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Iron(III) Modification of Bacillus subtilis Membranes Provides Record Sorption Capacity for Arsenic and Endows Unusual Selectivity for As(V)

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journal contribution
posted on 22.02.2016, 05:23 by Ting Yang, Ming-Li Chen, Lan-Hua Liu, Jian-Hua Wang, Purnendu K. Dasgupta
Bacillus subtilis is a spore forming bacterium that takes up both inorganic As­(III) and As­(V). Incubating the bacteria with Fe­(III) causes iron uptake (up to ∼0.5% w/w), and some of the iron attaches to the cell membrane as hydrous ferric oxide (HFO) with additional HFO as a separate phase. Remarkably, 30% of the Bacillus subtilis cells remain viable after treatment by 8 mM Fe­(III). At pH 3, upon metalation, As­(III) binding capacity becomes ∼0, while that for As­(V) increases more than three times, offering an unusual high selectivity for As­(V) against As­(III). At pH 10 both arsenic forms are sorbed, the As­(V) sorption capacity of the ferrated Bacillus subtilis is at least of 11 times higher than that of the native bacteria. At pH 8 (close to pH of most natural water), the arsenic binding capacity per mole iron for the ferrated bacteria is greater than those reported for any iron containing sorbent. A sensitive arsenic speciation approach is thus developed based on the binding of inorganic arsenic species by the ferrated bacteria and its unusual high selectivity toward As­(V) at low pH.