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Feng L, Os Andersen T, Heldal Hagen L, Bilgic B, Jarle Horn S. Bioaugmentation by enriched hydrogenotrophic methanogens into trickle bed reactors for H 2/CO 2 conversion. BIORESOURCE TECHNOLOGY 2024; 408:131225. [PMID: 39111397 DOI: 10.1016/j.biortech.2024.131225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 08/03/2024] [Accepted: 08/04/2024] [Indexed: 08/11/2024]
Abstract
Biomethanation represents a promising approach for biomethane production, with biofilm-based processes like trickle bed reactors (TBRs) being among the most efficient solutions. However, maintaining stable performance can be challenging, and both pure and mixed culture approaches have been applied to address this. In this study, inocula enriched with hydrogenotrophic methanogens were introduced to to TBRs as bioaugmentation strategy to assess their impacts on the process performance and microbial community dynamics. Metagenomic analysis revealed a metagenome-assembled genome belonging to the hydrogenotrophic genus Methanobacterium, which became dominant during enrichment and successfully colonized the TBR biofilm after bioaugmentation. The TBRs achieved a biogas production with > 96 % methane. The bioaugmented reactor consumed additional H2. This may be due to microbial species utilizing CO2 and H2 via various CO2 reduction pathways. Overall, implementing bioaugmentation in TBRs showed potential for establishing targeted species, although challenges remain in managing H2 consumption and optimizing microbial interactions.
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Affiliation(s)
- Lu Feng
- Norwegian Institute of Bioeconomy Research (NIBIO), P.O. Box 115, 1431 Ås, Norway.
| | - Thea Os Andersen
- Faculty of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences (NMBU), P.O. Box 5003, 1432 Ås, Norway
| | - Live Heldal Hagen
- Faculty of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences (NMBU), P.O. Box 5003, 1432 Ås, Norway
| | - Begum Bilgic
- Norwegian Institute of Bioeconomy Research (NIBIO), P.O. Box 115, 1431 Ås, Norway; Faculty of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences (NMBU), P.O. Box 5003, 1432 Ås, Norway
| | - Svein Jarle Horn
- Norwegian Institute of Bioeconomy Research (NIBIO), P.O. Box 115, 1431 Ås, Norway; Faculty of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences (NMBU), P.O. Box 5003, 1432 Ås, Norway
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Xie H, Wang Y, Chen Y, Hu Y, Adeleke R, Obi L, Wang Y, Cao W, Lin JG, Zhang Y. Carbon flow, energy metabolic intensity and metagenomic characteristics of a Fe (III)-enhanced anerobic digestion system during treating swine wastewater. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 935:173431. [PMID: 38782283 DOI: 10.1016/j.scitotenv.2024.173431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 05/16/2024] [Accepted: 05/19/2024] [Indexed: 05/25/2024]
Abstract
Deep treatment and bioenergy recovery of swine wastewater (SW) are beneficial for constructing a low-carbon footprint and resource-recycling society. In this study, Fe (III) addition from 0 to 600 mg/L significantly increased the methane (CH4) content of the recovered biogas from 61.4 ± 2.0 to 89.3 ± 2.0 % during SW treatment in an anaerobic membrane digestion system. The specific methane yields (SMY) also increased significantly from 0.20 ± 0.05 to 0.29 ± 0.02 L/g COD. Fe (III) and its bio-transformed products which participated in establishing direct interspecific electron transfer (DIET), upregulated the abundance of e-pili and Nicotinamide adenine dinucleotide (NADH), enriched electroactive bacteria. The increase in cellular adenosine triphosphate (cATP) from 6583 to 14,518 ng/gVSS and electron transport system (ETS) from 1468 to 1968 mg/(g·h) promoted the intensity of energy flow and electron flow during anaerobic digestion of SW. Moreover, Fe (III) promoted the hydrolysis and acidification of organic matters, and strengthened the acetoacetic methanogenesis pathway. This study established an approach for harvesting high quality bioenergy from SW and revealed the effects and mechanisms from the view of carbon flow, energy metabolic intensity and metagenomics.
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Affiliation(s)
- Hongyu Xie
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment & Ecology, Xiamen University, Xiamen, Fujian 361102, China
| | - Yuzheng Wang
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment & Ecology, Xiamen University, Xiamen, Fujian 361102, China
| | - Yuqi Chen
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment & Ecology, Xiamen University, Xiamen, Fujian 361102, China
| | - Yong Hu
- School of Environmental Science and Engineering, Nanjing Tech University, Nanjing 211816, China
| | - Rasheed Adeleke
- Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - Linda Obi
- University of South Africa, Department of Environmental Sciences, Pretoria, South Africa
| | - Yuanpeng Wang
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Key Laboratory for Chemical Biology of Fujian Province, Xiamen University, Xiamen 361005, China
| | - Wenzhi Cao
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment & Ecology, Xiamen University, Xiamen, Fujian 361102, China
| | - Jih-Gaw Lin
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment & Ecology, Xiamen University, Xiamen, Fujian 361102, China; National Yang Ming Chiao Tung University, Taiwan
| | - Yanlong Zhang
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment & Ecology, Xiamen University, Xiamen, Fujian 361102, China; Fujian Key Laboratory of Coastal Pollution Prevention and Control (CPPC), College of Environment & Ecology, Xiamen University, Xiamen, Fujian 361102, China; Fujian Institute for Sustainable Oceans, Xiamen University, Xiamen, Fujian 361102, China.
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Ye J, Zhuang M, Hong M, Zhang D, Ren G, Hu A, Yang C, He Z, Zhou S. Methanogenesis in the presence of oxygenic photosynthetic bacteria may contribute to global methane cycle. Nat Commun 2024; 15:5682. [PMID: 38971854 PMCID: PMC11227571 DOI: 10.1038/s41467-024-50108-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2024] [Accepted: 07/01/2024] [Indexed: 07/08/2024] Open
Abstract
Accumulating evidences are challenging the paradigm that methane in surface water primarily stems from the anaerobic transformation of organic matters. Yet, the contribution of oxygenic photosynthetic bacteria, a dominant species in surface water, to methane production remains unclear. Here we show methanogenesis triggered by the interaction between oxygenic photosynthetic bacteria and anaerobic methanogenic archaea. By introducing cyanobacterium Synechocystis PCC6803 and methanogenic archaea Methanosarcina barkeri with the redox cycling of iron, CH4 production was induced in coculture biofilms through both syntrophic methanogenesis (under anoxic conditions in darkness) and abiotic methanogenesis (under oxic conditions in illumination) during the periodic dark-light cycles. We have further demonstrated CH4 production by other model oxygenic photosynthetic bacteria from various phyla, in conjunction with different anaerobic methanogenic archaea exhibiting diverse energy conservation modes, as well as various common Fe-species. These findings have revealed an unexpected link between oxygenic photosynthesis and methanogenesis and would advance our understanding of photosynthetic bacteria's ecological role in the global CH4 cycle. Such light-driven methanogenesis may be widely present in nature.
