1
|
Dehghani B, Rodrigues CDA. SpoIIQ-dependent localization of SpoIIE contributes to septal stability and compartmentalization during the engulfment stage of Bacillus subtilis sporulation. J Bacteriol 2024; 206:e0022024. [PMID: 38904397 PMCID: PMC11270862 DOI: 10.1128/jb.00220-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Accepted: 06/01/2024] [Indexed: 06/22/2024] Open
Abstract
During spore development in bacteria, a polar septum separates two transcriptionally distinct cellular compartments, the mother cell and the forespore. The conserved serine phosphatase SpoIIE is known for its critical role in the formation of this septum and activation of compartment-specific transcription in the forespore. Signaling between the mother cell and forespore then leads to activation of mother cell transcription and a phagocytic-like process called engulfment, which involves dramatic remodeling of the septum and requires a balance between peptidoglycan synthesis and hydrolysis to ensure septal stability and compartmentalization. Using Bacillus subtilis, we identify an additional role for SpoIIE in maintaining septal stability and compartmentalization at the onset of engulfment. This role for SpoIIE is mediated by SpoIIQ, which anchors SpoIIE in the engulfing membrane. A SpoIIQ mutant (SpoIIQ Y28A) that fails to anchor SpoIIE, results in septal instability and miscompartmentalization during septal peptidoglycan hydrolysis, when other septal stabilization factors are absent. Our data support a model whereby SpoIIE and its interactions with the peptidoglycan synthetic machinery contribute to the stabilization of the asymmetric septum early in engulfment, thereby ensuring compartmentalization during spore development.IMPORTANCEBacterial sporulation is a complex process involving a vast array of proteins. Some of these proteins are absolutely critical and regulate key points in the developmental process. Once such protein is SpoIIE, known for its role in the formation of the polar septum, a hallmark of the early stages of sporulation, and activation of the first sporulation-specific sigma factor, σF, in the developing spore. Interestingly, SpoIIE has been shown to interact with SpoIIQ, an important σF-regulated protein that functions during the engulfment stage. However, the significance of this interaction has remained unclear. Here, we unveil the importance of the SpoIIQ-SpoIIE interaction and identify a role for SpoIIE in the stabilization of the polar septum and maintenance of compartmentalization at the onset of engulfment. In this way, we demonstrate that key sporulation proteins, like SpoIIQ and SpoIIE, function in multiple processes during spore development.
Collapse
Affiliation(s)
- Behzad Dehghani
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | | |
Collapse
|
2
|
Parrell D, Kroos L. Channels modestly impact compartment-specific ATP levels during Bacillus subtilis sporulation and a rise in the mother cell ATP level is not necessary for Pro-σ K cleavage. Mol Microbiol 2020; 114:563-581. [PMID: 32515031 DOI: 10.1111/mmi.14560] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Revised: 05/28/2020] [Accepted: 05/28/2020] [Indexed: 01/13/2023]
Abstract
Starvation of Bacillus subtilis initiates endosporulation involving formation of mother cell (MC) and forespore (FS) compartments. During engulfment, the MC membrane migrates around the FS and protein channels connect the two compartments. The channels are necessary for postengulfment FS gene expression, which relieves inhibition of SpoIVFB, an intramembrane protease that cleaves Pro-σK , releasing σK into the MC. SpoIVFB has an ATP-binding domain exposed to the MC cytoplasm, but the role of ATP in regulating Pro-σK cleavage has been unclear, as has the impact of the channels on MC and FS ATP levels. Using luciferase produced separately in each compartment to measure relative ATP concentrations during sporulation, we found that the MC ATP concentration rises about twofold coincident with increasing cleavage of Pro-σK , and the FS ATP concentration does not decline. Mutants lacking a channel protein or defective in channel protein turnover exhibited modest and varied effects on ATP levels, which suggested that low ATP concentration does not explain the lack of postengulfment FS gene expression in channel mutants. Furthermore, a rise in the MC ATP level was not necessary for Pro-σK cleavage by SpoIVFB, based on analysis of mutants that bypass the need for relief of SpoIVFB inhibition.
