title: Characterization of the 101-kilobase-pair megaplasmid pKB1, isolated from the rubber-degrading bacterium Gordonia westfalica Kb1.
abstract: The complete sequence of the circular 101,016-bp megaplasmid pKB1 from the cis-1,4-polyisoprene-degrading bacterium Gordonia westfalica Kb1, which represents the first described extrachromosomal DNA of a member of this genus, was determined. Plasmid pKB1 harbors 105 open reading frames. The predicted products of 46 of these are significantly related to proteins of known function. Plasmid pKB1 is organized into three functional regions that are flanked by insertion sequence (IS) elements: (i) a replication and putative partitioning region, (ii) a putative metabolic region, and (iii) a large putative conjugative transfer region, which is interrupted by an additional IS element. Southern hybridization experiments revealed the presence of another copy of this conjugational transfer region on the bacterial chromosome. The origin of replication (oriV) of pKB1 was identified and used for construction of Escherichia coli-Gordonia shuttle vectors, which was also suitable for several other Gordonia species and related genera. The metabolic region included the heavy-metal resistance gene cadA, encoding a P-type ATPase. Expression of cadA in E. coli mediated resistance to cadmium, but not to zinc, and decreased the cellular content of cadmium in this host. When G. westfalica strain Kb1 was cured of plasmid pKB1, the resulting derivative strains exhibited slightly decreased cadmium resistance. Furthermore, they had lost the ability to use isoprene rubber as a sole source of carbon and energy, suggesting that genes essential for rubber degradation are encoded by pKB1.
authors.affiliation: Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, D-48149 Münster, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bröker
authors.forename: Matthias
authors.initials: M
authors.lastname: Arenskötter
authors.forename: Antje
authors.initials: A
authors.lastname: Legatzki
authors.forename: Dietrich H
authors.initials: DH
authors.lastname: Nies
authors.forename: Alexander
authors.initials: A
authors.lastname: Steinbüchel
mesh_terms: D001673:Biodegradation, Environmental; D002070:Butadienes / Q000378:metabolism*; D002104:Cadmium / Q000494:pharmacology; D003227:Conjugation, Genetic; D003470:Culture Media; D024881:Drug Resistance, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D033601:Gordonia Bacterium / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D045782:Hemiterpenes / Q000378:metabolism*; D019216:Metals, Heavy / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D010420:Pentanes / Q000378:metabolism*; D010957:Plasmids / Q000737:chemistry / Q000235:genetics*; D018741:Replication Origin; D012408:Rubber / Q000378:metabolism*; D017422:Sequence Analysis, DNA
chemical_list: D002070:Butadienes; D003470:Culture Media; D045782:Hemiterpenes; D019216:Metals, Heavy; D010420:Pentanes; D002104:Cadmium; C005059:isoprene; D012408:Rubber