays indicated that there was no expression of cpe in either mutant. Results from gusA fusion assays and immunoblotting experiments indicate that sigma(E)-associated RNA polymerase and sigma(K)-associated RNA polymerase coregulate each other's expression. Transcription and translation of the spoIIID gene in C. perfringens were not affected by mutations in sigE and sigK, which differs from B. subtilis, in which spoIIID transcription requires sigma(E)-associated RNA polymerase. The results presented here show that the regulation of developmental events in the mother cell compartment of C. perfringens is not the same as that in B. subtilis and Clostridium acetobutylicum.
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Steil L, Serrano M, Henriques AO, Völker U. Genome-wide analysis of temporally regulated and compartment-specific gene expression in sporulating cells of Bacillus subtilis. Microbiology (Reading) 2005; 151:399-420. [PMID: 15699190 DOI: 10.1099/mic.0.27493-0] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Temporal and compartment-specific control of gene expression during sporulation inBacillus subtilisis governed by a cascade of four RNA polymerase subunits.σFin the prespore andσEin the mother cell control early stages of development, and are replaced at later stages byσGandσK, respectively. Ultimately, a comprehensive description of the molecular mechanisms underlying spore morphogenesis requires the knowledge of all the intervening genes and their assignment to specific regulons. Here, in an extension of earlier work, DNA macroarrays have been used, and members of the four compartment-specific sporulation regulons have been identified. Genes were identified and grouped based on: i) their temporal expression profile and ii) the use of mutants for each of the four sigma factors and abofAallele, which allowsσKactivation in the absence ofσG. As a further test, artificial production of active alleles of the sigma factors in non-sporulating cells was employed. A total of 439 genes were found, including previously characterized genes whose transcription is induced during sporulation: 55 in theσFregulon, 154σE-governed genes, 113σG-dependent genes, and 132 genes underσKcontrol. The results strengthen the view that the activities ofσF,σE,σGandσKare largely compartmentalized, both temporally as well as spatially, and that the major vegetative sigma factor (σA) is active throughout sporulation. The results provide a dynamic picture of the changes in the overall pattern of gene expression in the two compartments of the sporulating cell, and offer insight into the roles of the prespore and the mother cell at different times of spore morphogenesis.
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Affiliation(s)
- Leif Steil
- Ernst-Moritz-Arndt-University, Medical School, Laboratory for Functional Genomics, Walther-Rathenau-Str. 49A, D-17487 Greifswald, Germany
- Max-Planck-Institute for Terrestrial Microbiology, D-35043 Marburg, Germany
- Philipps-University Marburg, Department of Biology, Laboratory for Microbiology, D-35032 Marburg, Germany
| | - Mónica Serrano
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, Apartado 127, 2781-901 Oeiras Codex, Portugal
| | - Adriano O Henriques
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, Apartado 127, 2781-901 Oeiras Codex, Portugal
| | - Uwe Völker
- Ernst-Moritz-Arndt-University, Medical School, Laboratory for Functional Genomics, Walther-Rathenau-Str. 49A, D-17487 Greifswald, Germany
- Max-Planck-Institute for Terrestrial Microbiology, D-35043 Marburg, Germany
- Philipps-University Marburg, Department of Biology, Laboratory for Microbiology, D-35032 Marburg, Germany
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Hilbert DW, Piggot PJ. Compartmentalization of gene expression during Bacillus subtilis spore formation. Microbiol Mol Biol Rev 2004; 68:234-62. [PMID: 15187183 PMCID: PMC419919 DOI: 10.1128/mmbr.68.2.234-262.2004] [Citation(s) in RCA: 249] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gene expression in members of the family Bacillaceae becomes compartmentalized after the distinctive, asymmetrically located sporulation division. It involves complete compartmentalization of the activities of sporulation-specific sigma factors, sigma(F) in the prespore and then sigma(E) in the mother cell, and then later, following engulfment, sigma(G) in the prespore and then sigma(K) in the mother cell. The coupling of the activation of sigma(F) to septation and sigma(G) to engulfment is clear; the mechanisms are not. The sigma factors provide the bare framework of compartment-specific gene expression. Within each sigma regulon are several temporal classes of genes, and for key regulators, timing is critical. There are also complex intercompartmental regulatory signals. The determinants for sigma(F) regulation are assembled before septation, but activation follows septation. Reversal of the anti-sigma(F) activity of SpoIIAB is critical. Only the origin-proximal 30% of a chromosome is present in the prespore when first formed; it takes approximately 15 min for the rest to be transferred. This transient genetic asymmetry is important for prespore-specific sigma(F) activation. Activation of sigma(E) requires sigma(F) activity and occurs by cleavage of a prosequence. It must occur rapidly to prevent the formation of a second septum. sigma(G) is formed only in the prespore. SpoIIAB can block sigma(G) activity, but SpoIIAB control does not explain why sigma(G) is activated only after engulfment. There is mother cell-specific excision of an insertion element in sigK and sigma(E)-directed transcription of sigK, which encodes pro-sigma(K). Activation requires removal of the prosequence following a sigma(G)-directed signal from the prespore.
