Stability of IncQ and IncP-1 vector plasmids in Rhizobium spp.

Abstract The stability of cloning vectors belonging to incompatibility groups P and Q was investigated in Rhizobium meliloti and Bradyrhizobium japonicum . The IncQ plasmids pKT230 and pKT231 could not be established in B. japonicum CJ1. These plasmids were readily transferred into R. meliloti CM2. Under non-selective aerobic growth conditions, plasmid pKT231 segregated from R. meliloti CM2 at a rate of 2% per generation compared to a rate of B. japonicum was estimated to be 10% per generation which is significantly higher than the rate observed under aerobic growth conditions. The implications of these findings are discussed.