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Roberts DM. A new role for monomeric ParA/Soj in chromosome dynamics in Bacillus subtilis. Microbiologyopen 2023; 12:e1344. [PMID: 36825885 PMCID: PMC9841721 DOI: 10.1002/mbo3.1344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 01/10/2023] [Accepted: 01/10/2023] [Indexed: 01/17/2023] Open
Abstract
ParABS (Soj-Spo0J) systems were initially implicated in plasmid and chromosome segregation in bacteria. However, it is now increasingly understood that they play multiple roles in cell cycle events in Bacillus subtilis, and possibly other bacteria. In a recent study, monomeric forms of ParA/Soj have been implicated in regulating aspects of chromosome dynamics during B. subtilis sporulation. In this commentary, I will discuss the known roles of ParABS systems, explore why sporulation is a valuable model for studying these proteins, and the new insights into the role of monomeric ParA/Soj. Finally, I will touch upon some of the future work that remains.
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Roberts DM, Anchimiuk A, Kloosterman TG, Murray H, Wu LJ, Gruber S, Errington J. Chromosome remodelling by SMC/Condensin in B. subtilis is regulated by monomeric Soj/ParA during growth and sporulation. Proc Natl Acad Sci U S A 2022; 119:e2204042119. [PMID: 36206370 PMCID: PMC9564211 DOI: 10.1073/pnas.2204042119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 09/09/2022] [Indexed: 11/18/2022] Open
Abstract
SMC complexes, loaded at ParB-parS sites, are key mediators of chromosome organization in bacteria. ParA/Soj proteins interact with ParB/Spo0J in a pathway involving adenosine triphosphate (ATP)-dependent dimerization and DNA binding, facilitating chromosome segregation in bacteria. In Bacillus subtilis, ParA/Soj also regulates DNA replication initiation and along with ParB/Spo0J is involved in cell cycle changes during endospore formation. The first morphological stage in sporulation is the formation of an elongated chromosome structure called an axial filament. Here, we show that a major redistribution of SMC complexes drives axial filament formation in a process regulated by ParA/Soj. Furthermore, and unexpectedly, this regulation is dependent on monomeric forms of ParA/Soj that cannot bind DNA or hydrolyze ATP. These results reveal additional roles for ParA/Soj proteins in the regulation of SMC dynamics in bacteria and yet further complexity in the web of interactions involving chromosome replication, segregation and organization, controlled by ParAB and SMC.
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Affiliation(s)
- David M. Roberts
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4AX, United Kingdom
| | - Anna Anchimiuk
- Department of Fundamental Microbiology, University of Lausanne, Bâtiment Biophore, 015 Lausanne, Switzerland
| | - Tomas G. Kloosterman
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4AX, United Kingdom
| | - Heath Murray
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4AX, United Kingdom
| | - Ling Juan Wu
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4AX, United Kingdom
| | - Stephan Gruber
- Department of Fundamental Microbiology, University of Lausanne, Bâtiment Biophore, 015 Lausanne, Switzerland
| | - Jeff Errington
- Centre for Bacterial Cell Biology, Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4AX, United Kingdom
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RefZ and Noc Act Synthetically to Prevent Aberrant Divisions during Bacillus subtilis Sporulation. J Bacteriol 2022; 204:e0002322. [PMID: 35506695 DOI: 10.1128/jb.00023-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During sporulation, Bacillus subtilis undergoes an atypical cell division that requires overriding mechanisms that protect chromosomes from damage and ensure inheritance by daughter cells. Instead of assembling between segregated chromosomes at midcell, the FtsZ-ring coalesces polarly, directing division over one chromosome. The DNA-binding protein RefZ facilitates the timely assembly of polar Z-rings and partially defines the region of chromosome initially captured in the forespore. RefZ binds to motifs (RBMs) located proximal to the origin of replication (oriC). Although refZ and the RBMs are conserved across the Bacillus genus, a refZ deletion mutant sporulates with wild-type efficiency, so the functional significance of RefZ during sporulation remains unclear. To further investigate RefZ function, we performed a candidate-based screen for synthetic sporulation defects by combining ΔrefZ with deletions of genes previously implicated in FtsZ regulation and/or chromosome capture. Combining ΔrefZ with deletions of ezrA, sepF, parA, or minD did not detectably affect sporulation. In contrast, a ΔrefZ Δnoc mutant exhibited a sporulation defect, revealing a genetic interaction between RefZ and Noc. Using reporters of sporulation progression, we determined the ΔrefZ Δnoc mutant exhibited sporulation delays after Spo0A activation but prior to late sporulation, with a subset of cells failing to divide polarly or activate the first forespore-specific