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Affiliation(s)
- David W Hilbert
- Department of Microbiology and Immunology, Temple University School of Medicine, 3400 N. Broad St., Philadelphia, PA 19140, USA
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Rubio A, Pogliano K. Septal localization of forespore membrane proteins during engulfment in Bacillus subtilis. EMBO J 2004; 23:1636-46. [PMID: 15044948 PMCID: PMC391076 DOI: 10.1038/sj.emboj.7600171] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2004] [Accepted: 02/19/2004] [Indexed: 11/08/2022] Open
Abstract
In Bacillus subtilis, many membrane proteins localize to the sporulation septum, where they play key roles in spore morphogenesis and cell-specific gene expression, but the mechanism for septal targeting is not well understood. SpoIIQ, a forespore-expressed protein, is involved in engulfment and forespore-specific gene expression. We find that SpoIIQ dynamically localizes to the sporulation septum, tracks the engulfing mother cell membrane, assembles into helical arcs around the forespore and is finally degraded. Retention of SpoIIQ in the septum requires one or more mother cell-expressed proteins. We also observed that any forespore-expressed membrane protein initially localizes to the septum and later spreads throughout the forespore membrane, suggesting that membrane protein insertion occurs at the forespore septal region. This possibility provides an attractive mechanism for how activation of mother cell-specific gene expression is restricted to adjacent sister cells, since direct insertion of the signaling protein SpoIIR into the septum would spatially restrict its activity. In keeping with this hypothesis, we find that SpoIIR localizes to the septum and is transiently expressed.
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Affiliation(s)
- Aileen Rubio
- Division of Biological Sciences, University of California-San Diego, La Jolla, CA, USA
| | - Kit Pogliano
- Division of Biological Sciences, University of California-San Diego, La Jolla, CA, USA
- Division of Biological Sciences, University of California-San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0377, USA. Tel.: +1 858 822 1314; Fax: +1 858 822 1431; E-mail:
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Haraldsen JD, Sonenshein AL. Efficient sporulation in Clostridium difficile requires disruption of the sigmaK gene. Mol Microbiol 2003; 48:811-21. [PMID: 12694623 DOI: 10.1046/j.1365-2958.2003.03471.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A 14.6 kb prophage-like insertion, termed skinCd, was found to interrupt the sigK gene, which encodes an RNA polymerase sigma factor essential for sporulation, in six strains of Clostridium difficile. Until now, Bacillus subtilis was the only spore-former shown to carry such an insertion, and the presence of the insertion is not required for efficient sporulation in this organism. The B. subtilis and C. difficile skin elements proved to be divergent in sequence, inserted at different sites within the sigK gene and in opposite orientations. The skinCd element was excised from the chromosome specifically during sporulation, forming a circular molecule. Two natural isolates of C. difficile lacked the skinCd element and were defective in sporulation. When a merodiploid strain was created that carries both interrupted and uninterrupted versions of the sigK gene, the cells became Spo-, showing that the uninterrupted gene is dominant and inhibits sporulation. C. difficile sigK genes, whether skinCd+ or skinCd-, lack the N-terminal pro-sequence found in all other sigK genes studied to date. Thus, regulated excision of skinCd appears to be a critical mechanism for achieving proper temporal activation of sigmaK.
