Design of a new biosensor for algal H sub(2 production based on the H) sub(2)-sensing system of Rhodobacter capsulatus

The H sub(2)sensing system of Rhodobacter capsulatus was engineered to elicit a fluorescent response upon cell exposure to H sub(2).The system is surprisingly sensitive to H sub(2)and is capable of detecting levels of H sub(2)down to 200 pM in solution, which approximates the background concentration of H sub(2)in water exposed to the earth's atmosphere. The response was roughly linear between 0.3 and 300 ppm V of added headspace H sub(2) and gave a K sub(app) of 142 nM H sub(2), when cells were grown anaerobically for 12 h in the presence of H sub(2). Hydrogen-sensing R. capsulatus cells were grown fermentatively in the dark in co-culture with Chlamydomonas reinhardtii on microtiter plates and the bacteria fluoresced in proportion to H sub(2) production by the algae. This represents a promising, high-throughput assay for H sub(2) production in algal libraries, and an enhanced capability for developing H sub(2) as a clean and renewable fuel.