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Abstract

The capability of microbes to use certain compounds can be examined by measuring ectoenzyme activities. These enzymes are found on or near the surface of a cell and hydrolyze large molecules to a smaller size, serving as a key first step in organic matter use. A new instrument is under development for high-resolution measurements of in situ ectoenzyme activity intended for use at coastal ocean observatories. This system, the Multiple Enzyme Analyzer (MEA), measures up to four different enzyme activities in flow-through channels by quantifying the fluorescence increase associated with substrate hydrolysis over time. A description of the MEA design, a comparison of MEA performance with laboratory fluorometers, an exploration of instrument and reagent stability, and results from a preliminary experiment in a seawater tank are addressed. These results demonstrate that the MEA is capable of detecting variable ectoenzyme activity in seawater. As microbes are major players in organic matter transformations in the aquatic environment, such a tool may assist in characterizing the rapid metabolic activities of microbial communities on both short-term (e.g., diurnal, tidal) and more extended time scales. *Corresponding author: E-mail: gaas@marine.rutgers.edu AcknowledgmentsWe thank all of the people who made this development project possible. Special thanks to the electrical and software engineer R. Morrison and machinist J. Simpkins at Oregon State University for their technical expertise, design feedback, and mechanical construction of circuit boards, pressure housing, modified endcap connectors, and other miscellaneous parts. Thanks to J. Sylvan at Rutgers University for helpful comments on procedures and analyses, and J. Stecher and A. Ungerer at Oregon State University for field and lab support. Also, thanks to our collaborator on this project, R. J. Chant, for discussions on field deployment issues. V. Singer and the chemists at Molecular Probes/Invitrogen deserve mention for conversations and suggestions on substrate stability. This work was funded by NSF Biocomplexity IDEA (DBI 0216154) to