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Comparative analysis of microbial communities from full scale anaerobic digesters

In wastewater treatment plants (WWTPs), exploring the taxonomic composition and abundance of microbial communities has become an indispensable effort. It is essential for optimizing treatment processes, monitoring system health and ensuring compliance with environmental standards. Microorganisms play a crucial role in decomposing organic matter, removing contaminants and recovering resources. Knowledge of microbial communities leads to more efficient and resilient wastewater treatment plants (WWTPs), promoting public health and environmental sustainability. The use of 16S rRNA gene sequencing to examine microbial communities in large-scale anaerobic digesters at WWTPs has been growing. This methodology involves a series of computational processes, covering sequence quality assessment, noise removal, taxonomic classification, alignment and construction of phylogenetic trees. Notably, the Quantitative Insights Into Microbial Ecology version 2 (QIIME2) software suite has emerged as a valuable tool, simplifying analysis of 16S rRNA marker gene data. Facilitates end-to-end analysis of diverse microbiome datasets and facilitates comparative studies with publicly available data. QIIME2 equips researchers with tools to select appropriate sampling depths to conduct alpha and beta diversity analyses.

In this thesis, we present a comprehensive comparative analysis of the microbial communities inhabiting large-scale anaerobic digesters within WWTPs. The study uses next-generation sequencing, namely high-throughput sequencing of the 16S rRNA gene, and then uses Qiime2 to determine and analyze the taxonomic, diversity and relative abundance of digester communities within each WWTP and between them. Ion torrent was the technology used for next-generation high-throughput sequencing of the 16S rRNA gene. The workflow used in qiime2 consisted of importing data, quality control (denoising), clustering and only then analyzing diversity and taxonomy to find out the composition, diversity and abundance of communities. The results showed that the microbial communities were quite stable during different sampling points, but were distant when compared between different sludge digesters. However, some of the microorganisms that make up the methanogenic community present in the communities were Methanobacteriales, Methanomicrobiales, Methanosarcinales. Regarding the bacterial community, the most abundant microorganisms in a given digester and present in all digesters were attributed to Sedimentibacter, Phycicoccus, Thermovirgae, Cloacimonas, and Phycicoccus.