The ecology and physiology of anaerobic bacteria isolated from Tay Estuary sediments

Abstract

SynopsisThe spatial distribution of different physiological groups of bacteria (nitrifying bacteria, nitrate respiring bacteria, clostridia, phototrophic bacteria, sulphate reducing bacteria and methanogens) has been determined in the surface sediments of Kingoodie Bay in the Tay Estuary. The overall distribution of the different microbial populations is largely dependent upon the presence or absence of O2, i.e. populations of obligate aerobes were greater at the surface where O2was present, but with increasing depth and hence anoxia were successively displaced by populations of facultative and then strictly anaerobic bacteria. Thus, maximum rates of nitrification, an oxygen dependent process, were recorded in the 0–10 mm depth horizon (098μg of N per g dry weight of sediment per day) while nitrate respiration rates were maximal in the 10–20 mm horizon (2.92μg N per g dry weight of sediment per day). Dissimilatory sulphate reduction at 20–30 mm depth (102.1 n mol SO42reduced g dry weight sediment-1.d-1). Methanogenesis was similarly recorded at all depths investigated but higher rates were recorded at 40–50 mm depth (22.64 n mol CH4produced g dry weight sediment-1.d-1). These data are discussed in relation to the physico-chemical factors which arc generated in these estuarine sediments and which not only govern the spatial organisation of individual microbial populations but also modulate their metabolic activities.