Characterization of microbial activities in marine mudflat sediment using FDA hydrolase analysis

A method based on fluorescence spectrometry was developed to detect the microbial activities in marine mudflat sediment, where is characterized by high salinity, complex organic compounds and low microbial biomass. This paper optimized the sample extracts, the detection equipment for reaction products, the pretreatment methods, and the experimental conditions. The optimal procedure is described as following. Fresh sediment was first extracted with sterilized and aged seawater, followed by the addition of Tween-80 solution, then uniformly dispersed by thorough oscillating, and kept steady for precipitation. After filtration through a sterilized membrane (1. 2 microm, sterilized in boiling water repeatedly) , the supernatant was supplemented with an appropriate amount of FDA solution and allowed to react in dark for 180 min at temperature ranged 25-30 degrees C . The reaction was terminated by the addition of acetone, and the fluorescence intensity of the reaction mixture was measured within 25 min using a molecular fluorescence photometer at an excitation wavelength of 488 nm and an emission wavelength of 530 nm, and the detection range of this method (dry weight) was 3.0 x10(3)-1. 1 x 10(5) ind.g-1. The microbial activity was reported as fluorescence content in per unit sediment mass (microg.g-1, dry weight).