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Lastovetsky OA, Caruso T, Brennan FP, Wall D, Pylni S, Doyle E. Spores of arbuscular mycorrhizal fungi host surprisingly diverse communities of endobacteria. THE NEW PHYTOLOGIST 2024; 242:1785-1797. [PMID: 38403930 DOI: 10.1111/nph.19605] [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: 07/25/2023] [Accepted: 01/28/2024] [Indexed: 02/27/2024]
Abstract
Arbuscular mycorrhizal fungi (AMF) are ubiquitous plant root symbionts, which can house two endobacteria: Ca. Moeniiplasma glomeromycotorum (CaMg) and Ca. Glomeribacter gigasporarum (CaGg). However, little is known about their distribution and population structure in natural AMF populations and whether AMF can harbour other endobacteria. We isolated AMF from two environments and conducted detailed analyses of endobacterial communities associated with surface-sterilised AMF spores. Consistent with the previous reports, we found that CaMg were extremely abundant (80%) and CaGg were extremely rare (2%) in both environments. Unexpectedly, we discovered an additional and previously unknown level of bacterial diversity within AMF spores, which extended beyond the known endosymbionts, with bacteria belonging to 10 other phyla detected across our spore data set. Detailed analysis revealed that: CaGg were not limited in distribution to the Gigasporaceae family of AMF, as previously thought; CaMg population structure was driven by AMF host genotype; and a significant inverse correlation existed between the diversity of CaMg and diversity of all other endobacteria. Based on these data, we generate novel testable hypotheses regarding the function of CaMg in AMF biology by proposing that they might act as conditional mutualists of AMF.
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Affiliation(s)
- Olga A Lastovetsky
- School of Biology and Environmental Science, Science Centre East, University College Dublin, Belfield, Dublin 4, Ireland
| | - Tancredi Caruso
- School of Biology and Environmental Science, Science Centre East, University College Dublin, Belfield, Dublin 4, Ireland
| | - Fiona P Brennan
- Teagasc, Crops, Environment and Land-Use Programme, Johnstown Castle, Co. Wexford, Ireland
| | - David Wall
- Teagasc, Crops, Environment and Land-Use Programme, Johnstown Castle, Co. Wexford, Ireland
| | - Susanna Pylni
- School of Biology and Environmental Science, Science Centre East, University College Dublin, Belfield, Dublin 4, Ireland
| | - Evelyn Doyle
- School of Biology and Environmental Science, Science Centre East, University College Dublin, Belfield, Dublin 4, Ireland
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2
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Gryganskyi AP, Golan J, Muszewska A, Idnurm A, Dolatabadi S, Mondo SJ, Kutovenko VB, Kutovenko VO, Gajdeczka MT, Anishchenko IM, Pawlowska J, Tran NV, Ebersberger I, Voigt K, Wang Y, Chang Y, Pawlowska TE, Heitman J, Vilgalys R, Bonito G, Benny GL, Smith ME, Reynolds N, James TY, Grigoriev IV, Spatafora JW, Stajich JE. Sequencing the Genomes of the First Terrestrial Fungal Lineages: What Have We Learned? Microorganisms 2023; 11:1830. [PMID: 37513002 PMCID: PMC10386755 DOI: 10.3390/microorganisms11071830] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 07/13/2023] [Accepted: 07/16/2023] [Indexed: 07/30/2023] Open
Abstract
The first genome sequenced of a eukaryotic organism was for Saccharomyces cerevisiae, as reported in 1996, but it was more than 10 years before any of the zygomycete fungi, which are the early-diverging terrestrial fungi currently placed in the phyla Mucoromycota and Zoopagomycota, were sequenced. The genome for Rhizopus delemar was completed in 2008; currently, more than 1000 zygomycete genomes have been sequenced. Genomic data from these early-diverging terrestrial fungi revealed deep phylogenetic separation of the two major clades-primarily plant-associated saprotrophic and mycorrhizal Mucoromycota versus the primarily mycoparasitic or animal-associated parasites and commensals in the Zoopagomycota. Genomic studies provide many valuable insights into how these fungi evolved in response to the challenges of living on land, including adaptations to sensing light and gravity, development of hyphal growth, and co-existence with the first terrestrial plants. Genome sequence data have facilitated studies of genome architecture, including a history of genome duplications and horizontal gene transfer events, distribution and organization of mating type loci, rDNA genes and transposable elements, methylation processes, and genes useful for various industrial applications. Pathogenicity genes and specialized secondary metabolites have also been detected in soil saprobes and pathogenic fungi. Novel endosymbiotic bacteria and viruses have been discovered during several zygomycete genome projects. Overall, genomic information has helped to resolve a plethora of research questions, from the placement of zygomycetes on the evolutionary tree of life and in natural ecosystems, to the applied biotechnological and medical questions.
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Affiliation(s)
- Andrii P. Gryganskyi
- Division of Biological & Nanoscale Technologies, UES, Inc., Dayton, OH 45432, USA
| | - Jacob Golan
- Department of Botany, University of Wisconsin-Madison, Madison, WI 53706, USA;
| | - Anna Muszewska
- Institute of Biochemistry & Biophysics, Polish Academy of Sciences, 01-224 Warsaw, Poland;
| | - Alexander Idnurm
- School of BioSciences, University of Melbourne, Parkville, VIC 3010, Australia;
| | - Somayeh Dolatabadi
- Biology Department, Hakim Sabzevari University, Sabzevar 96179-76487, Iran;
| | - Stephen J. Mondo
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; (S.J.M.); (I.V.G.)
| | - Vira B. Kutovenko
- Department of Agrobiology, National University of Life & Environmental Sciences, 03041 Kyiv, Ukraine; (V.B.K.)
| | - Volodymyr O. Kutovenko
- Department of Agrobiology, National University of Life & Environmental Sciences, 03041 Kyiv, Ukraine; (V.B.K.)
