1
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Wang Y, He C, Xu C, Yang J, Feng J, Wang W. Influence of oxygen partial pressure on homoacetogenesis and promotion of acetic acid accumulation through low pH regulation under microaerobic conditions. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:42766-42778. [PMID: 38878240 DOI: 10.1007/s11356-024-33952-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Accepted: 06/05/2024] [Indexed: 07/04/2024]
Abstract
Homoacetogenesis is an important pathway for bio-utilization of CO2; however, oxygen is a key environmental influencing factor. This study explored the impact of different initial oxygen partial pressures (OPPs) on homoacetogenesis, while implementing low pH regulation enhanced acetic acid (HAc) accumulation under microaerobic conditions. Results indicated that cumulative HAc production increased by 18.2% in 5% OPP group, whereas decreases of 31.3% and 56.0% were observed in 10% and 20% OPP groups, respectively, compared to the control group. However, hydrogenotrophic methanogens adapted to microaerobic environment and competed with homoacetogens for CO2, thus limiting homoacetogenesis. Controlling influent pH 5.0 per cycle increased cumulative HAc production by 18.3% and 18.2% in 5% and 10% OPP groups, respectively, compared with the control group. Consequently, regulating low pH effectively inhibited methanogenic activity under microaerobic conditions, thus increasing HAc production. This study was expected to expand the practical application of homoacetogenesis in bio-utilization of CO2.
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Affiliation(s)
- Yuwei Wang
- Department of Municipal Engineering, School of Civil Engineering, Hefei University of Technology, Hefei, 230009, China
- Anhui Provincial Engineering Laboratory for Rural Water Environment and Resources, Hefei, 230009, China
| | - Chunhua He
- Department of Municipal Engineering, School of Environment and Energy Engineering, Anhui JianZhu University, Hefei, 230009, China
| | - Changwen Xu
- Department of Municipal Engineering, School of Civil Engineering, Hefei University of Technology, Hefei, 230009, China
- Anhui Provincial Engineering Laboratory for Rural Water Environment and Resources, Hefei, 230009, China
| | - Jing Yang
- Department of Municipal Engineering, School of Civil Engineering, Hefei University of Technology, Hefei, 230009, China
- Anhui Provincial Engineering Laboratory for Rural Water Environment and Resources, Hefei, 230009, China
| | - Jingwei Feng
- Department of Municipal Engineering, School of Civil Engineering, Hefei University of Technology, Hefei, 230009, China
- Anhui Provincial Engineering Laboratory for Rural Water Environment and Resources, Hefei, 230009, China
| | - Wei Wang
- Department of Municipal Engineering, School of Civil Engineering, Hefei University of Technology, Hefei, 230009, China.
- Anhui Provincial Engineering Laboratory for Rural Water Environment and Resources, Hefei, 230009, China.
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2
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Yamamoto Y. Roles of flavoprotein oxidase and the exogenous heme- and quinone-dependent respiratory chain in lactic acid bacteria. BIOSCIENCE OF MICROBIOTA, FOOD AND HEALTH 2024; 43:183-191. [PMID: 38966056 PMCID: PMC11220326 DOI: 10.12938/bmfh.2024-002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 04/22/2024] [Indexed: 07/06/2024]
Abstract
Lactic acid bacteria (LAB) are a type of bacteria that convert carbohydrates into lactate through fermentation metabolism. While LAB mainly acquire energy through this anaerobic process, they also have oxygen-consuming systems, one of which is flavoprotein oxidase and the other is exogenous heme- or heme- and quinone-dependent respiratory metabolism. Over the past two decades, research has contributed to the understanding of the roles of these oxidase machineries, confirming their suspected roles and uncovering novel functions. This review presents the roles of these oxidase machineries, which are anticipated to be critical for the future applications of LAB in industry and comprehending the virulence of pathogenic streptococci.