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Affiliation(s)
- Jeralyn D Haraldsen
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
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15
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Ichikawa H, Kroos L. Combined action of two transcription factors regulates genes encoding spore coat proteins of Bacillus subtilis. J Biol Chem 2000; 275:13849-55. [PMID: 10788508 DOI: 10.1074/jbc.275.18.13849] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During sporulation of Bacillus subtilis, spore coat proteins encoded by cot genes are expressed in the mother cell and deposited on the forespore. Transcription of the cotB, cotC, and cotX genes by final sigma(K) RNA polymerase is activated by a small, DNA-binding protein called GerE. The promoter region of each of these genes has two GerE binding sites. 5' deletions that eliminated the more upstream GerE site decreased expression of lacZ fused to cotB and cotX by approximately 80% and 60%, respectively but had no effect on cotC-lacZ expression. The cotC-lacZ fusion was expressed later during sporulation than the other two fusions. Primer extension analysis confirmed that cotB mRNA increases first during sporulation, followed by cotX and cotC mRNAs over a 2-h period. In vitro transcription experiments suggest that the differential pattern of cot gene expression results from the combined action of GerE and another transcription factor, SpoIIID. A low concentration of GerE activated cotB transcription by final sigma(K) RNA polymerase, whereas a higher concentration was needed to activate transcription of cotX or cotC. SpoIIID at low concentration repressed cotC transcription, whereas a higher concentration only partially repressed cotX transcription and had little effect on cotB transcription. DNase I footprinting showed that SpoIIID binds strongly to two sites in the cotC promoter region, binds weakly to one site in the cotX promoter, and does not bind specifically to cotB. We propose that late in sporulation the rising level of GerE and the falling level of SpoIIID, together with the position and affinity of binding sites for these transcription factors in cot gene promoters, dictates the timing and level of spore coat protein synthesis, ensuring optimal assembly of the protein shell on the forespore surface.
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Affiliation(s)
- H Ichikawa
- Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824, USA
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16
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Behravan J, Chirakkal H, Masson A, Moir A. Mutations in the gerP locus of Bacillus subtilis and Bacillus cereus affect access of germinants to their targets in spores. J Bacteriol 2000; 182:1987-94. [PMID: 10715007 PMCID: PMC101904 DOI: 10.1128/jb.182.7.1987-1994.2000] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The gerP1 transposon insertion mutation of Bacillus cereus is responsible for a defect in the germination response of spores to both L-alanine and inosine. The mutant is blocked at an early stage, before loss of heat resistance or release of dipicolinate, and the efficiency of colony formation on nutrient agar from spores is reduced fivefold. The protein profiles of alkaline-extracted spore coats and the spore cortex composition are unchanged in the mutant. Permeabilization of gerP mutant spores by coat extraction procedures removes the block in early stages of germination, although a consequence of the permeabilization procedure in both wild type and mutant is that late germination events are not complete. The complete hexacistronic operon that includes the site of insertion has been cloned and sequenced. Four small proteins encoded by the operon (GerPA, GerPD, GerPB, and GerPF) are related in sequence. A homologous operon (yisH-yisC) can be found in the Bacillus subtilis genome sequence; null mutations in yisD and yisF, constructed by integrational inactivation, result in a mutant phenotype similar to that seen in B. cereus, though somewhat less extreme and equally repairable by spore permeabilization. Normal rates of germination, as estimated by loss of heat resistance, are also restored to a gerP mutant by the introduction of a cotE mutation, which renders the spore coats permeable to lysozyme. The B. subtilis operon is expressed solely during sporulation, and is sigma K-inducible. We hypothesize that the GerP proteins are important as morphogenetic or structural components of the Bacillus spore, with a role in the establishment of normal spore coat structure and/or permeability, and that failure to synthesize these proteins during spore formation limits the opportunity for small hydrophilic organic molecules, like alanine or inosine, to gain access to their normal target, the germination receptor, in the spore.
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Affiliation(s)
- J Behravan
- Department of Molecular Biology & Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
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17
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Boland FM, Atrih A, Chirakkal H, Foster SJ, Moir A. Complete spore-cortex hydrolysis during germination of Bacillus subtilis 168 requires SleB and YpeB. MICROBIOLOGY (READING, ENGLAND) 2000; 146 ( Pt 1):57-64. [PMID: 10658652 DOI: 10.1099/00221287-146-1-57] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The role of the sleB gene of Bacillus subtilis, which encodes a putative spore-cortex-lytic enzyme, and the downstream ypeB gene were investigated. Both SleB and YpeB were required for normal germination to occur. The corresponding mutants formed phase-bright, heat-resistant spores with no apparent defects in dormancy. However, mutant spore suspensions lost optical density slower than the wild-type and spores were phase-grey even 12 h after the triggering of germination. Since the loss of heat resistance and release of dipicolinic acid was similar to the wild-type, these mutants were blocked in the later stages of germination. The mutants were nevertheless capable of outgrowth on rich agar to form colonies, indicating that other spore components can compensate for their function sufficiently to allow outgrowth. The expression and regulation of the operon was examined using a lacZ transcriptional fusion. Expression of the operon began 2 h after the onset of sporulation and was under the control of RNA polymerase containing the forespore-specific sigma factor, sigmaG. The application of reverse phase HPLC revealed that the mutants do not have any structural defect in the dormant spore cortex and therefore these genes are not required for normal spore-cortex synthesis. The analysis of peptidoglycan dynamics during germination showed, however, that the cortex was only partially hydrolysed in both mutants. This analysis also revealed that the likely hydrolytic bond specificity of SleB is likely to be that of a lytic transglycosylase.
