A Cross-section Metagenomics and 16S Ribosomal DNA Based Evaluation of the Bacterial and Archaeal Communities Resident in the Forumad Chromite Mine, Northeastern of Iran

Background: The Forumad chromite area from Sabzevar ophiolite belt, Northeastern Iran, is an environment with high concentration of heavy metals, particularly chromite and magnesite minerals, containing chromium and magnesium. Objectives: In this study for the first time, we analyzed and report the diversity of microbial (bacterial and archaeal) community inhabiting in Forumad chromite mine environment using metagenomics approach. Materials and Methods: Samples were obtained from different areas of the mine, and total DNA was extracted from water and soil samples. 16S rDNA was amplified using universal primers and the PCR products were cloned in pTz57R/T plasmid. Then, 43% of the positive clones were randomly sequenced. BLAST program in NCBI and EzTaxon databases were used to identify similar 16S rDNA sequences. Phylogenetic analysis was performed using the MEGA5 software and multiple alignments of sequences. Results: In the phylogenetic analyses, proteobacteria, which contains many heavy metals tolerant bacteria especially chromium, were the dominant population in bacterial libraries with Rheinheimera and Cedecaeas the most abundant genuses. Other phyla were Bacteroidetes, Firmicutes, Verrucomicrobia, Chloroflexi, Actinobacteria, Acidobacteria, Cyanobacteria, Gemmatimonadetes, and Planctomycetes. In the archaeal clone library, all the sequences were related to the phylum Thaumarchaeota. Further, 68.6% of the sequences had less than 98.7℅ similarity with the recorded strains which could represent new taxons. Conclusions: The results showed that there was a high microbial diversity in the Forumad chromite area. These results can be used for detoxification and bioremediation of regions contaminated with heavy metals, although more studies are needed.