Luminous bacteria in the deep-sea waters near the ANTARES underwater neutrino telescope (Mediterranean Sea)

Abstract

Marine luminous deep-sea bacteria may represent a potential source of signal perturbation for the ANTARES neutrino telescope installed between 2000 and 2475 m depth in the Mediterranean Sea. Using the CARD-FISH method, we have estimated the relative abundances of total prokaryotes of Bacteria, γ -proteobacteria and Vibrinoceae (domain, class and family affiliation of marine luminous bacteria, respectively) through the water column close to the ANTARES site. At 2200 m depth, Vibrionaceae appeared to be far from negligible, representing 40% of γ -proteobacteria, 25% of Bacteria and 9% of the total DAPI-stained cells, while Bacteria and Archaea represented 35% each. Furthermore, during a high luminous background period detected by the neutrino telescope, we isolated, from a 2200 m depth sample, a piezophilic luminous bacterium, phylogenetically determined as Photobacterium phosphoreum strain ANT-2200. We have used this strain to investigate the effect of hydrostatic pressure on bioluminescence by developing a new high-pressure apparatus. First assays showed that the bioluminescence intensity of Photobacterium phosphoreum strain ANT-2200 was 5 times higher at 22 MPa than at 0.1 MPa (atmospheric pressure).