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Affiliation(s)
- Yuji Yamamoto
- Laboratory of Cellular Microbiology, School of Veterinary Medicine, Kitasato University, 23-35-1 Higashi, Towada, Aomori 034-8628, Japan
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3
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Lachowicz JC, Lennox-Hvenekilde D, Myling-Petersen N, Salomonsen B, Verkleij G, Acevedo-Rocha CG, Caddell B, Gronenberg LS, Almo SC, Sommer MOA, Genee HJ, Grove TL. Discovery of a Biotin Synthase That Utilizes an Auxiliary 4Fe-5S Cluster for Sulfur Insertion. J Am Chem Soc 2024; 146:1860-1873. [PMID: 38215281 PMCID: PMC10813225 DOI: 10.1021/jacs.3c05481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Revised: 12/12/2023] [Accepted: 12/13/2023] [Indexed: 01/14/2024]
Abstract
Biotin synthase (BioB) is a member of the Radical SAM superfamily of enzymes that catalyzes the terminal step of biotin (vitamin B7) biosynthesis, in which it inserts a sulfur atom in desthiobiotin to form a thiolane ring. How BioB accomplishes this difficult reaction has been the subject of much controversy, mainly around the source of the sulfur atom. However, it is now widely accepted that the sulfur atom inserted to form biotin stems from the sacrifice of the auxiliary 2Fe-2S cluster of BioB. Here, we bioinformatically explore the diversity of BioBs available in sequence databases and find an unexpected variation in the coordination of the auxiliary iron-sulfur cluster. After in vitro characterization, including the determination of biotin formation and representative crystal structures, we report a new type of BioB utilized by virtually all obligate anaerobic organisms. Instead of a 2Fe-2S cluster, this novel type of BioB utilizes an auxiliary 4Fe-5S cluster. Interestingly, this auxiliary 4Fe-5S cluster contains a ligated sulfide that we propose is used for biotin formation. We have termed this novel type of BioB, Type II BioB, with the E. coli 2Fe-2S cluster sacrificial BioB representing Type I. This surprisingly ubiquitous Type II BioB has implications for our understanding of the function and evolution of Fe-S clusters in enzyme catalysis, highlighting the difference in strategies between the anaerobic and aerobic world.
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Affiliation(s)
- Jake C. Lachowicz
- Department
of Biochemistry, Albert Einstein College
of Medicine, Bronx, New York 10461, United States
| | - David Lennox-Hvenekilde
- The
Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark
- Biosyntia
ApS, Copenhagen, 2100, Denmark
| | | | | | | | - Carlos G. Acevedo-Rocha
- The
Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark
- Biosyntia
ApS, Copenhagen, 2100, Denmark
| | | | | | - Steven C. Almo
- Department
of Biochemistry, Albert Einstein College
of Medicine, Bronx, New York 10461, United States
| | - Morten O. A. Sommer
- The
Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kgs. Lyngby, 2800, Denmark
| | | | - Tyler L. Grove
- Department
of Biochemistry, Albert Einstein College
of Medicine, Bronx, New York 10461, United States
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4
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Ge Z, Ma Z, Hong W, Liu K, Yan S, Song W, Zhang J. Temporal variations in reactive oxygen species in biofilms of submerged macrophytes: The key role of microbial metabolism mediated by oxygen fluctuations. JOURNAL OF HAZARDOUS MATERIALS 2024; 461:132542. [PMID: 37734308 DOI: 10.1016/j.jhazmat.2023.132542] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 08/28/2023] [Accepted: 09/11/2023] [Indexed: 09/23/2023]
Abstract
Reactive oxygen species (ROS) play a crucial role in the biogeochemistry of aquatic environments, yet their occurrence and accumulation in the biofilm of submerged macrophytes have been poorly documented. Herein, we first investigated the light-dark cycling fluctuations of biofilm microenvironment and the temporal variations of a representative ROS (O2•-) during biofilm succession on the macrophyte leaves and subsequently quantified the photochemical processes in biofilms. The sustained production of O2•- exhibited a distinct rhythmic fluctuation from 32.49 ± 0.56 μmol/kg to 72.56 ± 0.92 μmol/kg FW, which simultaneously fluctuated with the dissolved oxygen, redox potential, and pH, all driven by the alternating oxic-anoxic conditions of biofilms. The intensities of O2•- and ROS firstly increased and then decreased throughout biofilm succession. The O2•- concentrations in biofilms from different waters followed the order of rural river water > landscape lake water > aquaculture pond water, and the leaf photosynthesis and microbial community played a key role. ROS production was significantly associated with Actinobacteria, Proteobacteria and Bacteroidetes, with contributions of 44.6%, 32.8%, and 15.2%, respectively. Partial least squares path modeling structural equation analysis showed that ROS production in leaf biofilms was mainly related to the microenvironment and microbial metabolism. These findings will facilitate the development of ecological restoration strategies in aquatic environments.
