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Abstract
In this issue of Structure, Rood and colleagues report that substrate architecture is a key factor in promoting the complete and processive degradation of the Caulobacter cell cycle regulator PdeA by the protease ClpXP. This investigation highlights the important role that the adaptor protein CpdR serves in regulating presentation of PdeA to ClpXP.
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152
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Gill JJ, Berry JD, Russell WK, Lessor L, Escobar-Garcia DA, Hernandez D, Kane A, Keene J, Maddox M, Martin R, Mohan S, Thorn AM, Russell DH, Young R. The Caulobacter crescentus phage phiCbK: genomics of a canonical phage. BMC Genomics 2012; 13:542. [PMID: 23050599 PMCID: PMC3556154 DOI: 10.1186/1471-2164-13-542] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 10/01/2012] [Indexed: 11/30/2022] Open
Abstract
Background The bacterium Caulobacter crescentus is a popular model for the study of cell cycle regulation and senescence. The large prolate siphophage phiCbK has been an important tool in C. crescentus biology, and has been studied in its own right as a model for viral morphogenesis. Although a system of some interest, to date little genomic information is available on phiCbK or its relatives. Results Five novel phiCbK-like C. crescentus bacteriophages, CcrMagneto, CcrSwift, CcrKarma, CcrRogue and CcrColossus, were isolated from the environment. The genomes of phage phiCbK and these five environmental phage isolates were obtained by 454 pyrosequencing. The phiCbK-like phage genomes range in size from 205 kb encoding 318 proteins (phiCbK) to 280 kb encoding 448 proteins (CcrColossus), and were found to contain nonpermuted terminal redundancies of 10 to 17 kb. A novel method of terminal ligation was developed to map genomic termini, which confirmed termini predicted by coverage analysis. This suggests that sequence coverage discontinuities may be useable as predictors of genomic termini in phage genomes. Genomic modules encoding virion morphogenesis, lysis and DNA replication proteins were identified. The phiCbK-like phages were also found to encode a number of intriguing proteins; all contain a clearly T7-like DNA polymerase, and five of the six encode a possible homolog of the C. crescentus cell cycle regulator GcrA, which may allow the phage to alter the host cell’s replicative state. The structural proteome of phage phiCbK was determined, identifying the portal, major and minor capsid proteins, the tail tape measure and possible tail fiber proteins. All six phage genomes are clearly related; phiCbK, CcrMagneto, CcrSwift, CcrKarma and CcrRogue form a group related at the DNA level, while CcrColossus is more diverged but retains significant similarity at the protein level. Conclusions Due to their lack of any apparent relationship to other described phages, this group is proposed as the founding cohort of a new phage type, the phiCbK-like phages. This work will serve as a foundation for future studies on morphogenesis, infection and phage-host interactions in C. crescentus.
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Affiliation(s)
- Jason J Gill
- Center for Phage Technology, 2128 TAMU, Texas A&M University, College Station, Texas, TX 77843, USA
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153
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154
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Rood KL, Clark NE, Stoddard PR, Garman SC, Chien P. Adaptor-dependent degradation of a cell-cycle regulator uses a unique substrate architecture. Structure 2012; 20:1223-32. [PMID: 22682744 DOI: 10.1016/j.str.2012.04.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Revised: 03/15/2012] [Accepted: 04/25/2012] [Indexed: 01/31/2023]
Abstract
In Caulobacter crescentus, the ClpXP protease degrades several crucial cell-cycle regulators, including the phosphodiesterase PdeA. Degradation of PdeA requires the response regulator CpdR and signals a morphological transition in concert with initiation of DNA replication. Here, we report the structure of a Per-Arnt-Sim (PAS) domain of PdeA and show that it is necessary for CpdR-dependent degradation in vivo and in vitro. CpdR acts as an adaptor, tethering the amino-terminal PAS domain to ClpXP and promoting recognition of the weak carboxyl-terminal degron of PdeA, a combination that ensures processive proteolysis. We identify sites on the PAS domain needed for CpdR recognition and find that one subunit of the PdeA dimer can be delivered to ClpXP by its partner. Finally, we show that improper stabilization of PdeA in vivo alters cellular behavior. These results introduce an adaptor/substrate pair for ClpXP and reveal broad diversity in adaptor-mediated proteolysis.
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Affiliation(s)
- Keith L Rood
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Amherst, MA 01003, USA
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155
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Fields AT, Navarrete CS, Zare AZ, Huang Z, Mostafavi M, Lewis JC, Rezaeihaghighi Y, Brezler BJ, Ray S, Rizzacasa AL, Barnett MJ, Long SR, Chen EJ, Chen JC. The conserved polarity factor podJ1 impacts multiple cell envelope-associated functions in Sinorhizobium meliloti. Mol Microbiol 2012; 84:892-920. [PMID: 22553970 DOI: 10.1111/j.1365-2958.2012.08064.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Although diminutive in size, bacteria possess highly diverse and spatially confined cellular structures. Two related alphaproteobacteria, Sinorhizobium meliloti and Caulobacter crescentus, serve as models for investigating the genetic basis of morphological variations. S. meliloti, a symbiont of leguminous plants, synthesizes multiple flagella and no prosthecae, whereas C. crescentus, a freshwater bacterium, has a single polar flagellum and stalk. The podJ gene, originally identified in C. crescentus for its role in polar organelle development, is split into two adjacent open reading frames, podJ1 and podJ2, in S. meliloti. Deletion of podJ1 interferes with flagellar motility, exopolysaccharide production, cell envelope integrity, cell division and normal morphology, but not symbiosis. As in C. crescentus, the S. meliloti PodJ1 protein appears to act as a polarity beacon and localizes to the newer cell pole. Microarray analysis indicates that podJ1 affects the expression of at least 129 genes, the majority of which correspond to observed mutant phenotypes. Together, phenotypic characterization, microarray analysis and suppressor identification suggest that PodJ1 controls a core set of conserved elements, including flagellar and pili genes, the signalling proteins PleC and DivK, and the transcriptional activator TacA, while alternative downstream targets have evolved to suit the distinct lifestyles of individual species.
