Luminescent bacteria from a brackish environment

Bioluminescent bacteria are ubiquitous in the marine environment and are also found in freshwater, brackish water, and soil environments. Luminous bacteria have been observed in marine environment living as planktonic or free-living, saprophytic, light organandgut-symbiotic, andpathogenic. Bioluminescent bacteria are used in biotechnological applications, in tests of water quality and toxicity, and as biosensors in environmental biomonitoring. Although phenotypic characterization is considered a valuable method in taxonomic investigations, it is time-consuming and often can be compromised by bacterial variability in the responses to biochemical tests. Bioluminescent bacteria were isolated from water samples of the meromictic Faro lake (Messina, Italy) and characterised phenotypically and genotypically by cultural and molecular assays. All strains were members of the family Vibrionaceae. Forty-four bioluminescent isolateswerepre-screenedbyAmplifiedRibosomalDNA Restriction Analysis (ARDRA) with five enzymes (EcoRI, DdeI, HhaI, HinfI, and RsaI) to clusterise them into homology groups before 16S rDNA gene sequencing. Culturable luminous bacteria in the water of Faro Lake were dominated by Vibrio harveyi and Photobacterium phosphoreum. For analysis of 16S rDNA gene sequences, 29 strains were selected as representative strains of the each ARDRA group. Phylogenetic analysis showed that eight strains were closely (98-99% sequence similarity) relatedwithV. harveyi, and other eight strainswere similar (98-99%) to different luminescent Vibrio spp. Four strains were affiliated (98-99%) with Photobacterium phosphoreum. Nine strains, possessing sequence similarity levels below97%with yet described species, could be considered new bacterial species. Five strains remained luminescent after one year of subculturing. The applications in biotechnological assays of the present luminous bacteria remain to be evaluated.