Collapse
Affiliation(s)
- Daniel Parrell
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
| | - Lee Kroos
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
| |
Collapse
|
3
|
Ramos-Silva P, Serrano M, Henriques AO. From Root to Tips: Sporulation Evolution and Specialization in Bacillus subtilis and the Intestinal Pathogen Clostridioides difficile. Mol Biol Evol 2020; 36:2714-2736. [PMID: 31350897 PMCID: PMC6878958 DOI: 10.1093/molbev/msz175] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Bacteria of the Firmicutes phylum are able to enter a developmental pathway that culminates with the formation of highly resistant, dormant endospores. Endospores allow environmental persistence, dissemination and for pathogens, are also infection vehicles. In both the model Bacillus subtilis, an aerobic organism, and in the intestinal pathogen Clostridioides difficile, an obligate anaerobe, sporulation mobilizes hundreds of genes. Their expression is coordinated between the forespore and the mother cell, the two cells that participate in the process, and is kept in close register with the course of morphogenesis. The evolutionary mechanisms by which sporulation emerged and evolved in these two species, and more broadly across Firmicutes, remain largely unknown. Here, we trace the origin and evolution of sporulation using the genes known to be involved in the process in B. subtilis and C. difficile, and estimating their gain-loss dynamics in a comprehensive bacterial macroevolutionary framework. We show that sporulation evolution was driven by two major gene gain events, the first at the base of the Firmicutes and the second at the base of the B. subtilis group and within the Peptostreptococcaceae family, which includes C. difficile. We also show that early and late sporulation regulons have been coevolving and that sporulation genes entail greater innovation in B. subtilis with many Bacilli lineage-restricted genes. In contrast, C. difficile more often recruits new sporulation genes by horizontal gene transfer, which reflects both its highly mobile genome, the complexity of the gut microbiota, and an adjustment of sporulation to the gut ecosystem.
Collapse
Affiliation(s)
- Paula Ramos-Silva
- Instituto Gulbenkian de Ciência, Oeiras, Portugal.,Marine Biodiversity Group, Naturalis Biodiversity Center, Leiden, The Netherlands
| | - Mónica Serrano
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Adriano O Henriques
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| |
Collapse
|
4
|
Shen A, Edwards AN, Sarker MR, Paredes-Sabja D. Sporulation and Germination in Clostridial Pathogens. Microbiol Spectr 2019; 7:10.1128/microbiolspec.GPP3-0017-2018. [PMID: 31858953 PMCID: PMC6927485 DOI: 10.1128/microbiolspec.gpp3-0017-2018] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Indexed: 12/14/2022] Open
Abstract
As obligate anaerobes, clostridial pathogens depend on their metabolically dormant, oxygen-tolerant spore form to transmit disease. However, the molecular mechanisms by which those spores germinate to initiate infection and then form new spores to transmit infection remain poorly understood. While sporulation and germination have been well characterized in Bacillus subtilis and Bacillus anthracis, striking differences in the regulation of these processes have been observed between the bacilli and the clostridia, with even some conserved proteins exhibiting differences in their requirements and functions. Here, we review our current understanding of how clostridial pathogens, specifically Clostridium perfringens, Clostridium botulinum, and Clostridioides difficile, induce sporulation in response to environmental cues, assemble resistant spores, and germinate metabolically dormant spores in response to environmental cues. We also discuss the direct relationship between toxin production and spore formation in these pathogens.
