Abstract
A polyphasic study was performed to determine the taxonomic position of two Aeromonas strains, 665N and 868ET, isolated from bivalve molluscs, that could not be identified at the species level in a previous numerical taxonomy study. The DNA G+C content of these isolates was 62.3 and 62.6 mol%, respectively. Sequence analysis of the 16S rRNA gene showed that the two new strains were closely related to members of the genus Aeromonas. Fluorescence amplified fragment length polymorphism fingerprinting revealed that strains 665N and 868ET clustered together with a similarity of 78 % but did not cluster with any of the Aeromonas genomospecies. DNADNA hybridization experiments revealed a high level of relatedness between the two new isolates (76 %) but low levels of relatedness between these and phylogenetically most closely related Aeromonas genomospecies (3044 %). Useful tests for the phenotypic differentiation of strains 665N and 868ET from other mesophilic Aeromonas species included those for gas from glucose, lysine decarboxylase, VogesProskauer reaction, acid from L-arabinose, hydrolysis of aesculin and utilization of L-lactate. On the basis of genotypic and phenotypic evidence, strains 665N and 868ET are considered to represent a novel species of the genus Aeromonas, for which the name Aeromonas bivalvium sp. nov. is proposed. The type strain is 868ET (=CECT 7113T=LMG 23376T).