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Affiliation(s)
- Alexander T Fields
- Department of Biology, San Francisco State University, San Francisco, CA 94132, USA
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156
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Abstract
Heterogeneity within a clonal population of cells can increase survival in the face of environmental stress. In a recent issue of Science, Aldridge et al. (2012) demonstrate that cell division in mycobacteria is asymmetric, producing daughter cells that differ in size, growth rate, and susceptibility to antibiotics.
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Affiliation(s)
- Christopher D Aakre
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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157
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Curtis PD, Quardokus EM, Lawler ML, Guo X, Klein D, Chen JC, Arnold RJ, Brun YV. The scaffolding and signalling functions of a localization factor impact polar development. Mol Microbiol 2012; 84:712-35. [PMID: 22512778 DOI: 10.1111/j.1365-2958.2012.08055.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In the differentiating alphaproteobacterium Caulobacter crescentus, organelle synthesis at cell poles is critical to forming different progeny after cell division. Co-ordination of polar organelle synthesis, including pili and holdfast, and flagellum ejection, is mediated in part by the scaffolding protein PodJ. At the time of cell division, PodJ undergoes regulated processing to a short form that persists at the flagellar pole of swarmer cells. This study analyses how PodJ's role in structural and signalling protein localization impacts organelle synthesis. A PodJ mutant with an internal deletion exhibits reduced sensitivity to pili-tropic phage ΦCbK, resulting from reduced pilA gene expression, which can be linked to altered signalling protein localization. The phage sensitivity defect of a ΔpodJ mutant can be partially suppressed by ectopic pilA expression. Induction of PodJ processing, by manipulation of podJ itself or controlled perP expression, resulted in decreased pilus biogenesis and, when coupled with a podJ mutation that reduced pilA expression, led to complete loss of phage sensitivity. As a whole, the results show that PodJ's scaffolding role for structural and signalling proteins both contribute to flagellar pole organelle development.
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Affiliation(s)
- Patrick D Curtis
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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158
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Analysis of the CtrA pathway in Magnetospirillum reveals an ancestral role in motility in alphaproteobacteria. J Bacteriol 2012; 194:2973-86. [PMID: 22467786 DOI: 10.1128/jb.00170-12] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Developmental events across the prokaryotic life cycle are highly regulated at the transcriptional and posttranslational levels. Key elements of a few regulatory networks are conserved among phylogenetic groups of bacteria, although the features controlled by these conserved systems are as diverse as the organisms encoding them. In this work, we probed the role of the CtrA regulatory network, conserved throughout the Alphaproteobacteria, in the magnetotactic bacterium Magnetospirillum magneticum strain AMB-1, which possesses unique intracellular organization and compartmentalization. While we have shown that CtrA in AMB-1 is not essential for viability, it is required for motility, and its putative phosphorylation state dictates the ability of CtrA to activate the flagellar biosynthesis gene cascade. Gene expression analysis of strains expressing active and inactive CtrA alleles points to the composition of the extended CtrA regulon, including both direct and indirect targets. These results, combined with a bioinformatic study of the AMB-1 genome, enabled the prediction of an AMB-1-specific CtrA binding site. Further, phylogenetic studies comparing CtrA sequences from alphaproteobacteria in which the role of CtrA has been experimentally examined reveal an ancestral role of CtrA in the regulation of motility and suggest that its essential functions in other alphaproteobacteria were acquired subsequently.
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159
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Collier J. Regulation of chromosomal replication in Caulobacter crescentus. Plasmid 2011; 67:76-87. [PMID: 22227374 DOI: 10.1016/j.plasmid.2011.12.007] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2011] [Revised: 12/19/2011] [Accepted: 12/21/2011] [Indexed: 01/12/2023]
Abstract
The alpha-proteobacterium Caulobacter crescentus is characterized by its asymmetric cell division, which gives rise to a replicating stalked cell and a non-replicating swarmer cell. Thus, the initiation of chromosomal replication is tightly regulated, temporally and spatially, to ensure that it is coordinated with cell differentiation and cell cycle progression. Waves of DnaA and CtrA activities control when and where the initiation of DNA replication will take place in C. crescentus cells. The conserved DnaA protein initiates chromosomal replication by directly binding to sites within the chromosomal origin (Cori), ensuring that DNA replication starts once and only once per cell cycle. The CtrA response regulator represses the initiation of DNA replication in swarmer cells and in the swarmer compartment of pre-divisional cells, probably by competing with DnaA for binding to Cori. CtrA and DnaA are controlled by multiple redundant regulatory pathways that include DNA methylation-dependent transcriptional regulation, temporally regulated proteolysis and the targeting of regulators to specific locations within the cell. Besides being critical regulators of chromosomal replication, CtrA and DnaA are also master transcriptional regulators that control the expression of many genes, thus connecting DNA replication with other events of the C. crescentus cell cycle.
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Affiliation(s)
- Justine Collier
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Quartier UNIL/Sorge, Lausanne, CH 1015, Switzerland.