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Affiliation(s)
- Zuhan Ge
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China
| | - Zihang Ma
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China
| | - Wenjie Hong
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China
| | - Kexuan Liu
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China
| | - Shuwen Yan
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China
| | - Weihua Song
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China
| | - Jibiao Zhang
- Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, PR China; Shanghai Shifang Ecology and Landscape Co., Ltd, Shanghai 200233, PR China.
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5
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Carvalho-de-Araújo AD, Carvalho-Kelly LF, Meyer-Fernandes JR. Anaerobic energy metabolism in human microaerophile parasites. Exp Parasitol 2023; 247:108492. [PMID: 36841468 DOI: 10.1016/j.exppara.2023.108492] [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: 09/29/2022] [Revised: 01/30/2023] [Accepted: 02/20/2023] [Indexed: 02/27/2023]
Abstract
Mucosal-associated parasites, such as Giardia intestinalis, Entamoeba histolytica, and Trichomonas vaginalis, have significant clinical relevance. The pathologies associated with infection by these parasites are among those with the highest incidence of gastroenteritis (giardiasis and amoebiasis) and sexually transmitted infections (trichomoniasis). The treatment of these diseases is based on drugs that act on the anaerobic metabolism of these parasites, such as nitroimidazole and benzimidazole derivatives. One interesting feature of parasites is their ability to produce ATP under anaerobic conditions. Due to the absence of enzymes capable of producing ATP under anaerobic conditions in the vertebrate host, they have become interesting therapeutic targets. This review discusses anaerobic energy metabolism in mucosal-associated parasites, focusing on the anaerobic metabolism of pyruvate, the importance of these enzymes as therapeutic targets, and the importance of treating their infections.
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Affiliation(s)
- Ayra Diandra Carvalho-de-Araújo
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, CCS, Bloco H, 2 andar, sala 13. Ilha do Fundão, Rio de Janeiro, 21941-902, Brazil; Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, Ilha do Fundão, Rio de Janeiro, 21941-902, Brazil
| | - Luiz Fernando Carvalho-Kelly
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, CCS, Bloco H, 2 andar, sala 13. Ilha do Fundão, Rio de Janeiro, 21941-902, Brazil
| | - José Roberto Meyer-Fernandes
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, CCS, Bloco H, 2 andar, sala 13. Ilha do Fundão, Rio de Janeiro, 21941-902, Brazil; Instituto Nacional de Ciência a Tecnologia em Biologia Estrutural e Bioimagem (INCTBEB), Cidade Universitária, Ilha do Fundão, 21941-902, Rio de Janeiro, RJ, Brazil.
