CLASSIFICATION OF CITROBACTERIA BY DNA HYBRIDIZATION - DESIGNATION OFCITROBACTER-FARMERI SP-NOV, CITROBACTER-YOUNGAE SP-NOV, CITROBACTER-BRAAKII SP-NOV, CITROBACTER-WERKMANII SP-NOV, CITROBACTER-SEDLAKII SP-NOV, AND 3 UNNAMED CITROBACTER GENOMOSPECIES

DNA relatedness studies (hydroxyapatite method) were done on 112 strai ns of citrobacteria. By using the recommended definition of a genomosp ecies 11 genomospecies were identified in the genus Citrobacter. These genomospecies were separable by their biochemical profiles. Citrobact er koseri (Citrobacter diversus) and Citrobacter amalonaticus proved t o be homogeneous species, as previously described. C. amalonaticus bio group 1, as described by Farmer et al. (J. Clin. Microbiol. 21:46-76, 1985), was shown to be a separate homogeneous species, which was named Citrobacter farmeri sp. nov. The Citrobacter freundii complex was qui te heterogeneous. C.freundii sensu stricto, as represented by the type strain, contained only 9 of 66 strains in this complex. The remaining 57 strains were members of seven genomospecies. Genomospecies 5, cont aining 21 strains, was named Citrobacter youngae sp. nov. Genomospecie s 6, containing 15 strains, was named Citrobacter braakii sp. nov. Gen omospecies 7 and 8, each containing six strains, were named Citrobacte r werkmanii sp. nov. and Citrobacter sedlakii sp. nov., respectively. Genomospecies 9, 10, and 11, each containing three strains, were not n amed.