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160
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Kirkpatrick CL, Viollier PH. Reflections on a sticky situation: how surface contact pulls the trigger for bacterial adhesion. Mol Microbiol 2011; 83:7-9. [PMID: 22092444 DOI: 10.1111/j.1365-2958.2011.07913.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Adhesion of bacterial cells to surfaces can be mediated by a wide variety of extracellular structures, which can either recognize specific molecular motifs or adhere in non-specific ways to multiple types of surfaces. The attachment is thought to be highly regulated, but the underlying sensory mechanism(s) are poorly understood. In the α-proteobacterium Caulobacter crescentus, the formation of adhesive organelles is 'hardwired' into the cell cycle regulatory circuitry. In this issue of Molecular Microbiology, Li et al. (2011) employed this model organism to examine the adhesion process and the transition from temporary to permanent attachment using total internal reflection fluorescence (TIRF) microscopy. Surprisingly, they observed that adhesin production was not only under developmental control, but was also stimulated by surface contact. Initial reversible contact of the pili with the surface was followed by flagellum rotation arrest and subsequent induction of the holdfast to allow irreversible surface adhesion. These findings demonstrate that Caulobacter produces its holdfast only at the appropriate time for surface attachment, preventing premature export of the adhesin, which could then be inactivated by 'curing' or be masked by occluding particles. Importantly, their results support the notion that the flagellum serves as a mechanosensor for adhesion.
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Affiliation(s)
- Clare L Kirkpatrick
- Department of Microbiology and Molecular Medicine, University of Geneva, 1 rue Michel-Servet, 1211 Geneva 4, Switzerland
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161
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Regulatory cohesion of cell cycle and cell differentiation through interlinked phosphorylation and second messenger networks. Mol Cell 2011; 43:550-60. [PMID: 21855795 DOI: 10.1016/j.molcel.2011.07.018] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 05/27/2011] [Accepted: 07/25/2011] [Indexed: 11/23/2022]
Abstract
In Caulobacter crescentus, phosphorylation of key regulators is coordinated with the second messenger cyclic di-GMP to drive cell-cycle progression and differentiation. The diguanylate cyclase PleD directs pole morphogenesis, while the c-di-GMP effector PopA initiates degradation of the replication inhibitor CtrA by the AAA+ protease ClpXP to license S phase entry. Here, we establish a direct link between PleD and PopA reliant on the phosphodiesterase PdeA and the diguanylate cyclase DgcB. PdeA antagonizes DgcB activity until the G1-S transition, when PdeA is degraded by the ClpXP protease. The unopposed DgcB activity, together with PleD activation, upshifts c-di-GMP to drive PopA-dependent CtrA degradation and S phase entry. PdeA degradation requires CpdR, a response regulator that delivers PdeA to the ClpXP protease in a phosphorylation-dependent manner. Thus, CpdR serves as a crucial link between phosphorylation pathways and c-di-GMP metabolism to mediate protein degradation events that irreversibly and coordinately drive bacterial cell-cycle progression and development.
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162
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Kirkpatrick CL, Viollier PH. Decoding Caulobacter development. FEMS Microbiol Rev 2011; 36:193-205. [PMID: 22091823 DOI: 10.1111/j.1574-6976.2011.00309.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Revised: 09/15/2011] [Accepted: 09/15/2011] [Indexed: 11/27/2022] Open
Abstract
Caulobacter crescentus uses a multi-layered system of oscillating regulators to program different developmental fates into each daughter cell at division. This is achieved by superimposing gene expression, subcellular localization, phosphorylation, and regulated proteolysis to form a complex regulatory network that integrates chromosome replication, segregation, polar differentiation, and cytokinesis. In this review, we outline the current state of research in the field of Caulobacter development, emphasizing new findings that elaborate how the developmental program is modulated by factors such as the environment or the metabolic state of the cell.
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Affiliation(s)
- Clare L Kirkpatrick
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
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163
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Gur E, Biran D, Ron EZ. Regulated proteolysis in Gram-negative bacteria--how and when? Nat Rev Microbiol 2011; 9:839-48. [PMID: 22020261 DOI: 10.1038/nrmicro2669] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Most bacteria live in a dynamic environment where temperature, availability of nutrients and the presence of various chemicals vary, which requires rapid adaptation. Many of the adaptive changes are determined by changes in the transcription of global regulatory networks, but this response is slow because most bacterial proteins are stable and their concentration remains high even after transcription slows down. To respond rapidly, an additional level of regulation has evolved: the degradation of key proteins. However, as proteolysis is an irreversible process, it is subject to tight regulation of substrate binding and degradation. Here we review the roles of the proteolytic enzymes in Gram-negative bacteria and how these enzymes can be regulated to target only a subset of proteins.
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Affiliation(s)
- Eyal Gur
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
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164
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ppGpp and polyphosphate modulate cell cycle progression in Caulobacter crescentus. J Bacteriol 2011; 194:28-35. [PMID: 22020649 DOI: 10.1128/jb.05932-11] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Caulobacter crescentus differentiates from a motile, foraging swarmer cell into a sessile, replication-competent stalked cell during its cell cycle. This developmental transition is inhibited by nutrient deprivation to favor the motile swarmer state. We identify two cell cycle regulatory signals, ppGpp and polyphosphate (polyP), that inhibit the swarmer-to-stalked transition in both complex and glucose-exhausted media, thereby increasing the proportion of swarmer cells in mixed culture. Upon depletion of available carbon, swarmer cells lacking the ability to synthesize ppGpp or polyP improperly initiate chromosome replication, proteolyze the replication inhibitor CtrA, localize the cell fate determinant DivJ, and develop polar stalks. Furthermore, we show that swarmer cells produce more ppGpp than stalked cells upon starvation. These results provide evidence that ppGpp and polyP are cell-type-specific developmental regulators.
