1
|
Qu Y, Yin Z, Kustatscher E, Nützel A, Peckmann J, Vajda V, Ivarsson M. Traces of Ancient Life in Oceanic Basalt Preserved as Iron-Mineralized Ultrastructures: Implications for Detecting Extraterrestrial Biosignatures. ASTROBIOLOGY 2023; 23:769-785. [PMID: 37222732 DOI: 10.1089/ast.2022.0075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Benefiting from their adaptability to extreme environments, subsurface microorganisms have been discovered in sedimentary and igneous rock environments on Earth and have been advocated as candidates in the search for extraterrestrial life. In this article, we study iron-mineralized microstructures in calcite-filled veins within basaltic pillows of the late Ladinian Fernazza group (Middle Triassic, 239 Ma) in Italy. These microstructures represent diverse morphologies, including filaments, globules, nodules, and micro-digitate stromatolites, which are similar to extant iron-oxidizing bacterial communities. In situ analyses including Raman spectroscopy have been used to investigate the morphological, elemental, mineralogical, and bond-vibrational modes of the microstructures. According to the Raman spectral parameters, iron minerals preserve heterogeneous ultrastructures and crystallinities, coinciding with the morphologies and precursor microbial activities. The degree of crystallinity usually represents a microscale gradient decreasing toward previously existing microbial cells, revealing a decline of mineralization due to microbial activities. This study provides an analog of possible rock-dwelling subsurface life on Mars or icy moons and advocates Raman spectroscopy as an efficient tool for in situ analyses. We put forward the concept that ultrastructural characteristics of minerals described by Raman spectral parameters corresponding to microscale morphologies could be employed as carbon-lean biosignatures in future space missions.
Collapse
Affiliation(s)
- Yuangao Qu
- Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya, China
| | - Zongjun Yin
- State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China
| | - Evelyn Kustatscher
- Museum of Nature South Tyrol, Bozen/Bolzano, Italy
- Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Ludwig-Maximilians-Universität, München, Germany
- SNSB-Bayerische Staatssammlung für Paläontologie und Geobiologie, München, Germany
| | - Alexander Nützel
- Department für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Ludwig-Maximilians-Universität, München, Germany
- SNSB-Bayerische Staatssammlung für Paläontologie und Geobiologie, München, Germany
- GeoBio-Center, Ludwig-Maximilians-Universität München, München, Germany
| | - Jörn Peckmann
- Institute für Geologie, Centrum für Erdsystemforschung und Nachhaltigkeit, Universität Hamburg, Hamburg, Germany
| | - Vivi Vajda
- Department of Paleobiology, Swedish Museum of Natural History, Stockholm, Sweden
| | - Magnus Ivarsson
- Department of Paleobiology, Swedish Museum of Natural History, Stockholm, Sweden
| |
Collapse
|
2
|
Quemener M, Mara P, Schubotz F, Beaudoin D, Li W, Pachiadaki M, Sehein TR, Sylvan JB, Li J, Barbier G, Edgcomb V, Burgaud G. Meta-omics highlights the diversity, activity and adaptations of fungi in deep oceanic crust. Environ Microbiol 2020; 22:3950-3967. [PMID: 32743889 DOI: 10.1111/1462-2920.15181] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 07/23/2020] [Accepted: 07/31/2020] [Indexed: 02/03/2023]
Abstract
The lithified oceanic crust, lower crust gabbros in particular, has remained largely unexplored by microbiologists. Recently, evidence for heterogeneously distributed viable and transcriptionally active autotrophic and heterotrophic microbial populations within low-biomass communities was found down to 750 m below the seafloor at the Atlantis Bank Gabbro Massif, Indian Ocean. Here, we report on the diversity, activity and adaptations of fungal communities in the deep oceanic crust from ~10 to 780 mbsf by combining metabarcoding analyses with mid/high-throughput culturing approaches. Metabarcoding along with culturing indicate a low diversity of viable fungi, mostly affiliated to ubiquitous (terrestrial and aquatic environments) taxa. Ecophysiological analyses coupled with metatranscriptomics point to viable and transcriptionally active fungal populations engaged in cell division, translation, protein modifications and other vital cellular processes. Transcript data suggest possible adaptations for surviving in the nutrient-poor, lithified deep biosphere that include the recycling of organic matter. These active communities appear strongly influenced by the presence of cracks and veins in the rocks where fluids and resulting rock alteration create micro-niches.
