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Tran NT, Le TBK. Control of a gene transfer agent cluster in Caulobacter crescentus by transcriptional activation and anti-termination. Nat Commun 2024; 15:4749. [PMID: 38834569 PMCID: PMC11150451 DOI: 10.1038/s41467-024-49114-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Accepted: 05/23/2024] [Indexed: 06/06/2024] Open
Abstract
Gene Transfer Agents (GTAs) are phage-like particles that cannot self-multiply and be infectious. Caulobacter crescentus, a bacterium best known as a model organism to study bacterial cell biology and cell cycle regulation, has recently been demonstrated to produce bona fide GTA particles (CcGTA). Since C. crescentus ultimately die to release GTA particles, the production of GTA particles must be tightly regulated and integrated with the host physiology to prevent a collapse in cell population. Two direct activators of the CcGTA biosynthetic gene cluster, GafY and GafZ, have been identified, however, it is unknown how GafYZ controls transcription or how they coordinate gene expression of the CcGTA gene cluster with other accessory genes elsewhere on the genome for complete CcGTA production. Here, we show that the CcGTA gene cluster is transcriptionally co-activated by GafY, integration host factor (IHF), and by GafZ-mediated transcription anti-termination. We present evidence that GafZ is a transcription anti-terminator that likely forms an anti-termination complex with RNA polymerase, NusA, NusG, and NusE to bypass transcription terminators within the 14 kb CcGTA cluster. Overall, we reveal a two-tier regulation that coordinates the synthesis of GTA particles in C. crescentus.
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Affiliation(s)
- Ngat T Tran
- Department of Molecular Microbiology, John Innes Centre, Norwich, NR4 7UH, UK
| | - Tung B K Le
- Department of Molecular Microbiology, John Innes Centre, Norwich, NR4 7UH, UK.
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2
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Banks EJ, Le TBK. Co-opting bacterial viruses for DNA exchange: structure and regulation of gene transfer agents. Curr Opin Microbiol 2024; 78:102431. [PMID: 38309246 DOI: 10.1016/j.mib.2024.102431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 01/03/2024] [Accepted: 01/09/2024] [Indexed: 02/05/2024]
Abstract
Horizontal gene transfer occurs via a range of mechanisms, including transformation, conjugation and bacteriophage transduction. Gene transfer agents (GTAs) are an alternative, less-studied route for interbacterial DNA exchange. Encoded within bacterial or archaeal genomes, GTAs assemble into phage-like particles that selflessly package and transmit host DNA to recipient bacteria. Several unique features distinguish GTAs from canonical phages such as an inability to self-replicate, thus producing non-infectious particles. GTAs are also deeply integrated into the physiology of the host cell and are maintained under tight host-regulatory control. Recent advances in understanding the structure and regulation of GTAs have provided further insights into a DNA transfer mechanism that is proving increasingly widespread across the bacterial tree of life.
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Affiliation(s)
- Emma J Banks
- Department of Molecular Microbiology, John Innes Centre, Norwich NR4 7UH, UK.
| | - Tung B K Le
- Department of Molecular Microbiology, John Innes Centre, Norwich NR4 7UH, UK.
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3
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Kogay R, Zhaxybayeva O. Co-evolution of gene transfer agents and their alphaproteobacterial hosts. J Bacteriol 2024; 206:e0039823. [PMID: 38240570 PMCID: PMC10883770 DOI: 10.1128/jb.00398-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 12/19/2023] [Indexed: 02/23/2024] Open
Abstract
Gene transfer agents (GTAs) are enigmatic elements that resemble small viruses and are known to be produced during nutritional stress by some bacteria and archaea. The production of GTAs is regulated by quorum sensing, under which a small fraction of the population acts as GTA producers, while the rest becomes GTA recipients. In contrast to canonical viruses, GTAs cannot propagate themselves because they package pieces of the producing cell's genome. In alphaproteobacteria, GTAs are mostly vertically inherited and reside in their hosts' genomes for hundreds of millions of years. While GTAs' ability to transfer genetic material within a population and their long-term preservation suggest an increased fitness of GTA-producing microbes, the associated benefits and type of selection that maintains GTAs are poorly understood. By comparing rates of evolutionary change in GTA genes to the rates in gene families abundantly present across 293 alphaproteobacterial genomes, we detected 59 gene families that likely co-evolve with GTA genes. These gene families are predominantly involved in stress response, DNA repair, and biofilm formation. We hypothesize that biofilm formation enables the physical proximity of GTA-producing cells, limiting GTA-derived benefits only to a group of closely related cells. We further conjecture that the population structure of biofilm-forming sub-populations ensures that the trait of GTA production is maintained despite the inevitable rise of "cheating" genotypes. Because release of GTA particles kills the producing cell, maintenance of GTAs is an exciting example of social evolution in a microbial population.IMPORTANCEGene transfer agents (GTAs) are viruses domesticated by some archaea and bacteria as vehicles for carrying pieces of the host genome. Produced under certain environmental conditions, GTA particles can deliver DNA to neighboring, closely related cells. The function of GTAs remains uncertain. While making GTAs is suicidal for a cell, GTA-encoding genes are widespread in genomes of alphaproteobacteria. Such GTA persistence implies functional benefits but raises questions about how selection maintains this lethal trait. By showing that GTA genes co-evolve with genes involved in stress response, DNA repair, and biofilm formation, we provide support for the hypothesis that GTAs facilitate DNA exchange during the stress conditions and present a model for how GTAs persist in biofilm-forming bacterial populations despite being lethal.
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Affiliation(s)
- Roman Kogay
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA
| | - Olga Zhaxybayeva
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA
- Department of Computer Science, Dartmouth College, Hanover, New Hampshire, USA
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4
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Loss of the Rhodobacter capsulatus Serine Acetyl Transferase Gene, cysE1, Impairs Gene Transfer by Gene Transfer Agents and Biofilm Phenotypes. Appl Environ Microbiol 2022; 88:e0094422. [PMID: 36098534 PMCID: PMC9552610 DOI: 10.1128/aem.00944-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Biofilms are widespread in the environment, where they allow bacterial species to survive adverse conditions. Cells in biofilms are densely packed, and this proximity is likely to increase the frequency of horizontal gene transfer. Gene transfer agents (GTAs) are domesticated viruses with the potential to spread any gene between bacteria. GTA production is normally restricted to a small subpopulation of bacteria, and regulation of GTA loci is highly coordinated, but the environmental conditions that favor GTA production are poorly understood. Here, we identified a serine acetyltransferase gene, cysE1, in Rhodobacter capsulatus that is required for optimal receipt of GTA DNA, accumulation of extracellular polysaccharide, and biofilm formation. The cysE1 gene is directly downstream of the core Rhodobacter-like GTA (RcGTA) structural gene cluster and upregulated in an RcGTA overproducer strain, although it is expressed on a separate transcript. The data we present suggest that GTA production and biofilm are coregulated, which could have important implications for the study of rapid bacterial evolution and understanding the full impact of GTAs in the environment. IMPORTANCE Direct exchange of genes between bacteria leads to rapid evolution and is the major factor underlying the spread of antibiotic resistance. Gene transfer agents (GTAs) are an unusual but understudied mechanism for genetic exchange that are capable of transferring any gene from one bacterium to another, and therefore, GTAs are likely to be important factors in genome plasticity in the environment. Despite the potential impact of GTAs, our knowledge of their regulation is incomplete. In this paper, we present evidence that elements of the cysteine biosynthesis pathway are involved in coregulation of various phenotypes required for optimal biofilm formation by Rhodobacter capsulatus and successful infection by the archetypal RcGTA. Establishing the regulatory mechanisms controlling GTA-mediated gene transfer is a key stepping stone to allow a full understanding of their role in the environment and wider impact.
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Sherlock D, Fogg PCM. The archetypal gene transfer agent RcGTA is regulated via direct interaction with the enigmatic RNA polymerase omega subunit. Cell Rep 2022; 40:111183. [PMID: 35947951 PMCID: PMC9638019 DOI: 10.1016/j.celrep.2022.111183] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 06/06/2022] [Accepted: 07/19/2022] [Indexed: 12/03/2022] Open
Abstract
Gene transfer agents (GTAs) are small virus-like particles that indiscriminately package and transfer any DNA present in their host cell, with clear implications for bacterial evolution. The first transcriptional regulator that directly controls GTA expression, GafA, was recently discovered, but its mechanism of action has remained elusive. Here, we demonstrate that GafA controls GTA gene expression via direct interaction with the RNA polymerase omega subunit (Rpo-ω) and also positively autoregulates its own expression by an Rpo-ω-independent mechanism. We show that GafA is a modular protein with distinct DNA and protein binding domains. The functional domains we observe in Rhodobacter GafA also correspond to two-gene operons in Hyphomicrobiales pathogens. These data allow us to produce the most complete regulatory model for a GTA and point toward an atypical mechanism for RNA polymerase recruitment and specific transcriptional activation in the Alphaproteobacteria.
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Affiliation(s)
- David Sherlock
- Biology Department, University of York, York YO10 5DD, UK
| | - Paul C M Fogg
- Biology Department, University of York, York YO10 5DD, UK; York Biomedical Research Institute (YBRI), University of York, York YO10 5NG, UK.
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6
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Shimizu T, Aritoshi T, Beatty JT, Masuda T. Persulfide-Responsive Transcription Factor SqrR Regulates Gene Transfer and Biofilm Formation via the Metabolic Modulation of Cyclic di-GMP in Rhodobacter capsulatus. Microorganisms 2022; 10:908. [PMID: 35630353 PMCID: PMC9143464 DOI: 10.3390/microorganisms10050908] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 04/24/2022] [Accepted: 04/25/2022] [Indexed: 12/04/2022] Open
Abstract
Bacterial phage-like particles (gene transfer agents-GTAs) are widely employed as a crucial genetic vector in horizontal gene transfer. GTA-mediated gene transfer is induced in response to various stresses; however, regulatory mechanisms are poorly understood. We found that the persulfide-responsive transcription factor SqrR may repress the expression of several GTA-related genes in the photosynthetic bacterium Rhodobacter capsulatus. Here, we show that the sqrR deletion mutant (ΔsqrR) produces higher amounts of intra- and extracellular GTA and gene transfer activity than the wild type (WT). The transcript levels of GTA-related genes are also increased in ΔsqrR. In spite of the presumption that GTA-related genes are regulated in response to sulfide by SqrR, treatment with sulfide did not alter the transcript levels of these genes in the WT strain. Surprisingly, hydrogen peroxide increased the transcript levels of GTA-related genes in the WT, and this alteration was abolished in the ΔsqrR strain. Moreover, the absence of SqrR changed the intracellular cyclic dimeric GMP (c-di-GMP) levels, and the amount of c-di-GMP was correlated with GTA activity and biofilm formation. These results suggest that SqrR is related to the repression of GTA production and the activation of biofilm formation via control of the intracellular c-di-GMP levels.