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Affiliation(s)
- Fiona M Boland
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK1
| | - Abdelmadjid Atrih
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK1
| | - Haridasan Chirakkal
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK1
| | - Simon J Foster
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK1
| | - Anne Moir
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK1
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18
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Resnekov O, Losick R. Negative regulation of the proteolytic activation of a developmental transcription factor in Bacillus subtilis. Proc Natl Acad Sci U S A 1998; 95:3162-7. [PMID: 9501233 PMCID: PMC19712 DOI: 10.1073/pnas.95.6.3162] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/20/1998] [Indexed: 02/06/2023] Open
Abstract
The sporulation transcription factor sigmaK of Bacillus subtilis is controlled by a signal transduction pathway that operates at the level of the proteolytic processing of the inactive precursor protein pro-sigmaK. The conversion of pro-sigmaK to sigmaK requires the putative processing enzyme SpoIVFB and is governed by the regulatory proteins SpoIVFA and BofA. We engineered vegetative cells to carry out processing of pro-sigmaK by inducing the synthesis of the proprotein, a modified form of the putative processing enzyme, and its two regulators during growth. The results showed that (i) modified SpoIVFB was the only sporulation protein necessary to achieve processing of pro-sigmaK; (ii) SpoIVFA stimulated processing, apparently by protecting the processing enzyme from degradation; (iii) BofA inhibited processing in a manner that did not involve degradation of SpoIVFB; and (iv) the inhibition of SpoIVFB by BofA was dependent on SpoIVFA. We conclude that BofA and SpoIVFA act synergistically and are the only two sporulation proteins needed to inhibit the function of SpoIVFB. Our results are consistent with the idea that activation of pro-sigmaK occurs by a reversal of the BofA/SpoIVFA-mediated inhibition of the processing enzyme.
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Affiliation(s)
- O Resnekov
- Department of Molecular and Cellular Biology, Harvard University, Biological Laboratories, 16 Divinity Avenue, Cambridge, MA 02138, USA
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19
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Johnson BD, Dombroski AJ. The role of the pro sequence of Bacillus subtilis sigmaK in controlling activity in transcription initiation. J Biol Chem 1997; 272:31029-35. [PMID: 9388252 DOI: 10.1074/jbc.272.49.31029] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The sigma (sigma) subunit of prokaryotic RNA polymerase is required for specific recognition of promoter DNA sequences and transcription initiation. Regulation of gene expression can therefore be achieved by modulating the activity of the sigma subunit. In Bacillus subtilis the mother cell-specific sporulation sigma factor, sigmaK, is synthesized as a precursor protein, pro-sigmaK, with a 20-amino acid pro sequence. This pro sequence renders sigmaK inactive for directing transcription of sigmaK-dependent genes in vivo until the pro sequence is proteolytically removed. To understand the role of the pro sequence in controlling sigmaK activity, we have constructed NH2-terminal truncations of pro-sigmaK and characterized their behavior in vitro at the gerE promoter. In this report we show that the pro sequence inactivates sigmaK by interfering with the ability of sigmaK to associate with the core subunits of polymerase and also influences the interactions between holoenzyme and promoter DNA. Additionally, removal of as few as 6 amino acids (pro-sigmaKDelta6) is sufficient to activate pro-sigmaK for DNA binding and transcription initiation. Surprisingly, pro-sigmaKDelta6 binds to DNA with higher affinity and stimulates transcription 30-fold more efficiently than sigmaK, under certain conditions.
