Determination of Microbial Activity in Marine Sediments by Resazurin Reduction

Abstract

Abstract A simple method is presented to evaluate microbial activity in aquatic sediments. The method is based on resazurin reduction by microbial electron transport chains and reduced chemical compounds present in the sample. The addition of m-cresol, which inhibits enzyme activity, allows one to measure microbial metabolism by difference. Small aliquots of sediment (about 1 g FW) are incubated at 20°C with resazurin solution, with and without m-cresol. The sample is then filtered and the unreduced resazurin is measured at 600 nm. Testing the method with a bacterial suspension gave a resazurin reduction of 89 μg/h/109 cells. In a few marine coastal sediment samples, the resazurin reduction in aerobic conditions was in the range of 0.31 to 219.3 μg/h/g DW, which is equivalent to an oxygen consumption of 0.02 to 15.32 μg/h/g DW.