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Arsenic contamination in soils causes poisoning in food and finally affects the food chain. Bioremediation by microorganisms is an environmentally friendly method that offers the possibility of detoxifying soil contaminated by arsenic. The present study aimed at isolating and screening bacteria which possess resistance to arsenic from contaminated highland soils. Among 40 isolates obtained, only nine isolates (22.5%) could tolerate a high level of arsenic with the highest MIC of 40 mM. Only four isolates (BAs8, BAs11, BAs19 and BAs29) exhibited promising resistant ability and were selected for further investigations. The selected isolates showed a high potential to solubilize insoluble Ca-phosphate (5.95 to 100.04 mg P L-1), and a moderate potential to produce IAA (9.36 to 20.32 mg IAA L-1). The ability of each isolate to solubilize Ca-phosphate was increased 2 to 6 times when exposed to an arsenite environment. Arsenic-sensitive isolate, BAs7 showed the highest ability to solubilize Ca-phosphate in medium without and with arsenite (55.56 and 100.04 mg L-1, respectively). The results implied that the increment of phosphate solubilization is an important mechanism to exclude arsenic uptake thus less toxicity. The similar results were found with IAA production and might also be another mechanism of bacteria to cope with arsenic toxicity. Our results seemed to be the first report on this clear phenomenon. Isolates BAs29 and BAs11 exhibited high arsenic resistance and established vigorous root growth and dense root hairs of Chinese kale seedlings thus can be used for bioremediation and seedlings growth enhancement.
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