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Affiliation(s)
- Takayuki Shimizu
- Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan; (T.A.); (T.M.)
| | - Toma Aritoshi
- Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan; (T.A.); (T.M.)
| | - J. Thomas Beatty
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada;
| | - Tatsuru Masuda
- Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan; (T.A.); (T.M.)
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Tomasch J, Koppenhöfer S, Lang AS. Connection Between Chromosomal Location and Function of CtrA Phosphorelay Genes in Alphaproteobacteria. Front Microbiol 2021; 12:662907. [PMID: 33995326 PMCID: PMC8116508 DOI: 10.3389/fmicb.2021.662907] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 04/09/2021] [Indexed: 12/28/2022] Open
Abstract
Most bacterial chromosomes are circular, with replication starting at one origin (ori) and proceeding on both replichores toward the terminus (ter). Several studies have shown that the location of genes relative to ori and ter can have profound effects on regulatory networks and physiological processes. The CtrA phosphorelay is a gene regulatory system conserved in most alphaproteobacteria. It was first discovered in Caulobacter crescentus where it controls replication and division into a stalked and a motile cell in coordination with other factors. The locations of the ctrA gene and targets of this response regulator on the chromosome affect their expression through replication-induced DNA hemi-methylation and specific positioning along a CtrA activity gradient in the dividing cell, respectively. Here we asked to what extent the location of CtrA regulatory network genes might be conserved in the alphaproteobacteria. We determined the locations of the CtrA phosphorelay and associated genes in closed genomes with unambiguously identifiable ori from members of five alphaproteobacterial orders. The location of the phosphorelay genes was the least conserved in the Rhodospirillales followed by the Sphingomonadales. In the Rhizobiales a trend toward certain chromosomal positions could be observed. Compared to the other orders, the CtrA phosphorelay genes were conserved closer to ori in the Caulobacterales. In contrast, the genes were highly conserved closer to ter in the Rhodobacterales. Our data suggest selection pressure results in differential positioning of CtrA phosphorelay and associated genes in alphaproteobacteria, particularly in the orders Rhodobacterales, Caulobacterales and Rhizobiales that is worth deeper investigation.
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Affiliation(s)
- Jürgen Tomasch
- Department of Molecular Bacteriology, Helmholtz-Center for Infection Research, Braunschweig, Germany
| | - Sonja Koppenhöfer
- Department of Biology, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Andrew S Lang
- Department of Biology, Memorial University of Newfoundland, St. John's, NL, Canada
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8
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The CckA-ChpT-CtrA Phosphorelay Controlling Rhodobacter capsulatus Gene Transfer Agent Production Is Bidirectional and Regulated by Cyclic di-GMP. J Bacteriol 2021; 203:JB.00525-20. [PMID: 33288624 DOI: 10.1128/jb.00525-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 12/03/2020] [Indexed: 12/15/2022] Open
Abstract
Protein phosphorylation is a universal mechanism for transducing cellular signals in prokaryotes and eukaryotes. The histidine kinase CckA, the histidine phosphotransferase ChpT, and the response regulator CtrA are conserved throughout the alphaproteobacteria. In Rhodobacter capsulatus, these proteins are key regulators of the gene transfer agent (RcGTA), which is present in several alphaproteobacteria. Using purified recombinant R. capsulatus proteins, we show in vitro autophosphorylation of CckA protein, and phosphotransfer to ChpT and thence to CtrA, to demonstrate biochemically that they form a phosphorelay. The secondary messenger cyclic di-GMP changed CckA from a kinase to a phosphatase, resulting in reversal of the phosphotransfer flow in the relay. The substitutions of two residues in CckA greatly affected the kinase or phosphatase activity of the protein in vitro, and production of mutant CckA proteins in vivo confirmed the importance of kinase but not phosphatase activity for the lytic release of RcGTA. However, phosphatase activity was needed to produce functional RcGTA particles. The binding of cyclic di-GMP to the wild-type and mutant CckA proteins was evaluated directly using a pulldown assay based on biotinylated cyclic di-GMP and streptavidin-linked beads.IMPORTANCE The CckA, ChpT, and CtrA phosphorelay proteins are widespread in the alphaproteobacteria, and there are two groups of organisms that differ in terms of whether this pathway is essential for cell viability. Little is known about the biochemical function of these proteins in organisms where the pathway is not essential, a group that includes Rhodobacter capsulatus This work demonstrates biochemically that CckA, ChpT, and CtrA also form a functional phosphorelay in the latter group and that the direction of phosphotransfer is reversed by cyclic di-GMP. It is important to improve understanding of more representatives of this pathway in order to obtain deeper insight into the function, composition, and evolutionary significance of a wider range of bacterial regulatory networks.
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9
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Pallegar P, Canuti M, Langille E, Peña-Castillo L, Lang AS. A Two-Component System Acquired by Horizontal Gene Transfer Modulates Gene Transfer and Motility via Cyclic Dimeric GMP. J Mol Biol 2020; 432:4840-4855. [PMID: 32634380 DOI: 10.1016/j.jmb.2020.07.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 06/08/2020] [Accepted: 07/01/2020] [Indexed: 10/23/2022]
Abstract
Bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) is an important intracellular signaling molecule that affects diverse physiological processes in bacteria. The intracellular levels of c-di-GMP are controlled by proteins acting as diguanylate cyclase (DGC) and phosphodiesterase (PDE) enzymes that synthesize and degrade c-di-GMP, respectively. In the alphaproteobacterium Rhodobacter capsulatus, flagellar motility and gene exchange via production of the gene transfer agent RcGTA are regulated by c-di-GMP. One of the R. capsulatus proteins involved in this regulation is Rcc00620, which contains an N-terminal two-component system response regulator receiver (REC) domain and C-terminal DGC and PDE domains. We demonstrate that the enzymatic activity of Rcc00620 is regulated through the phosphorylation status of its REC domain, which is controlled by a cognate histidine kinase protein, Rcc00621. In this system, the phosphorylated form of Rcc00620 is active as a PDE enzyme and stimulates gene transfer and motility. In addition, we discovered that the rcc00620 and rcc00621 genes are present in only one lineage within the genus Rhodobacter and were acquired via horizontal gene transfer from a distantly related alphaproteobacterium in the order Sphingomonadales. Therefore, a horizontally acquired regulatory system regulates gene transfer in the recipient organism.
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Affiliation(s)
- Purvikalyan Pallegar
- Department of Biology, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada.
| | - Marta Canuti
- Department of Biology, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada.
| | - Evan Langille
- Department of Chemistry, Memorial University of Newfoundland, St. John's, NL A1B 3X7, Canada.
| | - Lourdes Peña-Castillo
- Department of Biology, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada; Department of Computer Science, Memorial University of Newfoundland, St. John's, NL A1B 3X5, Canada.
| | - Andrew S Lang
- Department of Biology, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada.
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10
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Pallegar P, Peña-Castillo L, Langille E, Gomelsky M, Lang AS. Cyclic di-GMP-Mediated Regulation of Gene Transfer and Motility in Rhodobacter capsulatus. J Bacteriol 2020; 202:e00554-19. [PMID: 31659012 PMCID: PMC6941535 DOI: 10.1128/jb.00554-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 10/19/2019] [Indexed: 02/08/2023] Open
Abstract
Gene transfer agents (GTAs) are bacteriophage-like particles produced by several bacterial and archaeal lineages that contain small pieces of the producing cells' genomes that can be transferred to other cells in a process similar to transduction. One well-studied GTA is RcGTA, produced by the alphaproteobacterium Rhodobacter capsulatus RcGTA gene expression is regulated by several cellular regulatory systems, including the CckA-ChpT-CtrA phosphorelay. The transcription of multiple other regulator-encoding genes is affected by the response regulator CtrA, including genes encoding putative enzymes involved in the synthesis and hydrolysis of the second messenger bis-(3'-5')-cyclic dimeric GMP (c-di-GMP). To investigate whether c-di-GMP signaling plays a role in RcGTA production, we disrupted the CtrA-affected genes potentially involved in this process. We found that disruption of four of these genes affected RcGTA gene expression and production. We performed site-directed mutagenesis of key catalytic residues in the GGDEF and EAL domains responsible for diguanylate cyclase (DGC) and c-di-GMP phosphodiesterase (PDE) activities and analyzed the functions of the wild-type and mutant proteins. We also measured RcGTA production in R. capsulatus strains where intracellular levels of c-di-GMP were altered by the expression of either a heterologous DGC or a heterologous PDE. This adds c-di-GMP signaling to the collection of cellular regulatory systems controlling gene transfer in this bacterium. Furthermore, the heterologous gene expression and the four gene disruptions had similar effects on R. capsulatus flagellar motility as found for gene transfer, and we conclude that c-di-GMP inhibits both RcGTA production and flagellar motility in R. capsulatusIMPORTANCE Gene transfer agents (GTAs) are virus-like particles that move cellular DNA between cells. In the alphaproteobacterium Rhodobacter capsulatus, GTA production is affected by the activities of multiple cellular regulatory systems, to which we have now added signaling via the second messenger dinucleotide molecule bis-(3'-5')-cyclic dimeric GMP (c-di-GMP). Similar to the CtrA phosphorelay, c-di-GMP also affects R. capsulatus flagellar motility in addition to GTA production, with lower levels of intracellular c-di-GMP favoring increased flagellar motility and gene transfer. These findings further illustrate the interconnection of GTA production with global systems of regulation in R. capsulatus, providing additional support for the notion that the production of GTAs has been maintained in this and related bacteria because it provides a benefit to the producing organisms.
