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.

Microbial Community Responses to Vanadium Distributions in Mining Geological Environments and Bioremediation Assessment

“…Similar microorganisms have been identified in groundwater bioremediation efforts as a result of organic carbon source addition (Liu et al, ; Zhang, Hao, et al, ). Thauera is able to reduce Fe (III) under anaerobic conditions (Ma et al, ). Rhodococcus in leachate‐contaminated soil can reduce Pb (IV) (Emenike et al, ), and Brevundimonas in subtropical paddy soils of China is known to participate in Fe (III) reducing processes (Peng et al, ).…”

Magnetite nanoparticles facilitate methane production from ethanol via acting as electron acceptors

“…16S rRNA-based Illumina sequencing results from PEM-HZ revealed that Dechloromonas , Thauera , Desulfovibrio and Clostridium were the most abundant bacterial species. These dominant species have been demonstrated to reduce Fe (III) of iron oxides via respiratory 6 7 8 19 20 21 . Thus, these species detected in PEM-HZ indicated a strong possibility that they were closely related to reducing Fe (III) of magnetite.…”

Magnetite nanoparticles enable a rapid conversion of volatile fatty acids to methane

“…Thauera was also identied during the syntrophic oxidation of acetate and ethanol in paddy soil, 13,21 and has been described for its ability to reduce Fe(III) oxides using acetate and ethanol as electric donors under anaerobic conditions. 13,21,29 Thus, a high proportion of Thauera species identied in the SEM suggested that it was most closely related to reduction of Fe(III) in magnetite. Additionally, 16S rRNA-based Illumina sequencing of the archaeal community in the SEM revealed that Methanobacterium (11%) was the major dominant species, which utilizes H 2 and CO 2 to produce methane.…”