Aeromonas bivalvium sp. nov., isolated from bivalve molluscs

Departament de Microbiologia i Parasitologia Sanitàries, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII s/n, 08028 Barcelona, Spain Correspondence J. Gaspar Lorén jgloren{at}ub.edu A polyphasic study was performed to determine the taxonomic position of two Aeromonas strains, 665N and 868E T , 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 868E T clustered together with a similarity of 78 % but did not cluster with any of the Aeromonas genomospecies. DNA–DNA 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 (30–44 %). Useful tests for the phenotypic differentiation of strains 665N and 868E T from other mesophilic Aeromonas species included those for gas from glucose, lysine decarboxylase, Voges–Proskauer reaction, acid from L -arabinose, hydrolysis of aesculin and utilization of L -lactate. On the basis of genotypic and phenotypic evidence, strains 665N and 868E T 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 868E T (=CECT 7113 T =LMG 23376 T ). Abbreviations: FAFLP, fluorescence amplified fragment length polymorphism; HG, hybridization group The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains 868E T and 665N are DQ504429 and DQ504430 , respectively. A table giving levels of DNA–DNA hybridization between strains 868E T and 665N and strains of phylogenetically related Aeromonas species is available as supplementary material in IJSEM Online.