general structural groups were differentiated. Plasmids from
different environments showed little similarity as determined
by RFLP’s. The plasmids were further-tested for similarity
to known plasmid incompatibility groups using inc/rep
probes (Couturier et al., 1988). Hybridization studies
showed no similarity between any of the twelve groups of
naturally occurring marine plasmids and the well
characterized plasmids often used in gene transfer studies.
This study shows the need to develop more
environmentally relevant plasmids and probes for the study
of conjugation in situ