Insights into microbial communities of crude oil-contaminated soil and water samples based on 16S rRNA gene profiling and laboratory evaluation of indigenous hydrocarbon reducing microbial consortia

Crude oil contamination represents a major environmental challenge worldwide due to its persistent and toxic nature. Indigenous microbial communities from crude oil-polluted sites may provide a sustainable strategy for environmental restoration, as these microorganisms have been previously reported to possess intrinsic hydrocarbon tolerating capabilities. This study investigated crude oil- contaminated soil and water samples from Assam, India to identify native microbial populations and explore their potential for bioremediation. Microbial enrichment was performed using aliphatic and aromatic hydrocarbons as the sole carbon sources, and microbial growth under hydrocarbon enriched conditions was evaluated. The microbial communities from both native and enriched samples were analyzed using 16S rRNA profiling. Proteobacteria appeared to be the predominant phylum in native and enriched samples. Ochrobactrum and Acinetobacter were among the most abundant genera in the both native and enriched water and soil samples, respectively. Compositional variations appeared between soil and water microbial communities during comparative diversity analysis. After 90 days of treatment in a laboratory scale soil microcosm experiment,TPH removal of 61.60% and 42.54% was observed in the 10% and 20% crude oil contaminated soils,respectively, following treatment with enriched microbial consortia and bacterial isolates, indicating their potential for TPH removal. GC–MS profiling further suggested alterations in the chromatographic profiles of the residual hydrocarbon-associated fractions following microbial treatment. Overall, the study provides preliminary insights into microbial community composition associated with crude oil contamination and the potential of indigenous microbial consortia for TPH removal. However, the findings of microbial community and diversity analysis are considered preliminary and descriptive because biological replicates and untreated reference samples were not included, limiting the generalizability of the observed patterns that needs to be validated through replicate sampling across multiple sites and environmental conditions. Furthermore, the taxonomic observations do not establish the specific hydrocarbon degrading functions of individual taxa. 16S rRNA gene amplicon profiling revealed diverse microbial communities in crude oil-contaminated water and soil samples with 442 and 136 genera detected, respectively.The two enriched microbial consortia consisted of taxa previously associated with hydrocarbon tolerance and surface active activity.Proteobacteria appeared to be the most abundant phylum in the native and enriched water and soil samples.Ochrobactrum and Acinetobacter were among the most abundant genera in the native and enriched water and soil samples, respectively.61.60% and 42.54% TPH removal was observed from 10% and 20% crude oil contaminated soils, respectively, following treatment with enriched microbial consortia and the bacterial isolates after 90 days indicating their potential for TPH removal under laboratory conditions respectively. 16S rRNA gene amplicon profiling revealed diverse microbial communities in crude oil-contaminated water and soil samples with 442 and 136 genera detected, respectively. The two enriched microbial consortia consisted of taxa previously associated with hydrocarbon tolerance and surface active activity. Proteobacteria appeared to be the most abundant phylum in the native and enriched water and soil samples. Ochrobactrum and Acinetobacter were among the most abundant genera in the native and enriched water and soil samples, respectively. 61.60% and 42.54% TPH removal was observed from 10% and 20% crude oil contaminated soils, respectively, following treatment with enriched microbial consortia and the bacterial isolates after 90 days indicating their potential for TPH removal under laboratory conditions respectively.