Urbanization led to the abundance of Gram-negative, chemo-organo-heterotrophs, and antibiotic resistance genes in the downstream regions of the Ganga River water of India.

Abstract

The present investigation assesses the bacterial microbiome and antibiotic resistance genes (ARGs) of the river Ganga from Uttarakhand (upstream region; US group) and Uttar Pradesh (downstream region; DS group) regions using a 16S rRNA amplicon-based metagenomic approach. Gram-negative, aerobic, and chemo-organotrophic bacteria made up the majority of the bacterial genera during the overall analysis. Physicochemical analysis revealed a higher concentration of nitrate and phosphate in the downstream sites of the Ganga River. The prevalence of Gemmatimonas, Flavobacterium, Arenimonas, and Verrucomicrobia in the water of the DS region indicates a high organic load. Pseudomonas and Flavobacterium emerged as the most prevalent genera among the 35 significantly different shared genera (p-value < 0.05) in the US and DS regions, respectively. Overall antibiotic resistance analysis of the samples showed the dominance of β-lactam resistance (33.92%) followed by CAMP (cationic antimicrobial peptide) resistance (27.75%), and multidrug resistance (19.17%), vancomycin resistance (17.84%), and tetracycline resistance (0.77%). While comparing, the DS group exhibited a higher abundance of ARGs over the US group, where the CAMP resistance and β-lactam ARGs were dominant in the respective regions. The correlation (p-value < 0.05) analysis showed that most bacteria exhibit a significant correlation with tetracycline resistance followed by the phenicol antibiotic. The present findings draw attention to the need for regulated disposal of multiform human-derived wastes into the Ganga River to reduce the irrepressible ARGs dissemination.