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165
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Fernandez-Fernandez C, Gonzalez D, Collier J. Regulation of the activity of the dual-function DnaA protein in Caulobacter crescentus. PLoS One 2011; 6:e26028. [PMID: 22022497 PMCID: PMC3193534 DOI: 10.1371/journal.pone.0026028] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Accepted: 09/15/2011] [Indexed: 12/05/2022] Open
Abstract
DnaA is a conserved essential bacterial protein that acts as the initiator of chromosomal replication as well as a master transcriptional regulator in Caulobacter crescentus. Thus, the intracellular levels of active DnaA need to be tightly regulated during the cell cycle. Our previous work suggested that DnaA may be regulated at the level of its activity by the replisome-associated protein HdaA. Here, we describe the construction of a mutant DnaA protein [DnaA(R357A)]. The R357 residue in the AAA+ domain of the C. crescentus DnaA protein is equivalent to the R334 residue of the E. coli DnaA protein, which is required for the Regulatory Inactivation of DnaA (RIDA). We found that the expression of the DnaA(R357A) mutant protein in C. crescentus, but not the expression of the wild-type DnaA protein at similar levels, causes a severe phenotype of over-initiation of chromosomal replication and that it blocks cell division. Thus, the mutant DnaA(R357A) protein is hyper-active to promote the initiation of DNA replication, compared to the wild-type DnaA protein. DnaA(R357A) could not replace DnaA in vivo, indicating that the switch in DnaA activity once chromosomal replication has started may be an essential process in C. crescentus. We propose that the inactivation of DnaA is the main mechanism ensuring that chromosomal replication starts only once per cell cycle. We further observed that the R357A substitution in DnaA does not promote the activity of DnaA as a direct transcriptional activator of four important genes, encoding HdaA, the GcrA master cell cycle regulator, the FtsZ cell division protein and the MipZ spatial regulator of cell division. Thus, the AAA+ domain of DnaA may play a role in temporally regulating the bifunctionality of DnaA by reallocating DnaA molecules from initiating DNA replication to transcribing genes within the unique DnaA regulon of C. crescentus.
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Affiliation(s)
- Carmen Fernandez-Fernandez
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Diego Gonzalez
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Justine Collier
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
- * E-mail:
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166
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Non-transcriptional regulatory processes shape transcriptional network dynamics. Nat Rev Microbiol 2011; 9:817-28. [PMID: 21986901 DOI: 10.1038/nrmicro2667] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Information about the extra- or intracellular environment is often captured as biochemical signals that propagate through regulatory networks. These signals eventually drive phenotypic changes, typically by altering gene expression programmes in the cell. Reconstruction of transcriptional regulatory networks has given a compelling picture of bacterial physiology, but transcriptional network maps alone often fail to describe phenotypes. Cellular response dynamics are ultimately determined by interactions between transcriptional and non-transcriptional networks, with dramatic implications for physiology and evolution. Here, we provide an overview of non-transcriptional interactions that can affect the performance of natural and synthetic bacterial regulatory networks.
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167
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De Luca G, Barakat M, Ortet P, Fochesato S, Jourlin-Castelli C, Ansaldi M, Py B, Fichant G, Coutinho PM, Voulhoux R, Bastien O, Maréchal E, Henrissat B, Quentin Y, Noirot P, Filloux A, Méjean V, DuBow MS, Barras F, Barbe V, Weissenbach J, Mihalcescu I, Verméglio A, Achouak W, Heulin T. The cyst-dividing bacterium Ramlibacter tataouinensis TTB310 genome reveals a well-stocked toolbox for adaptation to a desert environment. PLoS One 2011; 6:e23784. [PMID: 21912644 PMCID: PMC3164672 DOI: 10.1371/journal.pone.0023784] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Accepted: 07/25/2011] [Indexed: 11/22/2022] Open
Abstract
Ramlibacter tataouinensis TTB310(T) (strain TTB310), a betaproteobacterium isolated from a semi-arid region of South Tunisia (Tataouine), is characterized by the presence of both spherical and rod-shaped cells in pure culture. Cell division of strain TTB310 occurs by the binary fission of spherical "cyst-like" cells ("cyst-cyst" division). The rod-shaped cells formed at the periphery of a colony (consisting mainly of cysts) are highly motile and colonize a new environment, where they form a new colony by reversion to cyst-like cells. This unique cell cycle of strain TTB310, with desiccation tolerant cyst-like cells capable of division and desiccation sensitive motile rods capable of dissemination, appears to be a novel adaptation for life in a hot and dry desert environment. In order to gain insights into strain TTB310's underlying genetic repertoire and possible mechanisms responsible for its unusual lifestyle, the genome of strain TTB310 was completely sequenced and subsequently annotated. The complete genome consists of a single circular chromosome of 4,070,194 bp with an average G+C content of 70.0%, the highest among the Betaproteobacteria sequenced to date, with total of 3,899 predicted coding sequences covering 92% of the genome. We found that strain TTB310 has developed a highly complex network of two-component systems, which may utilize responses to light and perhaps a rudimentary circadian hourglass to anticipate water availability at the dew time in the middle/end of the desert winter nights and thus direct the growth window to cyclic water availability times. Other interesting features of the strain TTB310 genome that appear to be important for desiccation tolerance, including intermediary metabolism compounds such as trehalose or polyhydroxyalkanoate, and signal transduction pathways, are presented and discussed.
