Diversity, antibiotic resistance, and biofilm profiling of the inhabitant bacteria of the Ganga River of India

Abstract

In this investigation, water and sediment samples from the Ganga River were studied to analyze bacterial diversity and its correlation with antibiotic resistance genes (ARGs). A significant microbial load was observed in water (0.37 × 10³–12.3 × 10³) and sediment (0.193 × 10⁵–11.26 × 10⁵) samples from the Ganga River. Of the 74 morphologically distinct bacteria, 52.70 % were Gram-negative. Molecular characterization of these bacteria classified them into three broad phyla: Firmicutes (65 %), Proteobacteria (30 %), and Bacteroidetes (5 %). Genera-level analysis indicated the dominance of Bacillus, Pseudomonas, Enterobacteriaceae, Bacteroides, Staphylococcus, and Exiguobacterium in the samples from the Ganga River. The MAR index analysis of the isolated bacteria revealed a high risk of antibiotic contamination and resistance potential. Specifically, resistance to clotrimazole (98.64 %), bacitracin (97.2 %), polymyxin (75.67 %), ampicillin (74.32 %), rifampicin, and vancomycin (52.70 %) was observed among approximately 50 % of the bacteria. Additionally, the biofilm formation activity of the isolated bacteria was assessed, with 43.24 % identified as having moderate biofilm formation activity. Therefore, the findings of this study enrich the limited information on the bacterial diversity of the Ganga River's water and sediment samples and their associated risk attributes, such as biofilm formation activity and the dissemination of ARGs. The study advocates for regulated monitoring of domestic and industrial waste before its disposal into the Ganga River. Furthermore, this study is the first report discussing the biofilm formation potential of the resident bacteria in the Ganga River.