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Affiliation(s)
- Purvikalyan Pallegar
- Department of Biology, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
| | - Lourdes Peña-Castillo
- Department of Biology, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
- Department of Computer Science, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
| | - Evan Langille
- Department of Chemistry, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
| | - Mark Gomelsky
- Department of Molecular Biology, University of Wyoming, Laramie, Wyoming, USA
| | - Andrew S Lang
- Department of Biology, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
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11
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Abstract
Prokaryotes commonly undergo genome reduction, particularly in the case of symbiotic bacteria. Genome reductions tend toward the energetically favorable removal of unnecessary, redundant, or nonfunctional genes. However, without mechanisms to compensate for these losses, deleterious mutation and genetic drift might otherwise overwhelm a population. Among the mechanisms employed to counter gene loss and share evolutionary success within a population, gene transfer agents (GTAs) are increasingly becoming recognized as important contributors. Although viral in origin, GTA particles package fragments of their "host" genome for distribution within a population of cells, often in a synchronized manner, rather than selfishly packaging genes necessary for their spread. Microbes as diverse as archaea and alpha-proteobacteria have been known to produce GTA particles, which are capable of transferring selective advantages such as virulence factors and antibiotic resistance. In this review, we discuss the various types of GTAs identified thus far, focusing on a defined set of symbiotic alpha-proteobacteria known to carry them. Drawing attention to the predicted presence of these genes, we discuss their potential within the selective marine and terrestrial environments occupied by mutualistic, parasitic, and endosymbiotic microbes.
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Affiliation(s)
- Steen Christensen
- Department of Biological Sciences, Florida International University, Miami, FL, USA.,Biomolecular Sciences Institute, Florida International University, Miami, FL, USA
| | - Laura R Serbus
- Department of Biological Sciences, Florida International University, Miami, FL, USA. .,Biomolecular Sciences Institute, Florida International University, Miami, FL, USA.
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12
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Ding H, Grüll MP, Mulligan ME, Lang AS, Beatty JT. Induction of Rhodobacter capsulatus Gene Transfer Agent Gene Expression Is a Bistable Stochastic Process Repressed by an Extracellular Calcium-Binding RTX Protein Homologue. J Bacteriol 2019; 201:e00430-19. [PMID: 31501287 PMCID: PMC6832060 DOI: 10.1128/jb.00430-19] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Accepted: 09/06/2019] [Indexed: 01/28/2023] Open
Abstract
Bacteriophage-like gene transfer agents (GTAs) have been discovered in both of the prokaryotic branches of the three-domain phylogenetic tree of life. The production of a GTA (RcGTA) by the phototrophic alphaproteobacterium Rhodobacter capsulatus is regulated by quorum sensing and a phosphorelay homologous to systems in other species that control essential functions such as the initiation of chromosome replication and cell division. In wild-type strains, RcGTA is produced in <3% of cells in laboratory cultures. Mutants of R. capsulatus that exhibit greatly elevated production of RcGTA were created decades ago by chemical mutagenesis, but the nature and molecular consequences of the mutation were unknown. We show that the number of cells in a population that go on to express RcGTA genes is controlled by a stochastic process, in contrast to a genetic process. We used transposon mutagenesis along with a fluorescent protein reporter system and genome sequence data to identify a gene, rcc00280, that encodes an RTX family calcium-binding protein homologue. The Rc280 protein acts as an extracellular repressor of RcGTA gene expression by decreasing the percentage of cells that induce the production of RcGTA.IMPORTANCE GTAs catalyze horizontal gene transfer (HGT), which is important for genomic evolution because the majority of genes found in bacterial genomes have undergone HGT at some point in their evolution. Therefore, it is important to determine how the production of GTAs is regulated to understand the factors that modulate the frequency of gene transfer and thereby specify the tempo of evolution. This work describes a new type of genetic regulation in which an extracellular calcium-binding protein homologue represses the induction of the Rhodobacter capsulatus GTA, RcGTA.
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Affiliation(s)
- Hao Ding
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Marc P Grüll
- Department of Biology, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
| | - Martin E Mulligan
- Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
| | - Andrew S Lang
- Department of Biology, Memorial University of Newfoundland, St. John's, Newfoundland and Labrador, Canada
| | - J Thomas Beatty
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
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13
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Grüll MP, Mulligan ME, Lang AS. Small extracellular particles with big potential for horizontal gene transfer: membrane vesicles and gene transfer agents. FEMS Microbiol Lett 2019; 365:5067299. [PMID: 30085064 DOI: 10.1093/femsle/fny192] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 08/04/2018] [Indexed: 12/18/2022] Open
Abstract
Bacteria are known to release different types of particles that serve various purposes such as the processing of metabolites, communication, and the transfer of genetic material. One of the most interesting aspects of the production of such particles is the biogenesis and trafficking of complex particles that can carry DNA, RNA, proteins or toxins into the surrounding environment to aid in bacterial survival or lead to gene transfer. Two important bacterial extracellular complexes are membrane vesicles and gene transfer agents. In this review, we will discuss the production, contents and functions of these two types of particles as related to their abilities to facilitate horizontal gene transfer.
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Affiliation(s)
| | - M E Mulligan
- Biochemistry, Memorial University of Newfoundland, St John's, NL, Canada
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14
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Koppenhöfer S, Wang H, Scharfe M, Kaever V, Wagner-Döbler I, Tomasch J. Integrated Transcriptional Regulatory Network of Quorum Sensing, Replication Control, and SOS Response in Dinoroseobacter shibae. Front Microbiol 2019; 10:803. [PMID: 31031742 PMCID: PMC6473078 DOI: 10.3389/fmicb.2019.00803] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 03/28/2019] [Indexed: 12/13/2022] Open
Abstract
Quorum sensing (QS) coordinates population wide gene expression of bacterial species. Highly adaptive traits like gene transfer agents (GTA), morphological heterogeneity, type 4 secretion systems (T4SS), and flagella are QS controlled in Dinoroseobacter shibae, a Roseobacter model organism. Its QS regulatory network is integrated with the CtrA phosphorelay that controls cell division in alphaproteobacteria. To elucidate the network topology, we analyzed the transcriptional response of the QS-negative D. shibae strain ΔluxI1 toward externally added autoinducer (AI) over a time period of 3 h. The signaling cascade is initiated by the CtrA phosphorelay, followed by the QS genes and other target genes, including the second messenger c-di-GMP, competence, flagella and pili. Identification of transcription factor binding sites in promoters of QS induced genes revealed the integration of QS, CtrA phosphorelay and the SOS stress response mediated by LexA. The concentration of regulatory genes located close to the origin or terminus of replication suggests that gene regulation and replication are tightly coupled. Indeed, addition of AI first stimulates and then represses replication. The restart of replication comes along with increased c-di-GMP levels. We propose a model in which QS induces replication followed by differentiation into GTA producing and non-producing cells. CtrA-activity is controlled by the c-di-GMP level, allowing some of the daughter cells to replicate again. The size of the GTA producing subpopulation is tightly controlled by QS via the AI Synthase LuxI2. Finally, induction of the SOS response allows for integration of GTA DNA into the host chromosome.
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Affiliation(s)
- Sonja Koppenhöfer
- Group Microbial Communication, Technical University of Braunschweig, Braunschweig, Germany.,Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, Oldenburg, Germany
| | - Hui Wang
- Group Microbial Communication, Technical University of Braunschweig, Braunschweig, Germany
| | - Maren Scharfe
- Group Genomic Analytics, Helmholtz Centre for Infection Research, Helmholtz Association of German Research Centers, Braunschweig, Germany
| | - Volkhard Kaever
- Research Core Unit Metabolomics, Institute of Pharmacology, Hannover Medical School, Hanover, Germany
| | - Irene Wagner-Döbler
- Group Microbial Communication, Technical University of Braunschweig, Braunschweig, Germany
| | - Jürgen Tomasch
- Group Microbial Communication, Technical University of Braunschweig, Braunschweig, Germany
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15
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Zhan Y, Chen F. Bacteriophages that infect marine roseobacters: genomics and ecology. Environ Microbiol 2019; 21:1885-1895. [DOI: 10.1111/1462-2920.14504] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 12/01/2018] [Accepted: 12/11/2018] [Indexed: 01/05/2023]
Affiliation(s)
- Yuanchao Zhan
- Institute of Marine and Environmental TechnologyUniversity of Maryland Center for Environmental Science Baltimore MD USA
| | - Feng Chen
- Institute of Marine and Environmental TechnologyUniversity of Maryland Center for Environmental Science Baltimore MD USA
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16
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Tomasch J, Wang H, Hall ATK, Patzelt D, Preusse M, Petersen J, Brinkmann H, Bunk B, Bhuju S, Jarek M, Geffers R, Lang AS, Wagner-Döbler I. Packaging of Dinoroseobacter shibae DNA into Gene Transfer Agent Particles Is Not Random. Genome Biol Evol 2018; 10:359-369. [PMID: 29325123 PMCID: PMC5786225 DOI: 10.1093/gbe/evy005] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/08/2018] [Indexed: 02/07/2023] Open
Abstract
Gene transfer agents (GTAs) are phage-like particles which contain a fragment of genomic DNA of the bacterial or archaeal producer and deliver this to a recipient cell. GTA gene clusters are present in the genomes of almost all marine Rhodobacteraceae (Roseobacters) and might be important contributors to horizontal gene transfer in the world’s oceans. For all organisms studied so far, no obvious evidence of sequence specificity or other nonrandom process responsible for packaging genomic DNA into GTAs has been found. Here, we show that knock-out of an autoinducer synthase gene of Dinoroseobacter shibae resulted in overproduction and release of functional GTA particles (DsGTA). Next-generation sequencing of the 4.2-kb DNA fragments isolated from DsGTAs revealed that packaging was not random. DNA from low-GC conjugative plasmids but not from high-GC chromids was excluded from packaging. Seven chromosomal regions were strongly overrepresented in DNA isolated from DsGTA. These packaging peaks lacked identifiable conserved sequence motifs that might represent recognition sites for the GTA terminase complex. Low-GC regions of the chromosome, including the origin and terminus of replication, were underrepresented in DNA isolated from DsGTAs. DNA methylation reduced packaging frequency while the level of gene expression had no influence. Chromosomal regions found to be over- and underrepresented in DsGTA-DNA were regularly spaced. We propose that a “headful” type of packaging is initiated at the sites of coverage peaks and, after linearization of the chromosomal DNA, proceeds in both directions from the initiation site. GC-content, DNA-modifications, and chromatin structure might influence at which sides GTA packaging can be initiated.
