Characterization of the 101-kilobase-pair megaplasmid pKB1, isolated from the rubber-degrading bacterium XXXX Kb1.

@entity21045 @entity15669 @entity70629 @entity219 @entity34643 @entity3409 @entity505 @entity70630 @entity526
The complete sequence of the circular 101,016-bp megaplasmid pKB1 from the @entity34643 -degrading bacterium @entity70629 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 @entity526 -Gordonia shuttle vectors, which was also suitable for several other @entity15669 and related genera. The metabolic region included the heavy-metal resistance gene @entity70630 , encoding a P-type ATPase. Expression of @entity70630 in @entity526 mediated resistance to @entity3409 , but not to @entity219 , and decreased the cellular content of @entity3409 in this host. When @entity70629 Kb1 was cured of plasmid pKB1, the resulting derivative strains exhibited slightly decreased @entity3409 resistance. Furthermore, they had lost the ability to use @entity21045 rubber as a sole source of @entity505 and energy, suggesting that genes essential for rubber degradation are encoded by pKB1.