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Affiliation(s)
- Jie Ye
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Minghan Zhuang
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Mingqiu Hong
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Dong Zhang
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Guoping Ren
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Andong Hu
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Chaohui Yang
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Zhen He
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA.
| | - Shungui Zhou
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
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Li Y, Huang Y, Li H, Gou M, Xu H, Wu H, Sun D, Qiu B, Dang Y. Riboflavin modified carbon cloth enhances anaerobic digestion treating food waste in a pilot-scale system. Front Bioeng Biotechnol 2024; 12:1395810. [PMID: 38863495 PMCID: PMC11166200 DOI: 10.3389/fbioe.2024.1395810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Accepted: 05/06/2024] [Indexed: 06/13/2024] Open
Abstract
Previous laboratory-scale studies have consistently shown that carbon-based conductive materials can notably improve the anaerobic digestion of food waste, typically employing reactors with regular capacity of 1-20 L. Furthermore, incorporating riboflavin-loaded conductive materials can further address the imbalance between fermentation and methanogenesis in anaerobic systems. However, there have been few reports on pilot-scale investigation. In this study, a 10 m2 of riboflavin modified carbon cloth was incorporated into a pilot-scale (2 m3) food waste anaerobic reactor to improve its treatment efficiency. The study found that the addition of riboflavin-loaded carbon cloth can increase the maximum organic loading rate (OLR) by 40% of the pilot-scale reactor, compared to the system using carbon cloth without riboflavin loading, while ensuring efficient operation of the reaction system, effectively alleviating system acidification, sustaining methanogen activity, and increasing daily methane production by 25%. Analysis of the microbial community structure revealed that riboflavin-loaded carbon cloth enriched the methanogenic archaea in the genera of Methanothrix and Methanobacterium, which are capable of extracellular direct interspecies electron transfer (DIET). And metabolic pathway analysis identified the methane production pathway, highly enriched on the reduction of acetic acid and CO2 at riboflavin-loaded carbon cloth sample. The expression levels of genes related to methane production via DIET pathway were also significantly upregulated. These results can provide important guidance for the practical application of food waste anaerobic digestion engineering.
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Affiliation(s)
- Yiqun Li
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
| | - Yinhui Huang
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
| | - Haoyong Li
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
| | - Mingyu Gou
- Paris Elite Institute of Technology, Shanghai Jiao Tong University, Shanghai, China
| | - Haiyu Xu
- Qinglin Chuangneng (Shanghai) Technology Co., Ltd., Shanghai, China
| | - Hongbin Wu
- Qinglin Chuangneng (Shanghai) Technology Co., Ltd., Shanghai, China
| | - Dezhi Sun
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
| | - Bin Qiu
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
| | - Yan Dang
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
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Holmes DE, Woodard TL, Smith JA, Musat F, Lovley DR. Electrobiocorrosion by microbes without outer-surface cytochromes. MLIFE 2024; 3:110-118. [PMID: 38827509 PMCID: PMC11139208 DOI: 10.1002/mlf2.12111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 10/14/2023] [Accepted: 12/03/2023] [Indexed: 06/04/2024]
Abstract
Anaerobic microbial corrosion of iron-containing metals causes extensive economic damage. Some microbes are capable of direct metal-to-microbe electron transfer (electrobiocorrosion), but the prevalence of electrobiocorrosion among diverse methanogens and acetogens is poorly understood because of a lack of tools for their genetic manipulation. Previous studies have suggested that respiration with 316L stainless steel as the electron donor is indicative of electrobiocorrosion, because, unlike pure Fe0, 316L stainless steel does not abiotically generate H2 as an intermediary electron carrier. Here, we report that all of the methanogens (Methanosarcina vacuolata, Methanothrix soehngenii, and Methanobacterium strain IM1) and acetogens (Sporomusa ovata and Clostridium ljungdahlii) evaluated respired with pure Fe0 as the electron donor, but only M. vacuolata, Mx. soehngenii, and S. ovata were capable of stainless steel electrobiocorrosion. The electrobiocorrosive methanogens required acetate as an additional energy source in order to produce methane from stainless steel. Cocultures of S. ovata and Mx. soehngenii demonstrated how acetogens can provide acetate to methanogens during corrosion. Not only was Methanobacterium strain IM1 not capable of electrobiocorrosion, but it also did not accept electrons from Geobacter metallireducens, an effective electron-donating partner for direct interspecies electron transfer to all methanogens that can directly accept electrons from Fe0. The finding that M. vacuolata, Mx. soehngenii, and S. ovata are capable of electrobiocorrosion, despite a lack of the outer-surface c-type cytochromes previously found to be important in other electrobiocorrosive microbes, demonstrates that there are multiple microbial strategies for making electrical contact with Fe0.
