Construction and Characterization of a Phosphate Biosensor.

Excess phosphate in the environment has the potential to accelerate eutrophication of lakes which has environmental as well as economical effects.  Agronomic soil test P methods that are currently used approximate bioavailability through chemical extraction.  In an effort to development an assay to directly measure bioavailable phosphate in samples, we propose to develop a microbial phosphate biosensor by taking advantage of the phosphate regulated tag and tua operons of Bacillus subtilis. The bacteria naturally regulates cell wall composition in response to available phosphate.  We utilize this regulation system along with a green fluorescent protein gene. B. subtilis 168 transformants were characterized on the basis of fluorescence in the presence of varying concentrations of phosphate in order to evaluate their effectiveness as a biosensor. Fluorescence was detected in the cultures, and a correlation between phosphate and fluorescence is observed.  This correlation can make it possible to use the reporting by this strain of bacteria to determine the bioavailable phosphate in soils or water.