A POSSIBLE ROLE FOR PLASMIDS IN MEDIATING THE CELL-CELL PROXIMITY REQUIRED FOR GENE FLUX

One of the major requirements for successful gene flux is a close prox imity between participating organisms. In previous articles, we have p roposed that plasmids act as powerful vehicles transporting genes coll ected by integration and transposition, mainly via the process of conj ugation. However, in addition to conjugation, there are other processe s, also mediated by plasmids, in which different cells come into very close contact with each other, such as symbiosis and the formation of multi-specific cellular communities. There is evidence that suggests t hat such intimate associations between cells may facilitate gene trans fer events, even between distantly related organisms. Examples of symb iotic endosymbiotic, and parasitic associations provide evidence in su pport of the role of plasmids in bridging the genetic gap between spec ies. In this purely theoretical article we attempt to conceptualize ex isting data on this subject, provide new insights and present testable predictions on how plasmids may facilitate gene flux by bringing cell s together. (C) 1996 Academic Press Limited.