Metabolic uncoupling of Shewanella oneidensis MR‐1, under the influence of excess substrate and 3, 3′, 4′, 5‐tetrachlorosalicylanilide (TCS)

Abstract

The dissociation between catabolism and anabolism is generally termed as metabolic uncoupling. Experimentally, metabolic uncoupling is characterized by a reduction in the observed biomass yield. This condition can be brought about by: (a) excess-substrate (as measured by S(0)/X(0)), and (b) addition of chemical uncouplers such as 3, 3', 4', 5-Tetrachlorosalicylanilide (TCS). An empirical model is proposed to quantify the uncoupling effects of both excess-substrate and uncoupler addition on the microbial cultures. Metabolic uncoupling of Shewanella oneidensis MR-1, under the influence of excess pyruvate and TCS, has been modeled using the proposed expression. The degree of uncoupling was measured as a fractional reduction in theoretical maximum observed yield. Excess-substrate was observed to successively reduce biomass yield as substrate concentration was increased. In the presence of TCS, conflicting trends were obtained for number yield and protein yield. This could, in part, be attributed to the observed increase in cellular protein content upon addition of TCS. Excess-substrate conditions dominated uncoupling, as compared to uncoupler addition. However, these two approaches were found to have additive effects and could, in conjunction, be employed to control biomass growth during microbial processes such as subsurface bioremediation and activated sludge treatment.