sigma factor, SigF. The ΔrefZ Δnoc mutant also exhibited extensive dysregulation of cell division, producing cells with extra, misplaced, or otherwise aberrant septa. Our results reveal a previously unknown epistatic relationship that suggests refZ and noc contribute synthetically to regulating cell division and supporting spore development. IMPORTANCE The DNA-binding protein RefZ and its binding sites (RBMs) are conserved in sequence and location on the chromosome across the Bacillus genus and contribute to the timing of polar FtsZ-ring assembly during sporulation. Only a small number of noncoding and nonregulatory DNA motifs are known to be conserved in chromosomal position in bacteria, suggesting there is strong selective pressure for their maintenance; however, a refZ deletion mutant sporulates efficiently, providing no clues as to their functional significance. Here, we find that in the absence of the nucleoid occlusion factor Noc, deletion of refZ results in a sporulation defect characterized by developmental delays and aberrant divisions.
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Beskrovnaya P, Sexton DL, Golmohammadzadeh M, Hashimi A, Tocheva EI. Structural, Metabolic and Evolutionary Comparison of Bacterial Endospore and Exospore Formation. Front Microbiol 2021; 12:630573. [PMID: 33767680 PMCID: PMC7985256 DOI: 10.3389/fmicb.2021.630573] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 02/15/2021] [Indexed: 12/20/2022] Open
Abstract
Sporulation is a specialized developmental program employed by a diverse set of bacteria which culminates in the formation of dormant cells displaying increased resilience to stressors. This represents a major survival strategy for bacteria facing harsh environmental conditions, including nutrient limitation, heat, desiccation, and exposure to antimicrobial compounds. Through dispersal to new environments via biotic or abiotic factors, sporulation provides a means for disseminating genetic material and promotes encounters with preferable environments thus promoting environmental selection. Several types of bacterial sporulation have been characterized, each involving numerous morphological changes regulated and performed by non-homologous pathways. Despite their likely independent evolutionary origins, all known modes of sporulation are typically triggered by limited nutrients and require extensive membrane and peptidoglycan remodeling. While distinct modes of sporulation have been observed in diverse species, two major types are at the forefront of understanding the role of sporulation in human health, and microbial population dynamics and survival. Here, we outline endospore and exospore formation by members of the phyla Firmicutes and Actinobacteria, respectively. Using recent advances in molecular and structural biology, we point to the regulatory, genetic, and morphological differences unique to endo- and exospore formation, discuss shared characteristics that contribute to the enhanced environmental survival of spores and, finally, cover the evolutionary aspects of sporulation that contribute to bacterial species diversification.
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Affiliation(s)
| | | | | | | | - Elitza I. Tocheva
- Department of Microbiology and Immunology, Life Sciences Institute, Health Sciences Mall, The University of British Columbia, Vancouver, BC, Canada
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Nowaczyk-Cieszewska M, Zyla-Uklejewicz D, Noszka M, Jaworski P, Mielke T, Zawilak-Pawlik AM. The role of Helicobacter pylori DnaA domain I in orisome assembly on a bipartite origin of chromosome replication. Mol Microbiol 2019; 113:338-355. [PMID: 31715026 DOI: 10.1111/mmi.14423] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 11/08/2019] [Accepted: 11/10/2019] [Indexed: 12/12/2022]
Abstract
The main roles of the DnaA protein are to bind the origin of chromosome replication (oriC), to unwind DNA and to provide a hub for the step-wise assembly of a replisome. DnaA is composed of four domains, with each playing a distinct functional role in the orisome assembly. Out of the four domains, the role of domain I is the least understood and appears to be the most species-specific. To better characterise Helicobacter pylori DnaA domain I, we have constructed a series of DnaA variants and studied their interactions with H. pylori bipartite oriC. We show that domain I is responsible for the stabilisation and organisation of DnaA-oriC complexes and provides cooperativity in DnaA-DNA interactions. Domain I mediates cross-interactions between oriC subcomplexes, which indicates that domain I is important for long-distance DnaA interactions and is essential for orisosme assembly on bipartite origins. HobA, which interacts with domain I, increases the DnaA binding to bipartite oriC; however, it does not stimulate but rather inhibits DNA unwinding. This suggests that HobA helps DnaA to bind oriC, but an unknown factor triggers DNA unwinding. Together, our results indicate that domain I self-interaction is important for the DnaA assembly on bipartite H. pylori oriC.
