title: In Situ Spectral Kinetics of Cr(VI) Reduction by c-Type Cytochromes in A Suspension of Living Shewanella putrefaciens 200.
abstract: Although c-type cytochromes (c-Cyts) mediating metal reduction have been mainly investigated with in vitro purified proteins of dissimilatory metal reducing bacteria, the in vivo behavior of c-Cyts is still unclear given the difficulty in measuring the proteins of intact cells. Here, c-Cyts in living Shewanella putrefaciens 200 (SP200) was successfully quantified using diffuse-transmission UV/Vis spectroscopy due to the strong absorbance of hemes, and the in situ spectral kinetics of Cr(VI) reduction by c-Cyts were examined over time. The reduced product Cr(III) observed on the cell surface may play a role in inhibiting the Cr(VI) reduction and reducing the cell numbers with high concentrations (>200 μM) of Cr(VI) evidenced by the 16S rRNA analysis. A brief kinetic model was established with two predominant reactions, redox transformation of c-Cyts and Cr(VI) reduction by reduced c-Cyts, but the fitting curves were not well-matched with c-Cyts data. The Cr(III)-induced inhibitory effect to the cellular function of redox transformation of c-Cyts was then added to the model, resulting in substantially improved the model fitting. This study provides a case of directly examining the reaction properties of outer-membrane enzyme during microbial metal reduction processes under physiological conditions.
authors.affiliation: Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou, 510650 P. R. China.
authors.forename: Tongxu
authors.initials: T
authors.lastname: Liu
authors.affiliation: Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou, 510650 P. R. China.|School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW, 2052 Australia.
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Li
authors.affiliation: Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou, 510650 P. R. China.
authors.forename: Fangbai
authors.initials: F
authors.lastname: Li
authors.affiliation: Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou, 510650 P. R. China.
authors.forename: Rui
authors.initials: R
authors.lastname: Han
authors.affiliation: Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou, 510650 P. R. China.
authors.forename: Yundang
authors.initials: Y
authors.lastname: Wu
authors.affiliation: School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW, 2052 Australia.
authors.forename: Xiu
authors.initials: X
authors.lastname: Yuan
authors.affiliation: Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou, 510650 P. R. China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
mesh_terms: D058491:Bacterial Load; D002857:Chromium / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism*; D007700:Kinetics; D010084:Oxidation-Reduction; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D020614:Shewanella putrefaciens / Q000378:metabolism*; D013053:Spectrophotometry
chemical_list: D012336:RNA, Ribosomal, 16S; D002857:Chromium; C074702:chromium hexavalent ion; D045304:Cytochromes c