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.

ABSTRACT

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.