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Affiliation(s)
- Gilles De Luca
- CEA, Lab Ecol Microbienne Rhizosphere & Environm Extre, iBEB, DSV, Saint-Paul-lez-Durance, France.
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169
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Cyclic dimeric GMP signaling regulates intracellular aggregation, sessility, and growth of Ehrlichia chaffeensis. Infect Immun 2011; 79:3905-12. [PMID: 21788390 DOI: 10.1128/iai.05320-11] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Cyclic dimeric GMP (c-di-GMP), a bacterial second messenger, is known to regulate bacterial biofilm and sessility. Replication of an obligatory intracellular pathogen, Ehrlichia chaffeensis, is characterized by formation of bacterial aggregates called morulae inside membrane-bound inclusions. When E. chaffeensis matures into an infectious form, morulae become loose to allow bacteria to exit from host cells to infect adjacent cells. E. chaffeensis expresses a sensor kinase, PleC, and a cognate response regulator, PleD, which can produce c-di-GMP. A hydrophobic c-di-GMP antagonist, 2'-O-di(tert-butyldimethysilyl)-c-di-GMP (CDGA) inhibits E. chaffeensis internalization into host cells by facilitating degradation of some bacterial surface proteins via endogenous serine proteases. In the present study, we found that PleC and PleD were upregulated synchronously during exponential growth of bacteria, concomitant with increased morula size. While CDGA did not affect host cells, when infected cells were treated with CDGA, bacterial proliferation was inhibited, morulae became less compact, and the intracellular movement of bacteria was enhanced. Concurrently, CDGA treatment facilitated the extracellular release of bacteria with lower infectivity than those spontaneously released from sham-treated cells. Addition of CDGA to isolated inclusions induced dispersion of the morulae, degradation of an inclusion matrix protein TRP120, and bacterial intrainclusion movement, all of which were blocked by a serine protease inhibitor. These results suggest that c-di-GMP signaling regulates aggregation and sessility of E. chaffeensis within the inclusion through stabilization of matrix proteins by preventing the serine protease activity, which is associated with bacterial intracellular proliferation and maturation.
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170
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Abstract
The Alphaproteobacteria comprise morphologically diverse bacteria, including many species of stalked bacteria. Here we announce the genome sequences of eight alphaproteobacteria, including the first genome sequences of species belonging to the genera Asticcacaulis, Hirschia, Hyphomicrobium, and Rhodomicrobium.
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171
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Modularity of the bacterial cell cycle enables independent spatial and temporal control of DNA replication. Curr Biol 2011; 21:1092-101. [PMID: 21683595 DOI: 10.1016/j.cub.2011.05.040] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 04/26/2011] [Accepted: 05/23/2011] [Indexed: 11/21/2022]
Abstract
BACKGROUND Complex regulatory circuits in biology are often built of simpler subcircuits or modules. In most cases, the functional consequences and evolutionary origins of modularity remain poorly defined. RESULTS Here, by combining single-cell microscopy with genetic approaches, we demonstrate that two separable modules independently govern the temporal and spatial control of DNA replication in the asymmetrically dividing bacterium Caulobacter crescentus. DNA replication control involves DnaA, which promotes initiation, and CtrA, which silences initiation. We show that oscillations in DnaA activity dictate the periodicity of replication while CtrA governs the asymmetric replicative fates of daughter cells. Importantly, we demonstrate that DnaA activity oscillates independently of CtrA. CONCLUSIONS The genetic separability of spatial and temporal control modules in Caulobacter reflects their evolutionary history. DnaA is the central component of an ancient and phylogenetically widespread circuit that governs replication periodicity in Caulobacter and most other bacteria. By contrast, CtrA, which is found only in the asymmetrically dividing α-proteobacteria, was integrated later in evolution to enforce replicative asymmetry on daughter cells.
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Tsokos CG, Perchuk BS, Laub MT. A dynamic complex of signaling proteins uses polar localization to regulate cell-fate asymmetry in Caulobacter crescentus. Dev Cell 2011; 20:329-41. [PMID: 21397844 DOI: 10.1016/j.devcel.2011.01.007] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Revised: 01/06/2011] [Accepted: 01/07/2011] [Indexed: 11/15/2022]
Abstract
Cellular asymmetry is critical to metazoan development and the life cycle of many microbes. In Caulobacter, cell cycle progression and the formation of asymmetric daughter cells depend on the polarly-localized histidine kinase CckA. How CckA is regulated and why activity depends on localization are unknown. Here, we demonstrate that the unorthodox kinase DivL promotes CckA activity and that the phosphorylated regulator DivK inhibits CckA by binding to DivL. Early in the cell cycle, CckA is activated by the dephosphorylation of DivK throughout the cell. However, in later stages, when phosphorylated DivK levels are high, CckA activation relies on polar localization with a DivK phosphatase. Localization thus creates a protected zone for CckA within the cell, without the use of membrane-enclosed compartments. Our results reveal the mechanisms by which CckA is regulated in a cell-type-dependent manner. More generally, our findings reveal how cells exploit subcellular localization to orchestrate sophisticated regulatory processes.
