Polyphasic approach to the characterisation of marine luminous bacteria

Fifteen luminous bacterial strains were isolated from the Tyrrhenian Sea co astal waters off northeastern Sicily and characterised by a combination of phenotypic and molecular tests in order to identify them and to determine t heir intraspecific genetic variability. Five luminous type strains, Vibrio splendidus NCIMB 1, Tr. harveyi NCIMB 1280, V. fischeri NCIMB 1281, Tr. ori entalis NCIMB 2195 and Photobacterium leiognathi NCIMB 2193, were used as r eference. On the basis of their phenotypic characters, the isolates were as signed to the family Vibrionaceae and all were related to the V. harveyi re ference strain. Amplified 16S ribosomal DNA restriction analysis (ARDRA) en abled the strains to be subdivided into three groups, two of which exhibite d the same restriction pattern as the two reference strains, V. harveyi and V. splendidus. Comparison of the full 16S rDNA sequence and of a 100-bp hi ghly variable 16S rDNA region (selected as a 'signature' sequence for the l uminous bacteria) confirmed ARDRA data and suggested that the strains of th e third group could be considered a subspecies of V. harveyi or a tyrrhenia n biovar, different from the other reference strains whose 16S rDNAs have a lready been sequenced. Random amplified polymorphic DNA (RAPD) fingerprinti ng and analysis of plasmid content suggested a high degree of intraspecific genetic variability within the largest ARDRA group. Data obtained suggest that the ARDRA method and the sequencing of the 16S rDNA signature region c ould be a powerful tool for a rapid identification of marine luminous bacte ria. (C) Elsevier, Paris.