1Biotechnology Research Center, The University of Tokyo
It is well-known that conjugative plasmid is an important agent in rapid adaptation of bacterial strains to some kind of environmental condition. In such evolutional process, the modification of host cell physiology by plasmid carriage and the survival of the resultant bacterial strains under in situ conditions generally occur. To understand the behavior of plasmid itself and its host in natural environmental conditions, it is quite important to clarify how plasmids affect the host cell physiology, and how much influence the modified host cell physiology has on host cell survival. We have investigated on the carbazole degradation system of Pseudomonas strains. Through the studies, the IncP-7 conjugative plasmid pCAR1 was found to play a key role in distribution of carbazole degradative capacity in pseudomonads. To understand the behavior of pCAR1-carrying Pseudomonas strains, we comprehensively surveyed the pCAR1 effects on host Pseudomonas strains by transcriptome and phenotype scanning analyses. Then, in vitro evolution experiments followed by the genetic characterization of evolved strains revealed that the pCAR1 cost to host P. putida cells is mainly caused by constitutive expression of some host chromosomal genes induced by pCAR1 carriage and expression of car genes from pCAR1.
keywords:plasmid,conjugation,horizontal gene transfer,evolution,fitness