Community Structure of Nitrifying and Denitrifying Bacteria from Effluents Discharged into Lake Victoria, Kenya

Abstract

An active microbial community of nitrifying and denitrifying bacteria is needed for efficient utilization of nitrogenous compounds from wastewater. In this study, we explored the bacterial community diversity and structure within rivers, treated and untreated wastewater treatment plants (WWTPs) discharging into Lake Victoria. Water samples were collected from rivers and WWTPs that drain into Lake Victoria. Physicochemical analysis was done to determine the level of nutrients or pollutant loading in the samples. Total community DNA was extracted, followed by Illumina high throughput sequencing to determine the total microbial community and abundance. Enrichment and isolation were then done to recover potential nitrifiers and denitrifiers. Physicochemical analysis pointed to high levels total nitrogen and ammonia in both treated and untreated WWTPs as compared to the samples from the lake and rivers. A total of 1,763 operational taxonomic units (OTUs) spread across 26 bacterial phyla were observed with the most dominant phylum being Proteobacteria. We observed a decreasing trend in diversity from the lake, rivers to WWTPs. The genus Planktothrix constituted 19% of the sequence reads in sample J2 collected from the lagoon. All the isolates recovered in this study were affiliated to three genera: Pseudomonas, Klebsiella and Enterobacter in the phylum Proteobacteria. A combination of metagenomic analysis and a culture-dependent approach helped us understand the relative abundance as well as potential nitrifiers and denitrifiers present in different samples. The recovered isolates could be used for in situ removal of nitrogenous compounds from contaminated wastewater.

Six complex microbial inoculants for removing ammonia nitrogen from waters

“…The dominant phyla observed after all samples were processed included Proteobacteria , Firmicutes , Bacteroidetes , Actinobacteria , etc. These results suggest that the addition of microbial agents can alter the bacterial community structure and may ultimately affect the biotransformation of nitrogen in water samples (Wachira et al, 2022). Proteobacteria were the most prominent dominant phylum in these samples.…”

Bacterial community and cyanotoxin gene distribution of the Winam Gulf, Lake Victoria, Kenya

“…There are limited molecular studies that have been done in Lake Victoria or the Winam Gulf. Of the studies available, only one aimed to characterize bacterial communities in river outflows and wastewater treatment plant effluents (Wachira et al, 2022 ). Additionally, one dissertation aimed to characterize cyanobacteria and mcyE through denaturing gradient gel electrophoresis, and one study had a goal of characterizing Microcystis aeruginosa across East Africa using molecular techniques (Chhun, 2007 ; Haande et al, 2007 ).…”