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Affiliation(s)
- B D Johnson
- Department of Microbiology and Molecular Genetics, the University of Texas Health Science Center, Houston, Texas 77030, USA
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20
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Zhang B, Kroos L. A feedback loop regulates the switch from one sigma factor to the next in the cascade controlling Bacillus subtilis mother cell gene expression. J Bacteriol 1997; 179:6138-44. [PMID: 9324264 PMCID: PMC179520 DOI: 10.1128/jb.179.19.6138-6144.1997] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Regulation of gene expression in the mother cell compartment of sporulating Bacillus subtilis involves sequential activation and inactivation of several transcription factors. Among them are two sigma factors, sigmaE and sigmaK, and a DNA-binding protein, SpoIIID. A decrease in the level of SpoIIID is thought to relieve its repressive effect on transcription by sigmaK RNA polymerase of certain spore coat genes. Previous studies showed that sigmaK negatively regulates the level of spoIIID mRNA. Here, it is shown that sigmaK does not affect the stability of spoIIID mRNA. Rather, sigmaK appears to negatively regulate the synthesis of spoIIID mRNA by accelerating the disappearance of sigmaE RNA polymerase, which transcribes spoIIID. As sigmaK begins to accumulate by 4 h into sporulation, the sigmaE level drops rapidly in wild-type cells but remains twofold to fivefold higher in sigK mutant cells during the subsequent 4 h. In a strain engineered to produce sigmaK 1 h earlier than normal, twofold less sigmaE than that in wild-type cells accumulates. SigmaK did not detectably alter the stability of sigmaE in pulse-chase experiments. However, beta-galactosidase expression from a sigE-lacZ transcriptional fusion showed a pattern similar to the level of sigmaE protein in sigK mutant cells and cells prematurely expressing sigmaK. These results suggest that the appearance of sigmaK initiates a negative feedback loop controlling not only transcription of spoIIID, but the entire sigmaE regulon, by directly or indirectly inhibiting the transcription of sigE.
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Affiliation(s)
- B Zhang
- Department of Biochemistry, Michigan State University, East Lansing 48824, USA
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21
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Cutting S, Anderson M, Lysenko E, Page A, Tomoyasu T, Tatematsu K, Tatsuta T, Kroos L, Ogura T. SpoVM, a small protein essential to development in Bacillus subtilis, interacts with the ATP-dependent protease FtsH. J Bacteriol 1997; 179:5534-42. [PMID: 9287010 PMCID: PMC179426 DOI: 10.1128/jb.179.17.5534-5542.1997] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The spoVM gene encodes a 26-amino-acid polypeptide that is essential for spore formation in Bacillus subtilis. A transposon insertion within the spoVM open reading frame has been shown to encode a chimeric protein which is biologically inactive and produces a phenotype identical to that of a deletion and insertion mutation. A genetic approach was used to identify possible interacting proteins, and the membrane-bound FtsH protease was identified. Mutations in ftsH suppressed the sporulation defect of certain spoVM mutants but not others. However, production of the mother cell sigma factors, sigmaE and sigmaK, was abnormal in the suppressed strains, and mutations in either spoVM or ftsH alone impaired sigma factor production and sporulation gene expression. Using FtsH purified from Escherichia coli, we demonstrated that in vitro (i) SpoVM inhibits FtsH protease activity and (ii) SpoVM is a substrate for the FtsH protease. We propose that during sporulation, SpoVM serves as a competitive inhibitor of FtsH activity. This interaction appears to be important for completion of the prespore engulfment step of sporulation, based on the phenotype of certain spoVM ftsH double mutants.
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Affiliation(s)
- S Cutting
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, United Kingdom.
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22
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Henriques AO, Beall BW, Moran CP. CotM of Bacillus subtilis, a member of the alpha-crystallin family of stress proteins, is induced during development and participates in spore outer coat formation. J Bacteriol 1997; 179:1887-97. [PMID: 9068633 PMCID: PMC178911 DOI: 10.1128/jb.179.6.1887-1897.1997] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We cloned and characterized a gene, cotM, that resides in the 173 degrees region of the Bacillus subtilis chromosome and is involved in spore outer coat assembly. We found that expression of the cotM gene is induced during development under sigma K control and is negatively regulated by the GerE transcription factor. Disruption of the cotM gene resulted in spores with an abnormal pattern of coat proteins. Electron microscopy revealed that the outer coat in cotM mutant spores had lost its multilayered type of organization, presenting a diffuse appearance. In particular, significant amounts of material were absent from the outer coat layers, which in some areas had a lamellar structure more typical of the inner coat. Occasionally, a pattern of closely spaced ridges protruding from its surface was observed. No deficiency associated with the inner coat or any other spore structure was found. CotM is related to the alpha-crystallin family of low-molecular-weight heat shock proteins, members of which can be substrates for transglutaminase-mediated protein cross-linking. CotM was not detected among the extractable spore coat proteins. These observations are consistent with a model according to which CotM is part of a cross-linked insoluble skeleton that surrounds the spore, serves as a matrix for the assembly of additional outer coat material, and confers structural stability to the final structure.