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Affiliation(s)
- Dawn E. Holmes
- Department of MicrobiologyUniversity of Massachusetts AmherstAmherstMassachusettsUSA
- Department of Physical and Biological ScienceWestern New England UniversitySpringfieldMassachusettsUSA
| | - Trevor L. Woodard
- Department of MicrobiologyUniversity of Massachusetts AmherstAmherstMassachusettsUSA
| | - Jessica A. Smith
- Department of MicrobiologyUniversity of Massachusetts AmherstAmherstMassachusettsUSA
- Department of Biomolecular SciencesCentral Connecticut State UniversityNew BritainConnecticutUSA
| | - Florin Musat
- Department of Biology, Section for MicrobiologyAarhus UniversityAarhusDenmark
- Department of Molecular Biology and Biotechnology, Faculty of Biology and GeologyBabeş‐Bolyai UniversityCluj‐NapocaRomania
| | - Derek R. Lovley
- Department of MicrobiologyUniversity of Massachusetts AmherstAmherstMassachusettsUSA
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Khairunisa BH, Heryakusuma C, Ike K, Mukhopadhyay B, Susanti D. Evolving understanding of rumen methanogen ecophysiology. Front Microbiol 2023; 14:1296008. [PMID: 38029083 PMCID: PMC10658910 DOI: 10.3389/fmicb.2023.1296008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Accepted: 10/12/2023] [Indexed: 12/01/2023] Open
Abstract
Production of methane by methanogenic archaea, or methanogens, in the rumen of ruminants is a thermodynamic necessity for microbial conversion of feed to volatile fatty acids, which are essential nutrients for the animals. On the other hand, methane is a greenhouse gas and its production causes energy loss for the animal. Accordingly, there are ongoing efforts toward developing effective strategies for mitigating methane emissions from ruminant livestock that require a detailed understanding of the diversity and ecophysiology of rumen methanogens. Rumen methanogens evolved from free-living autotrophic ancestors through genome streamlining involving gene loss and acquisition. The process yielded an oligotrophic lifestyle, and metabolically efficient and ecologically adapted descendants. This specialization poses serious challenges to the efforts of obtaining axenic cultures of rumen methanogens, and consequently, the information on their physiological properties remains in most part inferred from those of their non-rumen representatives. This review presents the current knowledge of rumen methanogens and their metabolic contributions to enteric methane production. It also identifies the respective critical gaps that need to be filled for aiding the efforts to mitigate methane emission from livestock operations and at the same time increasing the productivity in this critical agriculture sector.
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Affiliation(s)
| | - Christian Heryakusuma
- Genetics, Bioinformatics, and Computational Biology, Virginia Tech, Blacksburg, VA, United States
- Department of Biochemistry, Virginia Tech, Blacksburg, VA, United States
| | - Kelechi Ike
- Department of Biology, North Carolina Agricultural and Technical State University, Greensboro, NC, United States
| | - Biswarup Mukhopadhyay
- Genetics, Bioinformatics, and Computational Biology, Virginia Tech, Blacksburg, VA, United States
- Department of Biochemistry, Virginia Tech, Blacksburg, VA, United States
- Virginia Tech Carilion School of Medicine, Virginia Tech, Blacksburg, VA, United States
| | - Dwi Susanti
- Microbial Discovery Research, BiomEdit, Greenfield, IN, United States
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Ao Z, Li Y, Li Y, Zhao Z, Zhang Y. Facilitating direct interspecies electron transfer in anaerobic digestion via speeding up transmembrane transport of electrons and CO 2 reduction in methanogens by Na + adjustment. WASTE MANAGEMENT (NEW YORK, N.Y.) 2023; 170:252-260. [PMID: 37729842 DOI: 10.1016/j.wasman.2023.09.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 08/08/2023] [Accepted: 09/15/2023] [Indexed: 09/22/2023]
Abstract
The possibility of facilitating direct interspecies electron transfer (DIET) in anaerobic digestion with different concentrations of NaCl was explored. Additional NaCl at 2 or 4 g/L strengthened anaerobic digestion to resist the high-organic loading rate impacts, whereas the higher concentrations of NaCl (6 or 8 g/L) suppressed methanogenesis. Additional MgCl2 with the same ion strength as NaCl at 2 g/L had no effect on performances. Additional NaCl at 2 or 4 g/L dramatically increased the abundance of Methanosarcina species (20.7%/23.4% vs 8.6%) and stimulated the growth of Sphaerochaeta and Petrimonas species that could transfer electrons to the soluble Fe(III) or elemental sulfur. Electrochemical evidences showed that, additional NaCl at 2 or 4 g/L increased capacitances and decreased charge transfer resistances of Methanosarcina-dominant communities. Metagenomic evidences showed that, additional NaCl at 2 or 4 g/L increased the abundance of genes that encoded the type IV pilus assembly proteins (1.98E-04/1.87E-04 vs 1.85E-04) and cytochrome c-like proteins (5.51E-04/5.60E-04 vs 5.31E-04). In addition, additional NaCl at 2 or 4 g/L increased the abundance of genes for methanophenazine (MP)/MPH2 transformation (1.04E-05/1.24E-05 vs 8.06E-06) and CO2 reduction (1.64E-03/1.86E-03 vs 1.06E-03), suggesting a rapid transmembrane transport of electrons and CO2 reduction in methanogens. Both processes were closely associated with F420/F420H2 transformation that required ATP. Additional NaCl at 2 or 4 g/L increased the yield of ATP (256.0/249.3 vs 231.8 nmol/L) that might promote F420/F420H2 transformation in methanogens, which overcame the thermodynamic limitations of combining electrons with protons for the reduction of CO2 to methane and facilitated DIET.
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Affiliation(s)
- Zhipeng Ao
- Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Yuan Li
- Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Yang Li
- School of Ocean Science and Technology, Dalian University of Technology, Panjin 124221, China
| | - Zhiqiang Zhao
- Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
| | - Yaobin Zhang
- Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
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Zhou J, Smith JA, Li M, Holmes DE. Methane production by Methanothrix thermoacetophila via direct interspecies electron transfer with Geobacter metallireducens. mBio 2023; 14:e0036023. [PMID: 37306514 PMCID: PMC10470525 DOI: 10.1128/mbio.00360-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 04/13/2023] [Indexed: 06/13/2023] Open
Abstract
Methanothrix is widely distributed in natural and artificial anoxic environments and plays a major role in global methane emissions. It is one of only two genera that can form methane from acetate dismutation and through participation in direct interspecies electron transfer (DIET) with exoelectrogens. Although Methanothrix is a significant member of many methanogenic communities, little is known about its physiology. In this study, transcriptomics helped to identify potential routes of electron transfer during DIET between Geobacter metallireducens and Methanothrix thermoacetophila. Additions of magnetite to cultures significantly enhanced growth by acetoclastic methanogenesis and by DIET, while granular activated carbon (GAC) amendments impaired growth. Transcriptomics suggested that the OmaF-OmbF-OmcF porin complex and the octaheme outer membrane c-type cytochrome encoded by Gmet_0930, were important for electron transport across the outer membrane of G. metallireducens during DIET with Mx. thermoacetophila. Clear differences in the metabolism of Mx. thermoacetophila when grown via DIET or acetate dismutation were not apparent. However, genes coding for proteins involved in carbon fixation, the sheath fiber protein MspA, and a surface-associated quinoprotein, SqpA, were highly expressed in all conditions. Expression of gas vesicle genes was significantly lower in DIET- than acetate-grown cells, possibly to facilitate better contact between membrane-associated redox proteins during DIET. These studies reveal potential electron transfer mechanisms utilized by both Geobacter and Methanothrix during DIET and provide important insights into the physiology of Methanothrix in anoxic environments. IMPORTANCE Methanothrix is a significant methane producer in a variety of methanogenic environments including soils and sediments as well as anaerobic digesters. Its abundance in these anoxic environments has mostly been attributed to its high affinity for acetate and its ability to grow by acetoclastic methanogenesis. However, Methanothrix species can also generate methane by directly accepting electrons from exoelectrogenic bacteria through direct interspecies electron transfer (DIET). Methane production through DIET is likely to further increase their contribution to methane production in natural and artificial environments. Therefore, acquiring a better understanding of DIET with Methanothrix will help shed light on ways to (i) minimize microbial methane production in natural terrestrial environments and (ii) maximize biogas formation by anaerobic digesters treating waste.