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6
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Lin L, Zou M, Lu Z. The aerobic electron flux is deficient in fumarate respiration of a strict anaerobe Bacteroides thetaiotaomicron. Biochem Biophys Res Commun 2022; 614:213-218. [PMID: 35623108 DOI: 10.1016/j.bbrc.2022.05.017] [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: 04/18/2022] [Accepted: 05/05/2022] [Indexed: 11/28/2022]
Abstract
Why oxygen ceases the growth of strictly anaerobic bacteria is a longstanding question, yet the answer remains unclear. Studies have confirmed that the dehydratase-fumarase containing an iron-sulfur cluster ([4Fe-4S]) is inactivated upon exposure to oxygen in the intestinal obligate anaerobe, Bacteroides thetaiotaomicron (B. thetaiotaomicron); this blocks fumarate respiration, which is the essential energy-producing pathway in anaerobes. Here, we substituted the [4Fe-4S]-dependent fumarase in B. thetaiotaomicron with an iron-free isozyme from E. coli (Ec-FumC). Results show that Ec-FumC successfully performed the catalytic function of fumarase in B. thetaiotaomicron, as the fum-mutant strain that expressed Ec-FumC exhibited succinate-producing ability under anaerobic growth conditions. Ec-FumC is oxygen-resistant and remains active to produce fumarate upon aeration; however, B. thetaiotaomicron mutant that expressed Ec-FumC did not convert fumarate to succinate during air exposure. Biochemical assays of inverted membrane vesicles from wild-type B. thetaiotaomicron confirmed that the electron flux from NADH to fumarate was less efficient in the presence of air as compared to that without oxygen. Our findings suggest that the anaerobic fumarate respiration might be paralyzed due to electron dissipations upon aeration of the obligate anaerobe.
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Affiliation(s)
- Luyou Lin
- Department of Biology, Guangdong Provincial Key Laboratory of Marine Biotechnology, Institute of Marine Sciences, Shantou University, Shantou, 515063, China
| | - Meng Zou
- Department of Biology, Guangdong Provincial Key Laboratory of Marine Biotechnology, Institute of Marine Sciences, Shantou University, Shantou, 515063, China
| | - Zheng Lu
- Department of Biology, Guangdong Provincial Key Laboratory of Marine Biotechnology, Institute of Marine Sciences, Shantou University, Shantou, 515063, China.
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7
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Investigation and Alteration of Organic Acid Synthesis Pathways in the Mammalian Gut Symbiont Bacteroides thetaiotaomicron. Microbiol Spectr 2022; 10:e0231221. [PMID: 35196806 PMCID: PMC8865466 DOI: 10.1128/spectrum.02312-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Members of the gut-dwelling Bacteroides genus have remarkable abilities in degrading a diverse set of fiber polysaccharide structures, most of which are found in the mammalian diet. As part of their metabolism, they convert these fibers to organic acids that can in turn provide energy to their host. While many studies have identified and characterized the genes and corresponding proteins involved in polysaccharide degradation, relatively little is known about Bacteroides genes involved in downstream metabolic pathways. Bacteroides thetaiotaomicron is one of the most studied species from the genus and is representative of this group in producing multiple organic acids as part of its metabolism. We focused here on several organic acid synthesis pathways in B. thetaiotaomicron, including those involved in formate, lactate, propionate, and acetate production. We identified potential genes involved in each pathway and characterized these through gene deletions coupled to growth assays and organic acid quantification. In addition, we developed and employed a Golden Gate-compatible plasmid system to simplify alteration of native gene expression levels. Our work both validates and contradicts previous bioinformatic gene annotations, and we develop a model on which to base future efforts. A clearer understanding of Bacteroides metabolic pathways can inform and facilitate efforts to employ these bacteria for improved human health or other utilization strategies. IMPORTANCE Both humans and animals host a large community of bacteria and other microorganisms in their gastrointestinal tracts. This community breaks down dietary fiber and produces organic acids that are used as an energy source by the body and can also help the host resist infection by various pathogens. While the Bacteroides genus is one of the most common in the gut microbiota, it is only distantly related to bacteria with well-characterized metabolic pathways and it is therefore unclear whether research insights on organic acid production in those species can also be directly applied to the Bacteroides. By investigating multiple genetic pathways for organic acid production in Bacteroides thetaiotaomicron, we provide a basis for deeper understanding of these pathways. The work further enables greater understanding of Bacteroides–host relationships, as well as inter-species relationships in the microbiota, which are of importance for both human and animal gut health.
