Oxidation of short-chain fatty acids by sulfate-reducing bacteria in freshwater and in marine sediments

Abstract

Colony counts of acetate-, propionate- and L-lactate-oxidizing sulfate-reducing bacteria in marine sediments were made. The vertical distribution of these organisms were equal for the three types considered. The highest numbers were found just beneath the border of aerobic and anaerobic layers. Anaerobic mineralization of acetate, propionate and L-lactate was studied in the presence and in the absence of sulfate. In freshwater and in marine sediments, acetate and propionate were oxidized completely with concomitant reduction of sulfate. L-Lactate was always fermented. Lactate-oxidizing, sulfate-reducing bacteria could only be isolated from marine sediments, they belonged to the genus Desulfobacter and oxidized only acetate and ethanol by sulfate reduction. Propionate-oxidizing, sulfate-reducing bacteria belonged to the genus Desulfobulbus. They were isolated from freshwater as well as from marine sediments and showed a relatively large range of usable substrates: hydrogen, formate, propionate, L-lactate and ethanol were oxidized with concomitant sulfate reduction. L-Lactate and pyruvate could be fermented by most of the isolated strains.

Model for the distribution of sulfate reduction and methanogenesis in freshwater sediments

“…data). The metabolism of these fermentation products by sulfate-reducers has also been documented in the sulfate-reducing zone of marine sediments (S0-RENSEN et aI., 1981;LAANBROEK and PFENNIG, 1981;BALSA and NEDWELL, 1982;CHRISTENSEN, 1984;WINFREY and WARD, 1983;BANA T and NEDWELL, 1983;BANA T et aI., 1983;OREMLAND and TAYWR, 1978;ABRAM and NEDWELL, 1978). Although lactate is sometimes considered to be an important substrate for sulfate reducers, measurements of the rate of lactate production in sediments and other anaerobic ecosystems indicate that the fermentation of organic matter to lactate is minor when H2 is maintained at low partial pressures by methanogens or sulfate reducers and references therein).…”

Anaerobic Metabolism: Linkages to Trace Gases and Aerobic Processes

“…Enumerations of bacteria using MPN methods supplemented with specific substrates for SO|~-reducing groups have shown the presence of bacteria able to use many substrates including lactate, ethanol, acetate, malate, and propionate (Laanbroek and Pfennig, 1981). Lactate and acetate utilizers often outnumber other groups illustrating the importance of both incomplete and complete oxidizing SO 2 , reducers in sediments.…”

Sulfate-reducing bacteria in temporarily oxic sediments with bivalves

“…Our choice of lactate, acetate, and succinate (plus ethanol for spore formers) as single electron donors enabled us to d~stinguish between the major categories to be expected (Laanbroek & Pfennig 1981, Widdel 1988. Also, if lactate in selective media is replaced by alternate electron donors, maximum abundances are still noted for lactate utilizers (Laanbroek & Pfennig 1981, Battersby et al 1985. Presumably, many of the Desulfovibrio spp.…”

“…occurring in the partly oxidized environment ( Table 1) may indicate that oxygen tolerance of the spores is not the key for competitive advantage under unstable redox conditions. Survival and activity of SRB in oxidized marine sediments have been explained by anoxic microniches and trapplng of oxygen by the end product of sulfate reduction (Jsrgensen 1977, Laanbroek & Pfennig 1981, Battersby 1985. Furthermore, Desulfovibrio spp.…”

“…Jerrgensen 1978, Gunnarsson & Ronnow 1982, Hines & Buck 1982. The discovery of further metabolic types of SRB with different substrate requirements (Widdel 1980) made it necessary to extend the range of enrichment 0 Inter-Research/Printed in Germany substrates in order to update estimates for the standing crop of cultivable populations of SRB (Laanbroek & Pfennig 1981, Battersby et al 1985.…”