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Affiliation(s)
- A O Henriques
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta GA 30322, USA
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23
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Abstract
The process of sporulation in the bacterium Bacillus subtilis proceeds through a well-defined series of morphological stages that involve the conversion of a growing cell into a two-cell-chamber sporangium within which a spore is produced. Over 125 genes are involved in this process, the transcription of which is temporally and spatially controlled by four DNA-binding proteins and five RNA polymerase sigma factors. Through a combination of genetic, biochemical, and cell biological approaches, regulatory networks have been elucidated that explicitly link the activation of these sigma factors to landmark events in the course of morphogenesis and to each other through pathways of intercellular communication. Signals targeting proteins to specific subcellular localizations and governing the assembly of macromolecular structures have been uncovered but their nature remains to be determined.
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Affiliation(s)
- P Stragier
- Institut de Biologie Physico-Chimique, Paris, France.
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24
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Magill NG, Cowan AE, Leyva-Vazquez MA, Brown M, Koppel DE, Setlow P. Analysis of the relationship between the decrease in pH and accumulation of 3-phosphoglyceric acid in developing forespores of Bacillus species. J Bacteriol 1996; 178:2204-10. [PMID: 8636019 PMCID: PMC177926 DOI: 10.1128/jb.178.8.2204-2210.1996] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Analysis of the pH decrease and 3-phosphoglyceric acid (3PGA) accumulation in the forespore compartment of sporulating cells of Bacillus subtilis showed that the pH decrease of 1 to 1.2 units at approximately 4 h of sporulation preceded 3PGA accumulation, as observed previously in B. megaterium. These data, as well as analysis of the forespore pH decrease in asporogenous mutants of B. subtilis, indicated that sigma G-dependent forespore transcription, but not sigma K-dependent mother cell transcription, is required for the forespore pH decrease. Further analysis of these asporogenous mutants showed an excellent correlation between the forespore pH decrease and the forespore's accumulation of 3PGA. These latter results are consistent with our previous suggestion that the decrease in forespore pH results in greatly decreased activity of phosphoglycerate mutase in the forespore, which in turn leads to 3PGA accumulation. In further support of this suggestion, we found that (i) elevating the pH of developing forespores of B. megaterium resulted in rapid utilization of the forespore's 3PGA depot and (ii) increasing forespore levels of PGM approximately 10-fold in B. subtilis resulted in a large decrease in the spore's depot of 3PGA. The B. subtilis strain with a high phosphoglycerate mutase level sporulated, and the spores germinated and went through outgrowth normally, indicating that forespore accumulation of a large 3PGA depot is not essential for these processes.
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Affiliation(s)
- N G Magill
- Department of Biochemistry, University of Connecticut Health Center, Farmington 06030, USA
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25
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Carlson HC, Lu S, Kroos L, Haldenwang WG. Exchange of precursor-specific elements between Pro-sigma E and Pro-sigma K of Bacillus subtilis. J Bacteriol 1996; 178:546-9. [PMID: 8550479 PMCID: PMC177691 DOI: 10.1128/jb.178.2.546-549.1996] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
sigma E and sigma K are sporulation-specific sigma factors of Bacillus subtilis that are synthesized as inactive proproteins. Pro-sigma E and pro-sigma K are activated by the removal of 27 and 20 amino acids, respectively, from their amino termini. To explore the properties of the precursor-specific sequences, we exchanged the coding elements for these domains in the sigma E and sigma K structural genes and determined the properties of the resulting chimeric proteins in B. subtilis. The pro-sigma E-sigma K chimera accumulated and was cleaved into active sigma K, while the pro-sigma K-sigma E fusion protein failed to accumulate and is likely unstable in B. subtilis. A fusion of the sigE "pro" sequence to an unrelated protein (bovine rhodanese) also formed a protein that was cleaved by the pro-sigma E processing apparatus. The data suggest that the sigma E pro sequence contains sufficient information for pro-sigma E processing as well as a unique quality needed for sigma E accumulation.
