Dehalococcoides Genome Biology
Event details
| Date | 28.11.2008 |
| Hour | 11:00 |
| Speaker | Dr Alfred Spormann, Stanford University (USA) |
| Location |
GR B3 30
|
| Category | Conferences - Seminars |
Vinyl chloride (monochloroethene) is a human carcinogen and widespread priority pollutant associated with the commercial manufacture of some polymers as well as the microbial degradation of the industrial solvents perchloroethene and trichloroethene. Microorganisms of the genus Dehalococcoides have been shown to use chloroethenes and other organochlorine compounds as terminal electron acceptor in respiration (dehalorespiration), thereby contributing to bioremediation of contaminated sites. The first complete genome sequences of microorganisms able to couple growth with the reduction of vinyl chloride to ethene, Dehalococcoides sp. strains VS and BAV1 will be discussed. Comparative analyses of these genomes with two previously sequenced Dehalococcoides genomes revealed a stable 'core' genome comprised of more than 70% of all genes with high contextual conservation (synteny). This core genome is interrupted in two regions that have undergone multiple independent insertions, deletions, and rearrangements. These regions, termed 'high plasticity region' (HPR), contain the majority of genomic islands (GEIs) in the four strains, a significantly elevated number of repeated elements including insertion sequences (IS), as well as 95% of the genes encoding the terminal reductases in dehalorespiration (rdhA). Notably, strains VS and BAV1 harbor their respective vinyl chloride reductase encoding operons, vcrABC and bvcAB, in different genomic locations embedded in distinct GEIs with different predicted integration sites. Together with unusual codon usage bias, this suggests not only that vinyl chloride respiration is a horizontally acquired trait, but also that these operons were acquired independently and by different mechanisms. While the number of rdhA gene in the four genomes ranges from 11 in BAV1 to 36 in VS, only three rdhA orthologous groups were shared between the genomes, and of these three, only one type was found within a conserved gene context (synteny). Horizontal acquisition of novel rdhA genes is indicated for approximately one-third of the 96 total rdhA genes in the four genomes and is likely a fundamental ecological strategy for niche adaptation in Dehalococccoides.
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