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Li X, Ding L, Yuan H, Li X, Zhu Y. Identification of potential electrotrophic microbial community in paddy soils by enrichment of microbial electrolysis cell biocathodes. J Environ Sci (China) 2020; 87:411-420. [PMID: 31791514 DOI: 10.1016/j.jes.2019.07.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 07/18/2019] [Accepted: 07/22/2019] [Indexed: 06/10/2023]
Abstract
Electrotrophs are microbes that can receive electrons directly from cathode in a microbial electrolysis cell (MEC). They not only participate in organic biosynthesis, but also be crucial in cathode-based bioremediation. However, little is known about the electrotrophic community in paddy soils. Here, the putative electrotrophs were enriched by cathodes of MECs constructed from five paddy soils with various properties using bicarbonate as an electron acceptor, and identified by 16S rRNA-gene based Illumina sequencing. The electrons were gradually consumed on the cathodes, and 25%-45% of which were recovered to reduce bicarbonate to acetic acid during MEC operation. Firmicutes was the dominant bacterial phylum on the cathodes, and Bacillus genus within this phylum was greatly enriched and was the most abundant population among the detected putative electrotrophs for almost all soils. Furthermore, several other members of Firmicutes and Proteobacteria may also participate in electrotrophic process in different soils. Soil pH, amorphous iron and electrical conductivity significantly influenced the putative electrotrophic bacterial community, which explained about 33.5% of the community structural variation. This study provides a basis for understanding the microbial diversity of putative electrotrophs in paddy soils, and highlights the importance of soil properties in shaping the community of putative electrotrophs.
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Affiliation(s)
- Xiaomin Li
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Shuangqing Road, No. 18, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Longjun Ding
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Shuangqing Road, No. 18, Haidian District, Beijing 100085, China.
| | - Haiyan Yuan
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Shuangqing Road, No. 18, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaoming Li
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Shuangqing Road, No. 18, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yongguan Zhu
- State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Shuangqing Road, No. 18, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China; Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Jimei Road, No. 1799, Jimei District, Xiamen 361021, China
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Semenec L, Vergara IA, Laloo AE, Mathews ER, Bond PL, Franks AE. Enhanced Growth of Pilin-Deficient Geobacter sulfurreducens Mutants in Carbon Poor and Electron Donor Limiting Conditions. MICROBIAL ECOLOGY 2019; 78:618-630. [PMID: 30759269 DOI: 10.1007/s00248-019-01316-8] [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: 03/08/2018] [Accepted: 01/01/2019] [Indexed: 06/09/2023]
Abstract
Geobacter sulfurreducens pili enable extracellular electron transfer and play a role in secretion of c-type cytochromes such as OmcZ. PilA-deficient mutants of G. sulfurreducens have previously been shown to accumulate cytochromes within their membranes. This cytochrome retaining phenotype allowed for enhanced growth of PilA-deficient mutants in electron donor and carbon-limited conditions where formate and fumarate are provided as the sole electron donor and acceptor with no supplementary carbon source. Conversely, wild-type G. sulfurreducens, which has normal secretion of cytochromes, has comparative limited growth in these conditions. This growth is further impeded for OmcZ-deficient and OmcS-deficient mutants. A PilB-deficient mutant which prevents pilin production but allows for secretion of OmcZ had moderate growth in these conditions, indicating a role for cytochrome localization to enabling survival in the electron donor and carbon-limited conditions. To determine which pathways enhanced growth using formate, Sequential Window Acquisition of all Theoretical Mass Spectra mass spectrometry (SWATH-MS) proteomics of formate adapted PilA-deficient mutants and acetate grown wild type was performed. PilA-deficient mutants had an overall decrease in tricarboxylic acid (TCA) cycle enzymes and significant upregulation of electron transport chain associated proteins including many c-type cytochromes and [NiFe]-hydrogenases. Whole genome sequencing of the mutants shows strong convergent evolution and emergence of genetic subpopulations during adaptation to growth on formate. The results described here suggest a role for membrane constrained c-type cytochromes to the enhancement of survival and growth in electron donor and carbon-limited conditions.