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Affiliation(s)
- Jinjie Zhou
- Archaeal Biology Center, Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
- Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, Guangdong, China
- Department of Microbiology, University of Massachusetts‐Amherst, Amherst, Massachusetts, USA
- Shenzhen Key Laboratory of Marine Microbiome Engineering, Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
| | - Jessica A. Smith
- Department of Microbiology, University of Massachusetts‐Amherst, Amherst, Massachusetts, USA
- Department of Biomolecular Sciences, Central Connecticut State University, New Britain, Connecticut, USA
| | - Meng Li
- Archaeal Biology Center, Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
- Shenzhen Key Laboratory of Marine Microbiome Engineering, Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
| | - Dawn E. Holmes
- Department of Microbiology, University of Massachusetts‐Amherst, Amherst, Massachusetts, USA
- Department of Physical and Biological Science, Western New England University, Springfield, Massachusetts, USA
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Smith JA, Holmes DE, Woodard TL, Li Y, Liu X, Wang LY, Meier D, Schwarz IA, Lovley DR. Detrimental impact of the Geobacter metallireducens type VI secretion system on direct interspecies electron transfer. Microbiol Spectr 2023; 11:e0094123. [PMID: 37650614 PMCID: PMC10580878 DOI: 10.1128/spectrum.00941-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 07/02/2023] [Indexed: 09/01/2023] Open
Abstract
Direct interspecies electron transfer (DIET) is important in anaerobic communities of environmental and practical significance. Other than the need for close physical contact for electrical connections, the interactions of DIET partners are poorly understood. Type VI secretion systems (T6SSs) typically kill competitive microbes. Surprisingly, Geobacter metallireducens highly expressed T6SS genes when DIET-based co-cultures were initiated with Geobacter sulfurreducens. T6SS gene expression was lower when the electron shuttle anthraquinone-2,6-disulfonate was added to alleviate the need for interspecies contact. Disruption of hcp, the G. metallireducens gene for the main T6SS needle-tube protein subunit, and the most highly upregulated gene in DIET-grown cells eliminated the long lag periods required for the initiation of DIET. The mutation did not aid DIET in the presence of granular-activated carbon (GAC), consistent with the fact that DIET partners do not make physical contact when electrically connected through conductive materials. The hcp-deficient mutant also established DIET quicker with Methanosarcina barkeri. However, the mutant also reduced Fe(III) oxide faster than the wild-type strain, a phenotype not expected from the loss of the T6SS. Quantitative PCR revealed greater gene transcript abundance for key components of extracellular electron transfer in the hcp-deficient mutant versus the wild-type strain, potentially accounting for the faster Fe(III) oxide reduction and impact on DIET. The results highlight that interspecies interactions beyond electrical connections may influence DIET effectiveness. The unexpected increase in the expression of genes for extracellular electron transport components when hcp was deleted emphasizes the complexities in evaluating the electromicrobiology of highly adaptable Geobacter species. IMPORTANCE Direct interspecies electron transfer is an alternative to the much more intensively studied process of interspecies H2 transfer as a mechanism for microbes to share electrons during the cooperative metabolism of energy sources. DIET is an important process in anaerobic soils and sediments generating methane, a significant greenhouse gas. Facilitating DIET can accelerate and stabilize the conversion of organic wastes to methane biofuel in anaerobic digesters. Therefore, a better understanding of the factors controlling how fast DIET partnerships are established is expected to lead to new strategies for promoting this bioenergy process. The finding that when co-cultured with G. sulfurreducens, G. metallireducens initially expressed a type VI secretion system, a behavior not conducive to interspecies cooperation, illustrates the complexity of establishing syntrophic relationships.
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Affiliation(s)
- Jessica A. Smith
- Department of Microbiology, University of Massachusetts Amherst, Morrill IV N Science Center, Amherst, Massachusetts, USA
- Department of Biomolecular Sciences, Central Connecticut State University, New Britain, Connecticut, USA
| | - Dawn E. Holmes
- Department of Microbiology, University of Massachusetts Amherst, Morrill IV N Science Center, Amherst, Massachusetts, USA
- Department of Physical and Biological Sciences, Western New England University, Springfield, Massachusetts, USA
| | - Trevor L. Woodard
- Department of Microbiology, University of Massachusetts Amherst, Morrill IV N Science Center, Amherst, Massachusetts, USA
| | - Yang Li
- Department of Microbiology, University of Massachusetts Amherst, Morrill IV N Science Center, Amherst, Massachusetts, USA
- School of Ocean Science and Technology, Dalian University of Technology, Panjin, Liaoning, China
| | - Xinying Liu
- Department of Microbiology, University of Massachusetts Amherst, Morrill IV N Science Center, Amherst, Massachusetts, USA
- College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
| | - Li-Ying Wang
- Department of Microbiology, University of Massachusetts Amherst, Morrill IV N Science Center, Amherst, Massachusetts, USA
| | - David Meier
- Department of Microbiology, University of Massachusetts Amherst, Morrill IV N Science Center, Amherst, Massachusetts, USA
| | - Ingrid A. Schwarz
- Department of Biomolecular Sciences, Central Connecticut State University, New Britain, Connecticut, USA
| | - Derek R. Lovley
- Department of Microbiology, University of Massachusetts Amherst, Morrill IV N Science Center, Amherst, Massachusetts, USA
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10
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Zhou J, Zhang CJ, Li M. Desulfovibrio mangrovi sp. nov., a sulfate-reducing bacterium isolated from mangrove sediments: a member of the proposed genus "Psychrodesulfovibrio". Antonie Van Leeuwenhoek 2023; 116:499-510. [PMID: 36917346 DOI: 10.1007/s10482-023-01820-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 02/28/2023] [Indexed: 03/16/2023]
Abstract
