The incompatibility reactions of a group of 90 R plasmids, isolated from the fecal
Escherichia coli
of calves, pigs, and chickens, have been determined against reference plasmids of the incompatibility groups F
11
, I, N, P, and W. Twenty plasmids belonged to incompatibility groups F
11
, I, N, or P. Forty-nine plasmids were compatible with all of the five reference plasmids. Eight plasmids exhibited marked incompatibility with representatives of two or more of the above groups, whereas two strains showed incompatibility reactions consistent with the coexistence of two compatible plasmids. In addition, 19 plasmids remain untyped because they showed intermediate reactions with one or more reference plasmids.
From a group of naturally occurring antibiotic resistance plasmids, a number of plasmids were identified which were incompatible with members of incompatibility group P and also incompatibility group Ia or Iy. These plasmids also exhibited strong entry exclusion with members of group P only and showed a host range which resembled that of plasmids of group I rather than those of group P. Segregants of a number of these plasmids appeared to have lost some of the incompatibility and/or surface exclusion functions. Studies of nucleic acid homology indicated that these plasmids were very similar to one another. They exhibited 15 to 20% nucleic acid homology with representatives of the la and Iy groups, yet showed less than 2% homology with the group P plasmid RP4.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.