Unveiling of metal-tolerance bacterial consortia in chromite mine by metagenomic approaches

Heavy metal-contaminated soils are a widespread problem in mine field environments. To gain insights on the structural and functional diversity of bacterial community present in chromium contaminated mine soil obtained from Sukinda Chromite mine of Odisha (India), whole metagenomic analysis was performed by using Illumina HiSeq platform. Chromite mine soils contain high concentrations of heavy metals such as Mn, Fe, Cu besides chromium and low concentrations of organic carbon, available nitrogen, phosphorus and potassium. The bacterial community living in that hostile environment was correlated with the inherent abilities of these strains to be involved in the reduction of the major heavy metal Cr(VI). Our results showed that Proteobacteria (66.45%) were found to be the most abundant in the study area, followed by Actinobacteria (17.32%), Bacteroidetes (4.65%). The Keto Encyclopedia of Genes and Genomes (KEGG) functional category has 228543 predicted functions, 20% of which were involved in cellular metabolic functions, 5.21% in genetic information processing and 5.13% in environmental and information processing, while SEED functional category has 112542 predicted functions. Of which 11.73% are involved in carbohydrate metabolism with 13202 hits, followed by 10.57% amino acids and derivatives with 11899 hits, 8.24% protein metabolism with 9282 hits, 6.88% DNA metabolism with 7746 hits with and 5.94% cofactors, vitamins, prosthetic group, pigments with 6687 hits. The isolated bacterial consortia exhibited visible growth up to a Cr concentration of 800 mg L−1. The results presented in this study have important implications for understanding bacterial diversity in chromium-contaminated mine soils and their role in exhibiting Cr(VI) resistance.