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•Multiple mediators function as electron shuttles to promote anammox process;•The EET capability of anammox bacteria can be facilitated by external mediators;•The concurrent presence ...of mediators triggered the activation of essential enzymes;•The application perspective should focus on the EET-enhanced anammox optimization.
The anaerobic ammonium oxidation (anammox) process, transforming ammonia into nitrogen gas in oxygen-free environments using nitrite as an electron acceptor, is increasingly recognized for its potential in treating ammonium-rich wastewater. A major challenge for widespread application of this technology is the limited presence of nitrite in most wastewaters. The intrinsic electroactivity of anammox bacteria implies that the introduction of exogenous additives through the extracellular electron transfer (EET) process could effectively stimulate ammonia oxidation even in the absence of nitrite. This comprehensive review consolidates various approaches to enhance EET-dependent anammox, including the utilization of carbonaceous materials, metal ions, and humic substances. Molecular mechanisms involved in enhancing nitrogen removal performance based on extracellular electron transfer capacity are expounded. The co-occurrence of electron acceptors and exogenous electron shuttles is proposed to increase the activity of c-type cytochromes (c-Cyts) and N-acyl-homoserine lactones (AHLs) in extracellular polymeric substances (EPS), as well as enzymes such as hydrazine synthase (HZS) and hydrazine dehydrogenase (HDH), leading to stable a nitrogen removal performance. This review presents novel insights into the engineering of the EET-enhanced anammox process, providing a theoretical framework for its advancement and optimization.
A close relationship between CM and CO chondrites has been suggested by previous petrologic and isotopic studies, leading to the suggestion that they may originate from similar precursor materials or ...even a common parent body. In this study, we evaluate the genetic relationship between CM and CO chondrites using Ti, Cr, and O isotopes. We first provide additional constraints on the ranges of ε50Ti and ε54Cr values of bulk CM and CO chondrites by reporting the isotopic compositions of CM2 chondrites Murchison, Murray, and Aguas Zarcas and the CO3.8 chondrite Isna. We then report the ε50Ti and ε54Cr values for several ungrouped and anomalous carbonaceous chondrites that have been previously reported to exhibit similarities to the CM and/or CO chondrite groups, including Elephant Moraine (EET) 83226, EET 83355, Grosvenor Mountains (GRO) 95566, MacAlpine Hills (MAC) 87300, MAC 87301, MAC 88107, and Northwest Africa (NWA) 5958, and the O-isotope compositions of a subset of these samples. We additionally report the Ti, Cr, and O isotopic compositions of additional ungrouped chondrites LaPaz Ice Field (LAP) 04757, LAP 04773, Lewis Cliff (LEW) 85332, and Coolidge to assess their potential relationships with known carbonaceous and ordinary chondrite groups. LAP 04757 and LAP 04773 exhibit isotopic compositions indicating they are low-FeO ordinary chondrites. The isotopic compositions of Murchison, Murray, Aguas Zarcas, and Isna extend the compositional ranges defined by the CM and CO chondrites in ε50Ti versus ε54Cr space. The majority of the ungrouped carbonaceous chondrites with documented similarities to the CM and/or CO chondrites plot outside the CM and CO group fields in plots of ε50Ti versus ε54Cr, Δ17O versus ε50Ti, and Δ17O versus ε54Cr. Therefore, based on differences in their Ti, Cr, and O isotopic compositions, we conclude that the CM, CO, and ungrouped carbonaceous chondrites likely represent samples of multiple distinct parent bodies. We also infer that these parent bodies formed from precursor materials that shared similar isotopic compositions, which may indicate formation in regions of the protoplanetary disk that were in close proximity to each other.
Viscosity is a key parameter of mitochondria that related to several diseases. To design a probe acting as both the mitochondria-targeted viscosity sensor and photosensitizer is meaningful for ...diagnosis and therapies. Herein, we report a ratiometric viscosity sensor with dual-emission mediated by excitation energy transfer (EET) effect, which can detect the mitochondrial viscosity and serve as an efficient photosensitizer to eradicate cancer cells. The probe comprises of a blue-emitting imidazole moiety as the energy donor and a green-emitting boron dipyrromethene (BODIPY) core as the energy acceptor, respectively. Via viscosity-modulated EET effect, the dual-emissive probe can sensitively detect the medium viscosity in a ratiometric model. Directed by imidazole as the targeting factor, the probe can specifically accumulate in mitochondria and ratiometrically determine the intracellular viscosity increase induced by Nystatin treatment. Furthermore, it also exhibits light-triggered reactive oxygen species (ROS) generation including singlet oxygen and superoxide radical, which can efficiently kill the cancer cells under white light illumination. Thus, this work provides a versatile and promising candidate for disease diagnosis and phototherapy.
