Multiple Enzyme Analyzer (MEA): Steps toward the in situ detection of microbial community ectoenzyme activities

Stephanie A. Jaeger, Brian M. Gaas, Gary P. Klinkhammer, James W. Ammerman

Limnol. Oceanogr. Methods 7:716-729 (2009) | DOI: 10.4319/lom.2009.7.716

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.