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Affiliation(s)
- Jürgen Tomasch
- Group Microbial Communication, Helmholtz-Centre for Infection Research, Braunschweig, Germany.,Department of Molecular Bacteriology, Helmholtz-Centre for Infection Research, Braunschweig, Germany
| | - Hui Wang
- Group Microbial Communication, Helmholtz-Centre for Infection Research, Braunschweig, Germany
| | - April T K Hall
- Department of Biology, Memorial University of Newfoundland, St John's, Newfoundland and Labrador, Canada
| | - Diana Patzelt
- Group Microbial Communication, Helmholtz-Centre for Infection Research, Braunschweig, Germany
| | - Matthias Preusse
- Department of Molecular Bacteriology, Helmholtz-Centre for Infection Research, Braunschweig, Germany
| | - Jörn Petersen
- Department of Microbial Ecology and Diversity Research, Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Henner Brinkmann
- Department of Microbial Ecology and Diversity Research, Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Boyke Bunk
- Department of Microbial Ecology and Diversity Research, Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany
| | - Sabin Bhuju
- Group Genome Analytics, Helmholtz-Center for Infection Research, Braunschweig, Germany
| | - Michael Jarek
- Group Genome Analytics, Helmholtz-Center for Infection Research, Braunschweig, Germany
| | - Robert Geffers
- Group Genome Analytics, Helmholtz-Center for Infection Research, Braunschweig, Germany
| | - Andrew S Lang
- Department of Biology, Memorial University of Newfoundland, St John's, Newfoundland and Labrador, Canada
| | - Irene Wagner-Döbler
- Group Microbial Communication, Helmholtz-Centre for Infection Research, Braunschweig, Germany
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17
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Xue S, Biondi EG. Coordination of symbiosis and cell cycle functions in Sinorhizobium meliloti. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1862:691-696. [PMID: 29783033 DOI: 10.1016/j.bbagrm.2018.05.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 05/11/2018] [Accepted: 05/17/2018] [Indexed: 10/16/2022]
Abstract
The symbiotic nitrogen fixing species Sinorhizobium meliloti represents a remarkable model system for the class Alphaproteobacteria, which includes genera such as Caulobacter, Agrobacterium and Brucella. It is capable of living free in the soil, and is also able to establish a complex symbiosis with leguminous plants, during which its cell cycle program is completely rewired presumably due, at least in part, to the action of peptides secreted by the plant. Here we will discuss how the cell cycle regulation works in S. meliloti and the kinds of molecular mechanisms that take place during the infection. We will focus on the complex regulation of the master regulator of the S. meliloti cell cycle, the response regulator CtrA, discussing its implication in symbiosis.
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Affiliation(s)
- Shuanghong Xue
- Aix Marseille University, CNRS, IMM, LCB, 13009 Marseille, France
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18
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The Protease ClpXP and the PAS Domain Protein DivL Regulate CtrA and Gene Transfer Agent Production in Rhodobacter capsulatus. Appl Environ Microbiol 2018; 84:AEM.00275-18. [PMID: 29625982 DOI: 10.1128/aem.00275-18] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 03/29/2018] [Indexed: 01/01/2023] Open
Abstract
Several members of the Rhodobacterales (Alphaproteobacteria) produce a conserved horizontal gene transfer vector, called the gene transfer agent (GTA), that appears to have evolved from a bacteriophage. The model system used to study GTA biology is the Rhodobacter capsulatus GTA (RcGTA), a small, tailed bacteriophage-like particle produced by a subset of the cells in a culture. The response regulator CtrA is conserved in the Alphaproteobacteria and is an essential regulator of RcGTA production: it controls the production and maturation of the RcGTA particle and RcGTA release from cells. CtrA also controls the natural transformation-like system required for cells to receive RcGTA-donated DNA. Here, we report that dysregulation of the CckA-ChpT-CtrA phosphorelay either by the loss of the PAS domain protein DivL or by substitution of the autophosphorylation residue of the hybrid histidine kinase CckA decreased CtrA phosphorylation and greatly increased RcGTA protein production in R. capsulatus We show that the loss of the ClpXP protease or the three C-terminal residues of CtrA results in increased CtrA levels in R. capsulatus and identify ClpX(P) to be essential for the maturation of RcGTA particles. Furthermore, we show that CtrA phosphorylation is important for head spike production. Our results provide novel insight into the regulation of CtrA and GTAs in the RhodobacteralesIMPORTANCE Members of the Rhodobacterales are abundant in ocean and freshwater environments. The conserved GTA produced by many Rhodobacterales may have an important role in horizontal gene transfer (HGT) in aquatic environments and provide a significant contribution to their adaptation. GTA production is controlled by bacterial regulatory systems, including the conserved CckA-ChpT-CtrA phosphorelay; however, several questions about GTA regulation remain. Our identification that a short DivL homologue and ClpXP regulate CtrA in R. capsulatus extends the model of CtrA regulation from Caulobacter crescentus to a member of the Rhodobacterales We found that the magnitude of RcGTA production greatly depends on DivL and CckA kinase activity, adding yet another layer of regulatory complexity to RcGTA. RcGTA is known to undergo CckA-dependent maturation, and we extend the understanding of this process by showing that the ClpX chaperone is required for formation of tailed, DNA-containing particles.
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Lang AS, Westbye AB, Beatty JT. The Distribution, Evolution, and Roles of Gene Transfer Agents in Prokaryotic Genetic Exchange. Annu Rev Virol 2017; 4:87-104. [DOI: 10.1146/annurev-virology-101416-041624] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Andrew S. Lang
- Department of Biology, Memorial University of Newfoundland, St. John's, A1B 3X9, Canada
| | - Alexander B. Westbye
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, V6T 1Z3, Canada
| | - J. Thomas Beatty
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, V6T 1Z3, Canada
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20
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Westbye AB, O'Neill Z, Schellenberg-Beaver T, Beatty JT. The Rhodobacter capsulatus gene transfer agent is induced by nutrient depletion and the RNAP omega subunit. Microbiology (Reading) 2017; 163:1355-1363. [DOI: 10.1099/mic.0.000519] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Alexander B. Westbye
- Department of Microbiology and Immunology, The University of British Columbia, Vancouver, BC, Canada
- Present address: Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, 't Horntje (Texel), Netherlands
| | - Zoe O'Neill
- Department of Microbiology and Immunology, The University of British Columbia, Vancouver, BC, Canada
| | - Tegan Schellenberg-Beaver
- Department of Microbiology and Immunology, The University of British Columbia, Vancouver, BC, Canada
| | - J. Thomas Beatty
- Department of Microbiology and Immunology, The University of British Columbia, Vancouver, BC, Canada
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21
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Westbye AB, Beatty JT, Lang AS. Guaranteeing a captive audience: coordinated regulation of gene transfer agent (GTA) production and recipient capability by cellular regulators. Curr Opin Microbiol 2017; 38:122-129. [DOI: 10.1016/j.mib.2017.05.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 04/24/2017] [Accepted: 05/10/2017] [Indexed: 10/19/2022]
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22
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Landa M, Burns AS, Roth SJ, Moran MA. Bacterial transcriptome remodeling during sequential co-culture with a marine dinoflagellate and diatom. ISME JOURNAL 2017; 11:2677-2690. [PMID: 28731474 DOI: 10.1038/ismej.2017.117] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 05/17/2017] [Accepted: 06/07/2017] [Indexed: 01/01/2023]
Abstract
In their role as primary producers, marine phytoplankton modulate heterotrophic bacterial activities through differences in the types and amounts of organic matter they release. This study investigates the transcriptional response of bacterium Ruegeria pomeroyi, a member of the Roseobacter clade known to affiliate with diverse phytoplankton groups in the ocean, during a shift in phytoplankton taxonomy. The bacterium was initially introduced into a culture of the dinoflagellate Alexandrium tamarense, and then experienced a change in phytoplankton community composition as the diatom Thalassiosira pseudonana gradually outcompeted the dinoflagellate. Samples were taken throughout the 30-day experiment to track shifts in bacterial gene expression informative of metabolic and ecological interactions. Transcriptome data indicate fundamental differences in the exometabolites released by the two phytoplankton. During growth with the dinoflagellate, gene expression patterns indicated that the main sources of carbon and energy for R. pomeroyi were dimethysulfoniopropionate (DMSP), taurine, methylated amines, and polyamines. During growth with the diatom, dihydroxypropanesulfonate (DHPS), xylose, ectoine, and glycolate instead appeared to fuel the bulk of bacterial metabolism. Expression patterns of genes for quorum sensing, gene transfer agent, and motility suggest that bacterial processes related to cell communication and signaling differed depending on which phytoplankton species dominated the co-culture. A remodeling of the R. pomeroyi transcriptome implicating more than a quarter of the genome occurred through the change in phytoplankton regime.
