Characterization of microbial communities in the sewage of a major urban drain

Abstract

ABSTRACT Diverse bacterial assemblages were identified in a large, open stormwater drain (vernacular: nalah) built decades ago in a densely populated suburb of Delhi, India. Illumina-based next-generation sequencing (NGS) of 16S rRNA gene amplicons was conducted with metagenomic DNAs isolated from influent sewage water and sediment samples collected from Sahibabad drain, which now carries domestic and industrial wastes to downstream sewage treatment plants. Results are discussed with respect to diversity and adaptation to unique ecological niche(s) in these drains as well as the prevalence of potentially pathogenic bacteria. Recently, it has become a common practice to cover such drains with thick cement slabs to facilitate the construction of residential/commercial complexes. However, the impact of concrete covers on microbial communities that inhabit the Sahibabad drain is unknown. Results indicated that open drains with better aeration and exposure to sunlight contained microbes that likely enhance biodegradation in sewage water. The deposition of sediments along the course of the drain was dominated by methanogenic and sulphidogenic bacteria. Covering of the drain may have contributed to an increased abundance of anaerobic pathogens which settled in sediments and/or resuspended into sewage water. Such findings are important as the microbes active in sewage can impact public health and drain infrastructure.