Biodiversity and biotechnological potential of Luminescent bacteria associated with some Mediterranean deep-sea species

Bioluminescent marine bacteria are a fascinating group of microorganisms that possess the unique ability to emit light. This phenomenon, known as bioluminescence, has captured the attention of scientists and researchers due to its intriguing biological and ecological implications. Bioluminescent bacteria are found abundantly in various marine environments, including surface waters, deep-sea regions, and symbiotic associations. While extensive research has been conducted on bioluminescent bacteria from well-known organisms, the investigation of such bacteria in rare deep-sea species remains limited. The study was aimed at assessing the presence and taxonomic biodiversity of bioluminescent bacterial communities in deep-sea species and evaluating their potential use in biotechnology. A dual approach was employed to study the cultivable luminescent bacteria and the total bacterial communities associated with deep-sea species. Overall, 26 specimens of three different deep-sea fish (Coelorinchus caelorhincus , Hymenocephalus italicus , Nezumia sclerorhynchus), three individuals of the cephalopod Heteroteuthis dispar and one zoanthid, Zibrowius primnoidus were collected in the Mediterranean Sea. The specimens were used to attempt the isolation of luminescent bacteria from the respective light organ, and the taxonomic identification of associated microbial communities. The isolation of bioluminescent isolates was carried out on glycerol-supplemented medium (Sea Water Complete, SWC), while the total bacterial community characterization was performed by applying next generation techniques. A total of 29 strains were isolated and then phylogenetically characterized by amplification and sequencing of 16S rRNA gene. The presence of bioluminescent bacteria was ensured by checking the presence of luminescent taxa in the total bacterial communities associated with the target species. In addition the biotechnological potential of isolates was investigated by performing different screening procedures, including the production of specific enzymes (.e. esterase and lipase), the extracellular polymeric substance production, heavy metal toxicity tolerance and ability to degrade organic contaminants (biphenyls and pesticides). In conclusion, this study unveils the presence of bioluminescent bacteria within deep-sea species and shows the promising potential of these strains in the biotechnological field. Future research should focus on the specific mechanisms involved in their bioluminescence and biotechnological interest.