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8
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Ruhl IA, Sheremet A, Furgason CC, Krause S, Bowers RM, Jarett JK, Tran TM, Grasby SE, Woyke T, Dunfield PF. GAL08, an Uncultivated Group of Acidobacteria, Is a Dominant Bacterial Clade in a Neutral Hot Spring. Front Microbiol 2022; 12:787651. [PMID: 35087491 PMCID: PMC8787282 DOI: 10.3389/fmicb.2021.787651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 11/29/2021] [Indexed: 11/28/2022] Open
Abstract
GAL08 are bacteria belonging to an uncultivated phylogenetic cluster within the phylum Acidobacteria. We detected a natural population of the GAL08 clade in sediment from a pH-neutral hot spring located in British Columbia, Canada. To shed light on the abundance and genomic potential of this clade, we collected and analyzed hot spring sediment samples over a temperature range of 24.2–79.8°C. Illumina sequencing of 16S rRNA gene amplicons and qPCR using a primer set developed specifically to detect the GAL08 16S rRNA gene revealed that absolute and relative abundances of GAL08 peaked at 65°C along three temperature gradients. Analysis of sediment collected over multiple years and locations revealed that the GAL08 group was consistently a dominant clade, comprising up to 29.2% of the microbial community based on relative read abundance and up to 4.7 × 105 16S rRNA gene copy numbers per gram of sediment based on qPCR. Using a medium quality threshold, 25 single amplified genomes (SAGs) representing these bacteria were generated from samples taken at 65 and 77°C, and seven metagenome-assembled genomes (MAGs) were reconstructed from samples collected at 45–77°C. Based on average nucleotide identity (ANI), these SAGs and MAGs represented three separate species, with an estimated average genome size of 3.17 Mb and GC content of 62.8%. Phylogenetic trees constructed from 16S rRNA gene sequences and a set of 56 concatenated phylogenetic marker genes both placed the three GAL08 bacteria as a distinct subgroup of the phylum Acidobacteria, representing a candidate order (Ca. Frugalibacteriales) within the class Blastocatellia. Metabolic reconstructions from genome data predicted a heterotrophic metabolism, with potential capability for aerobic respiration, as well as incomplete denitrification and fermentation. In laboratory cultivation efforts, GAL08 counts based on qPCR declined rapidly under atmospheric levels of oxygen but increased slightly at 1% (v/v) O2, suggesting a microaerophilic lifestyle.
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Affiliation(s)
- Ilona A Ruhl
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Andriy Sheremet
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Chantel C Furgason
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Susanne Krause
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Robert M Bowers
- U.S. Department of Energy Joint Genome Institute, Berkeley, CA, United States
| | - Jessica K Jarett
- U.S. Department of Energy Joint Genome Institute, Berkeley, CA, United States
| | - Triet M Tran
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
| | - Stephen E Grasby
- Department of Geoscience, University of Calgary, Calgary, AB, Canada.,Geological Survey of Canada, Calgary, AB, Canada
| | - Tanja Woyke
- U.S. Department of Energy Joint Genome Institute, Berkeley, CA, United States
| | - Peter F Dunfield
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada
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9
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When anaerobes encounter oxygen: mechanisms of oxygen toxicity, tolerance and defence. Nat Rev Microbiol 2021; 19:774-785. [PMID: 34183820 PMCID: PMC9191689 DOI: 10.1038/s41579-021-00583-y] [Citation(s) in RCA: 84] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/19/2021] [Indexed: 02/06/2023]
Abstract
The defining trait of obligate anaerobes is that oxygen blocks their growth, yet the underlying mechanisms are unclear. A popular hypothesis was that these microorganisms failed to evolve defences to protect themselves from reactive oxygen species (ROS) such as superoxide and hydrogen peroxide, and that this failure is what prevents their expansion to oxic habitats. However, studies reveal that anaerobes actually wield most of the same defences that aerobes possess, and many of them have the capacity to tolerate substantial levels of oxygen. Therefore, to understand the structures and real-world dynamics of microbial communities, investigators have examined how anaerobes such as Bacteroides, Desulfovibrio, Pyrococcus and Clostridium spp. struggle and cope with oxygen. The hypoxic environments in which these organisms dwell - including the mammalian gut, sulfur vents and deep sediments - experience episodic oxygenation. In this Review, we explore the molecular mechanisms by which oxygen impairs anaerobes and the degree to which bacteria protect their metabolic pathways from it. The emergent view of anaerobiosis is that optimal strategies of anaerobic metabolism depend upon radical chemistry and low-potential metal centres. Such catalytic sites are intrinsically vulnerable to direct poisoning by molecular oxygen and ROS. Observations suggest that anaerobes have evolved tactics that either minimize the extent to which oxygen disrupts their metabolism or restore function shortly after the stress has dissipated.
