Polynucleotide Sequence Divergence in the Genus Citrobacter

Summary: Deoxyribonucleic acid reassociation was used to assess divergence in species of Citrobacter and Citrobacter-like strains. Typical strains of Citrobacter freundii were highly related. Antigenically atypical strains and most biochemically atypical strains showed a lower, but species level, of relatedness to typical C. freundii. Four additional relatedness groups were detected. One of these corresponded to C. diversus, including Levinea malonatica. A second contained L. amalonatica. A third group contained two indole+ strains which exhibited only 40 to 50 % relatedness to other groups of Citrobacter. The fourth group contained H2S −, lysine+ organisms that are more closely related to Serratia than to Citrobacter.