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Affiliation(s)
- Marine Landa
- Department of Marine Sciences, University of Georgia, Athens, GA, USA
| | - Andrew S Burns
- Department of Marine Sciences, University of Georgia, Athens, GA, USA
| | - Selena J Roth
- Department of Marine Sciences, University of Georgia, Athens, GA, USA
| | - Mary Ann Moran
- Department of Marine Sciences, University of Georgia, Athens, GA, USA
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23
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Grüll MP, Peña-Castillo L, Mulligan ME, Lang AS. Genome-wide identification and characterization of small RNAs in Rhodobacter capsulatus and identification of small RNAs affected by loss of the response regulator CtrA. RNA Biol 2017; 14:914-925. [PMID: 28296577 PMCID: PMC5546546 DOI: 10.1080/15476286.2017.1306175] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/30/2022] Open
Abstract
Small non-coding RNAs (sRNAs) are involved in the control of numerous cellular processes through various regulatory mechanisms, and in the past decade many studies have identified sRNAs in a multitude of bacterial species using RNA sequencing (RNA-seq). Here, we present the first genome-wide analysis of sRNA sequencing data in Rhodobacter capsulatus, a purple nonsulfur photosynthetic alphaproteobacterium. Using a recently developed bioinformatics approach, sRNA-Detect, we detected 422 putative sRNAs from R. capsulatus RNA-seq data. Based on their sequence similarity to sRNAs in a sRNA collection, consisting of published putative sRNAs from 23 additional bacterial species, and RNA databases, the sequences of 124 putative sRNAs were conserved in at least one other bacterial species; and, 19 putative sRNAs were assigned a predicted function. We bioinformatically characterized all putative sRNAs and applied machine learning approaches to calculate the probability of a nucleotide sequence to be a bona fide sRNA. The resulting quantitative model was able to correctly classify 95.2% of sequences in a validation set. We found that putative cis-targets for antisense and partially overlapping sRNAs were enriched with protein-coding genes involved in primary metabolic processes, photosynthesis, compound binding, and with genes forming part of macromolecular complexes. We performed differential expression analysis to compare the wild type strain to a mutant lacking the response regulator CtrA, an important regulator of gene expression in R. capsulatus, and identified 18 putative sRNAs with differing levels in the two strains. Finally, we validated the existence and expression patterns of four novel sRNAs by Northern blot analysis.
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Affiliation(s)
- Marc P Grüll
- a Department of Biology , Memorial University of Newfoundland , St. John's , NL , Canada
| | - Lourdes Peña-Castillo
- a Department of Biology , Memorial University of Newfoundland , St. John's , NL , Canada.,b Department of Computer Science , Memorial University of Newfoundland , St. John's , NL , Canada
| | - Martin E Mulligan
- c Department of Biochemistry , Memorial University of Newfoundland , St. John's , NL , Canada
| | - Andrew S Lang
- a Department of Biology , Memorial University of Newfoundland , St. John's , NL , Canada
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24
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Francis N, Poncin K, Fioravanti A, Vassen V, Willemart K, Ong TAP, Rappez L, Letesson JJ, Biondi EG, De Bolle X. CtrA controls cell division and outer membrane composition of the pathogenBrucella abortus. Mol Microbiol 2017; 103:780-797. [DOI: 10.1111/mmi.13589] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2016] [Indexed: 11/29/2022]
Affiliation(s)
- Nayla Francis
- Microorganisms Biology Research Unit (URBM); Narilis, University of Namur; Namur Belgium
| | - Katy Poncin
- Microorganisms Biology Research Unit (URBM); Narilis, University of Namur; Namur Belgium
| | - Antonella Fioravanti
- Unité de Glycobiologie Structurale et Fonctionnelle; UMR 8576 CNRS - Université de Lille; 50 Avenue Halley Villeneuve d'Ascq France
| | - Victoria Vassen
- Microorganisms Biology Research Unit (URBM); Narilis, University of Namur; Namur Belgium
| | - Kevin Willemart
- Microorganisms Biology Research Unit (URBM); Narilis, University of Namur; Namur Belgium
| | - Thi Anh Phuong Ong
- Microorganisms Biology Research Unit (URBM); Narilis, University of Namur; Namur Belgium
| | - Luca Rappez
- Microorganisms Biology Research Unit (URBM); Narilis, University of Namur; Namur Belgium
| | - Jean-Jacques Letesson
- Microorganisms Biology Research Unit (URBM); Narilis, University of Namur; Namur Belgium
| | - Emanuele G. Biondi
- Unité de Glycobiologie Structurale et Fonctionnelle; UMR 8576 CNRS - Université de Lille; 50 Avenue Halley Villeneuve d'Ascq France
- Laboratoire de Chimie Bactérienne; Institut de Microbiologie de la Méditerranée, Aix-Marseille Université, CNRS; UMR 7283 Marseille France
| | - Xavier De Bolle
- Microorganisms Biology Research Unit (URBM); Narilis, University of Namur; Namur Belgium
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25
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Hynes AP, Shakya M, Mercer RG, Grüll MP, Bown L, Davidson F, Steffen E, Matchem H, Peach ME, Berger T, Grebe K, Zhaxybayeva O, Lang AS. Functional and Evolutionary Characterization of a Gene Transfer Agent's Multilocus "Genome". Mol Biol Evol 2016; 33:2530-43. [PMID: 27343288 PMCID: PMC5026251 DOI: 10.1093/molbev/msw125] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Gene transfer agents (GTAs) are phage-like particles that can package and transfer a random piece of the producing cell’s genome, but are unable to transfer all the genes required for their own production. As such, GTAs represent an evolutionary conundrum: are they selfish genetic elements propagating through an unknown mechanism, defective viruses, or viral structures “repurposed” by cells for gene exchange, as their name implies? In Rhodobacter capsulatus, production of the R. capsulatus GTA (RcGTA) particles is associated with a cluster of genes resembling a small prophage. Utilizing transcriptomic, genetic and biochemical approaches, we report that the RcGTA “genome” consists of at least 24 genes distributed across five distinct loci. We demonstrate that, of these additional loci, two are involved in cell recognition and binding and one in the production and maturation of RcGTA particles. The five RcGTA “genome” loci are widespread within Rhodobacterales, but not all loci have the same evolutionary histories. Specifically, two of the loci have been subject to frequent, probably virus-mediated, gene transfer events. We argue that it is unlikely that RcGTA is a selfish genetic element. Instead, our findings are compatible with the scenario that RcGTA is a virus-derived element maintained by the producing organism due to a selective advantage of within-population gene exchange. The modularity of the RcGTA “genome” is presumably a result of selection on the host organism to retain GTA functionality.
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Affiliation(s)
- Alexander P Hynes
- Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada
| | - Migun Shakya
- Department of Biological Sciences, Dartmouth College
| | - Ryan G Mercer
- Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada
| | - Marc P Grüll
- Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada
| | - Luke Bown
- Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada
| | - Fraser Davidson
- Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada
| | - Ekaterina Steffen
- Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada
| | - Heidi Matchem
- Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada
| | - Mandy E Peach
- Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada
| | - Tim Berger
- Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada
| | - Katherine Grebe
- Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada
| | - Olga Zhaxybayeva
- Department of Biological Sciences, Dartmouth College Department of Computer Science, Dartmouth College
| | - Andrew S Lang
- Department of Biology, Memorial University of Newfoundland, St John's, NL, Canada
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26
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Jia N, Ding MZ, Du J, Pan CH, Tian G, Lang JD, Fang JH, Gao F, Yuan YJ. Insights into mutualism mechanism and versatile metabolism of Ketogulonicigenium vulgare Hbe602 based on comparative genomics and metabolomics studies. Sci Rep 2016; 6:23068. [PMID: 26979567 PMCID: PMC4793288 DOI: 10.1038/srep23068] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 02/29/2016] [Indexed: 02/02/2023] Open
Abstract
Ketogulonicigenium vulgare has been widely used in vitamin C two steps fermentation and requires companion strain for optimal growth. However, the understanding of K. vulgare as well as its companion strain is still preliminary. Here, the complete genome of K. vulgare Hbe602 was deciphered to provide insight into the symbiosis mechanism and the versatile metabolism. K. vulgare contains the LuxR family proteins, chemokine proteins, flagellar structure proteins, peptides and transporters for symbiosis consortium. Besides, the growth state and metabolite variation of K. vulgare were observed when five carbohydrates (D-sorbitol, L-sorbose, D-glucose, D-fructose and D-mannitol) were used as carbon source. The growth increased by 40.72% and 62.97% respectively when K. vulgare was cultured on D-mannitol/D-sorbitol than on L-sorbose. The insufficient metabolism of carbohydrates, amino acids and vitamins is the main reason for the slow growth of K. vulgare. The combined analysis of genomics and metabolomics indicated that TCA cycle, amino acid and nucleotide metabolism were significantly up-regulated when K. vulgare was cultured on the D-mannitol/D-sorbitol, which facilitated the better growth. The present study would be helpful to further understand its metabolic structure and guide the engineering transformation.
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Affiliation(s)
- Nan Jia
- Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- SynBio Research Platform, Collaborative Innovation Centre of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
| | - Ming-Zhu Ding
- Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- SynBio Research Platform, Collaborative Innovation Centre of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
| | - Jin Du
- Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- SynBio Research Platform, Collaborative Innovation Centre of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
| | - Cai-Hui Pan
- Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- SynBio Research Platform, Collaborative Innovation Centre of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
| | - Geng Tian
- Sequencing platform of Tsinghua University, Beijing, 100084, PR China
| | - Ji-Dong Lang
- Sequencing platform of Tsinghua University, Beijing, 100084, PR China
| | - Jian-Huo Fang
- Sequencing platform of Tsinghua University, Beijing, 100084, PR China
| | - Feng Gao
- Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- SynBio Research Platform, Collaborative Innovation Centre of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- Department of Physics, Tianjin University, Tianjin, 300072, PR China
| | - Ying-Jin Yuan
- Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
- SynBio Research Platform, Collaborative Innovation Centre of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, PR China
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von Wintersdorff CJH, Penders J, van Niekerk JM, Mills ND, Majumder S, van Alphen LB, Savelkoul PHM, Wolffs PFG. Dissemination of Antimicrobial Resistance in Microbial Ecosystems through Horizontal Gene Transfer. Front Microbiol 2016; 7:173. [PMID: 26925045 PMCID: PMC4759269 DOI: 10.3389/fmicb.2016.00173] [Citation(s) in RCA: 721] [Impact Index Per Article: 90.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 02/01/2016] [Indexed: 11/13/2022] Open
Abstract
The emergence and spread of antibiotic resistance among pathogenic bacteria has been a rising problem for public health in recent decades. It is becoming increasingly recognized that not only antibiotic resistance genes (ARGs) encountered in clinical pathogens are of relevance, but rather, all pathogenic, commensal as well as environmental bacteria—and also mobile genetic elements and bacteriophages—form a reservoir of ARGs (the resistome) from which pathogenic bacteria can acquire resistance via horizontal gene transfer (HGT). HGT has caused antibiotic resistance to spread from commensal and environmental species to pathogenic ones, as has been shown for some clinically important ARGs. Of the three canonical mechanisms of HGT, conjugation is thought to have the greatest influence on the dissemination of ARGs. While transformation and transduction are deemed less important, recent discoveries suggest their role may be larger than previously thought. Understanding the extent of the resistome and how its mobilization to pathogenic bacteria takes place is essential for efforts to control the dissemination of these genes. Here, we will discuss the concept of the resistome, provide examples of HGT of clinically relevant ARGs and present an overview of the current knowledge of the contributions the various HGT mechanisms make to the spread of antibiotic resistance.
