Quantitative analyses of the change in microbial diversity in a bioreactor for wastewater treatment based on respiratory quinones

The change in microbial diversity in a submerged aerobic biofilter, into which a persistent chemical of dimethylformamide was fed, were analyzed based on the quinone profiles using a new diversity index of the respiratory quinones (DQ) and an index of equitability of the distribution of quinone species (EQ) originally proposed in this study: D xQ = (Sigma f(k)(1.2))(2), EQ = DQ/n. Where, f(k) is the mole fraction of quinone species k and n is the number of quinone species, respectively. The DQ value increases with an increase in the number and the equitability of the distribution of quinone species. In the case where the mole fractions of all quinone species are equal. the value of DQ becomes equal to the number of quinone species and the EQ value becomes 1. A simulation analyses shows that DQ has a higher sensitivity to the change in number of quinone species than Shannon's index, i.e; one of the most widely used diversity indices. The relative sensitivity of DQ to the change in mole fraction of quinone species is higher than that of Shannon's diversity index for natural ecosystems in which many kinds of quinone species exist and occupy smaller fractions. The quinone profiles of the biofilm significantly changed and the values of DQ and EQ increased during the acclimation of the biofilm to dimethylformamide in the biofilter. The plot,of the mole fraction of dominant quinone species to the DQ values showed higher sensitivity to the change in the microbial community, These results indicated that DQ and EQ are useful indices for the evaluation of the changes;in the microbial community in response to environmental conditions. (C) 1999 Elsevier Science Ltd. All rights reserved.