Polynucleotide Sequence Relatedness Among Motile Aeromonas Species

Relatedness among 55 motile Aeromonas strains was assessed by determining the extent of reassociation in heterologous DNA preparations. S1 nuclease and diethylaminoethyl-cellulose filters were used to separate reassociated nucleotide sequences from nonreassociated sequences and to determine the thermal stability of related nucleotide sequences. The motile aeromonads would presently consist of three species: A. hydrophila (type strain ATCC 7966), A. caviae (type strain ATCC 15468), and A. sobria (type strain CIP 7433). These three species are clearly separated on the basis of both biochemical characteristics and similarities in DNA. Each of these three species contains more than one hybridization group: three groups in A. hydrophila ; two groups in A. caviae ; and at least two groups in A. sobria . DNA hybridization groups are biochemically similar within each species. Any decision to delineate species in terms of DNA hybridization groups must await a phenotypic basis for their separation.