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Affiliation(s)
- Christian J H von Wintersdorff
- Department of Medical Microbiology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center+ Maastricht, Netherlands
| | - John Penders
- Department of Medical Microbiology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center+Maastricht, Netherlands; Department of Medical Microbiology, Caphri School for Public Health and Primary Care, Maastricht University Medical Center+Maastricht, Netherlands
| | - Julius M van Niekerk
- Department of Medical Microbiology, Caphri School for Public Health and Primary Care, Maastricht University Medical Center+ Maastricht, Netherlands
| | - Nathan D Mills
- Department of Medical Microbiology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center+ Maastricht, Netherlands
| | - Snehali Majumder
- Department of Medical Microbiology, Caphri School for Public Health and Primary Care, Maastricht University Medical Center+ Maastricht, Netherlands
| | - Lieke B van Alphen
- Department of Medical Microbiology, Caphri School for Public Health and Primary Care, Maastricht University Medical Center+ Maastricht, Netherlands
| | - Paul H M Savelkoul
- Department of Medical Microbiology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center+Maastricht, Netherlands; Department of Medical Microbiology, Caphri School for Public Health and Primary Care, Maastricht University Medical Center+Maastricht, Netherlands; Department of Medical Microbiology and Infection Control, VU University Medical CenterAmsterdam, Netherlands
| | - Petra F G Wolffs
- Department of Medical Microbiology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University Medical Center+Maastricht, Netherlands; Department of Medical Microbiology, Caphri School for Public Health and Primary Care, Maastricht University Medical Center+Maastricht, Netherlands
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The SOS Response Master Regulator LexA Regulates the Gene Transfer Agent of Rhodobacter capsulatus and Represses Transcription of the Signal Transduction Protein CckA. J Bacteriol 2016; 198:1137-48. [PMID: 26833411 DOI: 10.1128/jb.00839-15] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 01/24/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The gene transfer agent of Rhodobacter capsulatus (RcGTA) is a genetic exchange element that combines central aspects of bacteriophage-mediated transduction and natural transformation. RcGTA particles resemble a small double-stranded DNA bacteriophage, package random ∼4-kb fragments of the producing cell genome, and are released from a subpopulation (<1%) of cells in a stationary-phase culture. RcGTA particles deliver this DNA to surrounding R. capsulatus cells, and the DNA is integrated into the recipient genome though a process that requires homologs of natural transformation genes and RecA-mediated homologous recombination. Here, we report the identification of the LexA repressor, the master regulator of the SOS response in many bacteria, as a regulator of RcGTA activity. Deletion of the lexA gene resulted in the abolition of detectable RcGTA production and an ∼10-fold reduction in recipient capability. A search for SOS box sequences in the R. capsulatus genome sequence identified a number of putative binding sites located 5' of typical SOS response coding sequences and also 5' of the RcGTA regulatory gene cckA, which encodes a hybrid histidine kinase homolog. Expression of cckA was increased >5-fold in the lexA mutant, and a lexA cckA double mutant was found to have the same phenotype as a ΔcckA single mutant in terms of RcGTA production. The data indicate that LexA is required for RcGTA production and maximal recipient capability and that the RcGTA-deficient phenotype of the lexA mutant is largely due to the overexpression of cckA. IMPORTANCE This work describes an unusual phenotype of a lexA mutant of the alphaproteobacterium Rhodobacter capsulatus in respect to the phage transduction-like genetic exchange carried out by the R. capsulatus gene transfer agent (RcGTA). Instead of the expected SOS response characteristic of prophage induction, this lexA mutation not only abolishes the production of RcGTA particles but also impairs the ability of cells to receive RcGTA-borne genes. The data show that, despite an apparent evolutionary relationship to lambdoid phages, the regulation of RcGTA gene expression differs radically.
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Westbye AB, Kuchinski K, Yip CK, Beatty JT. The Gene Transfer Agent RcGTA Contains Head Spikes Needed for Binding to the Rhodobacter capsulatus Polysaccharide Cell Capsule. J Mol Biol 2015; 428:477-91. [PMID: 26711507 DOI: 10.1016/j.jmb.2015.12.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 11/25/2015] [Accepted: 12/06/2015] [Indexed: 11/15/2022]
Abstract
Viruses and bacteriophages recognize cell surface proteins using receptor-binding proteins. In most tailed bacteriophages, receptor-binding proteins are located on the bacteriophage tail. The gene transfer agent of Rhodobacter capsulatus, RcGTA, morphologically resembles a tailed bacteriophage and binds to a capsular polysaccharide covering R. capsulatus cells. Here, we report that the RcGTA capsid (head) is decorated by spikes that are needed for binding to the capsule. The triangular spikes measured ~12nm and appeared to be attached at the capsid vertices. Head spike production required the putative carbohydrate-binding protein ghsB (rcc01080) previously thought to encode a side tail fiber protein. We found that ghsB is likely co-transcribed with ghsA (rcc01079) and that ghsA/ghsB is regulated by the CckA-ChpT-CtrA phosphorelay homologues and a quorum-sensing system. GhsA and GhsB were found to be CckA-dependent RcGTA maturation factors, as GhsA- and GhsB-deficient particles were found to have altered native-gel electrophoresis migration. Additionally, we provide electron microscopy images showing that RcGTA contains side tail fibers and a baseplate-like structure near the tip of the tail, which are independent of ghsB.
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Affiliation(s)
- Alexander B Westbye
- Department of Microbiology and Immunology, The University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - Kevin Kuchinski
- Department of Microbiology and Immunology, The University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - Calvin K Yip
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - J Thomas Beatty
- Department of Microbiology and Immunology, The University of British Columbia, Vancouver, BC, Canada V6T 1Z3.
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Homologues of Genetic Transformation DNA Import Genes Are Required for Rhodobacter capsulatus Gene Transfer Agent Recipient Capability Regulated by the Response Regulator CtrA. J Bacteriol 2015; 197:2653-63. [PMID: 26031909 DOI: 10.1128/jb.00332-15] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 05/27/2015] [Indexed: 01/23/2023] Open
Abstract
UNLABELLED Gene transfer agents (GTAs) morphologically resemble small, double-stranded DNA (dsDNA) bacteriophages; however, their only known role is to package and transfer random pieces of the producing cell genome to recipient cells. The best understood GTA is that of Rhodobacter capsulatus, termed RcGTA. We discovered that homologues of three genes involved in natural transformation in other bacteria, comEC, comF, and comM, are essential for RcGTA-mediated gene acquisition. This paper gives genetic and biochemical evidence that RcGTA-borne DNA entry into cells requires the ComEC and ComF putative DNA transport proteins and genetic evidence that putative cytoplasmic ComM protein of unknown function is required for recipient capability. Furthermore, the master regulator of RcGTA production in <1% of a cell population, CtrA, which is also required for gene acquisition in recipient cells, is expressed in the vast majority of the population. Our results indicate that RcGTA-mediated gene transfer combines key aspects of two bacterial horizontal gene transfer mechanisms, where donor DNA is packaged in transducing phage-like particles and recipient cells take up DNA using natural transformation-related machinery. Both of these differentiated subsets of a culture population, donors and recipients, are dependent on the same response regulator, CtrA. IMPORTANCE Horizontal gene transfer (HGT) is a major driver of bacterial evolution and adaptation to environmental stresses. Traits such as antibiotic resistance or metabolic properties can be transferred between bacteria via HGT; thus, HGT can have a tremendous effect on the fitness of a bacterial population. The three classically described HGT mechanisms are conjugation, transformation, and phage-mediated transduction. More recently, the HGT factor GTA was described, where random pieces of producing cell genome are packaged into phage-like particles that deliver DNA to recipient cells. In this report, we show that transport of DNA borne by the R. capsulatus RcGTA into recipient cells requires key genes previously thought to be specific to natural transformation pathways. These findings indicate that RcGTA combines central aspects of phage-mediated transduction and natural transformation in an efficient, regulated mode of HGT.
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Francez-Charlot A, Kaczmarczyk A, Vorholt JA. The branched CcsA/CckA-ChpT-CtrA phosphorelay of Sphingomonas melonis controls motility and biofilm formation. Mol Microbiol 2015; 97:47-63. [PMID: 25825287 DOI: 10.1111/mmi.13011] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/28/2015] [Indexed: 11/29/2022]
Abstract
The CckA-ChpT-CtrA phosphorelay is central to the regulation of the cell cycle in Caulobacter crescentus. The three proteins are conserved in Alphaproteobacteria, but little is known about their roles in most members of this class. Here, we characterized the system in Sphingomonas melonis. We found that the transcription factor CtrA is the master regulator of flagella synthesis genes, the hierarchical transcriptional organization of which is herein described. CtrA also regulates genes involved in exopolysaccharide synthesis and cyclic-di-GMP signaling, and is important for biofilm formation. In addition, the ctrA mutant exhibits an aberrant morphology, suggesting a role for CtrA in cell division. An analysis of the regulation of CtrA indicates that the phosphorelay composed of CckA and ChpT is conserved and that the absence of the bifunctional kinase/phosphatase CckA apparently results in overactivation of CtrA through ChpT. Suppressors of this phenotype identified the hybrid histidine kinase CcsA. Phosphorelays initiated by CckA or CcsA were reconstituted in vitro, suggesting that in S. melonis, CtrA phosphorylation is controlled by a branched pathway upstream of ChpT. This study thus suggests that signals can directly converge at the level of ChpT phosphorylation through multiple hybrid kinases to coordinate a number of important physiological processes.