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Affiliation(s)
- Malgorzata Nowaczyk-Cieszewska
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Dorota Zyla-Uklejewicz
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Mateusz Noszka
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Pawel Jaworski
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Thorsten Mielke
- Microscopy and Cryo-Electron Microscopy Group, Max Planck Institute for Molecular Genetics, Berlin, Germany
| | - Anna Magdalena Zawilak-Pawlik
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
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Matthews LA, Simmons LA. Cryptic protein interactions regulate DNA replication initiation. Mol Microbiol 2018; 111:118-130. [PMID: 30285297 DOI: 10.1111/mmi.14142] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 09/25/2018] [Accepted: 09/26/2018] [Indexed: 12/13/2022]
Abstract
DNA replication is a fundamental biological process that is tightly regulated in all cells. In bacteria, DnaA controls when and where replication begins by building a step-wise complex that loads the replicative helicase onto chromosomal DNA. In many low-GC Gram-positive species, DnaA recruits the DnaD and DnaB proteins to function as adaptors to assist in helicase loading. How DnaA, its adaptors and the helicase form a complex at the origin is unclear. We addressed this question using the bacterial two-hybrid assay to determine how the initiation proteins from Bacillus subtilis interact with each other. We show that cryptic interaction sites play a key role in this process and we map these regions for the entire pathway. In addition, we found that the SirA regulator that blocks initiation in sporulating cells binds to a surface on DnaA that overlaps with DnaD. The interaction between DnaA and DnaD was also mapped to the same DnaA surface in the human pathogen Staphylococcus aureus, demonstrating the broad conservation of this surface. Therefore, our study has unveiled key protein interactions essential for initiation and our approach is widely applicable for mapping interactions in other signaling pathways that are governed by cryptic binding surfaces.
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Affiliation(s)
- Lindsay A Matthews
- Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109-1048, USA
| | - Lyle A Simmons
- Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109-1048, USA
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Fournes F, Val ME, Skovgaard O, Mazel D. Replicate Once Per Cell Cycle: Replication Control of Secondary Chromosomes. Front Microbiol 2018; 9:1833. [PMID: 30131796 PMCID: PMC6090056 DOI: 10.3389/fmicb.2018.01833] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 07/23/2018] [Indexed: 12/13/2022] Open
Abstract
Faithful vertical transmission of genetic information, especially of essential core genes, is a prerequisite for bacterial survival. Hence, replication of all the replicons is tightly controlled to ensure that all daughter cells get the same genome copy as their mother cell. Essential core genes are very often carried by the main chromosome. However they can occasionally be found on secondary chromosomes, recently renamed chromids. Chromids have evolved from non-essential megaplasmids, and further acquired essential core genes and a genomic signature closed to that of the main chromosome. All chromids carry a plasmidic replication origin, belonging so far to either the iterons or repABC type. Based on these differences, two categories of chromids have been distinguished. In this review, we focus on the replication initiation controls of these two types of chromids. We show that the sophisticated mechanisms controlling their replication evolved from their plasmid counterparts to allow a timely controlled replication, occurring once per cell cycle.
