Josef Winter
Karlsruhe Institute of Technology, Germany
Title: Microbiology in arsenate and selenate containing groundwater
Biography
Biography: Josef Winter
Abstract
Groundwater of Punjab/Haryana in Northern India and of the Bengal delta in Southern India exceeds by far the WHO guidelines for Se and As, respectively. Se-containing groundwater is used for irrigation since about 30 years and due to crop rotation from wheat to rice instead of corn much more irrigation water is required and thus Se enriches in top soil. Se seems to adsorb to humic substances since Se concentrations decrease with depth. High Se-concentrations lead to irregular, patchy plant growth and fruit are poisonous to humans, causing lethal skin lesions called selenosis over the years. Selenite and selenate reducing bacteria in top soil convert water soluble Se into insoluble Se nanoparticles if enough bio-available DOC is supplied. Duganella and Arthrobacter species were isolated from soil of Punjab. Th ese soil bacteria form pure Se nanoparticles if grown in pure culture that can easily be isolated and applied in biotechnology and medicine. Geogenic arsenic of the Himalaya is eroded and transported with river water. With soil particles it sediments over decades in the Bengal delta in Southern India. Due to low solubility of arsenate in pure, oxygencontaining groundwater toxic arsenic concentrations in water from deep wells are below health-aff ecting concentrations. However, if groundwater from less deep wells is polluted by soluble DOC, oxygen is used up rapidly and bacteria such as Pseudomonas species respire or reduce arsenate to water-soluble arsenite, which is similar toxic as senenate if the water is consumed by animals or humans, causing arsenicosis. Solubilization of arsenate was shown in a large fi eld experiment. Pseudomonas sp. was isolated and rapid selenite production from selenate occurred during growth.