Nidhi Garg

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

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.

Pontibacter ramchanderi sp. nov., isolated from hexachlorocyclohexane-contaminated pond sediment

A Gram-stain-negative, motile, red pigmented, rod-shaped bacterium, designated strain LP43(T), was isolated from hexachlorocyclohexane (HCH)-contaminated soil sediment (Lucknow, India). Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate formed a cluster with the genus Pontibacter in the phylum Bacteroidetes with sequence similarities ranging from 92.9 to 97.0 % with species of the genus Pontibacter. The DNA G+C content of strain LP43(T) was 59.1 mol%. The polar lipid profile of strain LP43(T) showed the presence of phosphatidylethanolamine, an unidentified aminophospholipid, unknown aminolipids and unknown polar lipids. Strain LP43(T) contained MK-7 as the predominant menaquinone and sym-homospermidine as the major polyamine. The major cellular fatty acids of strain LP43(T) were, iso-C15 : 0 (15.74 %), iso-C15 : 0 3-OH (7.57 %), iso-C17 : 0 3-OH (7.32 %), summed feature 4 (iso-C17 : 1 I/anteiso-C17 : 1 B) (31.22 %) and summed feature 8 (C18 : 1ω7c/ C18 : 1ω6c) (7.60 %). Based on the results of DNA-DNA hybridization and phenotypic and genotypic characteristics, strain LP43(T) represents a novel species of the genus Pontibacter, for which the name Pontibacter ramchanderi is proposed. The type strain is LP43(T) (= CCM 8406(T) = MCC 2019(T)).

Pontibacter indicus sp. nov., isolated from hexachlorocyclohexane-contaminated soil.

An orange-pigmented bacterial strain, designated LP100(T), was isolated from hexachlorocyclohexane-contaminated soil (Lucknow, India). A neighbour-joining tree based on 16S rRNA gene sequences showed that strain LP100(T) occupied a distinct phylogenetic position in the Pontibacter species cluster, showing highest similarity with Pontibacter lucknowensis DM9(T) (97.4 %). Levels of similarity to strains of other Pontibacter species ranged between 94.0 and 96.8 %. Strain LP100(T) contained MK-7 as the predominant menaquinone and sym-homospermidine was the major polyamine in the cell. The major cellular fatty acids of strain LP100(T) were anteiso-C17 : 0 A, iso-C15 : 0 and iso-C18 : 1 H. The polar lipid profile of strain LP100(T) showed the presence of phosphatidylethanolamine, an unidentified aminophospholipid, three unknown aminolipids and two unknown polar lipids. The G+C content of strain LP100(T) 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 LP100(T) represents a novel species of the genus Pontibacter for which the name Pontibacter indicus is proposed. The type strain is LP100(T) ( = CCM8435(T) = MCC2027(T)).

Metabolomics of hexachlorocyclohexane (HCH) transformation: ratio of LinA to LinB determines metabolic fate of HCH isomers

Although the production and use of technical hexachlorocyclohexane (HCH) and lindane (the purified insecticidal isomer γ-HCH) are prohibited in most countries, residual concentrations still constitute an immense environmental burden. Many studies describe the mineralization of γ-HCH by bacterial strains under aerobic conditions. However, the metabolic fate of the other HCH isomers is not well known. In this study, we investigated the transformation of α-, β-, γ-, δ-, ε-HCH, and a heptachlorocyclohexane isomer in the presence of varying ratios of the two enzymes that initiate γ-HCH degradation, a dehydrochlorinase (LinA) and a haloalkane dehalogenase (LinB). Each substrate yielded a unique metabolic profile that was strongly dependent on the enzyme ratio. Comparison of these results to those of in vivo experiments with different bacterial isolates showed that HCH transformation in the tested strains was highly optimized towards productive metabolism of γ-HCH and that under these conditions other HCH-isomers were metabolized to mixtures of dehydrochlorinated and hydroxylated side-products. In view of these results, bioremediation efforts need very careful planning and toxicities of accumulating metabolites need to be evaluated.