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Affiliation(s)
- Florian Fournes
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, Paris, France.,UMR3525, Centre National de la Recherche Scientifique, Paris, France
| | - Marie-Eve Val
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, Paris, France.,UMR3525, Centre National de la Recherche Scientifique, Paris, France
| | - Ole Skovgaard
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
| | - Didier Mazel
- Unité Plasticité du Génome Bactérien, Département Génomes et Génétique, Institut Pasteur, Paris, France.,UMR3525, Centre National de la Recherche Scientifique, Paris, France
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García García T, Ventroux M, Derouiche A, Bidnenko V, Correia Santos S, Henry C, Mijakovic I, Noirot-Gros MF, Poncet S. Phosphorylation of the Bacillus subtilis Replication Controller YabA Plays a Role in Regulation of Sporulation and Biofilm Formation. Front Microbiol 2018; 9:486. [PMID: 29619013 PMCID: PMC5871692 DOI: 10.3389/fmicb.2018.00486] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 03/01/2018] [Indexed: 11/13/2022] Open
Abstract
Bacillus subtilis cells can adopt different life-styles in response to various environmental cues, including planktonic cells during vegetative growth, sessile cells during biofilm formation and sporulation. While switching life-styles, bacteria must coordinate the progression of their cell cycle with their physiological status. Our current understanding of the regulatory pathways controlling the decision-making processes and triggering developmental switches highlights a key role of protein phosphorylation. The regulatory mechanisms that integrate the bacterial chromosome replication status with sporulation involve checkpoint proteins that target the replication initiator DnaA or the kinase phosphorelay controlling the master regulator Spo0A. B. subtilis YabA is known to interact with DnaA to prevent over-initiation of replication during vegetative growth. Here, we report that YabA is phosphorylated by YabT, a Ser/Thr kinase expressed during sporulation and biofilm formation. The phosphorylation of YabA has no effect on replication initiation control but hyper-phosphorylation of YabA leads to an increase in sporulation efficiency and a strong inhibition of biofilm formation. We also provide evidence that YabA phosphorylation affects the level of Spo0A-P in cells. These results indicate that YabA is a multifunctional protein with a dual role in regulating replication initiation and life-style switching, thereby providing a potential mechanism for cross-talk and coordination of cellular processes during adaptation to environmental change.
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Affiliation(s)
| | - Magali Ventroux
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
| | | | - Vladimir Bidnenko
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
| | - Sara Correia Santos
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
| | - Céline Henry
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
| | - Ivan Mijakovic
- Systems and Synthetic Biology, Chalmers University of Technology, Göteborg, Sweden
| | | | - Sandrine Poncet
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
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Patel MJ, Bhatia L, Yilmaz G, Biswas-Fiss EE, Biswas SB. Multiple conformational states of DnaA protein regulate its interaction with DnaA boxes in the initiation of DNA replication. Biochim Biophys Acta Gen Subj 2017. [PMID: 28630006 DOI: 10.1016/j.bbagen.2017.06.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
DnaA protein is the initiator of genomic DNA replication in prokaryotes. It binds to specific DNA sequences in the origin of DNA replication and unwinds small AT-rich sequences downstream for the assembly of the replisome. The mechanism of activation of DnaA that enables it to bind and organize the origin DNA and leads to replication initiation remains unclear. In this study, we have developed double-labeled fluorescent DnaA probes to analyze conformational states of DnaA protein upon binding DNA, nucleotide, and Soj sporulation protein using Fluorescence Resonance Energy Transfer (FRET). Our studies demonstrate that DnaA protein undergoes large conformational changes upon binding to substrates and there are multiple distinct conformational states that enable it to initiate DNA replication. DnaA protein adopted a relaxed conformation by expanding ~15Å upon binding ATP and DNA to form the ATP·DnaA·DNA complex. Hydrolysis of bound ATP to ADP led to a contraction of DnaA within the complex. The relaxed conformation of DnaA is likely required for the formation of the multi-protein ATP·DnaA·DNA complex. In the initiation of sporulation, Soj binding to DnaA prevented relaxation of its conformation. Soj·ADP appeared to block the activation of DnaA, suggesting a mechanism for Soj·ADP in switching initiation of DNA replication to sporulation. Our studies demonstrate that multiple conformational states of DnaA protein regulate its binding to DNA in the initiation of DNA replication.
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Affiliation(s)
- Meera J Patel
- Department of Molecular Biology, Rowan University, Stratford, NJ 08084, United States; Program in Biotechnology, Department of Medical Laboratory Sciences, College of Health Sciences, University of Delaware, Newark, DE 19716, United States
| | - Lavesh Bhatia
- Department of Molecular Biology, Rowan University, Stratford, NJ 08084, United States
| | - Gulden Yilmaz
- Department of Molecular Biology, Rowan University, Stratford, NJ 08084, United States
| | - Esther E Biswas-Fiss
- Department of Molecular Biology, Rowan University, Stratford, NJ 08084, United States; Program in Biotechnology, Department of Medical Laboratory Sciences, College of Health Sciences, University of Delaware, Newark, DE 19716, United States
| | - Subhasis B Biswas
- Department of Molecular Biology, Rowan University, Stratford, NJ 08084, United States.
