Phenotypic characterization of culturable marine luminous bacteria isolated from coastal waters of the southern Adriatic Sea (Otranto, Italy).

To determine the abundance and species composition of luminous bacteria in the coastal waters of the southern Adriatic Sea (Otranto, Italy), samples were collected from three sites affected by different degrees of anthropogenic pollution. A total of 116 strains of marine luminous bacteria were isolated and subjected to phenotypic characterization, which included 36 biochemical tests. Numerical analysis of the data revealed five clusters with > 86% similarity, which were readily identified as Photobacterium leiognathi, Vibrio fischeri, Vibrio harveyi, Vibrio splendidus biovar I, and Shewanella hanedai. The relative abundance of each species shows that culturable luminous bacteria in the monitored waters are composed mainly of V. harveyi (69.0%), followed by V. fischeri (13.8%) and P. leiognathi (12.1%). In addition, human activity appears to affect the total abundance of luminous bacteria but not the selection of individual species, since the frequencies of the bacteria were similar at all examined sites.