Application and Validation of a Solid Phase Bioassay to Measure Bioavailable Soil Phosphorus

Abstract

Phosphorus (P) is an essential element needed by all living organism. Although P may be present in high concentration in soil, it is mostly not in plant available form. There is a need to measure bioavailable P. A microbial biosensor could provide an approach to determine the bioavailable P in soil. It has been shown that a P biosensor worked in aqueous systems. Yet the application and validation of a solid phase contact device to measure the response of luminescence marked Escherichia coli MG1655 to phosphate in a complex solid phase-like soil has not been done before. To test the applicability of such a biosensor in soil, four different pH agricultural soils were investigated chemically and with the biosensor. The expression of bioluminescence by the bioreporter (i.e. an induction by the presence of phosphate in a starvation system) enabled quantification of bioavailability in soil with increasing pH. Results from the experiments showed a correlation between the luminescence pattern and phosphate levels as determined by standard chemical procedure. It was indicated that a biological P sensor may serve as a tool for assessing phosphate bioavailability.

Keywords: Bioavailable, Bioreporter, Phosphorus, Escherichia cola, applicability