| | | | - Iryna M. Anishchenko
- MG Kholodny Institute of Botany, National Academy of Sciences, 01030 Kyiv, Ukraine;
| | - Julia Pawlowska
- Institute of Evolutionary Biology, Faculty of Biology, Biological & Chemical Research Centre, University of Warsaw, 02-089 Warsaw, Poland;
| | - Ngoc Vinh Tran
- Plant Pathology Department, University of Florida, Gainesville, FL 32611, USA; (N.V.T.); (G.L.B.); (M.E.S.)
| | - Ingo Ebersberger
- Leibniz Institute for Natural Product Research & Infection Biology, 07745 Jena, Germany; (I.E.); (K.V.)
| | - Kerstin Voigt
- Leibniz Institute for Natural Product Research & Infection Biology, 07745 Jena, Germany; (I.E.); (K.V.)
| | - Yan Wang
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 1A1, Canada;
- Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada
| | - Ying Chang
- Department of Biological Sciences, National University of Singapore, Singapore 119077, Singapore;
| | - Teresa E. Pawlowska
- School of Integrative Plant Science, Cornell University, Ithaca, NY 14850, USA; (T.E.P.); (N.R.)
| | - Joseph Heitman
- Department of Molecular Genetics & Microbiology, Duke University School of Medicine, Durham, NC 27710, USA;
| | - Rytas Vilgalys
- Biology Department, Duke University, Durham, NC 27708, USA;
| | - Gregory Bonito
- Department of Plant, Soil & Microbial Sciences, Michigan State University, East Lansing, MI 48824, USA;
| | - Gerald L. Benny
- Plant Pathology Department, University of Florida, Gainesville, FL 32611, USA; (N.V.T.); (G.L.B.); (M.E.S.)
| | - Matthew E. Smith
- Plant Pathology Department, University of Florida, Gainesville, FL 32611, USA; (N.V.T.); (G.L.B.); (M.E.S.)
| | - Nicole Reynolds
- School of Integrative Plant Science, Cornell University, Ithaca, NY 14850, USA; (T.E.P.); (N.R.)
| | - Timothy Y. James
- Department of Ecology & Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA;
| | - Igor V. Grigoriev
- U.S. Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; (S.J.M.); (I.V.G.)
- Department of Plant & Microbial Biology, University of California, Berkeley, CA 94720, USA
| | - Joseph W. Spatafora
- Department of Botany & Plant Pathology, Oregon State University, Corvallis, OR 97331, USA;
| | - Jason E. Stajich
- Department of Microbiology & Plant Pathology, University of California, Riverside, CA 93106, USA;
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3
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Desirò A, Takashima Y, Bonito G, Nishizawa T, Narisawa K, Bonfante P. Investigating Endobacteria that Thrive Within Mucoromycota. Methods Mol Biol 2022; 2605:293-323. [PMID: 36520400 DOI: 10.1007/978-1-0716-2871-3_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Metagenomics approaches have revealed the importance of Mucoromycota in the evolution and functioning of plant microbiomes. Comprised of three subphyla (Glomeromycotina, Mortierellomycotina, and Mucoromycotina), this early diverging lineage of fungi encompasses species of mycorrhizal fungi, root endophytes, plant pathogens, and many decomposers of plant debris. Interestingly, several taxa of Mucoromycota share a common feature, that is, the presence of endobacteria within their mycelia and spores. The study of these endosymbiotic bacteria is still a challenging task. However, given recent improvements in the sensitivity of culture-free approaches, a deeper understanding of such microbial interactions is now possible and fuels an emerging research field. In this chapter, we report how Mucoromycota, in particular Mortierellomycotina, and their endobacteria can be investigated using a combination of diverse cellular biology, microscopy, and molecular techniques.
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Affiliation(s)
- Alessandro Desirò
- Department of Plant Soil and Microbial Sciences, Michigan State University, East Lansing, MI, USA
| | - Yusuke Takashima
- Sugadaira Research Station, Mountain Science Center, University of Tsukuba, Nagano, Japan
| | - Gregory Bonito
- Department of Plant Soil and Microbial Sciences, Michigan State University, East Lansing, MI, USA
| | | | | | - Paola Bonfante
- Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy.
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Palomares-Rius JE, Gutiérrez-Gutiérrez C, Mota M, Bert W, Claeys M, Yushin VV, Suzina NE, Ariskina EV, Evtushenko LI, Subbotin SA, Castillo P. ' Candidatus Xiphinematincola pachtaicus' gen. nov., sp. nov., an endosymbiotic bacterium associated with nematode species of the genus Xiphinema (Nematoda, Longidoridae). Int J Syst Evol Microbiol 2021; 71:004888. [PMID: 34287117 PMCID: PMC8489844 DOI: 10.1099/ijsem.0.004888] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 05/31/2021] [Indexed: 11/18/2022] Open
Abstract
An intracellular bacterium, strain IAST, was observed to infect several species of the plant-parasitic nematode genus Xiphinema (Xiphinema astaregiense, Xiphinema incertum, Xiphinema madeirense, Xiphinema pachtaicum, Xiphinema parapachydermum and Xiphinema vallense). The bacterium could not be recovered on axenic medium. The 16S rRNA gene sequence of IAST was found to be new, being related to the family Burkholderiaceae, class Betaproteobacteria. Fungal endosymbionts Mycoavidus cysteinexigens B1-EBT (92.9 % sequence identity) and 'Candidatus Glomeribacter gigasporarum' BEG34 (89.8 % identity) are the closest taxa and form a separate phylogenetic clade inside Burkholderiaceae. Other genes (atpD, lepA and recA) also separated this species from its closest relatives using a multilocus sequence analysis approach. These genes were obtained using a partial genome of this bacterium. The localization of the bacterium (via light and fluorescence in situ hybridization microscopy) is in the X. pachtaicum females clustered around the developing oocytes, primarily found embedded inside the epithelial wall cells of the ovaries, from where they are dispersed in the intestine. Transmission electron microscopy (TEM) observations supported the presence of bacteria inside the nematode body, where they occupy ovaries and occur inside the intestinal epithelium. Ultrastructural analysis of the bacterium showed cells that appear as mostly irregular, slightly curved rods with rounded ends, 0.8-1.2 µm wide and 2.5-6.0 µm long, possessing a typical Gram-negative cell wall. The peptidoglycan layer is, however, evident only occasionally and not detectable by TEM in most cells. Another irregularly occurring shell surrounding the endosymbiont cells or the cell clusters was also revealed, probably originating from the host cell membrane. Flagella or spore-like cells do not occur and the nucleoid is diffusely distributed throughout the cell. This endosymbiont is transmitted vertically through nematode generations. These results support the proposal of IAST as a new species, although its obligate intracellular and obligate endosymbiont nature prevented isolation of a definitive type strain. Strain IAST is therefore proposed as representing 'Candidatus Xiphinematincola pachtaicus' gen. nov., sp. nov.
