Exploration on the Cr(VI) resistance mechanism of a novel thermophilic Cr(VI)‐reducing bacteria Anoxybacillus flavithermusABF1 isolated from Tengchong geothermal region, China

Abstract

Hexavalent chromium resistance and reduction mechanisms of microorganism provide a critical guidance for Cr(VI) bioremediation. However, related researches are limited in mesophiles and deficient for thermophiles. In this work, a novel alkaline Cr(VI)-reducing thermophile Anoxybacillus flavithermus ABF1 was isolated from geothermal region. The mechanisms of Cr(VI) resistance and reduction were investigated. The results demonstrated that A. flavithermus ABF1 could survive in a wide temperature range from 50 C to 70 C and in pH range of 7.0-9.0. Strain ABF1 showed excellent growth activity and Cr(VI) removal performance when initial Cr(VI) concentration was lower than 200 mg L À1 . 93.71% of Cr(VI) was removed at initial concentration of 20 mg L À1 after 72 h. The majority of Cr(VI) was found to be reduced extracellularly by enzymes secreted by cells. XPS and Raman analysis further manifested that Cr 2 O 3 was the product of Cr(VI) reduction. Moreover, the Cr(VI) transportation-related gene cysP and Cr(VI) reduction-related gene azoR of A. flavithermus ABF1 played key roles in inhibiting Cr(VI) entering cells and promoting extracellular Cr(VI) reduction respectively. This work provides novel insight into the mechanisms of Cr(VI) resistance and detoxication of thermophiles, which leads to a promising alternative strategy for heavy metal bioremediation in areas with elevated temperature.

Novel Approaches for Sustainable Management of Chromium Contaminated Wastewater

“…K1 Soil sample 43.6% reduction of 500 mg/l Cr (VI) [76] Stenotrophomonas sp. D6 Soil sample 87.6% reduction of 500 mg/l Cr (VI) [76] Sporosarcina saromensis M52 Sediment sample Complete reduction of 100 mg/l Cr (VI) [77] Bacillus cereus (TIB3) strain Mine tailings 82% reduction of 100 mg/l Cr (VI) [78] Bacillus strain TCL Coalmine lake Complete reduction of 200 mg/l Cr (VI) [55] Anoxybacillus flavithermus ABF1 Geothermal region 93.71% reduction of 20 mg/l Cr (VI) [79] Novel Approaches for Sustainable Management of Chromium Contaminated Wastewater DOI: http://dx.doi.org/10.5772/intechopen.1003944…”