"Psychrodesulfovibrio", a proposed genus within the family Desulfovibrionaceae, is a group of sulfate-reducing bacteria with biogeochemical significance but restricted child taxa availability. In this study, a strictly anaerobic bacterium, designed strain FT415T, was isolated from mangrove sediments in Futian Mangrove Nature Reserve in Shenzhen, China. The strain was Gram-stain-negative, motile, and vibrio-shaped with a single polar flagellum, which grew at the temperature range of 15-42 °C (optimum 37 °C), pH range of 6.0-7.5 (optimum 6.8), and in the presence of 0-36 g l-1 NaCl (optimum 6 g l-1 NaCl). In the presence of sulfate, electron donors including lactate, ethanol, pyruvate, malate, fumarate, succinate, cysteine, and glycerol were incompletely oxidized to acetate, and H2 and formate were used as electron donors with acetate as the carbon source by strain FT415T. Sulfate, thiosulfate, sulfide, and anthraquinone-2,6-disulfonate were reduced in the presence of lactate. Fe(III) oxide was reduced without cell growth. Fermentative growth was observed with pyruvate and cysteine. Vitamins were not required for growth. The major cellular fatty acids (> 10%) were C16:0, summed feature 10 (C18:1 c11/t9/t6 and/or unknown ECL 17.834), C16:1 cis 9, and C18:0. The major polar lipids were phosphatidylethanolamine, phospholipids, and aminolipids. The predominant menaquinone was MK-6(H2). The genomic DNA G+C content was 56.7%. Phylogenetic analysis showed that strain FT415T shared a 98.1% similarity in 16S rRNA gene sequence, an average nucleotide identity value of 84.0%, an average amino-acid identity value of 85.4%, and a digital DNA-DNA hybridization value of 25.7% with its closest relative Desulfovibrio subterraneus HN2T, which has been proposed to be transferred to the genus "Psychrodesulfovibrio". Based on phenotypic, phylogenetic, and genotypic evidence, a new species of the family Desulfovibrionaceae, Desulfovibrio mangrovi sp. nov. was proposed with the type strain FT415T (=GDMCC 1.3410T=KCTC 25525T).
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Affiliation(s)
- Jinjie Zhou
- Archaeal Biology Center, Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
- Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, China
- Shenzhen Key Laboratory of Marine Microbiome Engineering, Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
| | - Cui-Jing Zhang
- Archaeal Biology Center, Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
- Shenzhen Key Laboratory of Marine Microbiome Engineering, Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
| | - Meng Li
- Archaeal Biology Center, Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China.
- Shenzhen Key Laboratory of Marine Microbiome Engineering, Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China.
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11
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Huang Y, Cai B, Dong H, Li H, Yuan J, Xu H, Wu H, Xu Z, Sun D, Dang Y, Holmes DE. Enhancing anaerobic digestion of food waste with granular activated carbon immobilized with riboflavin. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 851:158172. [PMID: 35988634 DOI: 10.1016/j.scitotenv.2022.158172] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 08/16/2022] [Accepted: 08/16/2022] [Indexed: 06/15/2023]
Abstract
Previous studies have shown that anaerobic digestion of food waste can be enhanced by addition of conductive materials that stimulate direct interspecies electron transfer (DIET) between bacteria and methanogens. However, at extremely high organic loading rates (OLRs), volatile fatty acids (VFAs) still tend to accumulate even in the presence of conductive materials because of an imbalance between the formation of fermentation products and the rate of methanogenesis. In this study, granular activated carbon (GAC) immobilized with riboflavin (GAC-riboflavin) was added to an anaerobic digester treating food waste. The GAC-riboflavin reactor operated stably at OLRs as high as 11.5 kgCOD/ (m3·d) and kept VFA concentrations below 69.4 mM, COD removal efficiencies, methane production rates, and biogas methane concentrations were much higher in the GAC-riboflavin reactor than the GAC- and non-amended reactors. Transcripts associated with genes that code for proteins involved in DIET based metabolism were somewhat more highly expressed by Methanothrix in the GAC-riboflavin reactor. However, it is unlikely that riboflavin acted as an electron shuttle to stimulate DIET. Rather, it seemed to provide nutrients that enhanced the growth of microorganisms involved in the anaerobic digestion process, including those that are capable of DIET.
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Affiliation(s)
- Yinhui Huang
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China
| | - Boquan Cai
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China
| | - He Dong
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China
| | - Haoyong Li
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China
| | - Jie Yuan
- Wukong Chuangxiang Techolology Co, Ltd, Beijing 100083, China
| | - Haiyu Xu
- Xinneng Qinglin (Beijing) Technology Co., Ltd, Beijing 100083, China
| | - Hongbin Wu
- Xinneng Qinglin (Beijing) Technology Co., Ltd, Beijing 100083, China
| | - Ziyao Xu
- Lingxi Medical Technology (Beijing) Co., Ltd, Beijing 100083, China
| | - Dezhi Sun
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China
| | - Yan Dang
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China.
| | - Dawn E Holmes
- Department of Physical and Biological Sciences, Western New England University, 1215 Wilbraham Rd, Springfield, MA 01119, USA
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12
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Holmes DE, Tang H, Woodard T, Liang D, Zhou J, Liu X, Lovley DR. Cytochrome-mediated direct electron uptake from metallic iron by Methanosarcina acetivorans. MLIFE 2022; 1:443-447. [PMID: 38818487 PMCID: PMC10989991 DOI: 10.1002/mlf2.12044] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 09/01/2022] [Accepted: 09/06/2022] [Indexed: 06/01/2024]
Abstract
Methane-producing microorganisms accelerate the corrosion of iron-containing metals. Previous studies have inferred that some methanogens might directly accept electrons from Fe(0), but when this possibility was more intensively investigated, H2 was shown to be an intermediary electron carrier between Fe(0) and methanogens. Here, we report that Methanosarcina acetivorans catalyzes direct metal-to-microbe electron transfer to support methane production. Deletion of the gene for the multiheme, outer-surface c-type cytochrome MmcA eliminated methane production from Fe(0), consistent with the key role of MmcA in other forms of extracellular electron exchange. These findings, coupled with the previous demonstration that outer-surface c-type cytochromes are also electrical contacts for electron uptake from Fe(0) by Geobacter and Shewanella species, suggest that the presence of multiheme c-type cytochromes on corrosion surfaces might be diagnostic for direct metal-to-microbe electron transfer and that interfering with cytochrome function might be a strategy to mitigate corrosion.