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Affiliation(s)
- Christos G Tsokos
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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173
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Direct interaction of FliX and FlbD is required for their regulatory activity in Caulobacter crescentus. BMC Microbiol 2011; 11:89. [PMID: 21535897 PMCID: PMC3096577 DOI: 10.1186/1471-2180-11-89] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Accepted: 05/02/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The temporal and spatial expression of late flagellar genes in Caulobacter crescentus is activated by the transcription factor FlbD and its partner trans-acting factor FliX. The physical interaction of these two proteins represents an alternative mechanism for regulating the activity of σ54 transcription factors. This study is to characterize the interaction of the two proteins and the consequences of the interaction on their regulatory activity. RESULTS FliX and FlbD form stable complexes, which can stand the interference of 2.65 M NaCl. The stability of FliX and FlbD was affected by the co-existence of each other. Five FliX mutants (R71A, L85K, Δ117-118, T130L, and L136K) were created by site-directed mutagenesis in conserved regions of the protein. All mutants were successfully expressed in both wild-type and ΔfliX Caulobacter strains. All but FliXL85K could rescue the motility and cell division defects of a ΔfliX mutant strain. The ability of FliX to regulate the transcription of class II and class III/IV flagellar promoters was fully diminished due to the L85K mutation. Co-immunoprecipitation experiment revealed that FliXL85K was unable to physically interact with FlbD. CONCLUSIONS FliX interacts with FlbD and thereby directly regulates the activity of FlbD in response to flagellar assembly. Mutations in highly conserved regions of FliX could severely affect the recognition between FliX and FlbD and hence interrupt the normal progression of flagellar synthesis and other developmental events in Caulobacter.
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174
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Hulme SE, Whitesides GM. Die Chemie und der Wurm: Caenorhabditis elegans als Plattform für das Zusammenführen von chemischer und biologischer Forschung. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201005461] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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175
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Hulme SE, Whitesides GM. Chemistry and the Worm: Caenorhabditis elegans as a Platform for Integrating Chemical and Biological Research. Angew Chem Int Ed Engl 2011; 50:4774-807. [DOI: 10.1002/anie.201005461] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Indexed: 12/15/2022]
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176
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Regulatory response to carbon starvation in Caulobacter crescentus. PLoS One 2011; 6:e18179. [PMID: 21494595 PMCID: PMC3073932 DOI: 10.1371/journal.pone.0018179] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 02/22/2011] [Indexed: 11/19/2022] Open
Abstract
Bacteria adapt to shifts from rapid to slow growth, and have developed strategies for long-term survival during prolonged starvation and stress conditions. We report the regulatory response of C. crescentus to carbon starvation, based on combined high-throughput proteome and transcriptome analyses. Our results identify cell cycle changes in gene expression in response to carbon starvation that involve the prominent role of the FixK FNR/CAP family transcription factor and the CtrA cell cycle regulator. Notably, the SigT ECF sigma factor mediates the carbon starvation-induced degradation of CtrA, while activating a core set of general starvation-stress genes that respond to carbon starvation, osmotic stress, and exposure to heavy metals. Comparison of the response of swarmer cells and stalked cells to carbon starvation revealed four groups of genes that exhibit different expression profiles. Also, cell pole morphogenesis and initiation of chromosome replication normally occurring at the swarmer-to-stalked cell transition are uncoupled in carbon-starved cells.
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177
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Single-gene tuning of Caulobacter cell cycle period and noise, swarming motility, and surface adhesion. Mol Syst Biol 2011; 6:445. [PMID: 21179017 PMCID: PMC3018171 DOI: 10.1038/msb.2010.95] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Accepted: 10/21/2010] [Indexed: 01/25/2023] Open
Abstract
We established that the sensor histidine kinase DivJ has an important role in the regulation of C. crescentus cell cycle period and noise. This was accomplished by designing and conducting single-cell experiments to probe the dependence of cell cycle noise on divJ expression and constructing a simplified cell cycle model that captures the dependence of cell cycle noise on DivJ with molecular details. In addition to its role in regulating the cell cycle, DivJ also affects polar cell development in C. crescentus, regulating swarming motility and surface adhesion. We propose that pleiotropic control of polar cell development by the DivJ–DivK–PleC signaling pathway underlies divJ-dependent tuning of cell swarming and adhesion behaviors. We have integrated the study of single-cell fluorescence dynamics with a kinetic model simulation to provide direct quantitative evidence that the DivJ histidine kinase is localized to the cell pole through a dynamic diffusion-and-capture mechanism during the C. crescentus cell cycle.
