Phosphate is a limiting nutrient for many types of aquatic microorganisms. In unpolluted natural waters phosphate concentration is usually below 1.5 uM. When excess phosphate is present, overgrowth of indigenous organisms depletes oxygen in the water and obstructs light from penetrating the surface. The result is eutrophication, a type of pollution caused by excess nutrients, that disrupts aquatic ecosystems. Managing eutrophication requires the ability to monitor it. Unfortunately, the available methods of phosphate monitoring are time intensive, require specialized equipment and trained personnel, and produce dangerous wastes. Additionally, these methods are either colorimetric and are inaccurate for turbid water samples often found in lakes and streams, or they are total digestion methods which measure total phosphorus content, some of which would not otherwise be bioavailable to contribute to organism overgrowth. This study explores the possibility of using yeast CO2 output as a metric for bioavailable phosphate concentration in water. Yeast growth has a linear relationship with phosphate concentration between 1-60 uM phosphate. The negative impact of eutrophication becomes apparent at around 3 uM. Accordingly, yeast CO2 output should be able to report the concentration of phosphate in a given water sample. In this study yeast were grown in septum capped tubes and the pressure measured at 24 and 48 hour intervals to determine the relationship between phosphate concentration and CO2 pressure. Yeast were also grown in media with varying concentrations of phosphate and their growth measured by optical density. The results of this method were compared to a soluble reactive phosphate assay and a sulfuric acid digestion.

Developing a yeast biosensor for measuring phosphate in natural waters

255th National Meeting (2018)

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