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Formation of soluble Cr(III) end-products and nanoparticles during Cr(VI) reduction by Bacillus cereus strain XMCr-6

Dong, Guowen, Wang, Yuanpeng, Gong, Libo, Wang, Minggong, Wang, Haitao, He, Ning, Zheng, Yanmei, Li, Qingbiao
Biochemical engineering journal 2013 v.70 pp. 166-172
Bacillus cereus, aerobic conditions, bacteria, bioremediation, chromium, nanoparticles, nucleotide sequences, ribosomal RNA, sequence analysis, soil
The Bacillus cereus strain XMCr-6 was isolated from chromium-contaminated soils and was identified on the basis of biochemical characteristics and 16S rRNA gene sequence analysis. The bacterium exhibited complete reduction of 100mgL−1 Cr(VI) within 48h under aerobic conditions. The reduction of Cr(VI) by XMCr-6 was attributed to cell debris rather than cell free extract, and the reduction mechanism was found to be enzyme-mediated. It was demonstrated that the reduced Cr(III) could bind to cells by coordination with functional groups on the bacterial surfaces while it simultaneously formed soluble Cr(III) end-products through interactions with small organic molecules. Discrete spherical Cr2O3 nanoparticles were observed on the surface of the bacterial cells after Cr(VI) reduction by XMCr-6 in the absence of an appropriate chelating chemical. Our results offer insight into bacterial Cr(VI) reduction processes and will be valuable for understanding reduction mechanisms and Cr(VI) bioremediation.