Photomanipulation of antibiotic susceptibility and biofilm formation of Escherichia coli heterologously expressing photoactivated adenylyl cyclase.

A cyaA-deficient Escherichia coli strain was transformed by a plasmid carrying the gene for BsPAC, a photoactivated adenylyl cyclase identified from a Beggiatoa sp., and was subjected to an antibiotic susceptibility assay and biofilm formation assay under a light or dark condition. Cells expressing BsPAC that were incubated under blue light (470 nm) were more susceptible to fosfomycin, nalidixic acid and streptomycin than were cells incubated in the dark. Cells expressing BsPAC formed more biofilms when incubated under the light than did cells cultured in the dark. We concluded from these observations that it is possible to determine the importance of cAMP in antibiotic susceptibility and biofilm formation of E. coli by photomanipulating the cellular cAMP level by the use of BsPAC. A site-directed mutant of BsPAC in which Tyr7 was replaced by Phe functioned even in the dark, indicating that Tyr7 plays an important role in photoactivation of BsPAC. Results of mutational analysis of BsPAC should contribute to an understanding of the molecular basis for photoactivation of the protein.