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Affiliation(s)
- Dawn E. Holmes
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
- Department of Physical and Biological ScienceWestern New England UniversitySpringfieldMassachusettsUSA
| | - Haiyan Tang
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
- Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Jiangsu Collaborative Innovation Center of Solid Organic Wastes, Educational Ministry Engineering Center of Resource‐saving FertilizersNanjing Agricultural UniversityNanjingChina
| | - Trevor Woodard
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
| | - Dandan Liang
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
- Present address:
State Key Laboratory of Urban Water Resource and Environment, School of EnvironmentHarbin Institute of TechnologyHarbinChina
| | - Jinjie Zhou
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
- Present address:
Institute for Advanced StudyShenzhen UniversityShenzhenGuangdongChina
| | - Xinying Liu
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
- Present address:
College of Environmental Science and EngineeringBeijing Forestry UniversityBeijingChina
| | - Derek R. Lovley
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
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13
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Yang Z, Lu Y. Coupling methanogenesis with iron reduction by acetotrophic Methanosarcina mazei zm-15. ENVIRONMENTAL MICROBIOLOGY REPORTS 2022; 14:804-811. [PMID: 35641250 DOI: 10.1111/1758-2229.13098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Accepted: 05/16/2022] [Indexed: 06/15/2023]
Abstract
Application of ferric iron is conventionally considered to inhibit methanogenesis in anoxic environments. Here we show that Methanosarcina mazei zm-15, a strain isolated from the natural wetland of Tibetan plateau, is capable of Fe(III) reduction, which significantly promotes its growth and methanogenesis. We grew Ms. mazei zm-15 in a medium containing acetate supplemented with Fe(III) in ferric citrate or ferrihydrite and to some cultures anthraquinone-2,6-disulfonate (AQDS) was applied as an electron shuttle. The reduction of Fe(III) species occurred immediately. Ferric citrate was more readily reduced than ferrihydrite. The X-ray diffraction spectra analysis showed the formation of magnetite from ferrihydrite and amorphous reduced products from ferrihydrite plus AQDS. The analysis of protein contents revealed that Fe(III) reduction contributed 36%-46% of the cell growth. The growth yield, estimated as protein increment per acetate consumed for Fe(III) reduction, increased by 20- to 30-fold compared with methanogenesis, which is in consistence with the difference in free energy available by Fe(III) reduction relative to methanogenesis. We propose that the outer-surface multiheme c-type cytochrome predicted from Ms. mazei zm-15 genome serves as the terminal reductase with the energy-converting hydrogenase and F420 H2 dehydrogenase involved in electron transport chain for Fe(III) reduction. The findings shed a light to better understand the ecophysiology of Methanosarcina in anaerobic environments.
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Affiliation(s)
- Zhen Yang
- College of Urban and Environmental Science, Peking University, Beijing, China
| | - Yahai Lu
- College of Urban and Environmental Science, Peking University, Beijing, China
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14
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Holmes DE, Zhou J, Smith JA, Wang C, Liu X, Lovley DR. Different outer membrane c-type cytochromes are involved in direct interspecies electron transfer to Geobacter or Methanosarcina species. MLIFE 2022; 1:272-286. [PMID: 38818222 PMCID: PMC10989804 DOI: 10.1002/mlf2.12037] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 07/21/2022] [Accepted: 07/26/2022] [Indexed: 06/01/2024]
Abstract
Direct interspecies electron transfer (DIET) may be most important in methanogenic environments, but mechanistic studies of DIET to date have primarily focused on cocultures in which fumarate was the terminal electron acceptor. To better understand DIET with methanogens, the transcriptome of Geobacter metallireducens during DIET-based growth with G. sulfurreducens reducing fumarate was compared with G. metallireducens grown in coculture with diverse Methanosarcina. The transcriptome of G. metallireducens cocultured with G. sulfurreducens was significantly different from those with Methanosarcina. Furthermore, the transcriptome of G. metallireducens grown with Methanosarcina barkeri, which lacks outer-surface c-type cytochromes, differed from those of G. metallireducens cocultured with M. acetivorans or M. subterranea, which have an outer-surface c-type cytochrome that serves as an electrical connect for DIET. Differences in G. metallireducens expression patterns for genes involved in extracellular electron transfer were particularly notable. Cocultures with c-type cytochrome deletion mutant strains, ∆Gmet_0930, ∆Gmet_0557 and ∆Gmet_2896, never became established with G. sulfurreducens but adapted to grow with all three Methanosarcina. Two porin-cytochrome complexes, PccF and PccG, were important for DIET; however, PccG was more important for growth with Methanosarcina. Unlike cocultures with G. sulfurreducens and M. acetivorans, electrically conductive pili were not needed for growth with M. barkeri. Shewanella oneidensis, another electroactive microbe with abundant outer-surface c-type cytochromes, did not grow via DIET. The results demonstrate that the presence of outer-surface c-type cytochromes does not necessarily confer the capacity for DIET and emphasize the impact of the electron-accepting partner on the physiology of the electron-donating DIET partner.
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Affiliation(s)
- Dawn E. Holmes
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
- Department of Physical and Biological ScienceWestern New England UniversitySpringfieldMassachusettsUSA
| | - Jinjie Zhou
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
- Institute for Advanced StudyShenzhen UniversityShenzhenChina
| | - Jessica A. Smith
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
- Department of Biomolecular SciencesCentral Connecticut State UniversityNew BritainConnecticutUSA
| | - Caiqin Wang
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
- College of EnvironmentZhejiang University of TechnologyHangzhouChina
| | - Xinying Liu
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
- College of Environmental Science and EngineeringBeijing Forestry UniversityBeijingChina
| | - Derek R. Lovley
- Department of MicrobiologyUniversity of Massachusetts‐AmherstAmherstMassachusettsUSA
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15
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Allenby A, Cunningham MR, Hillebrand-Voiculescu A, Comte JC, Doherty R, Kumaresan D. Occurrence of methane-oxidizing bacteria and methanogenic archaea in earth’s cave systems—A metagenomic analysis. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.909865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Karst ecosystems represent up to 25% of the land surface and recent studies highlight their potential role as a sink for atmospheric methane. Despite this, there is limited knowledge of the diversity and distribution of methane-oxidizing bacteria (MOB) or methanogens in karst caves and the sub-surface environment in general. Here, we performed a survey of 14 shotgun metagenomes from cave ecosystems covering a broad set of environmental conditions, to compare the relative abundance and phylogenetic diversity of MOB and methanogens, targeting biomarker genes for methane monooxygenase (pmoA and mmoX) and methyl-coenzyme M reductase (mcrA). Taxonomic analysis of metagenomes showed 0.02–1.28% of classified reads were related to known MOB, of which Gammaproteobacterial MOB were the most abundant making up on average 70% of the surveyed caves’ MOB community. Potential for biogenic methane production in caves was also observed, with 0.008–0.39% of reads classified to methanogens and was dominated by sequences related to Methanosarcina. We have also generated a cave ecosystems protein database (CEPD) based on protein level assembly of cave metagenomes that can be used to profile genes of interest.