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Affiliation(s)
- Juan E. Palomares-Rius
- Institute for Sustainable Agriculture (IAS), Spanish National Research Council (CSIC), Avenida Menéndez Pidal s/n, 14004 Córdoba, Campus de Excelencia Internacional Agroalimentario, ceiA3, Spain
| | - Carlos Gutiérrez-Gutiérrez
- NemaLab, MED – Mediterranean Institute for Agriculture, Environment and Development, Institute for Advanced Studies and Research, Universidade de Évora, Pólo da Mitra, Ap. 94, 7006-554 Évora, Portugal
| | - Manuel Mota
- NemaLab, MED – Mediterranean Institute for Agriculture, Environment and Development, Institute for Advanced Studies and Research, Universidade de Évora, Pólo da Mitra, Ap. 94, 7006-554 Évora, Portugal
| | - Wim Bert
- Nematology Research Unit, Department of Biology, Ghent University, K.L. Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Myriam Claeys
- Nematology Research Unit, Department of Biology, Ghent University, K.L. Ledeganckstraat 35, 9000 Ghent, Belgium
| | - Vladimir V. Yushin
- A.V. Zhirmunsky National Scientific Center of Marine Biology, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690041, Russia
| | - Natalia E. Suzina
- All-Russian Collection of Microorganisms (VKM), G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino 142290, Russia
| | - Elena V. Ariskina
- All-Russian Collection of Microorganisms (VKM), G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino 142290, Russia
| | - Lyudmila I. Evtushenko
- All-Russian Collection of Microorganisms (VKM), G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino 142290, Russia
| | - Sergei A. Subbotin
- California Department of Food and Agriculture, Plant Pest Diagnostic Center, Sacramento, CA 95832, USA
- Center of Parasitology of A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences, Leninskii Prospect 33, Moscow 117071, Russia
| | - Pablo Castillo
- Institute for Sustainable Agriculture (IAS), Spanish National Research Council (CSIC), Avenida Menéndez Pidal s/n, 14004 Córdoba, Campus de Excelencia Internacional Agroalimentario, ceiA3, Spain
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5
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Bastías DA, Johnson LJ, Card SD. Symbiotic bacteria of plant-associated fungi: friends or foes? CURRENT OPINION IN PLANT BIOLOGY 2020; 56:1-8. [PMID: 31786411 DOI: 10.1016/j.pbi.2019.10.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 10/21/2019] [Accepted: 10/30/2019] [Indexed: 06/10/2023]
Abstract
Many bacteria form symbiotic associations with plant-associated fungi. The effects of these symbionts on host fitness usually depend on symbiont or host genotypes and environmental conditions. However, bacterial endosymbionts, that is those living within fungal cells, may positively regulate host performance as their survival is often heavily dependent on host fitness. Contrary to this, bacteria that establish ectosymbiotic associations with fungi, that is those located on the hyphal surface or in close vicinity to fungal mycelia, may not have an apparent net effect on fungal performance due to the low level of fitness dependency on their host. Our analysis supports the hypothesis that endosymbiotic bacteria of fungi are beneficial symbionts, and that effects of ectosymbiotic bacteria on fungal performance depends on the bacterial type involved in the interaction (e.g. helper versus pathogen of fungi). Ecological scenarios, where the presence of beneficial bacterial endosymbionts of fungi could be compromised, are also discussed.
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Affiliation(s)
- Daniel A Bastías
- Forage Science, AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand.
| | - Linda J Johnson
- Forage Science, AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
| | - Stuart D Card
- Forage Science, AgResearch Limited, Grasslands Research Centre, Palmerston North, New Zealand
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6
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Fungal Epigenetic Engineering. Fungal Biol 2020. [DOI: 10.1007/978-3-030-41870-0_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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7
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Haselkorn TS, DiSalvo S, Miller JW, Bashir U, Brock DA, Queller DC, Strassmann JE. The specificity of Burkholderia symbionts in the social amoeba farming symbiosis: Prevalence, species, genetic and phenotypic diversity. Mol Ecol 2019; 28:847-862. [PMID: 30575161 DOI: 10.1111/mec.14982] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 10/13/2018] [Accepted: 10/25/2018] [Indexed: 01/10/2023]
Abstract
The establishment of symbioses between eukaryotic hosts and bacterial symbionts in nature is a dynamic process. The formation of such relationships depends on the life history of both partners. Bacterial symbionts of amoebae may have unique evolutionary trajectories to the symbiont lifestyle, because bacteria are typically ingested as prey. To persist after ingestion, bacteria must first survive phagocytosis. In the social amoeba Dictyostelium discoideum, certain strains of Burkholderia bacteria are able to resist amoebal digestion and maintain a persistent relationship that includes carriage throughout the amoeba's social cycle that culminates in spore formation. Some Burkholderia strains allow their host to carry other bacteria, as food. This carried food is released in new environments in a trait called farming. To better understand the diversity and prevalence of Burkholderia symbionts and the traits they impart to their amoebae hosts, we first screened 700 natural isolates of D. discoideum and found 25% infected with Burkholderia. We next used a multilocus phylogenetic analysis and identified two independent transitions by Burkholderia to the symbiotic lifestyle. Finally, we tested the ability of 38 strains of Burkholderia from D. discoideum, as well as strains isolated from other sources, for traits relevant to symbiosis in D. discoideum. Only D. discoideum native isolates belonging to the Burkholderia agricolaris, B. hayleyella, and B. bonniea species were able to form persistent symbiotic associations with D. discoideum. The Burkholderia-Dictyostelium relationship provides a promising arena for further studies of the pathway to symbiosis in a unique system.