Collapse
Affiliation(s)
- Maxence Quemener
- Université de Brest, EA 3882 Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, Technopôle Brest-Iroise, Plouzané, France
| | - Paraskevi Mara
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA.,Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA
| | - Florence Schubotz
- MARUM-Center for Marine Environmental Sciences, University Bremen, Leobener Strasse 8, Bremen, 28359, Germany
| | - David Beaudoin
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA.,Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA
| | - Wei Li
- College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Maria Pachiadaki
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA.,Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA
| | - Taylor R Sehein
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA.,Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA
| | - Jason B Sylvan
- Department of Oceanography, Texas A&M University, College Station, TX, 77845, USA
| | - Jiangtao Li
- State Key Laboratory of Marine Geology, Tongji University, Shanghai, 200092, China
| | - Georges Barbier
- Université de Brest, EA 3882 Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, Technopôle Brest-Iroise, Plouzané, France
| | - Virginia Edgcomb
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA.,Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA
| | - Gaëtan Burgaud
- Université de Brest, EA 3882 Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, Technopôle Brest-Iroise, Plouzané, France
| |
Collapse
|
3
|
Luo Y, Wei X, Yang S, Gao YH, Luo ZH. Fungal diversity in deep-sea sediments from the Magellan seamounts as revealed by a metabarcoding approach targeting the ITS2 regions. Mycology 2020; 11:214-229. [PMID: 33062383 PMCID: PMC7534268 DOI: 10.1080/21501203.2020.1799878] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 07/03/2020] [Indexed: 12/11/2022] Open
Abstract
Recent reports have revealed diverse and abundant fungal communities in the deep-sea biosphere, while their composition, distribution, and variations in seamount zones are poorly understood. Using a metabarcoding approach targeting the ITS2 regions, we present the structure of the fungal community in 18 sediment samples from the Magellan seamount area of the northwest Pacific. A total of 1,979 fungal OTUs was obtained, which were taxonomically assigned to seven phyla, 17 classes, 43 orders, 7 families, and 98 genera. The majority of these OTUs were affiliated to Basidiomycota (873 OTUs, 44.11% of total OTUs) and Ascomycota (486 OTUs, 24.56% of total OTUs), followed by other five minor phyla (Mortierellomycota, Chytridiomycota, Mucoromycota, Glomeromycota, and Monoblepharidomycota). Sordriomycetes is the most abundant class, followed by Eurotiomycetes, and Dothideomycetes. Five genera were common in most of the samples, including worldwide reported genera Aspergillus, Cladosporium, Fusarium, Chaetomium, and Penicillium. The environmental data we collected (sampling depth, sampling location latitude and longitude, organic carbon content, and organic nitrogen content in the sediment) had no significant influence on the composition and distribution of fungal communities. Our findings provide valuable information for understanding the distribution and potential ecological functions of fungi in the deep-sea sediments of the Magellan seamounts.
