Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2005
Publication Date: 2/2/2006
Citation: Sadowsky, M.J., Koskinen, W.C., Seebinger, J., Barber, B.L., Kandeler, E. 2006. Automated robotic assay of alkaline phosphomonoesterase activity in soils. Soil Science Society of America Journal. 70:378-381.
Interpretive Summary: Many key biochemical reactions in soils have been shown to be due to microbial enzymes, which catalyze the transformation of both organic and inorganic compounds. These enzymes are of up-most importance for the biogeochemical cycling of elements and the mineralization and immobilization of biogenic materials. The phosphatase enzymes are important in phosphorus-cycling and allow for the growth of both plants and microorganisms in the biosphere. The activities of phosphatases are influenced by various soil properties, soil organism interactions, vegetation cover, leachate inputs and the presence of inhibitors or activators. Phosphomonoesterase activity has often been used to provide estimates of changes in soil quality and has been shown to be related to soil organic matter content. Determination of phosphatase activity in soils often relies on the use of colorimetric substrates or reactions, and assays generally require long incubation times and multiple steps, thereby limiting throughput. In order to analyze the large number of samples generated in field and laboratory experiments with high precision and accuracy, it is often necessary to automate analytical procedures. This is especially true of "soil quality" and landscape-level studies where large numbers of samples are often collected. In this study we developed and evaluated an automated procedure to quantify phosphomonoesterase activity in soils. The procedure utilized a commercially-available laboratory robotic system and results were compared to those obtained using manual procedures. Our results indicate that a robotic system can be adapted and used to automate the analysis of enzyme activities in soils. The automated method we used produced nearly equivalent results of phosphomonoesterase activity as compared with the manual method. However, the precision of the robotic method was superior to that obtained manually. This system will most likely have great utility in studies of "soil quality" and "soil health" and in landscape-level studies where large numbers of samples are often collected.
Technical Abstract: Phosphorus is a major limiting nutrient in most ecosystems and its cycling and use is dependent upon plant and microbiologically-derived phosphatase enzymes. Measurements of enzymes in soil systems are often time consuming and labor intensive. In this study we used a Zymark XP laboratory robotic system for soil handling, solvent addition and exchange, filtration, incubation, reagent addition, and final sample preparation. Phosphomonoesterase activity was measured using phenyl phosphate as substrate and samples were analyzed using a 96-well microplate reader. Results indicated that our robotic system was capable of effectively measuring phosphomonoesterase activity in soils differing in physical and chemical characteristics. Results obtained using manual and robotic procedures were comparable in accuracy and precision. The robotic system decreased labor associated with this assay by about a factor of 10 relative to the manual system, with considerable savings on reagent costs and labor.