Draft Genome Sequence of Thermus sp. Strain RL, Isolated from a Hot Water Spring Located atop the Himalayan Ranges at Manikaran, India

Thermus sp. strain RL was isolated from a hot water spring (90°C to 98°C) at Manikaran, Himachal Pradesh, India. Here we report the draft genome sequence (20,36,600 bp) of this strain. The draft genome sequence consists of 17 contigs and 1,986 protein-coding sequences and has an average G+C content of 68.77%.

Pontibacter chinhatensis sp. nov., isolated from pond sediment containing discarded hexachlorocyclohexane isomer waste.

A halotolerant, Gram-negative, rod-shaped and light-red-pigmented bacterium, designated LP51(T), was isolated from pond sediment near a hexachlorocyclohexane dumpsite located at Chinhat, Lucknow, India. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain LP51(T) formed a distinct phyletic clade along with the members of the genus Pontibacter. The 16S rRNA gene sequence similarity to members of the genus Pontibacter ranged from 94.2 to 99.4%. The cells were motile, aerobic and catalase- and oxidase-positive. The major fatty acids were iso-C15 : 0 (17.8%), iso-C15 : 0 3-OH (8.8%), iso-C17 : 0 3-OH (5.7%), summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c; 6.5%) and summed feature 4 (iso-C17 : 1 I and/or anteiso-C17  : 1 B; 30.7%). The polar lipid profile of strain LP51(T) showed the presence of phosphatidylethanolamine, an unidentified aminophospholipid, unknown aminolipids, unknown polar lipids and unknown glycolipids. DNA-DNA relatedness of strain LP51(T) with respect to the most closely related type strain, Pontibacter korlensis X14-1(T), was 47.2%. On the basis of this information, it is proposed that the isolate be assigned to a novel species of the genus Pontibacter, for which the name Pontibacter chinhatensis sp. nov. is proposed. The type strain is LP51(T) ( = CCM 8436(T) = MCC 2070(T)).

Changes in the bacterial community and lin genes diversity during biostimulation of indigenous bacterial community of hexachlorocyclohexane (HCH) dumpsite soil

In this study hexachlorocyclohexane (HCH) contaminated soil (with HCH level 84 g/kg of soil) from HCH dumpsite (Ummari village, Lucknow, India) was used to demonstrate biostimulation approach for HCH bioremediation. Different nutrients (molasses and ammonium phosphate) were used in different pits having contaminated soil to stimulate the indigenous microbial community. There was a substantial reduction in the total HCH content of the soil in 12 months long experiment. Maximum reduction was seen in the pit that received a combination of molasses and ammonium phosphate. A change in the microbial community concomitant with degradation of HCH was observed. Sphingomonads, which are known degraders of HCH, were found to dominate the experimental pits. Moreover changes in linA and linB gene (primary genes involved in HCH degradation) diversity and number were also seen as revealed by T-RFLP and RT-PCR respectively. The study suggests the prospects of biostimulation in decontaminating soils heavily contaminated with HCH.

Bioremediation of Hexachlorocyclohexane (HCH) Pollution at HCH Dump Sites

Globally, the period from early the 1950s to late 1980s has shown an increased use of primarily three pesticides namely DDT.

A new life in a bacterium through synthetic genome: a successful venture by craig venter

The fi rst synthetic genome, a stripped down version of a natural organism, is only the beginning. I now want to go further. My company Synthetic Genomics Inc., is already trying to develop cassettes-modules of genes-to turn an organism into a biofactory that could make clean hydrogen fuel from sunlight and water or soak up more carbon dioxide. From there I want to take us far from shore into unknown waters, to a new phase of evolution, to the day when one DNA-based species can sit down at a computer to design another. I plan to show that we understand the software of life by creating true artifi cial life. And in this way I want to discover whether a life decoded is truly a life understood [1]. – A Life Decoded By J. Craig Venter