Assessment of bacterial diversity associated with crude oil-contaminated soil samples from Assam

In this study, we are reporting bacterial diversity in crude oil-contaminated soil of Assam, India. Integration of physiological community profiling, culture-dependent and culture-independent (metagenome) approaches, was employed to obtain a complete picture of the total bacterial diversity. Samples collected from 10 sites contaminated with crude oil ranging from 0.22 to 89.36% were analysed, and altogether 160 culturable bacteria were isolated (117 Gram-positive and 43 Gram-negative bacteria). Molecular identification showed the predominance of genera Lysinibacillus, Alcaligenes, Bacillus, Clostridium, Enterobacter and Pseudomonas. Conversely, denaturing gradient gel electrophoresis (DGGE) profiles of 16S rDNA phylotypes showed the predominance of Sphingomonas, Ralstonia, Sphingobium, Massilia, Acinetobacter and Pseudomonas. Both culture-dependent and culture-independent approaches resulted in 11 genera of which Bacillus and Pseudomonas were the key inhabitants creating most favourable bacterial milieu in the presence of crude oil contaminants. Metabolic fingerprints data depicted in PCA plot demonstrated that sites CTF-D-1 and Core-10 were most diverged. It was further confirmed that variations of bacterial species dominance in different sites were due to origin of hydrocarbon contamination. We here claim that the present findings is a first-hand report on combined physiological community profiling, culture-based and culture-independent approaches in assessing total bacterial diversity in crude oil-contaminated soil of Assam.