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

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.

Evidence for the feasibility of transmembrane proton gradient regulating oxytetracycline extracellular biodegradation mediated by biosynthesized palladium nanoparticles.

Extracellular biodegradation is a promising technology for removing antibiotics and repressing the spread of resistance genes, but the strategy is limited by the low extracellular electron transfer (EET) efficiency of microorganisms. In this work, biogenic Pd0 nanoparticles (bio-Pd0) were introduced in cells in situ to enhance oxytetracycline (OTC) extracellular degradation and the effects of transmembrane proton gradient (TPG) on EET and energy metabolism mediated by bio-Pd0 were investigated. The results indicated that the intracellular OTC concentration gradually decreased with increase in pH due to the simultaneous decreases of OTC adsorption and TPG-dependent OTC uptake. On the contrary, the efficiency of OTC biodegradation mediated by bio-Pd0@B. megaterium showed a pH-dependent increase. The negligible intracellular OTC degradation, the high dependence of OTC biodegradation on respiration chain and the results on enzyme activity and respiratory chain inhibition experiments showed that NADH-dependent (rather than FADH2-dependent) EET process mediated by substrate-level phosphorylation modulated OTC biodegradation due to high energy storage and proton translocation capacity. Moreover, the results showed that altering TPG is an efficient approach to improve EET efficiency, which can be attributed to the increased NADH generation by the TCA cycle, enhanced transmembrane electron output efficiency (as evidenced by increased intracellular electron transfer system (IETS) activity, the negative shift of onset potential, and enhanced one-electron transfer through bound flavin) and stimulation of substrate-level phosphorylation energy metabolism catalyzed by succinic thiokinase (STH) under low TPG conditions. The results of structural equation model that OTC biodegradation was directly and positively modulated by the net outward proton flux as well as STH activity, and indirectly regulated by TPG through NADH level and IETS activity confirmed the previous findings. This study provides a new perspective for engineering microbial EET and application of bioelectrochemistry processes in bioremediation.

Bioaugmentation reconstructed nitrogen metabolism in full-scale simultaneous partial nitrification-denitrification, anammox and sulfur-dependent nitrite/nitrate reduction (SPAS).

To enhance nitrogen removal of fermentation pharmaceutical wastewater with high nitrogen load, a full-scale process based on simultaneous partial nitrification-denitrification/ anammox/ sulfur autotrophic denitrification (SPAS) was established via inoculating with bioaugmentation consortia in a modified two-stage AO. More than 93 % TN and 98 % NH4+-N removal were obtained at a rate of 0.8 kg-N/ m3/d in the first A/O stage, in which short-cut SND was involved with 96.05 % ESND when bioaugmented with SND, while S0-SAD could coordinate with anammox to exert further deep denitrification in the second A/O stage. KEGG analysis demonstrated that the SPAS process was synergism of HD, PN/PDN, SND, SAD and anammox metabolism, bioaugmentation could significantly up-regulate genes related to microbial metabolism (TCA cycle, Carbon metabolism, ABC transporters) and environmental adaptation (Two-component system, Quorum sensing) based on the FAPROTAX and Picrust2 functional prediction. This study provided a new perspective in engineering applications.

Highly sensitive α-hemolysin nanopore detection of MUC1 based on 3D DNA walker.

Mucin 1(MUC1) is an effective marker of breast cancer, so it is of great significance to develop a simple, sensitive and highly selective MUC1 detection sensor. Herein, we constructed a label-free nanopore biosensor for rapid and highly sensitive detection of MUC1. The presence of MUC1 triggered the modification of the DNAzyme walking chain on the surface of Fe3O4 nanoparticles and separation from the aptamer. In the presence of Zn2+, DNAzyme catalyzed hydrolytic cleavage of the hairpin substrate at the scissile rA. The DNAzyme was divided into two fragments and ssDNA was released. ssDNA products from the hairpin substrate can generate a current blocking signal during α-hemolysin nanopore testing. The frequency of signature events showed a linear response toward the concentration of MUC1 in the range of 0.01 nM-100 nM. The sensing system also exhibited high selectivity against other protein and can be used for the detection of real sample.