Wos M L, Pollard P C
Division of Microbiology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, Braunschweig 38124, Germany.
Water Sci Technol. 2009;60(3):783-91. doi: 10.2166/wst.2009.393.
In this study, native fluorescent nicotinamide adenine dinucleotide (NADH) was used as a direct indicator of bacterial metabolic activity in activated sludge. Specific NADH concentration was dynamic and varied between 10(6)-10(8) molecules per bacterial cell. Low concentrations (10(6)-10(7) NADH molecules cell(-1)) indicate efficient bacterial metabolic activity while high concentrations (10(7)-10(8) NADH molecules cell(-1)) indicate inefficient bacterial metabolic activity. Specific [NADH] did not correlate to changes in dissolved organic carbon, but increases correlated to decreases in oxygen uptake rates. Perhaps a lack of oxygen as the terminal electron acceptor prevented efficient reoxidization of NADH to NAD+, which resulted in an accumulation of NADH within the cells. Also, significant amounts of NADH were released and accumulated into the extracellular medium of metabolically active E. coli cells in log phase. Such overflow metabolism may be the product of favourable conditions. Thus, the flux of both specific intracellular and extracellular [NADH] indicates the dynamics of bacterial metabolic activity in activated sludge.
在本研究中，天然荧光烟酰胺腺嘌呤二核苷酸（NADH）被用作活性污泥中细菌代谢活性的直接指标。特定NADH浓度是动态变化的，每个细菌细胞中的浓度在10⁶ - 10⁸个分子之间。低浓度（10⁶ - 10⁷个NADH分子/细胞）表明细菌代谢活性高效，而高浓度（10⁷ - 10⁸个NADH分子/细胞）表明细菌代谢活性低效。特定的[NADH]与溶解有机碳的变化无关，但与氧气摄取率的降低相关。可能是作为末端电子受体的氧气缺乏，阻止了NADH有效地再氧化为NAD⁺，导致细胞内NADH积累。此外，大量的NADH被释放并积累到对数期代谢活跃的大肠杆菌细胞的细胞外培养基中。这种溢流代谢可能是有利条件的产物。因此，特定的细胞内和细胞外[NADH]通量表明了活性污泥中细菌代谢活性的动态变化。