Collapse
Affiliation(s)
- Ye Luo
- Key Laboratory of Marine Biogenetic Resources, Ministry of Natural Resources, Third Institute of Oceanography, Xiamen, PR China
| | - Xu Wei
- Key Laboratory of Marine Biogenetic Resources, Ministry of Natural Resources, Third Institute of Oceanography, Xiamen, PR China
| | - Shuai Yang
- Key Laboratory of Marine Biogenetic Resources, Ministry of Natural Resources, Third Institute of Oceanography, Xiamen, PR China
| | - Yuan-Hao Gao
- Key Laboratory of Marine Biogenetic Resources, Ministry of Natural Resources, Third Institute of Oceanography, Xiamen, PR China
| | - Zhu-Hua Luo
- Key Laboratory of Marine Biogenetic Resources, Ministry of Natural Resources, Third Institute of Oceanography, Xiamen, PR China
- School of Marine Sciences, Nanjing University of Information Science & Technology, Nanjing, PR China
- Co-Innovation Center of Jiangsu Marine Bioindustry Technology, Jiangsu Ocean University, Lianyungang, PR China
| |
Collapse
|
4
|
Exceptional Preservation of Fungi as H2-Bearing Fluid Inclusions in an Early Quaternary Paleo-Hydrothermal System at Cape Vani, Milos, Greece. MINERALS 2019. [DOI: 10.3390/min9120749] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The production of H2 in hydrothermal systems and subsurface settings is almost exclusively assumed a result of abiotic processes, particularly serpentinization of ultramafic rocks. The origin of H2 in environments not hosted in ultramafic rocks is, as a rule, unjustifiably linked to abiotic processes. Additionally, multiple microbiological processes among both prokaryotes and eukaryotes are known to involve H2-production, of which anaerobic fungi have been put forward as a potential source of H2 in subsurface environments, which is still unconfirmed. Here, we report fungal remains exceptionally preserved as fluid inclusions in hydrothermal quartz from feeder quartz-barite veins from the Cape Vani Fe-Ba-Mn ore on the Greek island of Milos. The inclusions possess filamentous or near-spheroidal morphologies interpreted as remains of fungal hyphae and spores, respectively. They were characterized by microthermometry, Raman spectroscopy, and staining of exposed inclusions with WGA-FITC under fluorescence microscopy. The spheroidal aqueous inclusions interpreted as fungal spores are unique by their coating of Mn-oxide birnessite, and gas phase H2. A biological origin of the H2 resulting from anaerobic fungal respiration is suggested. We propose that biologically produced H2 by micro-eukaryotes is an unrecognized source of H2 in hydrothermal systems that may support communities of H2-dependent prokaryotes.
Collapse
|
5
|
Fossilized Endolithic Microorganisms in Pillow Lavas from the Troodos Ophiolite, Cyprus. GEOSCIENCES 2019. [DOI: 10.3390/geosciences9110456] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The last decade has revealed the igneous oceanic crust to host a more abundant and diverse biota than previously expected. These underexplored rock-hosted deep ecosystems dominated Earth’s biosphere prior to plants colonized land in the Ordovician, thus the fossil record of deep endoliths holds invaluable clues to early life and the work to decrypt them needs to be intensified. Here, we present fossilized microorganisms found in open and sealed pore spaces in pillow lavas from the Troodos Ophiolite (91 Ma) on Cyprus. A fungal interpretation is inferred upon the microorganisms based on characteristic morphological features. Geochemical conditions are reconstructed using data from mineralogy, fluid inclusions and the fossils themselves. Mineralogy indicates at least three hydrothermal events and a continuous increase of temperature and pH. Precipitation of 1) celadonite and saponite together with the microbial introduction was followed by 2) Na and Ca zeolites resulting in clay adherence on the microorganisms as protection, and finally 3) Ca carbonates resulted in final fossilization and preservation of the organisms in-situ. Deciphering the fossil record of the deep subseafloor biosphere is a challenging task, but when successful, can unlock doors to life’s cryptic past.
Collapse
|
6
|
Onstott T, Ehlmann B, Sapers H, Coleman M, Ivarsson M, Marlow J, Neubeck A, Niles P. Paleo-Rock-Hosted Life on Earth and the Search on Mars: A Review and Strategy for Exploration. ASTROBIOLOGY 2019; 19:1230-1262. [PMID: 31237436 PMCID: PMC6786346 DOI: 10.1089/ast.2018.1960] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Accepted: 04/25/2019] [Indexed: 05/19/2023]
Abstract
Here we review published studies on the abundance and diversity of terrestrial rock-hosted life, the environments it inhabits, the evolution of its metabolisms, and its fossil biomarkers to provide guidance in the search for life on Mars. