Comparative Metagenomic Analysis of Soil Microbial Communities across Three Hexachlorocyclohexane Contamination Levels

Abstract

<div><p>This paper presents the characterization of the microbial community responsible for the <em>in-situ</em> bioremediation of hexachlorocyclohexane (HCH). Microbial community structure and function was analyzed using 16S rRNA amplicon and shotgun metagenomic sequencing methods for three sets of soil samples. The three samples were collected from a HCH-dumpsite (450 mg HCH/g soil) and comprised of a HCH/soil ratio of 0.45, 0.0007, and 0.00003, respectively. Certain bacterial; (<em>Chromohalobacter</em>, <em>Marinimicrobium, Idiomarina, Salinosphaera, Halomonas</em>, <em>Sphingopyxis, Novosphingobium, Sphingomonas</em> and <em>Pseudomonas</em>), archaeal; (<em>Halobacterium, Haloarcula</em> and <em>Halorhabdus</em>) and fungal (<em>Fusarium</em>) genera were found to be more abundant in the soil sample from the HCH-dumpsite. Consistent with the phylogenetic shift, the dumpsite also exhibited a relatively higher abundance of genes coding for chemotaxis/motility, chloroaromatic and HCH degradation (<em>lin</em> genes). Reassembly of a draft pangenome of <em>Chromohalobacter salaxigenes</em> sp. (∼8X coverage) and 3 plasmids (pISP3, pISP4 and pLB1; 13X coverage) containing <em>lin</em> genes/clusters also provides an evidence for the horizontal transfer of HCH catabolism genes.</p> </div