Cellular nicotinamide adenine dinucleotide (NADH) as an indicator of bacterial metabolic activity dynamics in activated sludge

摘要

In this study, native fluorescent nicotinamide adenine dinucleotide (NADH) was used as andirect indicator of bacterial metabolic activity in activated sludge. Specific NADH concentrationnwas dynamic and varied between 106–108 molecules per bacterial cell. Low concentrationsn(106–107 NADH molecules cell21) indicate efficient bacterial metabolic activity while highnconcentrations (107–108 NADH molecules cell21) indicate inefficient bacterial metabolic activity.nSpecific [NADH] did not correlate to changes in dissolved organic carbon, but increases correlatednto decreases in oxygen uptake rates. Perhaps a lack of oxygen as the terminal electron acceptornprevented efficient reoxidization of NADH to NAD+, which resulted in an accumulation of NADHnwithin the cells. Also, significant amounts of NADH were released and accumulated into thenextracellular medium of metabolically active E. coli cells in log phase. Such overflow metabolismnmay be the product of favourable conditions. Thus, the flux of both specific intracellular andnextracellular [NADH] indicates the dynamics of bacterial metabolic activity in activated sludge.