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Affiliation(s)
- Lucie Semenec
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria, Australia
| | - Ismael A Vergara
- Bioinformatics and Cancer Genomics, Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Andrew E Laloo
- Advanced Water Management Centre, The University of Queensland, Brisbane, Queensland, Australia
| | - Elizabeth R Mathews
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria, Australia
| | - Philip L Bond
- Advanced Water Management Centre, The University of Queensland, Brisbane, Queensland, Australia
| | - Ashley E Franks
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Melbourne, Victoria, Australia.
- Centre for Future Landscapes, La Trobe University, Melbourne, Australia.
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Semenec L, Laloo AE, Schulz BL, Vergara IA, Bond PL, Franks AE. Deciphering the electric code of Geobacter sulfurreducens in cocultures with Pseudomonas aeruginosa via SWATH-MS proteomics. Bioelectrochemistry 2018; 119:150-160. [DOI: 10.1016/j.bioelechem.2017.09.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2017] [Revised: 09/27/2017] [Accepted: 09/28/2017] [Indexed: 11/28/2022]
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Bell CA, Franks AE. Plugging in microbial metabolism for industrial applications. MICROBIOLOGY AUSTRALIA 2017. [DOI: 10.1071/ma17037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The ability of electric microbes to electrically interact with electrodes is opening up a number of possibilities with industrial applications. Microbes are able to utilise the electrode as an electron source to reduce CO2 for the production of organic compounds directly or produce H2 as a reducing equivalent for partner microbes for the production of commodity chemicals. Electrodes can also allow redox unbalanced fermentation processes to occur through the addition or subtraction of reducing equivalents that remove bottle necks in these pathways. Electrodes are also providing a physical refuge for electric microbes to maintain anaerobic fermenter stability. It can be expected that the role for electric microbes will continued to be expanded as part of industrial applications in the future.
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Blackall LL. Interesting anaerobes in the environment. MICROBIOLOGY AUSTRALIA 2015. [DOI: 10.1071/ma15046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Prokaryotes (Bacteria and Archaea) have a wide range of capacities to survive by generating energy in environments and situations lacking oxygen, which abound on Earth. Anaerobic metabolic strategies include anaerobic respiration (numerous types – e.g. nitrate reduction – Paracoccus denitrificans; sulfur respiration – Desulfuromonadales; methanogenesis – Methanosarsina spp.; iron reduction – Geobacter spp.; dehalorespiration – Dehalococcoides ethenogenes) and fermentation (sugars converted to simpler organic compounds like acids, gases and alcohols – e.g. Lactobacillus spp.). Relatively novel environmental anaerobic strategies include anaerobic ammonium oxidation (Anammox – e.g. Brocadia spp.) and anaerobic methane oxidation (AMO)1, which is a syntrophic association between anaerobic methanotrophic archaea (ANME) and sulfate-, iron-, manganese- or nitrate-reducing bacteria2. The classic anaerobic synthrophic example is interspecies hydrogen/formate transfer between a hydrogen/formate producing fatty acid oxidising bacterium (the syntroph) and a hydrogen/formate consumer (methanogen or sulfate-reducer)3. Microbes vary in their oxygen tolerance and are described as obligate anaerobes if they are killed by atmospheric levels of oxygen due to the lack of catalase and superoxide dismutase that provide oxygen radical protection.
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Bereza-Malcolm LT, Franks AE. Coupling anaerobic bacteria and microbial fuel cells as whole-cell environmental biosensors. MICROBIOLOGY AUSTRALIA 2015. [DOI: 10.1071/ma15045] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Microorganisms have evolved to respond to environmental factors allowing adaption to changing conditions and minimisation of potential harm. Microbes have the ability to sense a wide range of biotic and abiotic factors including nutrient levels, analytes, temperature, contaminants, community quorum, and metabolic activity. Due to this ability, the use of whole-cell microbes as biosensors is attractive as it can provide real-time in situ information on biologically relevant factors through qualitative and quantitative outputs. Interestingly, many of the environments where these biosensors will be of most of use lack oxygen; and as such the use of anaerobic microorganisms to sense environmental factors with easy to use outputs is essential. Furthermore, sensing of contaminants can be linked with bioremediation of known contaminated environments, allowing a flexible, multiplexed device.
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