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•Excitation energy transfer (EET) conjugated molecule shows viscosity-mediated dual-emission fluorescence property.•The fluorophore can specially target mitochondria and ratiometrically reveal the viscosity change.•Viscosity sensor exhibits light-triggered ROS generation for efficient photokilling on dysfunctional cells.
Electroactive microorganisms (EAMs) are ubiquitous in nature and have attracted considerable attention as they can be used for energy recovery and environmental remediation via their extracellular ...electron transfer (EET) capabilities. Although the EET mechanisms of Shewanella and Geobacter have been rigorously investigated and are well characterized, much less is known about the EET mechanisms of other microorganisms. For EAMs, efficient EET is crucial for the sustainable economic development of bioelectrochemical systems (BESs). Currently, the low efficiency of EET remains a key factor in limiting the development of BESs. In this review, we focus on the EET mechanisms of different microorganisms, (i.e., bacteria, fungi, and archaea). In addition, we describe in detail three engineering strategies for improving the EET ability of EAMs: (1) enhancing transmembrane electron transport via cytochrome protein channels; (2) accelerating electron transport via electron shuttle synthesis and transmission; and (3) promoting the microbe-electrode interface reaction via regulating biofilm formation. At the end of this review, we look to the future, with an emphasis on the cross-disciplinary integration of systems biology and synthetic biology to build high-performance EAM systems.
•Extracellular electron transfer mechanisms are summarized.•Extracellular electron transport pathways of microorganisms are summarized.•Engineering strategies for improving EET capabilities are reviewed.•New insights on further EET research are presented.
Interactions between anammox bacteria and ammonium-oxidizing archaea, complete ammonia-oxidizing bacteria, and nitrate/nitrite-dependent anaerobic methane oxidizing microorganisms offer a novel ...approach for the supply of nitrite to anammox bacteria for nitrogen removal from low-ammonium wastewater.Advances in material science reveal that interactions between anammox bacteria and carbonaceous materials, such as graphene oxide, granular activated carbon, biochar, and various forms of iron, can enhance anammox activity and nitrogen removal.The discovery of the extracellular electron transfer capability of anammox bacteria suggests a promising energy-efficient method for nitrogen removal with simultaneous energy recovery.The intrinsic adaptation of marine anammox bacteria to saline conditions positions them as a key tool for treating saline wastewater streams.
Anaerobic ammonium oxidation (anammox) is an energy-efficient method for nitrogen removal that opens the possibility for energy-neutral wastewater treatment. Research on anammox over the past decade has primarily focused on its implementation in domestic wastewater treatment. However, emerging studies are now expanding its use to novel biotechnological applications and wastewater treatment processes. This review highlights recent advances in the anammox field that aim to overcome conventional bottlenecks, and explores novel and niche-specific applications of the anammox process. Despite the promising results and potential of these advances, challenges persist for their real-world implementation. This underscores the need for a transition from laboratory achievements to practical, scalable solutions for wastewater treatment which mark the next crucial phase in the evolution of anammox research.
Anaerobic ammonium oxidation (anammox) is an energy-efficient method for nitrogen removal that opens the possibility for energy-neutral wastewater treatment. Research on anammox over the past decade has primarily focused on its implementation in domestic wastewater treatment. However, emerging studies are now expanding its use to novel biotechnological applications and wastewater treatment processes. This review highlights recent advances in the anammox field that aim to overcome conventional bottlenecks, and explores novel and niche-specific applications of the anammox process. Despite the promising results and potential of these advances, challenges persist for their real-world implementation. This underscores the need for a transition from laboratory achievements to practical, scalable solutions for wastewater treatment which mark the next crucial phase in the evolution of anammox research.
The low efficiency of extracellular electron transfer (EET) is a major bottleneck for
Shewanella oneidensis
MR-1 acting as an electroactive biocatalyst in bioelectrochemical systems. Although it is ...well established that a periplasmic
c
-type cytochrome (
c
-Cyt) network plays a critical role in regulating EET efficiency, the understanding of the network in terms of structure and electron transfer activity is obscure and partial. In this work, we attempted to systematically investigate the impacts of the network components on EET in their absence and overproduction individually in microbial fuel cell (MFC). We found that overexpression of
c
-Cyt CctA leads to accelerated electron transfer between CymA and the Mtr system, which function as the primary quinol oxidase and the outer-membrane (OM) electron hub in EET. In contrast, NapB, FccA, and TsdB in excess severely impaired EET, reducing EET capacity in MFC by more than 50%. Based on the results from both strategies, a series of engineered strains lacking FccA, NapB, and TsdB in combination while overproducing CctA were tested for a maximally optimized
c
-Cyt network. A strain depleted of all NapB, FccA, and TsdB with CctA overproduction achieved the highest maximum power density in MFCs (436.5 mW/m
2
), ∼3.62-fold higher than that of wild type (WT). By revealing that optimization of periplasmic
c
-Cyt composition is a practical strategy for improving EET efficiency, our work underscores the importance in understanding physiological and electrochemical characteristics of
c
-Cyts involved in EET.
