Abstract
Given the hostile environment provided by sewer water, bacteria have evolved to adapt, develop, and exploit compounds such as carbohydrates, proteins, and fats, as well as inorganic compounds such as heavy metals, nitrogen, phosphorus, high pH, high hydrogen sulphide concentrations, high salt, high soluble carbonate alkalinity as a food supply for energy and cell component production. These microorganisms have been shown to have specific enzymes and metabolic pathways that help them survive and thrive in these conditions. These enzymes could potentially have applications in industrial processes (disinfectants, detergents, and waste treatment) as well as pharmaceutical industries (antibiotics). Microbiome studies have been conducted globally on selected areas of sewer water treatment plants with particular emphasis on the microbiome of secondary effluent, but there is still paucity of knowledge on a full-scale wastewater treatment facility spatiotemporally (at a given point in time) as well as differential regulation of proteins/enzymes (metaproteomics). Thus, the aim of this study was to make a comprehensive description of the taxonomic profiling, functional profiling, and proteomic profiling of the microbial community of a full-scale sewage water system. 16S amplicon sequencing was performed to identify the shift in the microbiome from the primary to the tertiary effluent. PICRUSt ( Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) was used to infer functional potential. 16S rRNA sequencing revealed that the most predominant phyla identified throughout the WWTP (Wastewater treatment plant) was Proteobacteria and Firmicutes, with Patescibacteria uniquely abundant in the secondary and tertiary stages only. Predicted functional potential studies of the identified microbial communities were precalculated for protein-coding genes present in KEGG (Kyoto encyclopedia of Genes and Genomes gene families) and 16S rRNA gene copy number found significance in the primary and secondary effluents only. The most abundant pathways that were present in both primary and secondary stages include Valine synthesis pathways (VALSYN-PWY), L-isoleucine synthesis pathway (ILEUSYN-PWY), Branched chaine amino acids synthesis pathway (BRANCHEDCHAIN-AA-SYN), Non oxidative pentose phosphate pathway (NONOXIPENT PWY), Peptidoglycan synthesis pathway (PEPTIDOGLYCANSYN-PWY). Comparative quantitative proteomics through nano-LCMS (Liquid chromatography–mass spectrometry) analysis was conducted to establish the performance of the WWTP in terms of differentially and uniquely expressed proteins. A significant difference in the number of expressed proteins were visually observed through SDS-PAGE (Sodium dodecyl sulfate–polyacrylamide gel electrophoresis) and confirmed with LCMS with majority of the identified proteins involved in carbohydrate metabolism, protein metabolism, stress-related metabolism, amino acid biosynthesis and structural support proteins. This study has demonstrated that microbial populations can live and grow in sewer water conditions due to emerging properties of metabolic pathways. These specialized microbial genes have a lot of potential in various industries, and this study has further established that wastewater treatment plants provide a lot of information about bacteria that are important to human health.