Characterization of PBSX, a defective prophage of Bacillus subtilis

Wood, Heather E.; Dawson, M.; Devine, Kevin M.; McConnell, David J.

doi:10.1128/jb.172.5.2667-2674.1990

Cited by 71 publications

(68 citation statements)

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“…Another phage-like particle with some similarities to GTAs is the defective phage PBSX of Bacillus subtilis 119,120 . The 28 kb PBSX gene cluster in the B. subtilis genome contains phage head, tail, lysis and lysogeny genes but no replication functions 84,121 . The particles appear to contain random ~13 kb pieces of the B. subtilis genome, but the activity of these particles is very different to that of GTAs or the Bartonella BLPs.…”

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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Section: Boxmentioning

confidence: 99%

Gene transfer agents: phage-like elements of genetic exchange

2012

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“…xhi-1479 is thus analogous to the cIts857 mutation of bacteriophage lambda (36). An insertion mutation called 316, which lies upstream of the major late operon, abolishes induction of the prophage (40). This finding suggests that there are other genes, possibly between xre and the late operon, which are required for late gene expression.…”

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“…PBSX is therefore not propagated by these particles (25,26). PBSX appears to be a particulate bacteriocin which has evolved from a bacteriophage.Induction of PBSX is controlled by the repressor gene xre (6,27,40,41). The amino acid sequence of Xre predicts that it is a helix-turn-helix (HLH) protein resembling other DNAbinding proteins such as lambda cI and Cro (14, 41).…”

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confidence: 99%

“…Induction of PBSX is controlled by the repressor gene xre (6,27,40,41). The amino acid sequence of Xre predicts that it is a helix-turn-helix (HLH) protein resembling other DNAbinding proteins such as lambda cI and Cro (14, 41).…”

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confidence: 99%

“…la) (40). A number of mutations in regulatory genes, including xin (noninducible for PBSX) and xhi (heat inducible for PBSX), are located proximal to mutations affecting phage head and tail proteins such as xhd, xtl, and xki (6, 38).…”

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Genetic control of bacterial suicide: regulation of the induction of PBSX in Bacillus subtilis

et al. 1994

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PBSX is a phage-like bacteriocin (phibacin) of Bacilus subtilis 168. Bacteria carrying the PBSX genome are induced by DNA-damaging agents to lyse and produce PBSX particles. The particles cannot propagate the PBSX genome. The particles produced by this suicidal response kill strains nonlysogenic for PBSX. A 5.2-kb region which controls the induction of PBSX has been sequenced. The genes identified include the previously identified repressor gene xre and a positive control factor gene, pcf. Pcf is similar to known sigma factors and acts at the late promoter P which has been located distal to pcf. The first two genes expressed from the late promoter show homology to genes encoding the subunits of phage terminases.The defective bacteriophage PBSX of Bacillus subtilis 168 is a phage-like bacteriocin, or phibacin, with curious biological properties. PBSX lysogens exposed to DNA-damaging agents produce PBSX phage-like particles which kill other nonlysogenic Bacillus strains (25) by binding to and disrupting the cell wall. Each PBSX particle has a small head and a relatively long tail. Phage heads appear to contain randomly selected 13-kb segments of host DNA, which are not injected into susceptible cells. PBSX is therefore not propagated by these particles (25,26). PBSX appears to be a particulate bacteriocin which has evolved from a bacteriophage.Induction of PBSX is controlled by the repressor gene xre (6,27,40,41). The amino acid sequence of Xre predicts that it is a helix-turn-helix (HLH) protein resembling other DNAbinding proteins such as lambda cI and Cro (14, 41). However, little is known about the mechanism of action of Xre, and apart from the suggestion that xre and a neighboring gene, now called open reading frame 10 (ORF10), are regulated by Xre itself, nothing is known about how the late genes are regulated (41).All known structural and lytic protein genes have been shown to be clustered within a large operon of at least 19 kb in length, which appears to be expressed from a single late promoter region called PL (Fig. la) (40). A number of mutations in regulatory genes, including xin (noninducible for PBSX) and xhi (heat inducible for PBSX), are located proximal to mutations affecting phage head and tail proteins such as xhd, xtl, and xki (6, 38). A regulatory mutation, xhi-1479, renders PBSX thermoinducible (6). A 1.2-kb EcoRI fragment from a PBSX wild-type strain was found to complement the xhi-1479 mutation, and sequence analysis identified the xre gene as the site of the mutation (41). xhi-1479 is thus analogous to the cIts857 mutation of bacteriophage lambda (36 Media. B. subtilis and Escherichia coli were grown in LuriaBertani (LB) broth (1% tryptone, 0.5% yeast extract, 0.5% NaCl) or LB agar. For selection, media contained chloramphenicol (at 3 pug/ml for low-copy-number vectors and 5 jig/ml for higher-copy-number vectors) and kanamycin (5 pug/ml) for B. subtilis, or chloramphenicol (15 jig/ml) and ampicillin (100 pug/ml) for E. coli as appropriate. a-Amylase activity was detected by adding starch (...

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Gene Transfer Agents in Symbiotic Microbes

Christensen

Serbus

2020

Results and Problems in Cell Differentiation

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Characterization of PBSX, a defective prophage of Bacillus subtilis

Cited by 71 publications

References 43 publications

Gene transfer agents: phage-like elements of genetic exchange

Gene transfer agents: phage-like elements of genetic exchange

Genetic control of bacterial suicide: regulation of the induction of PBSX in Bacillus subtilis

Gene Transfer Agents in Symbiotic Microbes

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