Project description:Mercury (Hg) is one of the most toxic heavy metal and is extremely harmful for the environment. The permissible limit of mercury in industrial effluents is 0.001 ppm, whereas there are various sites having very high levels of mercury contamination. In the present study, 10 different mercury (Hg) resistant bacterial strains were isolated from Ulhas Estuary, Mumbai (Hg concentration of 107 ppm). All the strains were subsequently grown on higher concentration of mercuric chloride (HgCl2), one of the isolate (USP5) showed significant growth at high concentration of Hg (40 ppm) and 16S rRNA gene sequencing revealed the identity of the bacterium as Methylotenera mobilis, (Accession no. KT714144). The mer operon was isolated and cloned in E.coli and checked for its ability to tolerate higher concentration of Hg. It has shown growth up to 70 ppm of Hg, also presence of merA gene indicated its ability to detoxify Hg into less toxic volatile form. The atomic absorption spectrophotometry confirmed the ability of clone to efficiently detoxify 60-90 % of the Hg (10-70 ppm) within 48-72 h. This clone can be used for effective volatilization of Hg from contaminated areas.
Project description:Methylotenera species, unlike their close relatives in the genera Methylophilus, Methylobacillus, and Methylovorus, neither exhibit the activity of methanol dehydrogenase nor possess mxaFI genes encoding this enzyme, yet they are able to grow on methanol. In this work, we integrated a genome-wide proteomics approach, shotgun proteomics, and a genome-wide transcriptomics approach, shotgun transcriptome sequencing (RNA-seq), of Methylotenera mobilis JLW8 to identify genes and enzymes potentially involved in methanol oxidation, with special attention to alternative nitrogen sources, to address the question of whether nitrate could play a role as an electron acceptor in place of oxygen. Both proteomics and transcriptomics identified a limited number of genes and enzymes specifically responding to methanol. This set includes genes involved in oxidative stress response systems, a number of oxidoreductases, including XoxF-type alcohol dehydrogenases, a type II secretion system, and proteins without a predicted function. Nitrate stimulated expression of some genes in assimilatory nitrate reduction and denitrification pathways, while ammonium downregulated some of the nitrogen metabolism genes. However, none of these genes appeared to respond to methanol, which suggests that oxygen may be the main electron sink during growth on methanol. This study identifies initial targets for future focused physiological studies, including mutant analysis, which will provide further details into this novel process.
