Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2006
Publication Date: April 7, 2006
Citation: Stanton, T.B. Tales of the crypt(ics): Lateral gene transfer by 'defective' prophages [abstract]. American Society of Microbiology - Missouri Branch. p.7. Technical Abstract: An interesting discovery of sequencing projects is that bacterial genomes contain numerous cryptic bacteriophage genes and gene clusters. During efforts to develop genetic tools for the swine pathogenic spirochete Brachyspira hyodysenteriae, we discovered a cryptic, prophage-like element, named VSH-1. Composed of head (45 nm diameter) and simple tail structure (64 nm length), a VSH-1 virion morpho-logically resembles Lambda coliphage, but is smaller. Similar to well-studied prophages, VSH-1 is induced when B. hyodysenteriae cultures are treated with mitomycin C. Unlike many well-studied prophages, VSH-1 is defective, i.e. incapable of self-replication. VSH-1 virions package random 7.5 kb fragments of the B. hyodysenteriae genome and transfer genes, including genes for antibiotic resistance, between cells of the spirochete. The non-infectious nature and generalized transducing ability of VSH-1 have led to its classification as a novel, prophage-like, gene transfer agent (GTA). Genes for VSH-1 capsid, tail, and lysis proteins form two separate clusters within the B. hyodysenteriae genome. The clusters are 16.3 kb and 3.6 kb in size and contain fourteen identified genes and seven predicted ORFs. Inducers of VSH-1 gene transcription and virion production include H2O2, heat, and antibiotics, including antibiotics used in swine production. B. hyodysenteriae population structure has been shaped by a high degree of genetic recombination. As the only known gene transfer mechanism for B. hyodysenteriae, VSH-1 has likely contributed to the genetic diversity of this pathogenic spirochete. VSH-1-like agents are widely distributed among other Brachyspira species and likewise may mediate gene transfer within these species. ‘Defective’ prophages with VSH-1-like characteristics have been reported for several, diverse bacterial genera suggesting these genomic passengers are underappreciated ‘effective’ contributors to microbial ecology.