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10
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Baleeiro FCF, Ardila MS, Kleinsteuber S, Sträuber H. Effect of Oxygen Contamination on Propionate and Caproate Formation in Anaerobic Fermentation. Front Bioeng Biotechnol 2021; 9:725443. [PMID: 34568301 PMCID: PMC8460912 DOI: 10.3389/fbioe.2021.725443] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Accepted: 08/19/2021] [Indexed: 01/19/2023] Open
Abstract
Mixed microbial cultures have become a preferred choice of biocatalyst for chain elongation systems due to their ability to convert complex substrates into medium-chain carboxylates. However, the complexity of the effects of process parameters on the microbial metabolic networks is a drawback that makes the task of optimizing product selectivity challenging. Here, we studied the effects of small air contaminations on the microbial community dynamics and the product formation in anaerobic bioreactors fed with lactate, acetate and H2/CO2. Two stirred tank reactors and two bubble column reactors were operated with H2/CO2 gas recirculation for 139 and 116 days, respectively, at pH 6.0 and 32°C with a hydraulic retention time of 14 days. One reactor of each type had periods with air contamination (between 97 ± 28 and 474 ± 33 mL O2 L−1 d−1, lasting from 4 to 32 days), while the control reactors were kept anoxic. During air contamination, production of n-caproate and CH4 was strongly inhibited, whereas no clear effect on n-butyrate production was observed. In a period with detectable O2 concentrations that went up to 18%, facultative anaerobes of the genus Rummeliibacillus became predominant and only n-butyrate was produced. However, at low air contamination rates and with O2 below the detection level, Coriobacteriia and Actinobacteria gained a competitive advantage over Clostridia and Methanobacteria, and propionate production rates increased to 0.8–1.8 mmol L−1 d−1 depending on the reactor (control reactors 0.1–0.8 mmol L−1 d−1). Moreover, i-butyrate production was observed, but only when Methanobacteria abundances were low and, consequently, H2 availability was high. After air contamination stopped completely, production of n-caproate and CH4 recovered, with n-caproate production rates of 1.4–1.8 mmol L−1 d−1 (control 0.7–2.1 mmol L−1 d−1). The results underline the importance of keeping strictly anaerobic conditions in fermenters when consistent n-caproate production is the goal. Beyond that, micro-aeration should be further tested as a controllable process parameter to shape the reactor microbiome. When odd-chain carboxylates are desired, further studies can develop strategies for their targeted production by applying micro-aerobic conditions.
