This paper presents the characterization of the microbial community responsible for the in-situ 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; (Chromohalobacter, Marinimicrobium, Idiomarina, Salinosphaera, Halomonas, Sphingopyxis, Novosphingobium, Sphingomonas and Pseudomonas), archaeal; (Halobacterium, Haloarcula and Halorhabdus) and fungal (Fusarium) 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 (lin genes). Reassembly of a draft pangenome of Chromohalobacter salaxigenes sp. (∼8X coverage) and 3 plasmids (pISP3, pISP4 and pLB1; 13X coverage) containing lin genes/clusters also provides an evidence for the horizontal transfer of HCH catabolism genes.

The contamination levels in ground and river water suggest significant run-off from the dumped HCH wastes and contamination of drinking water resources. The extent of dumping urgently needs to be assessed regarding the risks to human and ecosystem health. A plan for securing the waste isomers needs to be developed and implemented together with a plan for their final elimination. As part of the assessment, any polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDF) generated during HCH recycling operations need to be monitored.

Sphingobium indicum B90A, an efficient degrader of hexachlorocyclohexane (HCH) isomers, was isolated in 1990 from sugarcane rhizosphere soil in Cuttack, India. Here we report the draft genome sequence of this bacterium, which has now become a model system for understanding the genetics, biochemistry, and physiology of HCH degradation.

A Gram-negative, strictly aerobic, yellow bacterial strain, designated DS-12T, was isolated from hexachlorocyclohexane-contaminated soil in Lucknow, Uttar Pradesh, India. Strain DS-12T showed the highest 16S rRNA gene sequence similarity with Flavobacterium ceti 454-2T (94.2 %). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain DS-12T belonged to the genus Flavobacterium . Strain DS-12T produced flexirubin-type pigments. Gliding motility was not observed. The major fatty acids of strain DS-12T were iso-C15 : 0 (48.0 %), summed feature 9 (comprising iso-C17 : 1ω9c and/or C16 : 0 10-methyl; 19.3 %), iso-C17 : 0 3-OH (8.5 %) and summed feature 3 (comprising one or more of C16 : 1ω7c, C16 : 1ω6c and iso-C15 : 0 2-OH; 7.2 %). The only respiratory quinone was menaquinone-6 and the major polyamine was homospermidine. Strain DS-12T contained phosphatidyldimethylethanolamine, phosphatidylserine, phosphatidylethanolamine, one unknown phospholipid and one unknown aminolipid. The DNA G+C content was 37.4 mol%. Phylogenetic inference and phenotypic properties indicated that strain DS-12T represents a novel species of the genus Flavobacterium , for which the name Flavobacterium ummariense sp. nov. is proposed. The type strain is DS-12T ( = CCM 7847T  = MTCC 10766T). An emended description of Flavobacterium ceti is also given.

An orange-pigmented bacterial strain, designated LP100T, was isolated from hexachlorocyclohexane-contaminated soil (Lucknow, India). A neighbour-joining tree based on 16S rRNA gene sequences showed that strain LP100T occupied a distinct phylogenetic position in the Pontibacter species cluster, showing highest similarity with Pontibacter lucknowensis DM9T (97.4 %). Levels of similarity to strains of other Pontibacter species ranged between 94.0 and 96.8 %. Strain LP100T contained MK-7 as the predominant menaquinone and sym-homospermidine was the major polyamine in the cell. The major cellular fatty acids of strain LP100T were anteiso-C17 : 0 A, iso-C15 : 0 and iso-C18 : 1 H. The polar lipid profile of strain LP100T showed the presence of phosphatidylethanolamine, an unidentified aminophospholipid, three unknown aminolipids and two unknown polar lipids. The G+C content of strain LP100T was 58.2 mol%. The results of DNA–DNA hybridization, biochemical and physiological tests clearly distinguish the novel strain from closely related species of the genus Pontibacter . Therefore, strain LP100T represents a novel species of the genus Pontibacter for which the name Pontibacter indicus is proposed. The type strain is LP100T ( = CCM8435T = MCC2027T).