DNA relatedness among species of Enterobacter and Serratia

Abstract

Species of Enterobacter and Serratia were examined for DNA relatedness to Klebsielleae, to atypical erwiniae and to other members of Enterobacteriaceae. DNA hybridization and then hydroxyapatite chromatography was the technique used to assess relatedness. Strains of E. cloacae formed 2 separate hybridization groups that correlate with the presence or absence of yellow pigment. Pigmented E. cloacae were 75-100% related, but they were only 40-50% related to unpigmented strains. Unpigmented strains were 70% or more related but were only 40-50% related to the pigmented strains. Both pigmented and unpigmented E. cloacae were 40-45% related to E. aerogenes and klebsiellae, and 20-30% related to Serratia spp. and E. hafniae. Atypical erwiniae were highly related to E. cloacae. S. marcescens strains formed 1 closely related group. S. liquefaciens strains formed a single, more disperse, relatedness group, as did isolates of S. rubidaea. These species were related throughout a substantial portion of their genomes. A group of lysine-positive Citrobacter-like strains were 40-50% related to Serratia spp. Only 4 E. hafniae strains were tested. Of these, 2 were highly related, while the other 2 were only 50% related to the reference strain. E. hafniae was only 15-20% related to other Enterobacteriaceae.