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Affiliation(s)
| | - Susanne DiSalvo
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, Illinois
| | - Jacob W Miller
- Department of Biological Sciences, Southern Illinois University Edwardsville, Edwardsville, Illinois
| | - Usman Bashir
- Department of Biology, Washington University in St. Louis, Missouri
| | - Debra A Brock
- Department of Biology, Washington University in St. Louis, Missouri
| | - David C Queller
- Department of Biology, Washington University in St. Louis, Missouri
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8
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Arora P, Riyaz-Ul-Hassan S. Endohyphal bacteria; the prokaryotic modulators of host fungal biology. FUNGAL BIOL REV 2019. [DOI: 10.1016/j.fbr.2018.08.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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9
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Deveau A, Bonito G, Uehling J, Paoletti M, Becker M, Bindschedler S, Hacquard S, Hervé V, Labbé J, Lastovetsky OA, Mieszkin S, Millet LJ, Vajna B, Junier P, Bonfante P, Krom BP, Olsson S, van Elsas JD, Wick LY. Bacterial-fungal interactions: ecology, mechanisms and challenges. FEMS Microbiol Rev 2018; 42:335-352. [PMID: 29471481 DOI: 10.1093/femsre/fuy008] [Citation(s) in RCA: 318] [Impact Index Per Article: 53.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 02/16/2018] [Indexed: 12/14/2022] Open
Abstract
Fungi and bacteria are found living together in a wide variety of environments. Their interactions are significant drivers of many ecosystem functions and are important for the health of plants and animals. A large number of fungal and bacterial families engage in complex interactions that lead to critical behavioural shifts of the microorganisms ranging from mutualism to antagonism. The importance of bacterial-fungal interactions (BFI) in environmental science, medicine and biotechnology has led to the emergence of a dynamic and multidisciplinary research field that combines highly diverse approaches including molecular biology, genomics, geochemistry, chemical and microbial ecology, biophysics and ecological modelling. In this review, we discuss recent advances that underscore the roles of BFI across relevant habitats and ecosystems. A particular focus is placed on the understanding of BFI within complex microbial communities and in regard of the metaorganism concept. We also discuss recent discoveries that clarify the (molecular) mechanisms involved in bacterial-fungal relationships, and the contribution of new technologies to decipher generic principles of BFI in terms of physical associations and molecular dialogues. Finally, we discuss future directions for research in order to stimulate synergy within the BFI research area and to resolve outstanding questions.
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Affiliation(s)
- Aurélie Deveau
- Université de Lorraine, INRA, UMR IAM, 54280 Champenoux, France
| | - Gregory Bonito
- Department of Plant Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824, USA
| | - Jessie Uehling
- Biology Department, Duke University, Box 90338, Durham, NC 27705, USA.,Plant and Microbial Biology, University of California, Berkeley, CA 94703, USA
| | - Mathieu Paoletti
- Institut de Biologie et Génétique Cellulaire, UMR 5095 CNRS et Université de Bordeaux, 1 rue Camille Saint-Saëns, 33077 Bordeaux cedex, France
| | - Matthias Becker
- IGZ, Leibniz-Institute of Vegetable and Ornamental Crops, 14979 Großbeeren, Germany
| | - Saskia Bindschedler
- Laboratory of Microbiology, Institute of Biology, University of Neuchâtel, CH-2000 Neuchâtel, Switzerland
| | - Stéphane Hacquard
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany
| | - Vincent Hervé
- Laboratory of Microbiology, Institute of Biology, University of Neuchâtel, CH-2000 Neuchâtel, Switzerland.,Laboratory of Biogeosciences, Institute of Earth Surface Dynamics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Jessy Labbé
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.,Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA
| | - Olga A Lastovetsky
- Graduate Field of Microbiology, Cornell University, Ithaca, NY 14853, USA
| | - Sophie Mieszkin
- Université de Lorraine, INRA, UMR IAM, 54280 Champenoux, France
| | - Larry J Millet
- Joint Institute for Biological Science, University of Tennessee, and the Biosciences Division of Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Balázs Vajna
- Department of Microbiology, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117 Budapest, Hungary
| | - Pilar Junier
- Laboratory of Microbiology, Institute of Biology, University of Neuchâtel, CH-2000 Neuchâtel, Switzerland
| | - Paola Bonfante
- Department of Life Science and Systems Biology, University of Torino, 10125 Torino, Italy
| | - Bastiaan P Krom
- Department of Preventive Dentistry, Academic Centre for Dentistry, G. Mahlerlaan 3004, 1081 LA, Amsterdam, The Netherlands
| | - Stefan Olsson
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University (FAFU), Fuzhou 350002, China
| | - Jan Dirk van Elsas
- Microbial Ecology group, GELIFES, University of Groningen, 9747 Groningen, The Netherlands
| | - Lukas Y Wick
- Helmholtz Centre for Environmental Research-UFZ, Department of Environmental Microbiology, Permoserstraße 15, 04318 Leipzig, Germany
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10
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Pawlowska TE, Gaspar ML, Lastovetsky OA, Mondo SJ, Real-Ramirez I, Shakya E, Bonfante P. Biology of Fungi and Their Bacterial Endosymbionts. ANNUAL REVIEW OF PHYTOPATHOLOGY 2018; 56:289-309. [PMID: 30149793 DOI: 10.1146/annurev-phyto-080417-045914] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Heritable symbioses, in which endosymbiotic bacteria (EB) are transmitted vertically between host generations, are an important source of evolutionary novelties. A primary example of such symbioses is the eukaryotic cell with its EB-derived organelles. Recent discoveries suggest that endosymbiosis-related innovations can be also found in associations formed by early divergent fungi in the phylum Mucoromycota with heritable EB from two classes, Betaproteobacteria and Mollicutes. These symbioses exemplify novel types of host-symbiont interactions. Studies of these partnerships fuel theoretical models describing mechanisms that stabilize heritable symbioses, control the rate of molecular evolution, and enable the establishment of mutualisms. Lastly, by altering host phenotypes and metabolism, these associations represent an important instrument for probing the basic biology of the Mucoromycota hosts, which remain one of the least explored filamentous fungi.
