Udita Mukherjee

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.

Modification of Rifamycin Polyketide Backbone Leads to Improved Drug Activity against Rifampicin-resistant Mycobacterium tuberculosis

Background: The emergence of drug-resistant tuberculosis has called for the discovery of new antitubercular drugs. Results: We successfully generated 24-desmethylrifampicin by modifying the rifamycin polyketide backbone. Conclusion: 24-Desmethylrifamycin showed better antibacterial activity than rifampicin against multidrug-resistant strains of Mycobacterium tuberculosis. Significance: The combined genetic-synthetic strategy used in the study has opened up new avenues for generating more rifamycin analogs. Rifamycin B, a product of Amycolatopsis mediterranei S699, is the precursor of clinically used antibiotics that are effective against tuberculosis, leprosy, and AIDS-related mycobacterial infections. However, prolonged usage of these antibiotics has resulted in the emergence of rifamycin-resistant strains of Mycobacterium tuberculosis. As part of our effort to generate better analogs of rifamycin, we substituted the acyltransferase domain of module 6 of rifamycin polyketide synthase with that of module 2 of rapamycin polyketide synthase. The resulting mutants (rifAT6::rapAT2) of A. mediterranei S699 produced new rifamycin analogs, 24-desmethylrifamycin B and 24-desmethylrifamycin SV, which contained modification in the polyketide backbone. 24-Desmethylrifamycin B was then converted to 24-desmethylrifamycin S, whose structure was confirmed by MS, NMR, and X-ray crystallography. Subsequently, 24-desmethylrifamycin S was converted to 24-desmethylrifampicin, which showed excellent antibacterial activity against several rifampicin-resistant M. tuberculosis strains.

Draft Genome Sequence of Sphingobium sp. Strain HDIPO4, an Avid Degrader of Hexachlorocyclohexane.

ABSTRACT Sphingobium sp. strain HDIPO4 was isolated from a hexachlorocyclohexane (HCH) dumpsite and degraded HCH isomers rapidly. The draft genome sequence of HDIPO4 (~4.7 Mbp) contains 143 contigs and 4,646 coding sequences with a G+C content of 65%.

Genome Sequence of Acinetobacter sp. Strain HA, Isolated from the Gut of the Polyphagous Insect Pest Helicoverpa armigera

In this study, Acinetobacter sp. strain HA was isolated from the midgut of a fifth-instar larva of Helicoverpa armigera. Here, we report the draft genome sequence (3,125,085 bp) of this strain that consists of 102 contigs, 2,911 predicted coding sequences, and a G+C content of 41%.

Luteimonas tolerans sp. nov., isolated from hexachlorocyclohexane-contaminated soil.

A Gram-stain-negative, aerobic, rod-shaped, non-spore-forming, yellow pigmented bacterial strain (UM1T) was isolated from the hexachlorocyclohexane (HCH)-contaminated dumpsite located at Ummari village in Lucknow, India. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain UM1T belongs to the genus Luteimonas with Luteimonas aestuarii B9T as the closest neighbour (97.2% 16S rRNA gene sequence similarity). The DNA G+C content of strain UM1T was 64.3 mol%. The major polar lipids were diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). Main fatty acids were iso-C15:0, iso-C11:0, iso-C11:0 3-OH, iso-C17:0 and summed feature 9 (C16:0 10-methyl and/or iso-C17:1ω9c). Ubiquinone (Q-8) was the only respiratory quinone. Spermidine was detected as the major polyamine. The DNA-DNA relatedness value of strain UM1T with respect to its closest neighbour Luteimonas aestuarii B9T was well below 70 % (∼49%). Thus, data obtained from phylogenetic analysis, DNA-DNA hybridization, and chemotaxonomical and biochemical analyses supports classification of strain UM1T as representative of a novel species of the genus Luteimonas, for which the name Luteimonas tolerans sp. nov. is proposed. The type strain is UM1T (=DSM 28473T=MCC 2572T=KCTC 42936T).

Draft Genome Sequence of the Rifamycin Producer Amycolatopsis rifamycinica DSM 46095

ABSTRACT Amycolatopsis rifamycinica DSM 46095 is an actinobacterium that produces rifamycin SV, an antibiotic used against Mycobacterium tuberculosis. Here, we present the draft genome of DSM 46095, which harbors a novel rifamycin polyketide biosynthetic gene cluster (rif PKS) that differed by 10% in nucleotide sequence from the already reported rif PKS cluster of Amycolatopsis mediterranei S699.

Draft Genome Sequence of Amycolatopsis mediterranei DSM 40773, a Tangible Antibiotic Producer

ABSTRACT Amycolatopsis mediterranei DSM 40773 has been of special interest as successors of this strain are in use for the commercial production of rifamycin B. Here we present the draft genome sequence (~10 Mb) of this strain, which contains 108 contigs, 9,198 genes, and has a G+C content of 71.3%.

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.