title: Anaerobic humus and Fe(III) reduction and electron transport pathway by a novel humus-reducing bacterium, Thauera humireducens SgZ-1.
abstract: In this study, an anaerobic batch experiment was conducted to investigate the humus- and Fe(III)-reducing ability of a novel humus-reducing bacterium, Thauera humireducens SgZ-1. Inhibition tests were also performed to explore the electron transport pathways with various electron acceptors. The results indicate that in anaerobic conditions, strain SgZ-1 possesses the ability to reduce a humus analog, humic acids, soluble Fe(III), and Fe(III) oxides. Acetate, propionate, lactate, and pyruvate were suitable electron donors for humus and Fe(III) reduction by strain SgZ-1, while fermentable sugars (glucose and sucrose) were not. UV-visible spectra obtained from intact cells of strain SgZ-1 showed absorption peaks at 420, 522, and 553 nm, characteristic of c-type cytochromes (cyt c). Dithionite-reduced cyt c was reoxidized by Fe-EDTA and HFO (hydrous ferric oxide), which suggests that cyt c within intact cells of strain SgZ-1 has the ability to donate electrons to extracellular Fe(III) species. Inhibition tests revealed that dehydrogenases, quinones, and cytochromes b/c (cyt b/c) were involved in reduction of AQS (9, 10-anthraquinone-2-sulfonic acid, humus analog) and oxygen. In contrast, only NADH dehydrogenase was linked to electron transport to HFO, while dehydrogenases and cyt b/c were found to participate in the reduction of Fe-EDTA. Thus, various different electron transport pathways are employed by strain SgZ-1 for different electron acceptors. The results from this study help in understanding the electron transport processes and environmental responses of the genus Thauera.
authors.affiliation: Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou, 510650, People's Republic of China.
authors.forename: Chen
authors.initials: C
authors.lastname: Ma
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yu
authors.forename: Qin
authors.initials: Q
authors.lastname: Lu
authors.forename: Li
authors.initials: L
authors.lastname: Zhuang
authors.forename: Shun-Gui
authors.initials: SG
authors.lastname: Zhou
mesh_terms: D000693:Anaerobiosis; D002264:Carboxylic Acids / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004579:Electron Transport; D007501:Iron / Q000378:metabolism*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism; D012987:Soil; D012988:Soil Microbiology; D020628:Thauera / Q000378:metabolism*
chemical_list: D002264:Carboxylic Acids; D012987:Soil; D045304:Cytochromes c; D007501:Iron; D010088:Oxidoreductases