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Affiliation(s)
- Teresa E Pawlowska
- School of Integrative Plant Science, Plant Pathology and Plant Microbe-Biology, Cornell University, Ithaca, New York 14853, USA;
| | - Maria L Gaspar
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853, USA
| | - Olga A Lastovetsky
- School of Biology and Environmental Science and Earth Institute, University College Dublin, Dublin, Ireland
| | - Stephen J Mondo
- US Department of Energy Joint Genome Institute, Walnut Creek, California 94598, USA
| | | | - Evaniya Shakya
- School of Integrative Plant Science, Plant Pathology and Plant Microbe-Biology, Cornell University, Ithaca, New York 14853, USA;
| | - Paola Bonfante
- Department of Life Sciences & Systems Biology, University of Torino, 10125 Torino, Italy
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11
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Distribution and population structure of endobacteria in arbuscular mycorrhizal fungi at North Atlantic dunes. ISME JOURNAL 2018; 12:3001-3013. [PMID: 30097664 DOI: 10.1038/s41396-018-0246-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 06/29/2018] [Accepted: 07/06/2018] [Indexed: 02/08/2023]
Abstract
Arbuscular mycorrhizal fungi (AMF, Glomeromycotina), in addition to forming symbioses with the majority of land plants, harbor vertically transmitted endosymbiotic bacteria 'Candidatus Glomeribacter gigasporarum' (CaGg) and 'Candidatus Moeniiplasma glomeromycotorum' (CaMg). CaGg is a nonessential mutualist of AMF, whereas the lifestyle of CaMg is unknown. To start unraveling the interactions between AMF and their endosymbionts in nature, we examined diversity and distribution of AMF-associated endobacteria in North Atlantic dunes at Cape Cod. Of nearly 500 foredune AMF isolates successfully genotyped during a systematic study, 94% were classified as Gigasporaceae. Two percent of all AMF spores harbored CaGg, and 88% contained CaMg. CaGg was found only in the Gigasporaceae, whereas CaMg was present in Gigasporaceae, Acaulosporaceae, and Diversisporaceae. Incidence of CaGg across AMF was not affected by any of the environmental parameters measured, whereas distribution of CaMg in one of the fungal hosts was impacted by plant density. CaMg populations associated with AMF individuals displayed high levels of genetic diversity but no evidence of gene flow, suggesting that host physical proximity is not sufficient to facilitate horizontal transmission of CaMg. Finally, in addition to a novel lineage of CaGg, we discovered that AMF likely harbor Burkholderia-related bacteria with close phylogenetic affinity to free-living Burkholderia and endobacteria of other Mucoromycota fungi.
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Abstract
The ecological modes of fungi are shaped not only by their intrinsic features and the environment in which they occur, but also by their interactions with diverse microbes. Here we explore the ecological and genomic features of diverse bacterial endosymbionts-endohyphal bacteria-that together are emerging as major determinants of fungal phenotypes and plant-fungi interactions. We first provide a historical perspective on the study of endohyphal bacteria. We then propose a functional classification of three main groups, providing an overview of their genomic, phylogenetic, and ecological traits. Last, we explore frontiers in the study of endohyphal bacteria, with special attention to those facultative and horizontally transmitted bacteria that associate with some of the most diverse lineages of fungi. Overall, our aim is to synthesize the rich literature from nearly 50 years of studies on endohyphal bacteria as a means to highlight potential applications and new research directions.
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13
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Sharmin D, Guo Y, Nishizawa T, Ohshima S, Sato Y, Takashima Y, Narisawa K, Ohta H. Comparative Genomic Insights into Endofungal Lifestyles of Two Bacterial Endosymbionts, Mycoavidus cysteinexigens and Burkholderia rhizoxinica. Microbes Environ 2018. [PMID: 29540638 PMCID: PMC5877345 DOI: 10.1264/jsme2.me17138] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Endohyphal bacteria (EHB), dwelling within fungal hyphae, markedly affect the growth and metabolic potential of their hosts. To date, two EHB belonging to the family Burkholderiaceae have been isolated and characterized as new taxa, Burkholderia rhizoxinica (HKI 454T) and Mycoavidus cysteinexigens (B1-EBT), in Japan. Metagenome sequencing was recently reported for Mortierella elongata AG77 together with its endosymbiont M. cysteinexigens (Mc-AG77) from a soil/litter sample in the USA. In the present study, we elucidated the complete genome sequence of B1-EBT and compared it with those of Mc-AG77 and HKI 454T. The genomes of B1-EBT and Mc-AG77 contained a higher level of prophage sequences and were markedly smaller than that of HKI 454T. Although the B1-EBT and Mc-AG77 genomes lacked the chitinolytic enzyme genes responsible for invasion into fungal cells, they contained several predicted toxin-antitoxin systems including an insecticidal toxin complex and PIN domain imposing an addiction-like mechanism essential for endohyphal growth control during host colonization. Despite the different host fungi, the alignment of amino acid sequences showed that the HKI 454T genome consisted of 1,265 (32.6%) and 1,221 (31.5%) orthologous coding sequences (CDSs) with those of B1-EBT and Mc-AG77, respectively. This comparative study of three phylogenetically associated endosymbionts has provided insights into their origin and evolution, and suggests the later bacterial invasion and adaptation of B1-EBT to its host metabolism.
