Dimethylsulfoxide (DMSO) reduction: a new approach to determine microbial activity in freshwater sediments

Abstract

A new method, adapted from a technique applied in soil microbiology, is described to determine microbial activity in freshwater sediments. Based on the enzymatic reduction of dimethylsulfoxide (DMSO) to dimethylsulfide (DMS) by microorganisms, the dimethylsulfoxide (DMSO) reduction method allows the measurement of respiratory activity in freshwater sediment biofilms. In these sets of experiments, DMSO reduction was shown to be only biologically mediated. DMS production is measured by gas chromatography. A multiple assay comparison resulted in significant correlations between the DMSO reduction activity and the electron transport system (ETS) activity ( r=0.81, p<0.001), the ectoenzymatic (α-glucosidase) activity ( r=0.70, p<0.01) and the incorporation of [methyl- 3H]thymidine into bacterial DNA ( r=0.58, p<0.05), respectively. Because of its high sensitivity, short experimental duration, and small sediment sample requirements, this method allows a quick and extensive measurement under laboratory or field conditions.