KINETICS OF SULFATE RESPIRATION BY FREE-LIVING AND PARTICLE-ASSOCIATED SULFATE-REDUCING BACTERIA

Effects on sulfate respiration of association of sulfate-reducing bact eria (SRB) with solid particles (anion exchange resin and FeS-precipit ate) were examined using Desulfovibrio desulfuricans. The rates of sul fide production by resin- and FeS-associated cells were 2-3% and 19-56 % of that by free-living ones, respectively, under sulfate- and lactat e-rich conditions. On the other hand, under sulfate-poor (less than 50 mu M) and lactate-rich conditions the rate by FeS-associated cells wa s higher than that by free-living ones. The values of K-m (mu M), half saturation constant of the Michaelis-Menten model, for sulfate were 2 44 for free-living cells, 8.96 for resin-associated ones and 8.42 for FeS-associated ones. Under lactate-poor and sulfate-rich conditions th e 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 freshwat er sediments.