Bacterial bioluminescence has mainly be studied in Vibrio species and its study has led to the discovery of quorum sensing. Indeed, in these strains, the production of light occurs when the cell density reaches a certain thereshold. Since then, bioluminescence has generally been considered as the reference mechanism for this phenomenon in these microorganisms. Photobacterium phosphoreum ANT-2200, a bioluminescent bacteria, has been isolated, by our group, from the NW Mediterranean Sea at 2200-m depth close to the ANTARES neutrino telescope. Its genome has been sequenced recently. In our lab, we have been interested in studying the bioluminescence in this Photobacterium strain through physiological and molecular approaches. The genetic organization of the lux operon in Photobacterium strains is completely different from the one in Vibrio species. Indeed, it lacks the genes luxI and luxR, the quorum sensing signature. Moreover, in Photobacterium, the operon coding for bioluminescence is longer and includes 4 more genes potentially coding for riboflavine synthesis, a luciferin precursor. Although bioluminescence control in Vibrio species has been thoroughly studied, almost nothing is known about the Photobacterium counterpart. Our aim is to correlate the gene expression, the bioluminescence production and the growth in P. phosphoreum ANT-2200 comparing various conditions of incubation such as in situ pressure and atmospheric pressure conditions.