Use of 16S rRNA Gene Terminal Restriction Fragment Analysis To Assess the Impact of Solids Retention Time on the Bacterial Diversity of Activated Sludge

Abstract

Terminal restriction fragment length polymorphism (T-RFLP) analysis of 16S rRNA genes was used to investigate the reproducibility and stability in the bacterial community structure of laboratory-scale sequencing batch bioreactors (SBR) and to assess the impact of solids retention time (SRT) on bacterial diversity. Two experiments were performed. In each experiment two sets of replicate SBRs were operated for a periods of three times the SRT. One set was operated at an SRT of 2 days and another set was operated at an SRT of 8 days. Samples for T-RFLP analysis were collected from the two sets of replicate reactors. HhaI, MspI, and RsaI T-RFLP profiles were analyzed using cluster analysis and diversity statistics. Cluster analysis with Ward's method using Jaccard distance and Hellinger distance showed that the bacterial community structure in both sets of reactors from both experimental runs was dynamic and that replicate reactors were clustered together and evolved similarly from startup. Richness (S), evenness (E), the Shannon-Weaver index (H), and the reciprocal of Simpson's index (1/D) were calculated, and the values were compared between the two sets of reactors. Evenness values were higher for reactors operated at an SRT of 2 days. Statistically significant differences in diversity (H and D) between the two sets of reactors were tested using a randomization procedure, and the results showed that reactors from both experimental runs that were operated at an SRT of 2 days had higher diversity (H and D) at the 5% level. T-RFLP analysis with diversity indices proved to be a powerful tool to analyze changes in the bacterial community diversity in response to changes in the operational parameters of activated-sludge systems.

Quantifying Community Dynamics of Nitrifiers in Functionally Stable Reactors

“…In another study, we ran the reactor setup in triplicate for more than 100 days, and both functional and microbial community structure dynamics were highly reproducible (unpublished data). These observations are in agreement with other studies showing minor differences between appropriately repeated lab-scale setups (5,25,32,43).…”

Effect of karst rocky desertification on soil fungal communities in Southwest China

“…The clustering algorithm used to calculate the dendrogram employed an unweighted pair group method with arithmetic mean, based on the Dice coefficient. Diversity of soil fungus communities was evaluated using the Shannon-Wiener index (H), richness (S), and evenness (E H ), based on Equations 1 and 2, as follows (Saikaly et al, 2005): where Pi is the ratio of the intensity of a single band to the total intensity of all bands within the same lane, and S is the total number of bands in each lane.…”

Active heterotrophic biomass and sludge retention time (SRT) as determining factors for biodegradation kinetics of pharmaceuticals in activated sludge

“…The SRT is a design criterion for WWTPs and strongly related to microbial growth. Nonetheless, the relation between SRT, microbial community structure and xenobiotic degradation performance is not fully understood and controversial findings have been reported (Clara et al, 2005;Gaulke et al, 2009;Kraigher et al, 2008;Saikaly et al, 2005;Schaar et al, 2010;Stasinakis et al, 2010).…”