Determination of the Substrates for Sulphate-reducing Bacteria within Marine and Esturaine Sediments with Different Rates of Sulphate Reduction

Abstract

The substrates used by sulphate-reducing bacteria in sediment slurries from Loch Eil, Loch Etive and the Tay estuary were determined by selectively inhibiting sulphate reduction with 20 mM-molybdate and measuring the resultant substrate accumulation. Substrate accumulation was linear after molybdate addition, and the rate of accumulation closely matched sulphate reduction rates, indicating that metabolic pathways other than those specifically involving sulphate reduction were not affected by the inhibitor. In sediments from all three sites acetate was a major substrate, although the percentage of sulphate reduced due to acetate oxidation varied considerably among the sites (Tay estuary, 35%; Loch Eil, 64%; Loch Etive, 100%). In addition to acetate, 17 individual substrates were shown to be involved in sulphate reduction to varying extents in the Tay estuary and Loch Eil sediments; these included lactate, H2, propionate, iso-and n-butyrate, iso-and n-valerate, 2-methylbutyrate and amino acids. At both sites propionate accounted for between 6 and 12% of sulphate reduction. Butyrate (n-and iso-), iso-valerate and 2-methylbutyrate were of approximately equal importance at each site and together accounted for 13 and 11 %, respectively, of the sulphate reduction in the Tay estuary and Loch Eil sediments. Lactate was only important in the Tay estuary sediments, where it accounted for 43 % of sulphate reduction. The rate of accumulation of amino acids was greatest in the Tay estuary sediments, but the contribution of amino acids to sulphate reduction was higher in the Loch Eil(9 %) than in the Tay estuary sediments (2 %). Of the 21 individual amino acids that were measured there was a linear increase in nine; the most important of these were serine, glutamate and arginine. In general, when sulphate reduction rates were high the substrates for this process were more varied than when rates were low. Combining the results of two experiments and assuming complete degradation of the individual substrates, almost all the sulphate reduction could be accounted for at each site (Tay estuary, 101 %; Loch Eil, 98%; Loch Etive, > 100%).

Three manganese oxide-rich marine sediments harbor similar communities of acetate-oxidizing manganese-reducing bacteria

“…Acetate has been shown previously to be the most important volatile fatty acid in terms of concentration and turnover, and identified as important substrate for anaerobic terminal electron-accepting processes in marine sediments (Sørensen et al, 1981;Parkes et al, 1989;Fukui et al, 1997;Finke et al, 2007). The addition of 170 mM acetate per day to our incubations exceeded these low concentrations of acetate in the control without acetate and stimulated its mineralization (Figures 1 and 3).…”

“…As acetate is an important electron donor for microbial iron and sulfate reduction in marine sediments (Sørensen et al, 1981;Parkes et al, 1989;Fukui et al, 1997;Finke et al, 2007), we chose ( 13 C-labeled) acetate as the substrate for RNA-SIP studies and MPN counts of manganese reducers.…”

Influence of invasiveAcer negundoleaf litter on benthic microbial abundance and activity in the littoral zone of a temperate river in Lithuania

“…During the summer-autumn period in bottom sediments of leaf litter accumulation zones under sufficient sulfate concentration, the activity of sulfate reducing bacteria was promoted due to accumulation of labile organic matter and partly because of temperature. A higher abundance of heterotrophic bacteria determined in bottom sediments of leaf litter accumulation zone in its turn could produce a greater variety of substrates for sulfate reducing bacteria (Parkes et al, 1989) and intensify SR process. In litter accumulation zone, in spite of the oxidative conditions in the near-bottom water, the abundance and activity of SRB were similar to those in profundal zone of stratified lakes with anaerobic hypolimnion (Krevs and Kucinskiene, 2012).…”

Mineralization of organic nitrogen and carbon (fish food) added to anoxic sediment microcosms: role of sulphate reduction

“…However, recent investigations have shown a probable involvement (Burdige 1989, 1991, Parkes et al 1989. Smith & Klug (1981) reported that sulphate reduction accounted for 85 % of the dissolved free amino acid (DFAA) oxidation in lake sediment.…”