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Affiliation(s)
- Dilruba Sharmin
- Ibaraki University College of Agriculture, Department of Bioresource Science
| | - Yong Guo
- Ibaraki University College of Agriculture, Department of Bioresource Science
| | - Tomoyasu Nishizawa
- Ibaraki University College of Agriculture, Department of Bioresource Science.,United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology
| | - Shoko Ohshima
- Ibaraki University College of Agriculture, Department of Bioresource Science
| | - Yoshinori Sato
- Center for Conservation and Restoration Techniques, Tokyo National Research Institute for Cultural Properties
| | - Yusuke Takashima
- United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology
| | - Kazuhiko Narisawa
- Ibaraki University College of Agriculture, Department of Bioresource Science.,United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology
| | - Hiroyuki Ohta
- Ibaraki University College of Agriculture, Department of Bioresource Science.,United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology
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14
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Desirò A, Hao Z, Liber JA, Benucci GMN, Lowry D, Roberson R, Bonito G. Mycoplasma-related endobacteria within Mortierellomycotina fungi: diversity, distribution and functional insights into their lifestyle. ISME JOURNAL 2018; 12:1743-1757. [PMID: 29476142 DOI: 10.1038/s41396-018-0053-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Revised: 12/22/2017] [Accepted: 01/10/2018] [Indexed: 11/09/2022]
Abstract
Bacterial interactions with animals and plants have been examined for over a century; by contrast, the study of bacterial-fungal interactions has received less attention. Bacteria interact with fungi in diverse ways, and endobacteria that reside inside fungal cells represent the most intimate interaction. The most significant bacterial endosymbionts that have been studied are associated with Mucoromycota and include two main groups: Burkholderia-related and Mycoplasma-related endobacteria (MRE). Examples of Burkholderia-related endobacteria have been reported in the three Mucoromycota subphyla. By contrast, MRE have only been identified in Glomeromycotina and Mucoromycotina. This study aims to understand whether MRE dwell in Mortierellomycotina and, if so, to determine their impact on the fungal host. We carried out a large-scale screening of 394 Mortierellomycotina strains and employed a combination of microscopy, molecular phylogeny, next-generation sequencing and qPCR. We detected MRE in 12 strains. These endosymbionts represent novel bacterial phylotypes and show evidence of recombination. Their presence in Mortierellomycotina demonstrates that MRE occur within fungi across Mucoromycota and they may have lived in their common ancestor. We cured the fungus of its endosymbionts with antibiotics and observed improved biomass production in isogenic lines lacking MRE, demonstrating that these endobacteria impose some fitness costs to their fungal host. Here we provided the first functional insights into the lifestyle of MRE. Our findings indicate that MRE may be antagonistic to their fungal hosts, and adapted to a non-lethal parasitic lifestyle in the mycelium of Mucoromycota. However, context-dependent adaptive benefits to their host at minimal cost cannot not be excluded. Finally, we conclude that Mortierellomycotina represent attractive model organisms for exploring interactions between MRE and fungi.
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Affiliation(s)
- Alessandro Desirò
- Department of Plant Soil and Microbial Sciences, Michigan State University, East Lansing, MI, USA.
| | - Zhen Hao
- Department of Plant Soil and Microbial Sciences, Michigan State University, East Lansing, MI, USA
| | - Julian A Liber
- Department of Plant Soil and Microbial Sciences, Michigan State University, East Lansing, MI, USA
| | | | - David Lowry
- School of Life Sciences, Arizona State University, Tempe, AZ, USA
| | - Robert Roberson
- School of Life Sciences, Arizona State University, Tempe, AZ, USA
| | - Gregory Bonito
- Department of Plant Soil and Microbial Sciences, Michigan State University, East Lansing, MI, USA
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15
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Poosakkannu A, Nissinen R, Kytöviita MM. Native arbuscular mycorrhizal symbiosis alters foliar bacterial community composition. MYCORRHIZA 2017; 27:801-810. [PMID: 28812152 DOI: 10.1007/s00572-017-0796-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 08/04/2017] [Indexed: 06/07/2023]
Abstract
The effects of arbuscular mycorrhizal (AM) fungi on plant-associated microbes are poorly known. We tested the hypothesis that colonization by an AM fungus affects microbial species richness and microbial community composition of host plant tissues. We grew the grass, Deschampsia flexuosa in a greenhouse with or without the native AM fungus, Claroideoglomus etunicatum. We divided clonally produced tillers into two parts: one inoculated with AM fungus spores and one without AM fungus inoculation (non-mycorrhizal, NM). We characterized bacterial (16S rRNA gene) and fungal communities (internal transcribed spacer region) in surface-sterilized leaf and root plant compartments. AM fungus inoculation did not affect microbial species richness or diversity indices in leaves or roots, but the AM fungus inoculation significantly affected bacterial community composition in leaves. A total of three OTUs in leaves belonging to the phylum Firmicutes positively responded to the presence of the AM fungus in roots. Another six OTUs belonging to the Proteobacteria (Alpha, Beta, and Gamma) and Bacteroidetes were significantly more abundant in NM plants when compared to AM fungus-inoculated plants. Further, there was a significant correlation between plant dry weight and leaf microbial community compositional shift. Also, there was a significant correlation between leaf bacterial community compositional shift and foliar nitrogen content changes due to AM fungus inoculation. The results suggest that AM fungus colonization in roots has a profound effect on plant physiology that is reflected in leaf bacterial community composition.
