Conjugative Selectivity of Plasmids Is Affected by Coexisting Recipient Candidates.

Understanding the mechanisms underlying plasmid behavior under conditions of various environments is important to predict the fate of plasmids in nature. Most previous studies on plasmid transfer employed two strains: one as a donor and the other as a recipient. However, in natural environments, there are usually different recipient cells available to which plasmid can be transferred.

Divalent cations increase the conjugation efficiency of the incompatibility P-7 group plasmid pCAR1 among different Pseudomonas hosts.

The incompatibility (Inc) P-7 group plasmid pCAR1 can be efficiently transferred among bacteria in artificial microcosms in the presence of divalent cations Ca and Mg. One-on-one mating assays between Pseudomonas strains with different plasmids showed that the promotion of conjugation efficiency by divalent cations was exhibited in other plasmids, including pB10 and NAH7; however, this effect was larger in IncP-7 plasmids. The impact on pCAR1 conjugation differed according to donor-recipient pairs, and conjugation efficiency promotion was clearly detected between the donors P.

Comparisons of the transferability of plasmids pCAR1, pB10, R388, and NAH7 among Pseudomonas putida at different cell densities.

The transferability of plasmids pCAR1, pB10, R388, and NAH7 was compared using the same donor-recipient system at different cell density combinations in liquid or on a solid surface. pCAR1 was efficiently transferred in liquid, whereas the other plasmids were preferentially transferred on a solid surface. Difference of liquid or solid affected the transfer frequency especially at lower cell densities.