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?"
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.