Cytochrome P450 (CYP) metabolism of arachidonic acid (ARA) produces epoxy fatty acids (EpFAs) such as epoxyeicosatrienoic acids (EETs) that are known to exert protective effects in inflammatory ...disorders. Endogenous EpFAs are further metabolized into corresponding diols by the soluble epoxide hydrolase (sEH). Through inhibition of sEH, many studies have demonstrated the cardioprotective and renoprotective effects of EpFAs; however, the role of sEH inhibition in modulating the pathogenesis of neuroinflammatory disorders is less well described. In this review, we discuss the current knowledge surrounding the effects of sEH inhibition and EpFA action in neuroinflammatory disorders such as Parkinson’s Disease (PD), stroke, depression, epilepsy, and Alzheimer’s Disease (AD), as well as the potential mechanisms that underlie the therapeutic effects of sEH inhibition.
Microbiologically influenced corrosion (MIC) is a major cause of corrosion damages, facility failures, and financial losses, making MIC an important research topic. Due to complex microbiological ...activities and a lack of deep understanding of the interactions between biofilms and metal surfaces, MIC occurrences and mechanisms are difficult to predict and interpret. Many theories and mechanisms have been proposed to explain MIC. In this review, the mechanisms of MIC are discussed using bioenergetics, microbial respiration types, and biofilm extracellular electron transfer (EET). Two main MIC types, namely EET-MIC and metabolite MIC (M-MIC), are discussed. This brief review provides a state of the art insight into MIC mechanisms and it helps the diagnosis and prediction of occurrences of MIC under anaerobic conditions in the oil and gas industry.
Nickel-titanium (NiTi) alloys are key in making medical implants due to their mechanical properties and biocompatibility, yet suffer from microbiologically influenced corrosion (MIC). This study ...isolated three samples of intestinal microbiotas from patient’s stents to investigate their corrosion behavior on NiTi alloy. Using metagenomic analysis, corrosion electrochemistry, and morphology characterization, we found that different microbiota samples formed biofilms on NiTi alloy, causing varying degrees of pitting corrosion. The corrosion was linked to riboflavin-mediated MIC, with differences in riboflavin synthesis genes affecting corrosion rates. This research offers new insights into the MIC of NiTi alloys and helps develop more corrosion resistant materials.
•Human intestinal microbiota significantly accelerates MIC of NiTi alloy.•Different human intestinal microbiota samples lead to distinct patterns of pitting corrosion and varying corrosion rates.•Riboflavin is identified as a facilitator of MIC by intestinal microbiota.
Polyunsaturated fatty acids (PUFA) are oxidized by cytochrome P450 epoxygenases to PUFA epoxides which function as potent lipid mediators. The major metabolic pathways of PUFA epoxides are ...incorporation into phospholipids and hydrolysis to the corresponding PUFA diols by soluble epoxide hydrolase. Inhibitors of soluble epoxide hydrolase stabilize PUFA epoxides and potentiate their functional effects. The epoxyeicosatrienoic acids (EETs) synthesized from arachidonic acid produce vasodilation, stimulate angiogenesis, have anti-inflammatory actions, and protect the heart against ischemia–reperfusion injury. EETs produce these functional effects by activating receptor-mediated signaling pathways and ion channels. The epoxyeicosatetraenoic acids synthesized from eicosapentaenoic acid and epoxydocosapentaenoic acids synthesized from docosahexaenoic acid are potent inhibitors of cardiac arrhythmias. Epoxydocosapentaenoic acids also inhibit angiogenesis, decrease inflammatory and neuropathic pain, and reduce tumor metastasis. These findings indicate that a number of the beneficial functions of PUFA may be due to their conversion to PUFA epoxides. This article is part of a Special Issue entitled “Oxygenated metabolism of PUFA: analysis and biological relevance”.
•PUFA are oxidized to PUFA epoxides by cytochrome P450 epoxygenases.•PUFA epoxides function as mediators in the cardiovascular, renal and nervous system.•PUFA epoxides activate receptor-mediated signaling pathways and ion channels.•Soluble epoxide hydrolase inactivates PUFA epoxides by hydrolysis to PUFA diols.•Inhibition of soluble epoxide hydrolase potentiates the action of PUFA epoxides.
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