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Affiliation(s)
- Anbu Poosakkannu
- Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, FI-40014, Jyvaskyla, Finland.
| | - Riitta Nissinen
- Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, FI-40014, Jyvaskyla, Finland
| | - Minna-Maarit Kytöviita
- Department of Biological and Environmental Science, University of Jyvaskyla, PO Box 35, FI-40014, Jyvaskyla, Finland
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16
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Torres-Cruz TJ, Billingsley Tobias TL, Almatruk M, Hesse CN, Kuske CR, Desirò A, Benucci GMN, Bonito G, Stajich JE, Dunlap C, Arnold AE, Porras-Alfaro A. Bifiguratus adelaidae, gen. et sp. nov., a new member of Mucoromycotina in endophytic and soil-dwelling habitats. Mycologia 2017; 109:363-378. [PMID: 28876195 DOI: 10.1080/00275514.2017.1364958] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Illumina amplicon sequencing of soil in a temperate pine forest in the southeastern United States detected an abundant, nitrogen (N)-responsive fungal genotype of unknown phylogenetic affiliation. Two isolates with ribosomal sequences consistent with that genotype were subsequently obtained. Examination of records in GenBank revealed that a genetically similar fungus had been isolated previously as an endophyte of moss in a pine forest in the southwestern United States. The three isolates were characterized using morphological, genomic, and multilocus molecular data (18S, internal transcribed spacer [ITS], and 28S rRNA sequences). Phylogenetic and maximum likelihood phylogenomic reconstructions revealed that the taxon represents a novel lineage in Mucoromycotina, only preceded by Calcarisporiella, the earliest diverging lineage in the subphylum. Sequences for the novel taxon are frequently detected in environmental sequencing studies, and it is currently part of UNITE's dynamic list of most wanted fungi. The fungus is dimorphic, grows best at room temperature, and is associated with a wide variety of bacteria. Here, a new monotypic genus, Bifiguratus, is proposed, typified by Bifiguratus adelaidae.
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Affiliation(s)
- Terry J Torres-Cruz
- a Department of Biological Sciences , Western Illinois University , Macomb , Illinois 61455
| | | | - Maryam Almatruk
- a Department of Biological Sciences , Western Illinois University , Macomb , Illinois 61455
| | - Cedar N Hesse
- b Bioscience Division, Los Alamos National Laboratory , Los Alamos , New Mexico 87545
| | - Cheryl R Kuske
- b Bioscience Division, Los Alamos National Laboratory , Los Alamos , New Mexico 87545
| | - Alessandro Desirò
- c Department of Plant, Soil and Microbial Sciences , Michigan State University , East Lansing , Michigan 48824
| | - Gian Maria Niccolò Benucci
- c Department of Plant, Soil and Microbial Sciences , Michigan State University , East Lansing , Michigan 48824
| | - Gregory Bonito
- c Department of Plant, Soil and Microbial Sciences , Michigan State University , East Lansing , Michigan 48824
| | - Jason E Stajich
- d Department of Plant Pathology and Microbiology , University of California , Riverside , California 92521
| | - Christopher Dunlap
- e National Center for Agricultural Utilization Research, Agricultural Research Service , U.S. Department of Agriculture , Peoria , Illinois 61604
| | - A Elizabeth Arnold
- f School of Plant Sciences and Department of Ecology and Evolutionary Biology, The University of Arizona , Tucson , Arizona 85721
| | - Andrea Porras-Alfaro
- a Department of Biological Sciences , Western Illinois University , Macomb , Illinois 61455
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17
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Naito M, Desirò A, González JB, Tao G, Morton JB, Bonfante P, Pawlowska TE. 'Candidatus Moeniiplasma glomeromycotorum', an endobacterium of arbuscular mycorrhizal fungi. Int J Syst Evol Microbiol 2017; 67:1177-1184. [PMID: 28073398 DOI: 10.1099/ijsem.0.001785] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Arbuscular mycorrhizal fungi (AMF, subphylum Glomeromycotina) are symbionts of most terrestrial plants. They commonly harbour endobacteria of a largely unknown biology, referred to as MRE (Mollicutes/mycoplasma-related endobacteria). Here, we propose to accommodate MRE in the novel genus 'Candidatus Moeniiplasma.' Phylogeny reconstructions based on the 16S rRNA gene sequences cluster 'Ca.Moeniiplasma' with representatives of the class Mollicutes, whereas phylogenies derived from amino acid sequences of 19 genes indicate that it is a discrete lineage sharing ancestry with the members of the family Mycoplasmataceae. Cells of 'Ca.Moeniiplasma' reside directly in the host cytoplasm and have not yet been cultivated. They are coccoid, ~500 nm in diameter, with an electron-dense layer outside the plasma membrane. However, the draft genomes of 'Ca.Moeniiplasma' suggest that this structure is not a Gram-positive cell wall. The evolution of 'Ca.Moeniiplasma' appears to be driven by an ultrarapid rate of mutation accumulation related to the loss of DNA repair mechanisms. Moreover, molecular evolution patterns suggest that, in addition to vertical transmission, 'Ca.Moeniiplasma' is able to transmit horizontally among distinct Glomeromycotina host lineages and exchange genes. On the basis of these unique lifestyle features, the new species 'Candidatus Moeniiplasma glomeromycotorum' is proposed.