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Zawilak-Pawlik A, Nowaczyk M, Zakrzewska-Czerwińska J. The Role of the N-Terminal Domains of Bacterial Initiator DnaA in the Assembly and Regulation of the Bacterial Replication Initiation Complex. Genes (Basel) 2017; 8:genes8050136. [PMID: 28489024 PMCID: PMC5448010 DOI: 10.3390/genes8050136] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 04/28/2017] [Accepted: 05/04/2017] [Indexed: 12/22/2022] Open
Abstract
The primary role of the bacterial protein DnaA is to initiate chromosomal replication. The DnaA protein binds to DNA at the origin of chromosomal replication (oriC) and assembles into a filament that unwinds double-stranded DNA. Through interaction with various other proteins, DnaA also controls the frequency and/or timing of chromosomal replication at the initiation step. Escherichia coli DnaA also recruits DnaB helicase, which is present in unwound single-stranded DNA and in turn recruits other protein machinery for replication. Additionally, DnaA regulates the expression of certain genes in E. coli and a few other species. Acting as a multifunctional factor, DnaA is composed of four domains that have distinct, mutually dependent roles. For example, C-terminal domain IV interacts with double-stranded DnaA boxes. Domain III drives ATP-dependent oligomerization, allowing the protein to form a filament that unwinds DNA and subsequently binds to and stabilizes single-stranded DNA in the initial replication bubble; this domain also interacts with multiple proteins that control oligomerization. Domain II constitutes a flexible linker between C-terminal domains III–IV and N-terminal domain I, which mediates intermolecular interactions between DnaA and binds to other proteins that affect DnaA activity and/or formation of the initiation complex. Of these four domains, the role of the N-terminus (domains I–II) in the assembly of the initiation complex is the least understood and appears to be the most species-dependent region of the protein. Thus, in this review, we focus on the function of the N-terminus of DnaA in orisome formation and the regulation of its activity in the initiation complex in different bacteria.
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Affiliation(s)
- Anna Zawilak-Pawlik
- Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Weigla 12, Wroclaw 53-114, Poland.
| | - Małgorzata Nowaczyk
- Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Weigla 12, Wroclaw 53-114, Poland.
| | - Jolanta Zakrzewska-Czerwińska
- Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Weigla 12, Wroclaw 53-114, Poland.
- Department of Molecular Microbiology, Faculty of Biotechnology, University of Wrocław, ul. Joliot-Curie 14A, Wrocław 50-383, Poland.
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Jameson KH, Wilkinson AJ. Control of Initiation of DNA Replication in Bacillus subtilis and Escherichia coli. Genes (Basel) 2017; 8:E22. [PMID: 28075389 PMCID: PMC5295017 DOI: 10.3390/genes8010022] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Revised: 12/16/2016] [Accepted: 12/20/2016] [Indexed: 01/21/2023] Open
Abstract
Initiation of DNA Replication is tightly regulated in all cells since imbalances in chromosomal copy number are deleterious and often lethal. In bacteria such as Bacillus subtilis and Escherichia coli, at the point of cytokinesis, there must be two complete copies of the chromosome to partition into the daughter cells following division at mid-cell during vegetative growth. Under conditions of rapid growth, when the time taken to replicate the chromosome exceeds the doubling time of the cells, there will be multiple initiations per cell cycle and daughter cells will inherit chromosomes that are already undergoing replication. In contrast, cells entering the sporulation pathway in B. subtilis can do so only during a short interval in the cell cycle when there are two, and only two, chromosomes per cell, one destined for the spore and one for the mother cell. Here, we briefly describe the overall process of DNA replication in bacteria before reviewing initiation of DNA replication in detail. The review covers DnaA-directed assembly of the replisome at oriC and the multitude of mechanisms of regulation of initiation, with a focus on the similarities and differences between E. coli and B. subtilis.
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Affiliation(s)
- Katie H Jameson
- Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK.
| | - Anthony J Wilkinson
- Structural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, UK.
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