Temporally-coordinated localization of various structural and signaling proteins is critical for proper cell cycle regulation and polar cell development in the bacterium, Caulobacter crescentus. Included among these dynamically-localized regulatory proteins is the sensor histidine kinase, DivJ (Wheeler and Shapiro, 1999). Co-localized with DivJ in the early stalked phase is the phosphorylated response regulator DivK∼P (Jacobs et al, 2001), and the protease ClpXP (McGrath et al, 2006), which degrades the master cell cycle regulator, CtrA (Jenal and Fuchs, 1998). Recent single-cell measurements of surface attached C. crescentus cells have revealed an intriguing role for DivJ in the control of noise in cell division period (Siegal-Gaskins and Crosson, 2008). The noise of the cell cycle increases significantly upon disruption of the divJ gene, with a relatively small accompanying increase in the mean cell cycle time. The deterministic nature of the existing cell cycle models (Li et al, 2008, 2009; Shen et al, 2008) cannot explain the measured increase in cell cycle period and noise in a divJ null strain. Moreover, mechanistic descriptions of how DivJ and its signaling partners are localized and how these proteins underlie the control of polar cell development and cell adhesion in C. crescentus remain immature. The single-cell experiments and analysis presented herein reveal that C. crescentus cell cycle period and noise can be tuned by DivJ (Figure 2). Specifically, in the case of low (or no) divJ expression the cell cycle is perturbed, and this is quantified by way of the (measured) noise in the cell cycle period. The level of noise is readily controlled through regulated expression of the divJ gene (Figure 2B). A simplified protein interaction network of stalked C. crescentus cell cycle regulation involving minimal components (CtrA, CtrA∼P, DivK, DivK∼P, and DivJ) was constructed to explore such tunability at the molecular level. The agreement of our model with our (and other) experiments suggests this simplified protein regulatory network is sufficient to explain the major features of the C. crescentus cell cycle. Indeed, stochastic simulations of this model using the Gillespie method (Gillespie, 1976) establish the importance of robust DivJ-mediated phosphorylation of its cognate receiver protein, DivK, in regulating the variance of cell cycle oscillations. Increased variability in the concentration of DivK∼P at the single cell level under divJ depletion subsequently leads to increased noise in the regulation of CtrA phosphorylation and degradation. Our experiments and simulations provide evidence that the steady state level of DivK∼P at the single-cell level (as maintained by DivJ) is essential in maintaining regular timing of the cell division period in C. crescentus. In addition to its role in regulating cell cycle, divJ expression also affects polar cell development in C. crescentus. Specifically, the capacity of swarmer cells to adhere to a glass surface is suppressed at high levels of divJ expression. The effect of elevated divJ expression on the adhesive capacity of the cell is reflected in a reduced rate of two-dimensional biofilm formation. This effect is quantitatively captured by our mathematical model that relates single-cell surface adhesion physiology and biofilm formation dynamics. This result, and our observation that divJ expression tunes swarming motility in semi-solid growth medium, suggests a model in which increased DivJ concentration in the swarmer compartment (due to constitutive overexpression) ultimately results in improper development of polar organelles that are required for adhesion of swarming motility. Despite the appreciated significance of protein localization for bacterial physiological functions, the molecular mechanism of how polar protein localization is achieved has only been tested in a few cases (Shapiro et al, 2002; Thanbichler and Shapiro, 2008). Mechanisms such as the polar insertion model and diffusion-and-capture have been proposed but the community's knowledge is limited to very few examples (Charles et al, 2001; Rudner et al, 2002). We provide direct evidence from experiments and simulations that the DivJ histidine kinase becomes localized to the cell pole through a dynamic diffusion-and-capture mechanism during the C. crescentus cell cycle (Figure 7). We show that a kinetic model based on a Langmuir adsorption/desorption relationship (Figure 7D) is sufficient to explain the time evolution of the single cell fluorescence time traces (Figure 7C and E) and allows establishing quantitative correspondences between the simulated dynamics and experimentally determined DivJ–EGFP dynamics. This localization mechanism is consistent with a diffusion-and-capture model. In short, the model posits that proteins are randomly distributed and are freely diffusing until they are captured at the site where they ultimately reside (Rudner et al, 2002; Shapiro et al, 2002; Bardy and Maddock, 2007). With a diffusion-and-capture pathway, it has been argued that proteins can be adsorbed either dynamically or statically (Shapiro et al, 2009). Our analysis of DivJ–EGFP in single cells supports a dynamic diffuse-and-capture mechanism for DivJ localization. Sensor histidine kinases underlie the regulation of a range of physiological processes in bacterial cells, from chemotaxis to cell division. In the gram-negative bacterium Caulobacter crescentus, the membrane-bound histidine kinase, DivJ, is a polar-localized regulator of cell cycle progression and development. We show that DivJ localizes to the cell pole through a dynamic diffusion and capture mechanism rather than by active localization. Analysis of single C. crescentus cells in microfluidic culture demonstrates that controlled expression of divJ permits facile tuning of both the mean and noise of the cell division period. Simulations of the cell cycle that use a simplified protein interaction network capture previously measured oscillatory protein profiles, and recapitulate the experimental observation that deletion of divJ increases the cell cycle period and noise. We further demonstrate that surface adhesion and swarming motility of C. crescentus in semi-solid media can also be tuned by divJ expression. We propose a model in which pleiotropic control of polar cell development by the DivJ–DivK–PleC signaling pathway underlies divJ-dependent tuning of cell swarming and adhesion behaviors.
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178
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Vendeville A, Larivière D, Fourmentin E. An inventory of the bacterial macromolecular components and their spatial organization. FEMS Microbiol Rev 2011; 35:395-414. [DOI: 10.1111/j.1574-6976.2010.00254.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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179
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Scholefield G, Veening JW, Murray H. DnaA and ORC: more than DNA replication initiators. Trends Cell Biol 2010; 21:188-94. [PMID: 21123069 DOI: 10.1016/j.tcb.2010.10.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 10/15/2010] [Accepted: 10/25/2010] [Indexed: 12/17/2022]
Abstract
Mutations in DNA replication initiator genes in both prokaryotes and eukaryotes lead to a pleiotropic array of phenotypes, including defects in chromosome segregation, cytokinesis, cell cycle regulation and gene expression. For years, it was not clear whether these diverse effects were indirect consequences of perturbed DNA replication, or whether they indicated that DNA replication initiator proteins had roles beyond their activity in initiating DNA synthesis. Recent work from a range of organisms has demonstrated that DNA replication initiator proteins play direct roles in many cellular processes, often functioning to coordinate the initiation of DNA replication with essential cell-cycle activities. The aim of this review is to highlight these new findings, focusing on the pathways and mechanisms utilized by DNA replication initiator proteins to carry out a diverse array of cellular functions.
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Affiliation(s)
- Graham Scholefield
- Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle Upon Tyne, NE2 4AX, UK
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180
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Abstract
Growing populations of Bacillus subtilis exhibit bistability: motile cells co-exist with long chains of sessile cells. An epigenetic switch has been characterized that controls the transition between the two cell types.