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Affiliation(s)
- Mizue Naito
- Graduate Field of Microbiology, Cornell University, Ithaca, NY, USA
| | - Alessandro Desirò
- Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy.,Present address: Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824, USA
| | - Jonathan B González
- School of Integrative Plant Science, Plant Pathology & Plant-Microbe Biology, Cornell University, Ithaca, NY, USA
| | - Gang Tao
- School of Integrative Plant Science, Plant Pathology & Plant-Microbe Biology, Cornell University, Ithaca, NY, USA.,Present address: Guizhou Academy of Agricultural Sciences, Guizhou Institute of Plant Protection, Guiyang 550006, PR China
| | - Joseph B Morton
- Division of Plant & Soil Sciences, West Virginia University, Morgantown, WV, USA
| | - Paola Bonfante
- Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy
| | - Teresa E Pawlowska
- School of Integrative Plant Science, Plant Pathology & Plant-Microbe Biology, Cornell University, Ithaca, NY, USA
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18
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Who lives in a fungus? The diversity, origins and functions of fungal endobacteria living in Mucoromycota. ISME JOURNAL 2017; 11:1727-1735. [PMID: 28387771 DOI: 10.1038/ismej.2017.21] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 01/13/2017] [Accepted: 01/19/2017] [Indexed: 01/07/2023]
Abstract
Bacterial interactions with plants and animals have been examined for many years; differently, only with the new millennium the study of bacterial-fungal interactions blossomed, becoming a new field of microbiology with relevance to microbial ecology, human health and biotechnology. Bacteria and fungi interact at different levels and bacterial endosymbionts, which dwell inside fungal cells, provide the most intimate example. Bacterial endosymbionts mostly occur in fungi of the phylum Mucoromycota and include Betaproteobacteria (Burkhoderia-related) and Mollicutes (Mycoplasma-related). Based on phylogenomics and estimations of divergence time, we hypothesized two different scenarios for the origin of these interactions (early vs late bacterial invasion). Sequencing of the genomes of fungal endobacteria revealed a significant reduction in genome size, particularly in endosymbionts of Glomeromycotina, as expected by their uncultivability and host dependency. Similar to endobacteria of insects, the endobacteria of fungi show a range of behaviours from mutualism to antagonism. Emerging results suggest that some benefits given by the endobacteria to their plant-associated fungal host may propagate to the interacting plant, giving rise to a three-level inter-domain interaction.
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19
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Partida‐Martínez LP. The fungal holobiont: Evidence from early diverging fungi. Environ Microbiol 2017; 19:2919-2923. [DOI: 10.1111/1462-2920.13731] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 03/11/2017] [Indexed: 01/02/2023]
Affiliation(s)
- Laila P. Partida‐Martínez
- Departamento de Ingeniería GenéticaCentro de Investigación y de Estudios Avanzados del IPNIrapuato 36821, Gto México
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20
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Defying Muller's Ratchet: Ancient Heritable Endobacteria Escape Extinction through Retention of Recombination and Genome Plasticity. mBio 2016; 7:mBio.02057-15. [PMID: 27329757 PMCID: PMC4916391 DOI: 10.1128/mbio.02057-15] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Heritable endobacteria, which are transmitted from one host generation to the next, are subjected to evolutionary forces that are different from those experienced by free-living bacteria. In particular, they suffer consequences of Muller’s ratchet, a mechanism that leads to extinction of small asexual populations due to fixation of slightly deleterious mutations combined with the random loss of the most-fit genotypes, which cannot be recreated without recombination. Mycoplasma-related endobacteria (MRE) are heritable symbionts of fungi from two ancient lineages, Glomeromycota (arbuscular mycorrhizal fungi) and Mucoromycotina. Previous studies revealed that MRE maintain unusually diverse populations inside their hosts and may have been associated with fungi already in the early Paleozoic. Here we show that MRE are vulnerable to genomic degeneration and propose that they defy Muller’s ratchet thanks to retention of recombination and genome plasticity. We suggest that other endobacteria may be capable of raising similar defenses against Muller’s ratchet.
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21
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Naito M, Pawlowska TE. The role of mobile genetic elements in evolutionary longevity of heritable endobacteria. Mob Genet Elements 2015; 6:e1136375. [PMID: 27066304 DOI: 10.1080/2159256x.2015.1136375] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 12/15/2015] [Accepted: 12/18/2015] [Indexed: 12/15/2022] Open
Abstract
The movement of mobile genetic elements (MGEs), including bacteriophages, insertion sequence (IS) elements, and integrative and conjugative elements (ICEs) can have profound effects on bacterial evolution by introducing novel genes, or disrupting the existing ones. Obligate endobacteria are a distinctive group of bacteria that reside within the intracellular compartments of their eukaryotic hosts. Many obligate endobacteria are reproductively dependent on their hosts. Vertical transmission, in addition to degenerative genome contraction and loss of MGEs, makes heritable endobacteria vulnerable to Muller's ratchet, a process that jeopardizes evolutionary longevity of small populations. Mycoplasma-related endobacteria (MRE) are ancient heritable endosymbionts of arbuscular mycorrhizal fungi. Their genomes harbour numerous MGEs. To explore the significance of MGEs in the evolution of MRE and other obligate endobacteria, we analyze the impact of transmission mode, recombination, and evolutionary age on the maintenance of MGEs. Furthermore, we discuss the ability of MGEs to act as sites of gene conversion and recombination in endobacterial genomes. We propose that MGEs are important instruments of genome shuffling, contributing to population heterogeneity and evolutionary longevity in heritable obligate endobacteria.
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Affiliation(s)
- Mizue Naito
- Graduate Field of Microbiology, Cornell University, Ithaca, NY, USA; Present address: Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Teresa E Pawlowska
- School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology, Cornell University , Ithaca, NY, USA
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