Kinetics of sulfate respiration by free-living and particle-associated sulfate-reducing bacteria

Effects on sulfate respiration of association of sulfate-reducing bacteria (SRB) with solid particles (anion exchange resin and FeS-precipitate) were examined using Desulfovibrio desulfuricans. The rates of sulfide production by resin- and FeS-associated cells were 2–3% and 19–56% of that by free-living ones, respectively, under sulfate- and lactate-rich conditions. On the other hand, under sulfate-poor (less than 50 μM) and lactate-rich conditions the rate by FeS-associated cells was higher than that by free-living ones. The values of Km (μM), half saturation constant of the Michaelis-Menten model, for sulfate were 244 for free-living cells, 8.96 for resin-associated ones and 8.42 for FeS-associated ones. Under lactate-poor and sulfate-rich conditions the rate by FeS-associated cells was similar to that by free-living ones. These results suggest that FeS-associated SRB are more advantageous than free-living ones under sulfate-poor environments such as freshwater sediments.