R factors from Providence

Of more than 100 R factors transferred from naturally occurring Providence strains, approximately 60 % belonged to the A-C compatibility complex. Plasmids of groups F 1 , J, N, P and X, and the prototype of a new group G were also transferred. The Providence R factor set differs from those of Proteus rettgeri and P. morganii most strikingly in the abundance of plasmids of the A-C group and the infrequency of N group plasmids.