Rare taxa have potential to make metabolic contributions in enhanced biological phosphorus removal ecosystems

Abstract

SummaryEnhanced biological phosphorus removal (EBPR) relies on diverse but specialized microbial communities to mediate the cycling and ultimate removal of phosphorus from municipal wastewaters. However, little is known about microbial activity and dynamics in relation to process fluctuations in EBPR ecosystems. Here, we monitored temporal changes in microbial community structure and potential activity across each bioreactor zone in a pilot-scale EBPR treatment plant by examining the ratio of small subunit ribosomal RNA (SSU rRNA) to SSU rRNA gene (rDNA) over a 120 day study period. Although the majority of operational taxonomic units (OTUs) in the EBPR ecosystem were rare, many maintained high potential activities based on SSU rRNA : rDNA ratios, suggesting that rare OTUs contribute substantially to protein synthesis potential in EBPR ecosystems. Few significant differences in OTU abundance and activity were observed between bioreactor redox zones, although differences in temporal activity were observed among phylogenetically cohesive OTUs. Moreover, observed temporal activity patterns could not be explained by measured process parameters, suggesting that other ecological drivers, such as grazing or viral lysis, modulated community interactions. Taken together, these results point towards complex interactions selected for within the EBPR ecosystem and highlight a previously unrecognized functional potential among low abundance microorganisms in engineered ecosystems.

Comparing Bacterial Diversity in Two Full-Scale Enhanced Biological Phosphate Removal Reactors Using 16S Amplicon Pyrosequencing

“…3). This study is in agreement with Tian et al [32], who also reported the predominance of Proteobacteria, Bacteriodetes, Firmicutes, Actinobacteria, and Planctomycetes in wastewater treatment plants containing approximately 51 phyla and 900 genera. Bond et al [8], in their study investigating the bacterial community structures of phosphate-removing and non-phosphate-removing activated sludges from sequencing batch reactors, also revealed that Proteobacteria, Planctomycete, Flexibacter, Cytophaga, and Bacteroides were the dominant microbial groups.…”

“…4). The observed unique phyla have similarly been reported elsewhere in low proportions in activated sludge [5,8,32]. In terms of their abundance in both plants separately, five phyla -Proteobacteria (72.37%), Bacteriodetes, Firmicutes, Actinobacteria, and Chloroflexi -occupied approximately 95.71% of all classified bacteria from the failed EBPR, while in the successful EBPR Proteobacteria, Bacteriodetes, Firmicutes, Actinobacteria, and Planctomycetes were the most abundant with approximately 95.77% of the entire classified bacterial population (Fig.…”

“…This finding disagrees with the results by Zhang et al [31], who reported a similar level of diversity between the bacterial structure and activity of 14 EBPR. Lawson et al [32] also stated that functional similarity in several EBPRs is mostly translated by the number of OTUs having similar genus-level affiliation. A significant shift of the dominant microbial community highlighting high dissimilarity between anaerobic-anoxic has also been reported by Lv et al [21] when comparing the bacterial community in EBPRs.…”

Integrating biogeochemistry with multiomic sequence information in a model oxygen minimum zone

“…For example, for some prokaryotic transcription cascades, the basic time unit may be the cell doubling time (which can reach several weeks in anoxic environments) (51) because of regulation by long-lived transcription factors (52). Hence, the decay times estimated here may reflect a hysteresis in gene down-regulation after nutrient depletion, perhaps in anticipation of potential future opportunities for growth (53,54). Overall, these observations suggest that future metatranscriptomic sequencing efforts and models for environmental mRNA dynamics would benefit from a consideration of additional control mechanisms (for example, derived from cell-centric transcription models) (55,56).…”

Lifestyles of rarity: understanding heterotrophic strategies to inform the ecology of the microbial rare biosphere

“…There are many additional recent studies documenting the diversity or dynamics of the rare biosphere in various habitats (e.g. Elshahed et al 2008, Youssef et al 2010, Hugoni et al 2013, Gies et al 2014, Lawson et al 2015. Thus, patterns of rare taxa are readily documented and described using commonplace cultivation-independent methods, like 16S rRNA gene amplicon sequencing.…”