Go for the link below, you will find an article on "How do marine bacteria produce light, why are they luminescent, and can we employ bacterial bioluminescence in aquatic biotechnology?"
www.biology-online.org/articles/marine_bacteria_produce_light/abstract.html
From this article :
> The question remains whether quorum sensing regulation of bacterial luminescence is a kind of a ‘social behaviour’ in which cells ‘predict’ the possibility of increased mutagenesis where conditions allow for efficient metabolism leading to extensive bacterial growth. Such conditions may cause the appearance of large quantities of metabolites, including mutagenic agents. Thus, one could speculate that enhanced light emission at a high cell density may ensure more efficient DNA repair in response to potentially increased concentrations of mutagens. Alternatively, quorum sensing may be needed for another role of bacterial bioluminescence, besides stimulation of photoreactivation.