Replication and inheritance of Nocardia plasmid pC1.

Nocardia sp. C-14-1, isolated from acrylic fiber wastewater, can degrade long-chain alkanes and succinonitrile efficiently. Here we report the characterization of an indigenous plasmid pC1. The overall nucleotide sequence of pC1 consisted of 5841 bp. The five ORFs, encoding a DNA recombinase, replication protein (Rep(pC1)) and three proteins of unknown function, were predicted on pC1. The Rep(pC1) displayed its homology with the Rep of Rhodococcus large plasmid p33701, suggesting a theta type of replication. An Escherichia coli plasmid (containing the single rep(pC1) gene) propagated autonomously in low copy number in Nocardia or Rhodococcus, suggesting that rep(pC1) was an essential gene for plasmid replication. The plasmid (containing the single rep(pC1) gene) presented as inheritance unstable hints that other pC1 loci were required for the stable inheritance of plasmids. By comparison of the plasmid-borne Rep proteins, we classify Rhodococcus or Nocardia plasmids into four groups.