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Affiliation(s)
| | | | - Julia A Vorholt
- Institute of Microbiology, ETH Zurich, 8093, Zurich, Switzerland
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Panis G, Murray SR, Viollier PH. Versatility of global transcriptional regulators in alpha-Proteobacteria: from essential cell cycle control to ancillary functions. FEMS Microbiol Rev 2014; 39:120-33. [PMID: 25793963 DOI: 10.1093/femsre/fuu002] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Recent data indicate that cell cycle transcription in many alpha-Proteobacteria is executed by at least three conserved functional modules in which pairs of antagonistic regulators act jointly, rather than in isolation, to control transcription in S-, G2- or G1-phase. Inactivation of module components often results in pleiotropic defects, ranging from cell death and impaired cell division to fairly benign deficiencies in motility. Expression of module components can follow systemic (cell cycle) or external (nutritional/cell density) cues and may be implemented by auto-regulation, ancillary regulators or other (unknown) mechanisms. Here, we highlight the recent progress in understanding the molecular events and the genetic relationships of the module components in environmental, pathogenic and/or symbiotic alpha-proteobacterial genera. Additionally, we take advantage of the recent genome-wide transcriptional analyses performed in the model alpha-Proteobacterium Caulobacter crescentus to illustrate the complexity of the interactions of the global regulators at selected cell cycle-regulated promoters and we detail the consequences of (mis-)expression when the regulators are absent. This review thus provides the first detailed mechanistic framework for understanding orthologous operational principles acting on cell cycle-regulated promoters in other alpha-Proteobacteria.
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Affiliation(s)
- Gaël Panis
- Department of Microbiology and Molecular Medicine, Institute of Genetics and Genomics in Geneva (iGE3), Faculty of Medicine/CMU, University of Geneva, Rue Michel Servet 1, 1211 Genève 4, Switzerland
| | - Sean R Murray
- Department of Biology, Center for Cancer and Developmental Biology, Interdisciplinary Research Institute for the Sciences, California State University Northridge, 18111 Nordhoff Street, Northridge, CA 91330-8303, USA
| | - Patrick H Viollier
- Department of Microbiology and Molecular Medicine, Institute of Genetics and Genomics in Geneva (iGE3), Faculty of Medicine/CMU, University of Geneva, Rue Michel Servet 1, 1211 Genève 4, Switzerland
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The flagellar set Fla2 in Rhodobacter sphaeroides is controlled by the CckA pathway and is repressed by organic acids and the expression of Fla1. J Bacteriol 2014; 197:833-47. [PMID: 25512309 DOI: 10.1128/jb.02429-14] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Rhodobacter sphaeroides has two different sets of flagellar genes. Under the growth conditions commonly used in the laboratory, the expression of the fla1 set is constitutive, whereas the fla2 genes are not expressed. Phylogenetic analyses have previously shown that the fla1 genes were acquired by horizontal transfer from a gammaproteobacterium and that the fla2 genes are endogenous genes of this alphaproteobacterium. In this work, we characterized a set of mutants that were selected for swimming using the Fla2 flagella in the absence of the Fla1 flagellum (Fla2(+) strains). We determined that these strains have a single missense mutation in the histidine kinase domain of CckA. The expression of these mutant alleles in a Fla1(-) strain allowed fla2-dependent motility without selection. Motility of the Fla2(+) strains is also dependent on ChpT and CtrA. The mutant versions of CckA showed an increased autophosphorylation activity in vitro. Interestingly, we found that cckA is transcriptionally repressed by the presence of organic acids, suggesting that the availability of carbon sources could be a part of the signal that turns on this flagellar set. Evidence is presented showing that reactivation of fla1 gene expression in the Fla2(+) background strongly reduces the number of cells with Fla2 flagella.
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Peña-Castillo L, Mercer RG, Gurinovich A, Callister SJ, Wright AT, Westbye AB, Beatty JT, Lang AS. Gene co-expression network analysis in Rhodobacter capsulatus and application to comparative expression analysis of Rhodobacter sphaeroides. BMC Genomics 2014; 15:730. [PMID: 25164283 PMCID: PMC4158056 DOI: 10.1186/1471-2164-15-730] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 08/21/2014] [Indexed: 01/05/2023] Open
Abstract
Background The genus Rhodobacter contains purple nonsulfur bacteria found mostly in freshwater environments. Representative strains of two Rhodobacter species, R. capsulatus and R. sphaeroides, have had their genomes fully sequenced and both have been the subject of transcriptional profiling studies. Gene co-expression networks can be used to identify modules of genes with similar expression profiles. Functional analysis of gene modules can then associate co-expressed genes with biological pathways, and network statistics can determine the degree of module preservation in related networks. In this paper, we constructed an R. capsulatus gene co-expression network, performed functional analysis of identified gene modules, and investigated preservation of these modules in R. capsulatus proteomics data and in R. sphaeroides transcriptomics data. Results The analysis identified 40 gene co-expression modules in R. capsulatus. Investigation of the module gene contents and expression profiles revealed patterns that were validated based on previous studies supporting the biological relevance of these modules. We identified two R. capsulatus gene modules preserved in the protein abundance data. We also identified several gene modules preserved between both Rhodobacter species, which indicate that these cellular processes are conserved between the species and are candidates for functional information transfer between species. Many gene modules were non-preserved, providing insight into processes that differentiate the two species. In addition, using Local Network Similarity (LNS), a recently proposed metric for expression divergence, we assessed the expression conservation of between-species pairs of orthologs, and within-species gene-protein expression profiles. Conclusions Our analyses provide new sources of information for functional annotation in R. capsulatus because uncharacterized genes in modules are now connected with groups of genes that constitute a joint functional annotation. We identified R. capsulatus modules enriched with genes for ribosomal proteins, porphyrin and bacteriochlorophyll anabolism, and biosynthesis of secondary metabolites to be preserved in R. sphaeroides whereas modules related to RcGTA production and signalling showed lack of preservation in R. sphaeroides. In addition, we demonstrated that network statistics may also be applied within-species to identify congruence between mRNA expression and protein abundance data for which simple correlation measurements have previously had mixed results. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-730) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lourdes Peña-Castillo
- Department of Biology, Memorial University of Newfoundland, St, John's, NL A1B 3X5, Canada.
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Brimacombe CA, Ding H, Beatty JT. Rhodobacter capsulatus DprA is essential for RecA-mediated gene transfer agent (RcGTA) recipient capability regulated by quorum-sensing and the CtrA response regulator. Mol Microbiol 2014; 92:1260-78. [DOI: 10.1111/mmi.12628] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/24/2014] [Indexed: 01/18/2023]
Affiliation(s)
- Cedric A. Brimacombe
- Department of Microbiology and Immunology; The University of British Columbia; 2350 Health Sciences Mall Vancouver BC Canada V6T 1Z3
| | - Hao Ding
- Department of Microbiology and Immunology; The University of British Columbia; 2350 Health Sciences Mall Vancouver BC Canada V6T 1Z3
| | - J. Thomas Beatty
- Department of Microbiology and Immunology; The University of British Columbia; 2350 Health Sciences Mall Vancouver BC Canada V6T 1Z3
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Mercer RG, Lang AS. Identification of a predicted partner-switching system that affects production of the gene transfer agent RcGTA and stationary phase viability in Rhodobacter capsulatus. BMC Microbiol 2014; 14:71. [PMID: 24645667 PMCID: PMC3999984 DOI: 10.1186/1471-2180-14-71] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 03/12/2014] [Indexed: 11/30/2022] Open
Abstract
Background Production of the gene transfer agent RcGTA in the α-proteobacterium Rhodobacter capsulatus is dependent upon the response regulator protein CtrA. Loss of this regulator has widespread effects on transcription in R. capsulatus, including the dysregulation of numerous genes encoding other predicted regulators. This includes a set of putative components of a partner-switching signaling pathway with sequence homology to the σ-regulating proteins RsbV, RsbW, and RsbY that have been extensively characterized for their role in stress responses in gram-positive bacteria. These R. capsulatus homologues, RbaV, RbaW, and RbaY, have been investigated for their possible role in controlling RcGTA gene expression. Results A mutant strain lacking rbaW showed a significant increase in RcGTA gene expression and production. Mutation of rbaV or rbaY led to a decrease in RcGTA gene expression and production, and these mutants also showed decreased viability in the stationary phase and produced unusual colony morphologies. In vitro and in vivo protein interaction assays demonstrated that RbaW and RbaV interact. A combination of gene disruptions and protein-protein interaction assays were unsuccessful in attempts to identify a cognate σ factor, and the genetic data support a model where the RbaV protein that is the determinant regulator of RcGTA gene expression in this system. Conclusions These findings provide new information about RcGTA regulation by a putative partner-switching system and further illustrate the integration of RcGTA production into R. capsulatus physiology.
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Affiliation(s)
| | - Andrew S Lang
- Department of Biology, Memorial University of Newfoundland, 232 Elizabeth Ave, St, John's A1B 3X9, NL, Canada.
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Phosphate concentration and the putative sensor kinase protein CckA modulate cell lysis and release of the Rhodobacter capsulatus gene transfer agent. J Bacteriol 2013; 195:5025-40. [PMID: 23995641 DOI: 10.1128/jb.00669-13] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The gene transfer agent of Rhodobacter capsulatus (RcGTA) is a bacteriophage-like genetic element with the sole known function of horizontal gene transfer. Homologues of RcGTA genes are present in many members of the alphaproteobacteria and may serve an important role in microbial evolution. Transcription of RcGTA genes is induced as cultures enter the stationary phase; however, little is known about cis-active sequences. In this work, we identify the promoter of the first gene in the RcGTA structural gene cluster. Additionally, gene transduction frequency depends on the growth medium, and the reason for this is not known. We report that millimolar concentrations of phosphate posttranslationally inhibit the lysis-dependent release of RcGTA from cells in both a complex medium and a defined medium. Furthermore, we found that cell lysis requires the genes rcc00555 and rcc00556, which were expressed and studied in Escherichia coli to determine their predicted functions as an endolysin and holin, respectively. Production of RcGTA is regulated by host systems, including a putative histidine kinase, CckA, and we found that CckA is required for maximal expression of rcc00555 and for maturation of RcGTA to yield gene transduction-functional particles.
