Considering the negligent degradation of sulfamethoxazole (SMX) by Citrobacter freundii JH , the incorporation of bio-FeS could initiate the SMX biodegradation to 0.0444 (S-FeS), and further to 0.0564 mg L −1 mg −1 protein d −1 (SN-FeS) when coexisted with nitrate. Electrochemical (LSV, I-t , DPV, EIS and EDC) and respiratory inhibition experiments clarified that the bio-FeS could greatly switch/redistribute electron transmembrane-transfer from intracellular to extracellular mainly via FDH/Hases-S-chain, as revealed by the significant increase of ipa- FDH/Hases / ipa- FC-Cyts and ipc- FDH/Hases / ipc- FC-Cyts (from 1.09 and 1.07 (SN-native) to 1.50 and 3.58 (SN-FeS)), while nitrate (linear fitting with NADH ( R 2 = 0.9903)) mainly intensified CoQ-L-chain related INET from Complex I to CoQ to compensate for the electronic competition with SMX. SN-FeS system detoxified the SMX on microbial metabolism (such as membrane rupture and oxidative stress induction) with high SOD activity (737.93 U g FW −1 ). Structural equation modeling indicated that bio-FeS up-regulated PMF-mediated ATP synthesis ( P PMF-ATPs from 0.12 (SN-native) to 0.74 (SN-FeS)) and PMF-mediated NADH ( P PMF-NADH from -0.72 (SN-native) to 0.63 (SN-FeS)), and the nitrate addition intensified this positive feedback. Overall, this study provides a new perspective for bionanoparticles via electron transfer/redistribution to detoxify and launch the antibiotics biodegradation in ecological environment.
Jinghao Wang,Wenmin Lin,Yuancai Chen,Yongyou Hu,Qijin Luo
Due to the excellent hydrogen affinity and high conductivity, palladium nanoparticles (Pd NPs) were considered as a potential strategy to regulate bacterial electron transfer and energy metabolism. Herein, Citrobacter freundii JH, capable of in-situ biosynthesizing Pd(0) NPs, was employed to promote Pt(IV) reduction. The results showed that the Pt(IV) reduction to Pt(II) was accomplished mainly via the flavins-mediated extracellular electron transfer (EET) process, while Pt(II) reduction to Pt(0) was limit step, and proceeded via two intracellular respiratory chains, including FDH/Hases-based short chain (S-chain) and typical CoQ-involved long respiratory chain ( L -chain). Noteworthily, the incorporation of Pd(0) NPs mainly diverted the electrons to S-chain (as high as 71.7%−73.4%) by improving the hydrogenases (Hases) activity. Furthermore, Pd(0) NPs could stimulate the secreting of flavins and the combination between flavins and cytochrome c (c-Cyt), which converted electron transfer manner of L -chain. Additionally, Pd(0) NPs might also act as alternative proton channels to improve the energy metabolism. These findings provided significant insights into the promotion by Pd(0) NPs in terms of electron generation, electron consumption and proton translocation.
Jinghao Wang,Huimin Liu,Song Song,Yuancai Chen,Yongyou Hu
Microbial electron output capacity is critical for organic contaminants biodegradation. Herein, original C. freundii JH could oxidate formate in anaerobic respiration, but lack the ability to degrade sulfamethoxazole (SMX). While the incorporation of Pd(0) could effectively improve the electron output via improving the combination between flavins and c-type cytochromes (c-Cyts), increasing the activities of key enzymes (formate dehydrogenase , hydrogenase, F 0 F 1 -ATPases), etc. More importantly, the presence of Pd(0) caused the NADH dehydrogenase (complex I) nearly in idle, and triggered the decrease of NADH/NAD + ratio and increase of H + -efflux transmembrane gradient, eventually resulting in the electrons diverting from CoQ-involved long respiratory chain (decreasing from 91.67% to 36.25%) to FDH/Hases-based hydrogen-producing short chain (increasing from 22.44% to 84.88%), which further intensified the electron output. Above changes effectively launched and guaranteed the high-level SMX degradation by palladized C. freundii JH, alleviating the ecotoxicity of SMX in aquatic and terrestrial environments. These conclusions provided the new view to regulate the microbial electron output behaviors.
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