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181
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Curtis PD, Brun YV. A novel effector protein modulates response regulator activity without altering phosphorylation. Mol Cell 2010; 39:319-20. [PMID: 20705235 DOI: 10.1016/j.molcel.2010.07.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Genes positively regulated by the global transcriptional response regulator CtrA are not expressed during a life cycle stage of Caulobacter crescentus when the regulator is activated by phosphorylation. Gora et al. (2010), in this issue of Molecular Cell, have discovered a novel effector protein that prevents activation but not repression by the regulator without altering its phosphorylation.
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Affiliation(s)
- Patrick D Curtis
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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182
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Ksiazek K. Bacterial aging: from mechanistic basis to evolutionary perspective. Cell Mol Life Sci 2010; 67:3131-7. [PMID: 20526791 PMCID: PMC11115482 DOI: 10.1007/s00018-010-0417-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Revised: 04/22/2010] [Accepted: 05/12/2010] [Indexed: 01/08/2023]
Abstract
Aging-defined as the progressive impairment of an organism's functional capacity, resulting from deleterious changes in cells, organs, and biological systems-is one of the most fundamental features of Eukaryotes, from humans to the unicellular budding yeast Saccharomyces cerevisiae. It has recently been reported that this may also be the case for certain (if not all) types of bacteria. In this paper, the current view on the mechanistic background and evolutionary significance of bacterial kind of aging is presented, with particular emphasis on the role of asymmetric cell division, the characteristics of stationary growth phase, and the role of oxidative protein damage.
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Affiliation(s)
- Krzysztof Ksiazek
- Department of Pathophysiology, University of Medical Sciences, Swiecickiego 6, 60-781, Poznań, Poland.
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183
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CspC and CspD are essential for Caulobacter crescentus stationary phase survival. Arch Microbiol 2010; 192:747-58. [PMID: 20607520 DOI: 10.1007/s00203-010-0602-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Revised: 06/02/2010] [Accepted: 06/10/2010] [Indexed: 10/19/2022]
Abstract
The cold shock response in bacteria involves the expression of low-molecular weight cold shock proteins (CSPs) containing a nucleic acid-binding cold shock domain (CSD), which are known to destabilize secondary structures on mRNAs, facilitating translation at low temperatures. Caulobacter crescentus cspA and cspB are induced upon cold shock, while cspC and cspD are induced during stationary phase. In this work, we determined a new coding sequence for the cspC gene, revealing that it encodes a protein containing two CSDs. The phenotypes of C. crescentus csp mutants were analyzed, and we found that cspC is important for cells to maintain viability during extended periods in stationary phase. Also, cspC and cspCD strains presented altered morphology, with frequent non-viable filamentous cells, and cspCD also showed a pronounced cell death at late stationary phase. In contrast, the cspAB mutant presented increased viability in this phase, which is accompanied by an altered expression of both cspC and cspD, but the triple cspABD mutant loses this characteristic. Taken together, our results suggest that there is a hierarchy of importance among the csp genes regarding stationary phase viability, which is probably achieved by a fine tune balance of the levels of these proteins.
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184
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Changes in DnaA-dependent gene expression contribute to the transcriptional and developmental response of Bacillus subtilis to manganese limitation in Luria-Bertani medium. J Bacteriol 2010; 192:3915-24. [PMID: 20511500 DOI: 10.1128/jb.00210-10] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The SOS response to DNA damage in bacteria is a well-known component of the complex transcriptional responses to genotoxic environmental stresses such as exposure to reactive oxygen species, alkylating agents, and many of the antibiotics targeting DNA replication. However, bacteria such as Bacillus subtilis also respond to conditions that perturb DNA replication via a transcriptional response mediated by the replication initiation protein DnaA. In addition to regulating the initiation of DNA replication, DnaA directly regulates the transcription of specific genes. Conditions that perturb DNA replication can trigger the accumulation of active DnaA, activating or repressing the transcription of genes in the DnaA regulon. We report here that simply growing B. subtilis in LB medium altered DnaA-dependent gene expression in a manner consistent with the accumulation of active DnaA and that this was part of a general transcriptional response to manganese limitation. The SOS response to DNA damage was not induced under these conditions. One of the genes positively regulated by DnaA in Bacillus subtilis encodes a protein that inhibits the initiation of sporulation, Sda. Sda expression was induced as cells entered stationary phase in LB medium but not in LB medium supplemented with manganese, and the induction of Sda inhibited sporulation-specific gene expression and the onset of spore morphogenesis. In the absence of Sda, manganese-limited cells initiated spore development but failed to form mature spores. These data highlight that DnaA-dependent gene expression may influence the response of bacteria to a range of environmental conditions, including conditions that are not obviously associated with genotoxic stress.
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185
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Książek K. Let's stop overlooking bacterial aging. Biogerontology 2010; 11:717-23. [PMID: 20440559 DOI: 10.1007/s10522-010-9278-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Accepted: 04/19/2010] [Indexed: 02/02/2023]
Abstract
It has long been believed that bacteria, the organisms displaying symmetrical pattern of divisions, cannot age, and thereby constitute essentially immortal creatures. In recent years, the discovery of morphologically (Caulobacter crescentus) and functionally (Escherichia coli) asymmetrical cell fission as well as an observation of cell behavior in the stationary growth phase (Escherichia coli) overthrew, at least partly, the myth of bacterial immortality. In fact, the body of evidence has accumulated that bacteria may also get old similarly as eukaryotic cells and organisms do. In this paper a brief overview of the state-of-art in the field of bacterial aging is discussed, and the major challenges and limitations in these research are delineated.
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Affiliation(s)
- Krzysztof Książek
- Department of Pathophysiology, Poznan University of Medical Sciences, Poland.
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