Collapse
Affiliation(s)
- Aimee Shen
- Department of Molecular Biology and Microbiology, Tufts University Medical School, Boston, MA
| | - Adrianne N Edwards
- Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA
| | - Mahfuzur R Sarker
- Department of Microbiology, College of Science, Oregon State University, Corvallis, OR
- Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR
| | - Daniel Paredes-Sabja
- Department of Gut Microbiota and Clostridia Research Group, Departamento de Ciencias Biolo gicas, Facultad de Ciencias Biologicas, Universidad Andres Bello, Santiago, Chile
| |
Collapse
|
5
|
Abstract
Bacteria employ a number of dedicated secretion systems to export proteins to the extracellular environment. Several of these comprise large complexes that assemble in and around the bacterial membrane(s) to form specialized channels through which only selected proteins are actively delivered. Although typically associated with bacterial pathogenicity, a specialized variant of these secretion systems has been proposed to play a central part in bacterial sporulation, a primitive protective process that allows starving cells to form spores that survive in extreme environments. Following asymmetric division, the mother cell engulfs the forespore, leaving it surrounded by two bilayer membranes. During the engulfment process an essential channel apparatus is thought to cross both membranes to create a direct conduit between the mother cell and forespore. At least nine proteins are essential for channel formation, including SpoIIQ under forespore control and the eight SpoIIIA proteins (SpoIIIAA to -AH) under mother cell control. Presumed to form a core channel complex, several of these proteins share similarity with components of Gram-negative bacterial secretion systems, including the type II, III, and IV secretion systems and the flagellum. Based on these similarities it has been suggested that the sporulation channel represents a hybrid, secretion-like transport machinery. Recently, in-depth biochemical and structural characterization of the individual channel components accompanied by in vivo studies has further reinforced this model. Here we review and discuss these recent studies and suggest an updated model for the unique sporulation channel apparatus architecture.
Collapse
|
6
|
The New Kid on the Block: A Specialized Secretion System during Bacterial Sporulation. Trends Microbiol 2018; 26:663-676. [DOI: 10.1016/j.tim.2018.01.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 01/03/2018] [Accepted: 01/09/2018] [Indexed: 01/09/2023]
|
7
|
Mearls EB, Jackter J, Colquhoun JM, Farmer V, Matthews AJ, Murphy LS, Fenton C, Camp AH. Transcription and translation of the sigG gene is tuned for proper execution of the switch from early to late gene expression in the developing Bacillus subtilis spore. PLoS Genet 2018; 14:e1007350. [PMID: 29702640 PMCID: PMC5942855 DOI: 10.1371/journal.pgen.1007350] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 05/09/2018] [Accepted: 04/03/2018] [Indexed: 12/01/2022] Open
Abstract
A cascade of alternative sigma factors directs developmental gene expression during spore formation by the bacterium Bacillus subtilis. As the spore develops, a tightly regulated switch occurs in which the early-acting sigma factor σF is replaced by the late-acting sigma factor σG. The gene encoding σG (sigG) is transcribed by σF and by σG itself in an autoregulatory loop; yet σG activity is not detected until σF-dependent gene expression is complete. This separation in σF and σG activities has been suggested to be due at least in part to a poorly understood intercellular checkpoint pathway that delays sigG expression by σF. Here we report the results of a careful examination of sigG expression during sporulation. Unexpectedly, our findings argue against the existence of a regulatory mechanism to delay sigG transcription by σF and instead support a model in which sigG is transcribed by σF with normal timing, but at levels that are very low. This low-level expression of sigG is the consequence of several intrinsic features of the sigG regulatory and coding sequence—promoter spacing, secondary structure potential of the mRNA, and start codon identity—that dampen its transcription and translation. Especially notable is the presence of a conserved hairpin in the 5’ leader sequence of the sigG mRNA that occludes the ribosome-binding site, reducing translation by up to 4-fold. Finally, we demonstrate that misexpression of sigG from regulatory and coding sequences lacking these features triggers premature σG activity in the forespore during sporulation, as well as inappropriate σG activity during vegetative growth. Altogether, these data indicate that transcription and translation of the sigG gene is tuned to prevent vegetative expression of σG and to ensure the precise timing of the switch from σF to σG in the developing spore. Global changes in gene expression occur during normal cellular growth and development, as well as during cancer cell transformation and bacterial pathogenesis. In this study we have investigated the molecular mechanisms that drive the switch from early to late developmental gene expression during spore formation by the model bacterium Bacillus subtilis. At early times, gene expression in the developing spore is directed by the transcription factor σF; at later times σF is replaced by σG. An important, yet poorly understood aspect of this σF-to-σG transition is how σG activation is delayed until the early, σF-directed phase of gene expression is complete. Here we have carefully examined expression of the gene encoding σG, sigG, and found that its transcription and translation are ordinarily dampened by several features of its regulatory and coding sequences. Moreover, we have found that this “tuning” of sigG expression is required for proper timing of the switch to σG. These results reframe our understanding of how sigG is regulated during B. subtilis sporulation and, more broadly, advance our understanding of how global changes in gene expression can be precisely executed at the molecular/genetic level.