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Affiliation(s)
- Flávio C F Baleeiro
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.,Institute of Process Engineering in Life Science 2, Technical Biology, Karlsruhe Institute of Technology - KIT, Karlsruhe, Germany
| | - Magda S Ardila
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.,Institute of Process Engineering in Life Science 2, Technical Biology, Karlsruhe Institute of Technology - KIT, Karlsruhe, Germany
| | - Sabine Kleinsteuber
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Heike Sträuber
- Department of Environmental Microbiology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
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11
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Morvan C, Folgosa F, Kint N, Teixeira M, Martin-Verstraete I. Responses of Clostridia to oxygen: from detoxification to adaptive strategies. Environ Microbiol 2021; 23:4112-4125. [PMID: 34245087 DOI: 10.1111/1462-2920.15665] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 07/02/2021] [Accepted: 07/07/2021] [Indexed: 11/30/2022]
Abstract
Clostridia comprise bacteria of environmental, biotechnological and medical interest and many commensals of the gut microbiota. Because of their strictly anaerobic lifestyle, oxygen is a major stress for Clostridia. However, recent data showed that these bacteria can cope with O2 better than expected for obligate anaerobes through their ability to scavenge, detoxify and consume O2 . Upon O2 exposure, Clostridia redirect their central metabolism onto pathways less O2 -sensitive and induce the expression of genes encoding enzymes involved in O2 -reduction and in the repair of oxidized damaged molecules. While Faecalibacterium prausnitzii efficiently consumes O2 through a specific extracellular electron shuttling system requiring riboflavin, enzymes such as rubrerythrins and flavodiiron proteins with NAD(P)H-dependent O2 - and/or H2 O2 -reductase activities are usually encoded in other Clostridia. These two classes of enzymes play indeed a pivotal role in O2 tolerance in Clostridioides difficile and Clostridium acetobutylicum. Two main signalling pathways triggering O2 -induced responses have been described so far in Clostridia. PerR acts as a key regulator of the O2 - and/or reactive oxygen species-defence machinery while in C. difficile, σB , the sigma factor of the general stress response also plays a crucial role in O2 tolerance by controlling the expression of genes involved in O2 scavenging and repair systems.
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Affiliation(s)
- Claire Morvan
- Laboratoire Pathogenèses des Bactéries Anaérobies, Institut Pasteur, Université de Paris, Paris, F-75015, France
| | - Filipe Folgosa
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, 2780-157, Portugal
| | - Nicolas Kint
- Laboratoire Pathogenèses des Bactéries Anaérobies, Institut Pasteur, Université de Paris, Paris, F-75015, France
| | - Miguel Teixeira
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, Oeiras, 2780-157, Portugal
| | - Isabelle Martin-Verstraete
- Laboratoire Pathogenèses des Bactéries Anaérobies, Institut Pasteur, Université de Paris, Paris, F-75015, France
- Institut Universitaire de France, Paris, France
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12
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Khademian M, Imlay JA. How Microbes Evolved to Tolerate Oxygen. Trends Microbiol 2021; 29:428-440. [PMID: 33109411 PMCID: PMC8043972 DOI: 10.1016/j.tim.2020.10.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 10/03/2020] [Accepted: 10/05/2020] [Indexed: 12/24/2022]
Abstract
Ancient microbes invented biochemical mechanisms and assembled core metabolic pathways on an anoxic Earth. Molecular oxygen appeared far later, forcing microbes to devise layers of defensive tactics that fend off the destructive actions of both reactive oxygen species (ROS) and oxygen itself. Recent work has pinpointed the enzymes that ROS attack, plus an array of clever protective strategies that abet the well known scavenging systems. Oxygen also directly damages the low-potential metal centers and radical-based mechanisms that optimize anaerobic metabolism; therefore, committed anaerobes have evolved customized tactics that defend these various enzymes from occasional oxygen exposure. Thus a more comprehensive, detailed, and surprising view of oxygen toxicity is coming into view.
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Affiliation(s)
- Maryam Khademian
- Department of Microbiology, University of Illinois, Urbana, IL 61801, USA.
| | - James A Imlay
- Department of Microbiology, University of Illinois, Urbana, IL 61801, USA
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