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16
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Chen L, Fang W, Chang J, Liang J, Zhang P, Zhang G. Improvement of Direct Interspecies Electron Transfer via Adding Conductive Materials in Anaerobic Digestion: Mechanisms, Performances, and Challenges. Front Microbiol 2022; 13:860749. [PMID: 35432222 PMCID: PMC9005980 DOI: 10.3389/fmicb.2022.860749] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Accepted: 03/09/2022] [Indexed: 11/30/2022] Open
Abstract
Anaerobic digestion is an effective and sustainable technology for resource utilization of organic wastes. Recently, adding conductive materials in anaerobic digestion to promote direct interspecies electron transfer (DIET) has become a hot topic, which enhances the syntrophic conversion of various organics to methane. This review comprehensively summarizes the recent findings of DIET mechanisms with different mediating ways. Meanwhile, the influence of DIET on anaerobic digestion performance and the underlying mechanisms of how DIET mediated by conductive materials influences the lag phase, methane production, and system stability are systematically explored. Furthermore, current challenges such as the unclear biological mechanisms, influences of non-DIET mechanisms, limitations of organic matters syntrophically oxidized by way of DIET, and problems in practical application of DIET mediated by conductive materials are discussed in detail. Finally, the future research directions for practical application of DIET are outlined.
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Affiliation(s)
- Le Chen
- Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China.,Engineering Research Center for Water Pollution Source Control and Eco-Remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
| | - Wei Fang
- Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China.,Engineering Research Center for Water Pollution Source Control and Eco-Remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
| | - Jianning Chang
- Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China.,Engineering Research Center for Water Pollution Source Control and Eco-Remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
| | - Jinsong Liang
- Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China.,Engineering Research Center for Water Pollution Source Control and Eco-Remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
| | - Panyue Zhang
- Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China.,Engineering Research Center for Water Pollution Source Control and Eco-Remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing, China
| | - Guangming Zhang
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, China
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17
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Gupta D, Shalvarjian KE, Nayak DD. An archaea-specific c-type cytochrome maturation machinery is crucial for methanogenesis in Methanosarcina acetivorans. eLife 2022; 11:76970. [PMID: 35380107 PMCID: PMC9084895 DOI: 10.7554/elife.76970] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 04/04/2022] [Indexed: 11/13/2022] Open
Abstract
c-Type cytochromes (cyt c) are proteins that undergo post-translational modification to covalently bind heme, which allows them to facilitate redox reactions in electron transport chains across all domains of life. Genomic evidence suggests that cyt c are involved in electron transfer processes among the Archaea, especially in members that produce or consume the potent greenhouse gas methane. However, neither the maturation machinery for cyt c in Archaea nor their role in methane metabolism has ever been functionally characterized. Here, we have used CRISPR-Cas9 genome editing tools to map a distinct pathway for cyt c biogenesis in the model methanogenic archaeon Methanosarcina acetivorans, and have also identified substrate-specific functional roles for cyt c during methanogenesis. Although the cyt c maturation machinery from M. acetivorans is universally conserved in the Archaea, our evolutionary analyses indicate that different clades of Archaea acquired this machinery through multiple independent horizontal gene transfer events from different groups of Bacteria. Overall, we demonstrate the convergent evolution of a novel Archaea-specific cyt c maturation machinery and its physiological role during methanogenesis, a process which contributes substantially to global methane emissions. Archaea are single-celled organisms that were discovered over half a century ago. Recently, there has been a renewed interest in these microbes because theyplay a key role in climate change by controlling greenhouse gas emissions, like methane. Indeed, methane-producing Archaea generate nearly 70% of the methane gas released into the atmosphere. A group of proteins called c-type cytochromes are essential to energy generation in several methane-producing archaea. However, it is a mystery how Archaea assemble their c-type cytochromes. In fact, genomic studies suggest that Archaea are missing some of the c-type cytochrome assembly machinery that bacteria use. This has led scientists to suspect that Archaea have an alternate mechanism for building these essential components. To solve this mystery, Gupta, Shalvarjian, and Nayak used CRISPR-Cas9 gene-editing tools to characterize which proteins are essential for c-type cytochrome production in Methanosarcina acetivorans, a species of Archaea that produces methane. These experiments showed that M. acetivorans discarded a few parts of the process used by bacteria to generate c-type cytochromes, streamlining the assembly of these proteins. By comparing the genes of different Archaeal species, Gupta, Shalvarjian and Nayak were able to determine that Archaea acquired the genes for producing c-type cytochromes from bacteria via horizontal gene transfer, a process in which genes move directly from one organism into another. The streamlining of the process took place later, as different Archaeal species evolved independently, but losing the same parts of the process. Gupta Shalvajiran and Nayak’s experiments also showed that c-type cytochromes are essential for the growth and fitness of methane-producing Archaea like M. acetivorans. The role of c-type cytochromes in methane production varies in different species of Archaea depending on their growth substrate or where they live. These results provide vital information about how Archaea produce methane, and the tools and techniques developed will aid further investigation of the role of Archaea in climate change.
