Abstract
Complex and dynamic communities of microbes reside in aquatic environments. These communities are influenced by interactions between the abiotic and biotic components of the ecosystem. Understanding the mechanisms by which these communities change is very important for assessing their recovery following major disturbance events. The purpose of this study was to determine the diversity of microorganisms and potentially novel ones that exist in river catchments as well as their enzyme-related networks using a 16S amplicon sequencing approach. These microorganisms have been shown to have unique enzymes and metabolic pathways that are able to assist them to survive and thrive in these conditions. This study focused on the Jukskei River in which the most notable issue about the catchment area of the river is that it receives largely untreated waste dumps and agriculture wastewater. Thus, this study is of utmost importance in a bid to make a comprehensive description of the taxonomic and functional profiles of the microbial community in an urban lotic environment.
The river is characterized by extremely high soluble carbonate alkalinity, high pH, high salt and high concentrations of hydrogen sulphide containing nutrients of various types of compounds such as fats, sugars and proteins. Genomic DNA was isolated from water samples using a modified CTAB-based method. PCR amplification of the 16S rRNA V3 and V4 regions was performed, and Operational Taxonomic Unit (OTU) assignment was conducted to analyse bacterial communities.
The findings of the amplicon sequences were presented in terms of order, class, family and species. In the relative abundance of bacterial order in samples of the Jukskei River, the most dominant phylum was that of Proteobacteria and Firmicutes. In terms of families, the most dominant families were Rhizobiaceae, Armatimonadacea, Arcobacteracea and Acidaminobacteraceae. In terms of species, results show the most dominant forms were uncultured actinobacterium. The findings shows that some of the bacterium may have been unculturable. The inferred functional analysis of the bacterial communities revealed several differences in gene abundance. The KEGG pathway predictions revealed a significance in the functional potential data between upstream and downstream. In terms of upstream processes, related pathways identified were more concerned with lipid biosynthesis, lipid oxidation, pentose phosphate and gluconeogenesis. The downstream pathways tend to be more focused towards maintenance of regulatory processes.
XI
The upstream and downstream components of the streams were also sampled for physico- chemical parameters and the results revealed a non-significant statistical variance in the two characteristics between the two sites (upstream and downstream). The characteristics fluctuated greatly depending on the site and most of the characteristics were under the permitted standards for safe water as per South African Water Quality.