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Affiliation(s)
- H C Carlson
- Department of Microbiology, University of Texas Health Science Center, San Antonio 78284, USA
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26
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Webb CD, Decatur A, Teleman A, Losick R. Use of green fluorescent protein for visualization of cell-specific gene expression and subcellular protein localization during sporulation in Bacillus subtilis. J Bacteriol 1995; 177:5906-11. [PMID: 7592342 PMCID: PMC177417 DOI: 10.1128/jb.177.20.5906-5911.1995] [Citation(s) in RCA: 114] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We report the use of the green fluorescent protein (GFP) of Aequorea victoria to visualize cell-specific gene expression and protein subcellular localization during sporulation in Bacillus subtilis. Sporangia bearing the gene (gfp) for the green fluorescent protein fused to genes under the control of the sporulation transcription factor sigma F exhibited a forespore-specific pattern of fluorescence. Forespore-specific fluorescence could be detected with fusions to promoters that are utilized with low (csfB) and high (sspE-2G) efficiency by sigma F-containing RNA polymerase. Conversely, a mother cell-specific pattern of fluorescence was observed in sporangia bearing a transcriptional fusion of gfp to a spore coat protein gene (cotE) under the control of sigma E and an in-frame fusion to a regulatory gene (gerE) under the control of sigma K. An in-frame fusion of gfp to cotE demonstrated that GFP can also be used to visualize protein subcellular localization. In sporangia producing the CotE-GFP fusion protein, fluorescence was found to localize around the developing spore, and this localization was dependent upon SpoIVA, a morphogenetic protein known to determine proper localization of CotE.
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Affiliation(s)
- C D Webb
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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27
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Losick R. Differentiation and Cell Fate in a Simple Organism. Bioscience 1995. [DOI: 10.2307/1312720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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28
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Halberg R, Oke V, Kroos L. Effects of Bacillus subtilis sporulation regulatory protein SpoIIID on transcription by sigma K RNA polymerase in vivo and in vitro. J Bacteriol 1995; 177:1888-91. [PMID: 7896717 PMCID: PMC176822 DOI: 10.1128/jb.177.7.1888-1891.1995] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
SpoIIID is a sequence-specific, DNA-binding protein that activates or represses transcription of different genes by sigma K RNA polymerase in vitro. A Bacillus subtilis strain engineered to produce both sigma K and SpoIIID during growth showed effects of SpoIIID on expression of sigma K-dependent genes that were consistent with the effects of a small amount of SpoIIID on transcription of these genes in vitro, indicating that the strain provides a simple, in vivo method to screen for effects of SpoIIID on transcription of sigma K-dependent genes.
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Affiliation(s)
- R Halberg
- Department of Biochemistry, Michigan State University, East Lansing 48824
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29
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Abstract
The specificity of DNA-dependent RNA polymerase for target promotes is largely due to the replaceable sigma subunit that it carries. Multiple sigma proteins, each conferring a unique promoter preference on RNA polymerase, are likely to be present in all bacteria; however, their abundance and diversity have been best characterized in Bacillus subtilis, the bacterium in which multiple sigma factors were first discovered. The 10 sigma factors thus far identified in B. subtilis directly contribute to the bacterium's ability to control gene expression. These proteins are not merely necessary for the expression of those operons whose promoters they recognize; in many instances, their appearance within the cell is sufficient to activate these operons. This review describes the discovery of each of the known B. subtilis sigma factors, their characteristics, the regulons they direct, and the complex restrictions placed on their synthesis and activities. These controls include the anticipated transcriptional regulation that modulates the expression of the sigma factor structural genes but, in the case of several of the B. subtilis sigma factors, go beyond this, adding novel posttranslational restraints on sigma factor activity. Two of the sigma factors (sigma E and sigma K) are, for example, synthesized as inactive precursor proteins. Their activities are kept in check by "pro-protein" sequences which are cleaved from the precursor molecules in response to intercellular cues. Other sigma factors (sigma B, sigma F, and sigma G) are inhibited by "anti-sigma factor" proteins that sequester them into complexes which block their ability to form RNA polymerase holoenzymes. The anti-sigma factors are, in turn, opposed by additional proteins which participate in the sigma factors' release. The devices used to control sigma factor activity in B, subtilis may prove to be as widespread as multiple sigma factors themselves, providing ways of coupling sigma factor activation to environmental or physiological signals that cannot be readily joined to other regulatory mechanisms.
