title: rRNA Gene Expression of Abundant and Rare Activated-Sludge Microorganisms and Growth Rate Induced Micropollutant Removal.
abstract: The role of abundant and rare taxa in modulating the performance of wastewater-treatment systems is a critical component of making better predictions for enhanced functions such as micropollutant biotransformation. In this study, we compared 16S rRNA genes (rDNA) and rRNA gene expression of taxa in an activated-sludge-treatment plant (sequencing batch membrane bioreactor) at two solids retention times (SRTs): 20 and 5 days. These two SRTs were used to influence the rates of micropollutant biotransformation and nutrient removal. Our results show that rare taxa (<1%) have disproportionally high ratios of rRNA to rDNA, an indication of higher protein synthesis, compared to abundant taxa (≥1%) and suggests that rare taxa likely play an unrecognized role in bioreactor performance. There were also significant differences in community-wide rRNA expression signatures at 20-day SRT: anaerobic-oxic-anoxic periods were the primary driver of rRNA similarity. These results indicate differential expression of rRNA at high SRTs, which may further explain why high SRTs promote higher rates of micropollutant biotransformation. An analysis of micropollutant-associated degradation genes via metagenomics and direct measurements of a suite of micropollutants and nutrients further corroborates the loss of enhanced functions at 5-day SRT operation. This work advances our knowledge of the underlying ecosystem properties and dynamics of abundant and rare organisms associated with enhanced functions in engineered systems.
authors.affiliation: NSF Engineering Research Center ReNUWIt, Department of Civil and Environmental Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.|Division of Earth and Ecosystem Sciences, Desert Research Institute , Reno, Nevada 89512, United States.
authors.forename: David C
authors.initials: DC
authors.lastname: Vuono
authors.affiliation: NSF Engineering Research Center ReNUWIt, Department of Civil and Environmental Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.
authors.forename: Julia
authors.initials: J
authors.lastname: Regnery
authors.affiliation: NSF Engineering Research Center ReNUWIt, Department of Civil and Environmental Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.
authors.forename: Dong
authors.initials: D
authors.lastname: Li
authors.affiliation: NSF Engineering Research Center ReNUWIt, Department of Civil and Environmental Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.
authors.forename: Zackary L
authors.initials: ZL
authors.lastname: Jones
authors.affiliation: NSF Engineering Research Center ReNUWIt, Department of Civil and Environmental Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Holloway
authors.affiliation: NSF Engineering Research Center ReNUWIt, Department of Civil and Environmental Engineering, Colorado School of Mines , Golden, Colorado 80401, United States.|Chair of Urban Water Systems Engineering, Technical University of Munich 85748, Garching, Germany.
authors.forename: Jörg E
authors.initials: JE
authors.lastname: Drewes
mesh_terms: D019149:Bioreactors; D020459:Genes, rRNA; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D062065:Wastewater
chemical_list: D012336:RNA, Ribosomal, 16S; D012722:Sewage; D062065:Wastewater