The goal of our project is to formulate an inexpensive and convenient method to help farmers identify bioavailable phosphate in the soil. Our school, Wisconsin Lutheran College, is located in Wisconsin in the Midwestern part of the U.S. In this part of the country, agriculture is one of the biggest industries in the state and the crops produced here go all over the world. Because we are within only a few miles of abundant farmland we have decided to engineer a soil sensor to gather the information needed to balance nutrient levels in soil and maximize crop growth. Additionally, there are numerous lakes and streams scattered across the state; thus, we want to minimize potential eutrophication.
Soil is an important aspect of plant quality and unhealthy soil can lead to inconsistency in crop yield and crop health. Phosphate is an important nutrient that plants need but there are some forms of phosphate in soil that the plant can’t use. The phosphate that plants can use is called bioavailable or inorganic phosphate. While there are several easy tests that can be done to measure the overall phosphate in soil, there are no chemical tests available to detect just the inorganic phosphate in soil. Therefore our soil sensor for bioavailable phosphate would be a novel method. Since the Escherichia coli (E. coli) in our sensor can only use the bioavailable phosphate, we do not have to worry about skewed results from other phosphates that are inaccessible to plants.
Our team has engineered the bla gene in E. coli to sense bioavailable phosphate in soil and provide a colorimetric readout of concentration. We aspire to be able to measure the concentration of phosphate using nutrient-specific promoters controlling the expression of Beta-lactamase. The bla gene was used as an indicator gene because beta-lactamase cleaves nitrocefin which produces a red color. We aim to provide laboratory service for agriculturists that is cheaper and has the ability to detect bioavailable phosphate in soil to aid in proper soil fertilization.
We are aiming to produce a standard curve of known phosphate concentrations that can be determined using a colorimetric analysis using a spectrophotometer. Then comparing soil samples that farmers would send into a lab equipped with our construct and protocol, the results could be compared to that standard curve enabling the phosphate concentration in the soil to be accurately determined.