Evidence for plasmid DNA in Alcaligenes faecalis

A 10.6 megadalton plasmid was isolated from a virulent strain (NC-D) of Alcaligenes faecalis. Virulence and antibiotic sensitivity of this strain were compared with those characteristics of a mutant plasmid-free derivative, strain NC-D1. Strain NC-D1 was avirulent and lacked the streptomycin and sulfonamide resistances of the parent strain.