Open AccessTurnover of glucose and acetate coupled to reduction of nitrate, ferric iron and sulfate and to methanogenesis in anoxic rice field soil
Author(s) -
Chidthaisong Amnat,
Conrad Ralf
Publication year - 2000
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/j.1574-6941.2000.tb00673.x
Subject(s) - sulfate , methanogenesis , anoxic waters , ferrihydrite , nitrate , nitrite , chemistry , fermentation , inorganic chemistry , ferric , biochemistry , environmental chemistry , organic chemistry , adsorption , methane
Abstract Turnover of glucose and acetate in the presence of active reduction of nitrate, ferric iron and sulfate was investigated in anoxic rice field soil by using [U‐ 14 C]glucose and [2‐ 14 C]acetate. The turnover of glucose was not much affected by addition of ferrihydrite or sulfate, but was partially inhibited (60%) by addition of nitrate. Nitrate addition also strongly reduced acetate production from glucose while ferrihydrite and sulfate addition did not. These results demonstrate that ferric iron and sulfate reducers did not outcompete fermenting bacteria for glucose at endogenous concentrations. Nitrate reducers may have done so, but glucose fermentation may also have been inhibited by accumulation of toxic denitrification intermediates (nitrite, NO, N 2 O). Addition of nitrate resulted in complete inhibition of CH 4 production from [U‐ 14 C]glucose and [2‐ 14 C]acetate. However, addition of ferrihydrite or sulfate decreased the production of 14 CH 4 from [U‐ 14 C]glucose by only 70 and 65%, respectively. None of the electron acceptors significantly increased the production of 14 CO 2 from [U‐ 14 C]glucose, but all increased the production of 14 CO 2 from [2‐ 14 C]acetate. Uptake of acetate was faster in the presence of either nitrate, ferrihydrite or sulfate than in the unamended control. Addition of ferrihydrite and sulfate reduced 14 CH 4 production from [2‐ 14 C]acetate by 83 and 92%, respectively. Chloroform completely inhibited the methanogenic consumption of acetate. It also inhibited the oxidation of acetate, completely in the presence of sulfate, but not in the presence of nitrate or ferrihydrite. Our results show that, besides the possible toxic effect of products of nitrate reduction (NO, NO 2 − and N 2 O) on methanogens, nitrate reducers, ferric iron reducers and sulfate reducers were active enough to outcompete methanogens for acetate and channeling the flow of electrons away from CH 4 towards CO 2 production.