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Affiliation(s)
- W G Haldenwang
- Department of Microbiology, University of Texas Health Science Center, San Antonio 78284-7758
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30
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Lu S, Cutting S, Kroos L. Sporulation protein SpoIVFB from Bacillus subtilis enhances processing of the sigma factor precursor Pro-sigma K in the absence of other sporulation gene products. J Bacteriol 1995; 177:1082-5. [PMID: 7860587 PMCID: PMC176705 DOI: 10.1128/jb.177.4.1082-1085.1995] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Processing of inactive pro-sigma K to active sigma K in the mother cell compartment of sporulating Bacillus subtilis is governed by a signal transduction pathway emanating from the forespore and involving SpoIVFB in the mother cell. Coexpression of spoIVFB and sigK (encoding pro-sigma K) genes in growing B. subtilis or Escherichia coli enhanced pro-sigma K processing in the absence of other sporulation-specific gene products. The simplest explanation of these results is that SpoIVFB is a protease that processes pro-sigma K.
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Affiliation(s)
- S Lu
- Department of Biochemistry, Michigan State University, East Lansing 48824
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31
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Schmidt R, Decatur AL, Rather PN, Moran CP, Losick R. Bacillus subtilis lon protease prevents inappropriate transcription of genes under the control of the sporulation transcription factor sigma G. J Bacteriol 1994; 176:6528-37. [PMID: 7961403 PMCID: PMC197006 DOI: 10.1128/jb.176.21.6528-6537.1994] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The Bacillus subtilis RNA polymerase sigma factor sigma G is a cell-type-specific regulatory protein that governs the transcription of genes that are expressed at an intermediate to late stage of sporulation in the forespore compartment of the sporangium. Here we report the identification of a mutation (lon-1) that causes inappropriate transcription of genes under the control of sigma G under nutritional and genetic conditions in which sporulation is prevented. The mutation is located at 245 degrees on the genetic map and lies within a newly identified open reading frame that is predicted to encode a homolog to Lon protease. Inappropriate transcription of sigma G-controlled genes in the lon-1 mutant is not prevented by mutations in genes that are normally required for the appearance of sigma G during sporulation but is prevented by a mutation in the structural gene (spoIIIG) for sigma G itself. In light of previous work showing that spoIIIG is subject to positive autoregulation, we propose that Lon protease is responsible (possibly by causing degradation of sigma G) for preventing sigma G-directed transcription of spoIIIG and hence the accumulation of sigma G in cells that are not undergoing sporulation. An integrated physical and genetic map is presented that encompasses 36 kb of uninterrupted DNA sequence from the lon pheA region of the chromosome, corresponding to 245 degrees to 239 degrees on the genetic map.
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Affiliation(s)
- R Schmidt
- Biological Laboratory, Harvard University, Cambridge, Massachusetts 02138
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Lu S, Kroos L. Overproducing the Bacillus subtilis mother cell sigma factor precursor, Pro-sigma K, uncouples sigma K-dependent gene expression from dependence on intercompartmental communication. J Bacteriol 1994; 176:3936-43. [PMID: 8021176 PMCID: PMC205591 DOI: 10.1128/jb.176.13.3936-3943.1994] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
During sporulation of Bacillus subtilis, proteolytic activation of pro-sigma K and ensuing sigma K-dependent gene expression normally require the activity of many sporulation gene products. We report here that overproducing pro-sigma K at the onset of sporulation substantially uncouples sigma K-dependent gene expression from its normal dependency. Overproducing pro-sigma K in strains with a mutation in spoIIIG, spoIIIA, spoIIIE, or spoIVB partially restored sigma K-dependent gene expression in the mother cell and resulted in accumulation of a small amount of polypeptide that comigrated with sigma K, but these mutants still failed to form spores. In contrast, sporulation of spoIVF mutants was greatly enhanced by pro-sigma K overproduction. The products of the spoIVF operon are made in the mother cell and normally govern pro-sigma K processing, but overproduction of pro-sigma K appears to allow accumulation of a small amount of sigma K, which is sufficient to partially restore mother cell gene expression and spore formation. This spoIVF-independent mechanism for processing pro-sigma K depends on sigma E, an earlier-acting mother cell-specific sigma factor. The spoIIID gene, which encodes a mother cell-specific DNA-binding protein that is normally required for pro-sigma K production, was shown to be required for efficient pro-sigma K processing as well. bof (bypass of forespore) mutations bypassed this requirement for spoIIID, suggesting that SpoIIID is less directly involved in pro-sigma K processing than are spoIVF gene products. However, bof spoIIID double mutants overproducing pro-sigma K still failed to sporulate, indicating that SpoIIID serves another essential role(s) in sporulation in addition to its multiple roles in the production of sigma K.
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Affiliation(s)
- S Lu
- Department of Biochemistry, Michigan State University, East Lansing 48824
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