FDH/Hases-S-chain mediated electron redistributing in Citrobacter freundii JH@FeS during degradation of sulfamethoxazole and nitrate

Abstract

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 (R2 = 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 gFW−1). Structural equation modeling indicated that bio-FeS up-regulated PMF-mediated ATP synthesis (PPMF-ATPs from 0.12 (SN-native) to 0.74 (SN-FeS)) and PMF-mediated NADH (PPMF-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.