Regulatory systems controlling motility and gene transfer agent production and release in Rhodobacter capsulatus

Mercer, Ryan G.; Quinlan, Matthew; Rose, Alexandra R.; Noll, Stephan; Beatty, J. Thomas; Lang, Andrew S.

doi:10.1111/j.1574-6968.2012.02553.x

Cited by 49 publications

(87 citation statements)

References 41 publications

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“…A previous study found that the CckA sensor kinase protein is needed for maximal release of RcGTA from WT SB1003 cells (16), and so the possibility of phosphate signal transduction through CckA was investigated. To facilitate the study of RcGTA production and release, we exploited the RcGTA-overproducer phenotype of DE442, which has a higher proportion of cells in the population expressing RcGTA than does SB1003 (14,20).…”

Section: Resultsmentioning

confidence: 99%

“…Disruption of ctrA in R. capsulatus severely diminishes RcGTA mRNA levels and transduction frequencies, indicating that CtrA is required for transcription of the gene cluster (18). RcGTA transduction is similarly reduced by disruption of cckA; however, the RcGTA capsid protein is still produced, and so it appears that CckA is not needed for transcription of the RcGTA gene cluster (16,19). Mercer et al (16) recently reported that the CckA protein is needed for release of the RcGTA capsid protein from cells, but it remained unclear how release is blocked and whether the capsid protein that accumulates in ⌬cckA mutant cells comprises functional RcGTA particles.…”

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confidence: 99%

“…RcGTA production is regulated by several host proteins, including the quorum-sensing proteins GtaI and GtaR (15), and proteins homologous to the sensor kinase CckA and response regulator CtrA proteins that control the cell cycle in Caulobacter crescentus (16,17). Disruption of ctrA in R. capsulatus severely diminishes RcGTA mRNA levels and transduction frequencies, indicating that CtrA is required for transcription of the gene cluster (18).…”

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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

et al. 2013

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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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Section: Resultsmentioning

confidence: 99%

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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

et al. 2013

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“…A cellular phosphorelay involving the R. capsulatus response regulator CtrA is also involved, as loss of this response regulator causes a complete loss of transcription of RcGTA structural genes 32,38 . However, the exact mechanism of CtrAmediated regulation remains to be determined 41 . The control of RcGTA gene expression by cellular systems is consistent with the absence of RcGTA induction by treatment with the DNA-damaging agents mitomycin C or ultraviolet light; such induction would indicate that transcription of the RcGTA cluster is controlled by a phage repressor protein, which is not the case.…”

Section: Boxmentioning

confidence: 99%

Gene transfer agents: phage-like elements of genetic exchange

2012

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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.The prevalence of horizontal gene transfer (HGT), in which DNA is exchanged between closely or distantly related lineages, has altered the way we think about evolution 1,2 , having profound effects on our views of the evolutionary relationships among living organisms. It has caused a shift from a bifurcating 'tree of life' view to a 'net of life' or 'web of life' view [3][4][5] , in which "highways of gene sharing" (REF. 6) represent major connections, with genes (or DNA segments) viewed as "public goods, available for all organisms to integrate into their genomes" (REF. 7). HGT occurs within and between all three domains of life, and it has been estimated that 0.05-80% of genes in bacterial and archaeal genomes have been affected by HGT, depending on the analytical method used and the genome analysed [8][9][10] . Although HGT is widespread, it is not random: patterns of preferential gene exchange among specific groups of organisms that share ancestry or habitat have been * Present address. aslang@mun.ca; olgazh@dartmouth.edu; j.beatty@mail.ubc.ca Competing interests statementThe authors declare no competing financial interests. 6,9,11,12 . Such patterns are probably a consequence of existing barriers to HGT, which have been reviewed in detail elsewhere 13,14 . FURTHER INFORMATIONAlthough we have known about some HGT mechanisms for decades, novel processes that expand the existing repertoire of gene exchange methods are continually being identified. Transformation was the first mechanism of gene exchange to be discovered 15 , wherein DNA is taken up directly from the environment (reviewed elsewhere 16,17 ). In transduction, DNA transfer is mediated by viral particles (BOX 1). In conjugation, which was discovered in the 1940s 18 , DNA is transferred from a donor to a recipient cell during cell-to-cell contact; conjugation is used in the transfer of plasmids, transposons, integrons, and integrative and conjugative elements (ICEs) [19][20][21] . There are other modes of gene exchange that do not fit well into any of these three canonical mechanisms, including temporary cell fusion followed by chromosomal recombination and plasmid exchange 22 , intercellular connection through nanotubes 23 , and the release of membrane vesicles containing chromosomal, plasmid and phage DNA that can then merge with nearby cells 24 . In addition, a novel mechanism of gene transfer that has feature...

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“…Although R. capsulatus CtrA is essential for both RcGTA production and recipient capability (13,60,62), the RcGTA promoter is activated in Ͻ1% of WT cells in the stationary phase (7,46). In contrast, the essential recipient capability factor (dprA) promoter is expressed in essentially all cells in a population (13), as we found here for ctrA itself (Fig.…”

Section: Wt B10mentioning

confidence: 56%

Homologues of Genetic Transformation DNA Import Genes Are Required for Rhodobacter capsulatus Gene Transfer Agent Recipient Capability Regulated by the Response Regulator CtrA

et al. 2015

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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. IMPORTANCEHorizontal 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.T he first evidence of prokaryotic genetic exchange was transformation, a term coined in 1928 by Griffith (1). Subsequently, conjugation was observed in 1946 (2), followed by transduction, which was discovered in 1952 (3). More recently, another prokaryotic mode of horizontal gene transfer, dependent on an extracellular particle called a gene transfer agent (GTA), was described (4), and GTAs subsequently have been discovered in diverse prokaryotes (5).GTAs varying in morphology have been reported, although most resemble small, tailed double-stranded DNA (dsDNA) bacteriophages. The general criteria that define a GTA are (i) the DNA packaged within the head is insufficient to carry the GTA structural genes; (ii) all GTA particles package only random parts o...

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Regulatory systems controlling motility and gene transfer agent production and release in Rhodobacter capsulatus

Cited by 49 publications

References 41 publications

Phosphate Concentration and the Putative Sensor Kinase Protein CckA Modulate Cell Lysis and Release of the Rhodobacter capsulatus Gene Transfer Agent

Phosphate Concentration and the Putative Sensor Kinase Protein CckA Modulate Cell Lysis and Release of the Rhodobacter capsulatus Gene Transfer Agent

Gene transfer agents: phage-like elements of genetic exchange

Homologues of Genetic Transformation DNA Import Genes Are Required for Rhodobacter capsulatus Gene Transfer Agent Recipient Capability Regulated by the Response Regulator CtrA

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