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Zan J, Heindl JE, Liu Y, Fuqua C, Hill RT. The CckA-ChpT-CtrA phosphorelay system is regulated by quorum sensing and controls flagellar motility in the marine sponge symbiont Ruegeria sp. KLH11. PLoS One 2013; 8:e66346. [PMID: 23825536 PMCID: PMC3692519 DOI: 10.1371/journal.pone.0066346] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 05/08/2013] [Indexed: 01/12/2023] Open
Abstract
Bacteria respond to their environment via signal transduction pathways, often two-component type systems that function through phosphotransfer to control expression of specific genes. Phosphorelays are derived from two-component systems but are comprised of additional components. The essential cckA-chpT-ctrA phosphorelay in Caulobacter crescentus has been well studied and is important in orchestrating the cell cycle, polar development and flagellar biogenesis. Although cckA, chpT and ctrA homologues are widespread among the Alphaproteobacteria, relatively few is known about their function in the large and ecologically significant Roseobacter clade of the Rhodobacterales. In this study the cckA-chpT-ctrA system of the marine sponge symbiont Ruegeria sp. KLH11 was investigated. Our results reveal that the cckA, chpT and ctrA genes positively control flagellar biosynthesis. In contrast to C. crescentus, the cckA, chpT and ctrA genes in Ruegeria sp. KLH11 are non-essential and do not affect bacterial growth. Gene fusion and transcript analyses provide evidence for ctrA autoregulation and the control of motility-related genes. In KLH11, flagellar motility is controlled by the SsaRI system and acylhomoserine lactone (AHL) quorum sensing. SsaR and long chain AHLs are required for cckA, chpT and ctrA gene expression, providing a regulatory link between flagellar locomotion and population density in KLH11.
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Affiliation(s)
- Jindong Zan
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, Maryland, United States of America
| | - Jason E. Heindl
- Department of Biology, Indiana University, Bloomington, Indiana, United States of America
| | - Yue Liu
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, Maryland, United States of America
| | - Clay Fuqua
- Department of Biology, Indiana University, Bloomington, Indiana, United States of America
| | - Russell T. Hill
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, Maryland, United States of America
- * E-mail:
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A gene transfer agent and a dynamic repertoire of secretion systems hold the keys to the explosive radiation of the emerging pathogen Bartonella. PLoS Genet 2013; 9:e1003393. [PMID: 23555299 PMCID: PMC3610622 DOI: 10.1371/journal.pgen.1003393] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 01/08/2013] [Indexed: 12/31/2022] Open
Abstract
Gene transfer agents (GTAs) randomly transfer short fragments of a bacterial genome. A novel putative GTA was recently discovered in the mouse-infecting bacterium Bartonella grahamii. Although GTAs are widespread in phylogenetically diverse bacteria, their role in evolution is largely unknown. Here, we present a comparative analysis of 16 Bartonella genomes ranging from 1.4 to 2.6 Mb in size, including six novel genomes from Bartonella isolated from a cow, two moose, two dogs, and a kangaroo. A phylogenetic tree inferred from 428 orthologous core genes indicates that the deadly human pathogen B. bacilliformis is related to the ruminant-adapted clade, rather than being the earliest diverging species in the genus as previously thought. A gene flux analysis identified 12 genes for a GTA and a phage-derived origin of replication as the most conserved innovations. These are located in a region of a few hundred kb that also contains 8 insertions of gene clusters for type III, IV, and V secretion systems, and genes for putatively secreted molecules such as cholera-like toxins. The phylogenies indicate a recent transfer of seven genes in the virB gene cluster for a type IV secretion system from a cat-adapted B. henselae to a dog-adapted B. vinsonii strain. We show that the B. henselae GTA is functional and can transfer genes in vitro. We suggest that the maintenance of the GTA is driven by selection to increase the likelihood of horizontal gene transfer and argue that this process is beneficial at the population level, by facilitating adaptive evolution of the host-adaptation systems and thereby expansion of the host range size. The process counters gene loss and forces all cells to contribute to the production of the GTA and the secreted molecules. The results advance our understanding of the role that GTAs play for the evolution of bacterial genomes. Viruses are selfish genetic elements that replicate and transfer their own DNA, often killing the host cell in the process. Unlike viruses, gene transfer agents (GTAs) transfer random pieces of the bacterial genome rather than their own DNA. GTAs are widespread in bacterial genomes, but it is not known whether they are beneficial to the bacterium. In this study, we have used the emerging pathogen Bartonella as our model to study the evolution of GTAs. We sequenced the genomes of six isolates of Bartonella, including two new strains isolated from wild moose in Sweden. Using a comparative genomics approach, we searched for innovations in the last common ancestor that could help explain the explosive radiation of the genus. Surprisingly, we found that a gene cluster for a GTA and a phage-derived origin of replication was the most conserved innovation, indicative of strong selective constraints. We argue that the reason for the remarkable stability of the GTA is that it provides a mechanism to duplicate and recombine genes for secretion systems. This leads to adaptability to a broad range of hosts.
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Leung MM, Brimacombe CA, Beatty JT. Transcriptional regulation of the Rhodobacter capsulatus response regulator CtrA. MICROBIOLOGY-SGM 2012; 159:96-106. [PMID: 23154973 DOI: 10.1099/mic.0.062349-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Rhodobacter capsulatus response regulator CtrA controls the expression of 227 genes, some of which are upregulated by both the phosphorylated and unphosphorylated forms of CtrA. Therefore, CtrA concentration alone, regardless of phosphorylation state, may determine expression of downstream genes, yet little is known about the regulation of ctrA in R. capsulatus. In this study we used a ctrA : : lacZ fusion plasmid to study the effects of medium composition, growth conditions and growth phase on R. capsulatus ctrA gene expression. These experiments indicate that ctrA expression is higher when cultures are grown in phototrophic (anaerobic) conditions compared with chemotrophic (aerobic) conditions, and is higher when grown in a minimal medium compared with a rich medium. We used several mutants to investigate possible regulatory pathways, and found that in R. capsulatus ctrA is not autoregulated but is regulated by a quorum-sensing system. The expression of ctrA increased as cell cultures moved through exponential phase and into stationary phase, with high levels of expression persisting long after culture turbidity plateaued. Although this growth phase-dependent pattern of expression was also observed in a quorum-sensing mutant, the magnitude of ctrA expression was about 50% of the wild-type strain at all phases. Furthermore, reduction of phosphate concentration in the growth medium decreased ctrA expression in a culture density-independent manner, whereas reduction of malic acid (carbon source) or ammonium (nitrogen source) concentration had no effect. The regulation of ctrA expression in R. capsulatus appears to require the coordination of multiple pathways involved in detecting a variety of environmental conditions.
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Affiliation(s)
- Molly M Leung
- Department of Microbiology and Immunology, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Cedric A Brimacombe
- Department of Microbiology and Immunology, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - J Thomas Beatty
- Department of Microbiology and Immunology, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
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Hynes AP, Mercer RG, Watton DE, Buckley CB, Lang AS. DNA packaging bias and differential expression of gene transfer agent genes within a population during production and release of the Rhodobacter capsulatus gene transfer agent, RcGTA. Mol Microbiol 2012; 85:314-25. [PMID: 22640804 DOI: 10.1111/j.1365-2958.2012.08113.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Rhodobacter capsulatus produces a gene transfer agent (GTA) called RcGTA. RcGTA is a phage-like particle that packages R. capsulatus DNA and transfers it to other R. capsulatus cells. We quantified the relative frequency of packaging for each gene in the genome by hybridization of DNA from RcGTA particles to an R. capsulatus microarray. All genes were found within the RcGTA particles. However, the genes encoding the RcGTA particle were under-packaged compared with other regions. Gene transfer bioassays confirmed that the transfer of genes within the RcGTA structural cluster is reduced relative to those of other genes. Single-cell expression analysis, by flow cytometry analysis of cells containing RcGTA-reporter gene fusion constructs, demonstrated that RcGTA gene expression is not uniform within a culture. This phenomenon was accentuated when the constructs were placed in a strain lacking a putative lysis gene involved in RcGTA release; a small subpopulation was found to be responsible for ∼ 95% of RcGTA activity. We propose a mechanism whereby high levels of RcGTA gene transcription in the most active RcGTA-producing cells cause a reduction in their packaging frequency. This subpopulation's role in producing and releasing the RcGTA particles explains the lack of observed cell lysis in cultures.
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Affiliation(s)
- Alexander P Hynes
- Department of Biology, Memorial University of Newfoundland, 232 Elizabeth Ave., St John's, NL, A1B 3X9, Canada
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Lang AS, Zhaxybayeva O, Beatty JT. Gene transfer agents: phage-like elements of genetic exchange. Nat Rev Microbiol 2012; 10:472-82. [PMID: 22683880 DOI: 10.1038/nrmicro2802] [Citation(s) in RCA: 254] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Horizontal gene transfer is important in the evolution of bacterial and archaeal genomes. An interesting genetic exchange process is carried out by diverse phage-like gene transfer agents (GTAs) that are found in a wide range of prokaryotes. Although GTAs resemble phages, they lack the hallmark capabilities that define typical phages, and they package random pieces of the producing cell's genome. In this Review, we discuss the defining characteristics of the GTAs that have been identified to date, along with potential functions for these agents and the possible evolutionary forces that act on the genes involved in their production.
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Affiliation(s)
- Andrew S Lang
- Department of Biology, Memorial University, St. John's, Newfoundland and Labrador A1B 3X9, Canada.
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