UBC Theses and Dissertations
Population dynamics and metabolic potential of a pilot-scale microbial community performing enhanced biological phosphorus removal Lawson, Christopher Evan
Enhanced biological phosphorus removal (EBPR) is an environmental biotechnology of global importance, essential for protecting receiving waters from eutrophication and enabling phosphorus recovery. Current understanding of EBPR is largely based on empirical evidence and black-box models that fail to appreciate the driving force responsible for nutrient cycling and ultimate phosphorus removal, namely microbial communities. Accordingly, this thesis focused on understanding the microbial ecology of a pilot-scale microbial community performing EBPR to better link bioreactor processes to underlying microbial agents. Initially, temporal changes in microbial community structure and activity were monitored in a pilot-scale EBPR treatment plant by examining the ratio of small subunit ribosomal RNA (SSU rRNA) to SSU rRNA gene 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, suggesting that rare OTUs made significant contributions to protein synthesis potential. 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 alternate ecological forces shaped community interactions in the bioreactor milieu. Subsequently, a metagenome was generated from pilot plant biomass samples using 454 pyrosequencing. Comparison of microbial community metabolism across multiple metagenomes from different environments revealed that EBPR community function was enriched in biofilm formation, phosphorus metabolism, and aromatic compound degradation, reflective of local bioreactor conditions. Population genomes binned from metagenomic contigs showed that M. parvicella genomes displayed remarkable genomic cohesion across EBPR ecosystems, where functional differences related to biofilm formation and antibiotic resistance, likely reflecting adaptation to habitat-specific selection pressures. Additionally, novel metabolic insights into Gordonia spp. in the EBPR ecosystem suggested a potential role for its involvement in polyphosphate and triacylglycerol cycling. Overall, these findings offer valuable insight on EBPR microbial ecology and will guide future studies aimed at monitoring spatiotemporal patterns in population dyanmics and gene expression. Moreover, this work demonstrates that molecular sequencing approaches can be successfully used to gain deeper insight on microbial communities responsible for wastewater remediation.
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