Collapse
MESH Headings
- Bacillus subtilis/genetics
- Bacillus subtilis/physiology
- Bacterial Proteins/biosynthesis
- Bacterial Proteins/genetics
- Gene Expression Regulation, Bacterial
- Genes, Bacterial
- Inverted Repeat Sequences
- Models, Genetic
- Nucleic Acid Conformation
- Promoter Regions, Genetic
- Protein Biosynthesis
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Sigma Factor/biosynthesis
- Sigma Factor/genetics
- Signal Transduction
- Spores, Bacterial/genetics
- Spores, Bacterial/physiology
- Transcription, Genetic
Collapse
Affiliation(s)
- Elizabeth B. Mearls
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA, USA
| | - Jacquelin Jackter
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA, USA
| | | | - Veronica Farmer
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA, USA
| | - Allison J. Matthews
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA, USA
| | - Laura S. Murphy
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA, USA
| | - Colleen Fenton
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA, USA
| | - Amy H. Camp
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA, USA
- * E-mail:
| |
Collapse
|
8
|
Rodrigues CDA, Ramírez-Guadiana FH, Meeske AJ, Wang X, Rudner DZ. GerM is required to assemble the basal platform of the SpoIIIA-SpoIIQ transenvelope complex during sporulation in Bacillus subtilis. Mol Microbiol 2016; 102:260-273. [PMID: 27381174 DOI: 10.1111/mmi.13457] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/02/2016] [Indexed: 11/29/2022]
Abstract
Sporulating Bacillus subtilis cells assemble a multimeric membrane complex connecting the mother cell and developing spore that is required to maintain forespore differentiation. An early step in the assembly of this transenvelope complex (called the A-Q complex) is an interaction between the extracellular domains of the forespore membrane protein SpoIIQ and the mother cell membrane protein SpoIIIAH. This interaction provides a platform onto which the remaining components of the complex assemble and also functions as an anchor for cell-cell signalling and morphogenetic proteins involved in spore development. SpoIIQ is required to recruit SpoIIIAH to the sporulation septum on the mother cell side; however, the mechanism by which SpoIIQ specifically localizes to the septal membranes on the forespore side has remained enigmatic. Here, we identify GerM, a lipoprotein previously implicated in spore germination, as the missing factor required for SpoIIQ localization. Our data indicate that GerM and SpoIIIAH, derived from the mother cell, and SpoIIQ, from the forespore, have reciprocal localization dependencies suggesting they constitute a tripartite platform for the assembly of the A-Q complex and a hub for the localization of mother cell and forespore proteins.
Collapse
Affiliation(s)
- Christopher D A Rodrigues
- Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115, USA
| | - Fernando H Ramírez-Guadiana
- Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115, USA
| | - Alexander J Meeske
- Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115, USA
| | - Xindan Wang
- Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115, USA
| | - David Z Rudner
- Department of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA, 02115, USA.
| |
Collapse
|