Microbial consortium and impact of industrial mining on the Natural High Background Radiation Area (NHBRA), India - Characteristic role of primordial radionuclides in influencing the community structure and extremophiles pattern.

The present investigation is the first of its kind which aims to study the characteristics of microbial consortium inhabiting one of the natural high background radiation areas of the world, Chavara Coast in Kerala, India. The composition of the microbial community and their structural changes were evaluated under the natural circumstances with exorbitant presence of radionuclides in the sediments and after the radionuclide's recession due to mining effects. For this purpose, the concentration of radionuclides, heavy metals, net radioactivity estimation via gross alpha and beta emitters and other physiochemical characteristics were assessed in the sediments throughout the estuarine stretch. According to the results, the radionuclides had a significant effect in shaping the community structure and composition, as confirmed by the bacterial heterogeneity achieved between the samples. The results indicate that high radioactivity in the background environment reduced the abundance and growth of normal microbial fauna and favoured only the growth of certain extremophiles belonging to families of Piscirickettsiacea, Rhodobacteriacea and Thermodesulfovibrionaceae, which were able to tolerate and adapt towards the ionizing radiation present in the environment. In contrast, communities from Comamondacea, Sphingomonadacea, Moraxellacea and Erythrobacteracea were present in the sediments collected from industrial outlet, reinforcing the potent role of radionuclides in governing the community pattern of microbes present in the natural environment. The study confirms the presence of these novel and unidentified bacterial communities and further opens the possibility of utilizing their usefulness in future prospects.

Intracellular toxicity exerted by PCBs and role of VBNC bacterial strains in biodegradation.

Polychlorinated biphenyls (PCBs) are xenobiotic compounds that persists in the environment for long-term, though its productivity is banned. Abatement of the pollutants have become laborious due to it's recalcitrant nature in the environment leading to toxic effects in humans and other living beings. Biphenyl degrading bacteria co-metabolically degrade low chlorinated PCBs using the active metabolic pathway. bph operon possess different genetic arrangements in gram positive and gram negative bacteria. The binding ability of the genes and the active sites were determined by PCB docking studies. The active site of bphA gene with conserved amino acid residues determines the substrate specificity and biodegradability. Accumulation of toxic intermediates alters cellular behaviour, biomass production and downturn the metabolic activity. Several bacteria in the environment attain unculturable state which is viable and metabolically active but not cultivable (VBNC). Resuscitation-promoting factor (Rpf) and Rpf homologous protein retrieve the culturability of the so far uncultured bacteria. Recovery of this adaptive mechanism against various physical and chemical stressors make a headway in understanding the functionality of both environmental and medically important unculturable bacteria. Thus, this paper review about the general aspects of PCBs, cellular toxicity exerted by PCBs, role of unculturable bacterial strains in biodegradation, genes involved and degradation pathways. It is suggested to extrapolate the research findings on extracellular organic matters produced in culture supernatant of VBNC thus transforming VBNC to culturable state.

Spatial variance of POPs and heavy metals in transformer oil-contaminated soil around Tamil Nadu.

The persistent organic pollutants in the environment are one of the global issues to their unregulated disposal and informal recycling. This study investigates the contamination of soil with polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), phenolic compounds and heavy metals via spillage of transformer oil (TO). Fresh TO (FTO), used TO (UTO) and soil samples were analysed using GC-MS to confirm the presence of 8 PCB congeners, 16 PAHs and 24 types of phenolic compounds and using inductively coupled plasma optical emission spectrometry to confirm the presence of 7 heavy metals. The chromatographic analysis revealed the levels of mono-, di-, tri-, tetra-, penta-, hexa-, hepta- and octachlorobiphenyls in FTO to be 5.63, 25.24, 0.195, 0.185, 2.169, 1.023 and 5.28 mg/L and the level of mono-, di-, tri-, tetra-, penta- and hexachlorobiphenyls in UTO to be 0.27, 1.21, 1.31, 0.80, 1.77 and 3.90 mg/L. Analysis of soil from 10 different TO-contaminated sites showed the presence of PCBs, PAHs, phenolic compounds and heavy metals in the concentration range of 0.53-42.87 mg/kg, 3.19-246.6 µg/kg, 0.01-4086.45 µg/kg and 1.0-401.3 mg/kg, respectively. The variation in the concentration of these compounds and heavy metals among different sampling sites was determined using principal component analysis (PCA), metric multi-dimensional scaling (MDS) and Bray-Curtis cluster analysis (Bu-CA). The toxicity equivalence factor and the mechanism involved in the disruption of endocrine system are discussed. Thus, this study exemplifies the need for complete ban of PCB-containing TOs in developing countries and urges the need for technology for the disposal of TO.