Microbial residence time is a controlling parameter of the taxonomic composition and functional profile of microbial communities

Abstract

A remaining challenge within microbial ecology is to understand the determinants of richness and diversity observed in environmental microbial communities. In a range of systems, including activated sludge bioreactors, the microbial residence time (MRT) has been previously shown to shape the microbial community composition. However, the physiological and ecological mechanisms driving this influence have remained unclear. Here, this relationship is explored by analyzing an activated sludge system fed with municipal wastewater. Using a model designed in this study based on Monod-growth kinetics, longer MRTs were shown to increase the range of growth parameters that enable persistence, resulting in increased richness and diversity in the modelled community. In laboratory experiments, six sequencing batch reactors treating domestic wastewater were operated in parallel at MRTs between 1-15 d. The communities were characterized using both 16S ribosomal RNA and non-target messenger RNA sequencing (metatranscriptomic analysis), and model-predicted monotonic increases in richness were confirmed in both profiles. Accordingly, taxonomic Shannon diversity also increased with MRT. In contrast, the diversity in enzyme class annotations resulting from the metatranscriptomic analysis displayed a non-monotonic trend over the MRT gradient. Disproportionately high abundances of transcripts encoding for rarer enzymes occur at longer MRTs and contribute to the disconnect between taxonomic and functional diversity profiles.

Clustering micropollutants based on initial biotransformations for improved prediction of micropollutant removal during conventional activated sludge treatment

“…High SRT allows for enrichment of slowgrowing microorganisms that can increase the functional diversity of the microbial community. 70,71 Higher SRT generally enhances biodegradation of typically moderately biodegradable micropollutants. 3,67 The strong positive associations between SRT and R% for the ACE+BEZ, TRI, and IBP clusters presented in Figure 4 are consistent with this expectation and with literature.…”

Molecular biological methods in environmental engineering

“…The relationship between microbial residence time (MRT) and microbial community structure and function was studied by transcriptomics (Mansfeldt et al, 2019). The results show that appropriate extension of MRT can increase the abundance of microorganisms in the activated sludge reactor.…”

Gene Transmission in the One Health Microbiosphere and the Channels of Antimicrobial Resistance

“…One aspect that is not yet fully understood is the construction of gene exchange communities, particularly when the microbiome emerges de novo in virgin habitats, as in newborns (Skippington and Ragan, 2011;Boon et al, 2014;Mansfeldt et al, 2019). An important aspect to be considered is whether these communities "replicate" in newborns, maintaining an identical member composition, or whether new members (originated in other hosts or environments) are accepted in the genetic exchange club in these early stages of microbiota construction.…”