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Affiliation(s)
- Dinesh Gupta
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Katie E Shalvarjian
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Dipti D Nayak
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
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18
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Jiang Z, Yu Q, Sun C, Wang Z, Jin Z, Zhu Y, Zhao Z, Zhang Y. Additional electric field alleviates acidity suppression in anaerobic digestion of kitchen wastes via enriching electro-active methanogens in cathodic biofilms. WATER RESEARCH 2022; 212:118118. [PMID: 35091224 DOI: 10.1016/j.watres.2022.118118] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 01/15/2022] [Accepted: 01/21/2022] [Indexed: 06/14/2023]
Abstract
The aim of this study was to investigate the feasibility that the suppression of acidity in anaerobic digestion of kitchen wastes could be alleviated with additional electric field. The results showed that, the accumulation of acidity seriously suppressed methanogenesis, and no methane was detected in the electrode-supplemented digester without applied voltage. In contrast, with applied voltages of 0.6-1.2 V, the suppression of acidity was alleviated, and methane production rates reached 558-669 L/kg-volatile suspended solid that were higher than that previously reported with carbon-based conductive materials, such as granular active carbon and biochar. Although the reduced peak with a potential ranging from -0.3 V to -0.2 V close to the reduced potential of CO2/CH4 detected via cyclic voltammetry, the maximum methane yield derived from cathodic reduction of CO2 only accounted for 0.13-0.33% of total methane yield with applied voltages. Microbial community analysis showed that, Methanosarcina species were specially enriched with applied voltages, accounting for ca. 40-70% of the communities. Together with the increase in the relative abundance of Syntrophomonas species, Methanosarcina species directly accepting electrons from Syntrophomonas species via DIET might be the primary reason for alleviating the suppression of acidity. Further investigations via three-dimensional excitation emission matrix and in-situ electrochemical Fourier transform infrared spectroscopy found that additional electric field stimulated the secretion of EPS primarily comprised of protein-like substance, which might mediate the EET between Syntrophomonas and Methanosarcina species.
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Affiliation(s)
- Zhihao Jiang
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Qilin Yu
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Cheng Sun
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Zhenxin Wang
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Zhen Jin
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Yahui Zhu
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Zhiqiang Zhao
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Yaobin Zhang
- Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
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19
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Lovley DR. Electrotrophy: Other microbial species, iron, and electrodes as electron donors for microbial respirations. BIORESOURCE TECHNOLOGY 2022; 345:126553. [PMID: 34906705 DOI: 10.1016/j.biortech.2021.126553] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 12/06/2021] [Accepted: 12/08/2021] [Indexed: 06/14/2023]
Abstract
Electrotrophy, the growth of microbes on extracellular electron donors, drives important biogeochemical cycles and has practical applications. Studies of Fe(II)-based electrotrophy have provided foundational cytochrome-based mechanistic models for electron transport into cells. Direct electron uptake from other microbial species, Fe(0), or cathodes is of intense interest due to its potential roles in the production and anaerobic oxidation of methane, corrosion, and bioelectrochemical technologies. Other cells or Fe(0) can serve as the sole electron donor supporting the growth of several Geobacter and methanogen strains that are unable to use H2 as an electron donor, providing strong evidence for electrotrophy. Additional evidence for electrotrophy in Geobacter strains and Methanosarcina acetivorans is a requirement for outer-surface c-type cytochromes. However, in most instances claims for electrotrophy in anaerobes are based on indirect inference and the possibility that H2 is actually the electron donor supporting growth has not been rigorously excluded.
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Affiliation(s)
- Derek R Lovley
- Electrobiomaterials Institute, Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China; Department of Microbiology and Institute for Applied Life Sciences (IALS), University of Massachusetts, Amherst, MA, USA.
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20
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Holmes DE, Zhou J, Ueki T, Woodard T, Lovley DR. Mechanisms for Electron Uptake by Methanosarcina acetivorans during Direct Interspecies Electron Transfer. mBio 2021; 12:e0234421. [PMID: 34607451 PMCID: PMC8546582 DOI: 10.1128/mbio.02344-21] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 08/31/2021] [Indexed: 12/13/2022] Open
Abstract
Direct interspecies electron transfer (DIET) between bacteria and methanogenic archaea appears to be an important syntrophy in both natural and engineered methanogenic environments. However, the electrical connections on the outer surface of methanogens and the subsequent processing of electrons for carbon dioxide reduction to methane are poorly understood. Here, we report that the genetically tractable methanogen Methanosarcina acetivorans can grow via DIET in coculture with Geobacter metallireducens serving as the electron-donating partner. Comparison of gene expression patterns in M. acetivorans grown in coculture versus pure-culture growth on acetate revealed that transcripts for the outer-surface multiheme c-type cytochrome MmcA were higher during DIET-based growth. Deletion of mmcA inhibited DIET. The high aromatic amino acid content of M. acetivorans archaellins suggests that they might assemble into electrically conductive archaella. A mutant that could not express archaella was deficient in DIET. However, this mutant grew in DIET-based coculture as well as the archaellum-expressing parental strain in the presence of granular activated carbon, which was previously shown to serve as a substitute for electrically conductive pili as a conduit for long-range interspecies electron transfer in other DIET-based cocultures. Transcriptomic data suggesting that the membrane-bound Rnf, Fpo, and HdrED complexes also play a role in DIET were incorporated into a charge-balanced model illustrating how electrons entering the cell through MmcA can yield energy to support growth from carbon dioxide reduction. The results are the first genetics-based functional demonstration of likely outer-surface electrical contacts for DIET in a methanogen. IMPORTANCE The conversion of organic matter to methane plays an important role in the global carbon cycle and is an effective strategy for converting wastes to a useful biofuel. The reduction of carbon dioxide to methane accounts for approximately a third of the methane produced in anaerobic soils and sediments as well as waste digesters. Potential electron donors for carbon dioxide reduction are H2 or electrons derived from direct interspecies electron transfer (DIET) between bacteria and methanogens. Elucidating the relative importance of these electron donors has been difficult due to a lack of information on the electrical connections on the outer surfaces of methanogens and how they process the electrons received from DIET. Transcriptomic patterns and gene deletion phenotypes reported here provide insight into how a group of Methanosarcina organisms that play an important role in methane production in soils and sediments participate in DIET.
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Affiliation(s)
- Dawn E. Holmes
- Department of Microbiology, University of Massachusetts—Amherst, Amherst, Massachusetts, USA
- Department of Physical and Biological Science, Western New England University, Springfield, Massachusetts, USA
| | - Jinjie Zhou
- Department of Microbiology, University of Massachusetts—Amherst, Amherst, Massachusetts, USA
- Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
| | - Toshiyuki Ueki
- Department of Microbiology, University of Massachusetts—Amherst, Amherst, Massachusetts, USA
| | - Trevor Woodard
- Department of Microbiology, University of Massachusetts—Amherst, Amherst, Massachusetts, USA
| | - Derek R. Lovley
- Department of Microbiology, University of Massachusetts—Amherst, Amherst, Massachusetts, USA
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