Study of the response of a biofilm bacterial community to UV radiation

We have developed a bioluminescent whole-cell biosensor that can be incorpo rated into biofilm ecosystems. RM4440 is a Pseudomonas aeruginosa FRD1 deri vative that carries a plasmid-based recA-luxCDABE fusion. We immobilized RM 4440 in an alginate matrix to simulate a biofilm, and we studied its respon se to UV radiation damage. The biofilm showed a protective property by phys ical shielding against UV C, UV B, and UV A, Absorption of UV light by the alginate matrix translated into a higher survival rate than observed with p lanktonic cells at similar input flueuces, UV A was shown to be effectively blocked by the biofilm matrix and to have no detectable effects on cells c ontained in the biofilm. However, in the presence of photosensitizers (i.e. , psoralen), UV A was effective in inducing light production and cell death . RM4440 has proved to be a useful tool to study microbial communities in a noninvasive manner.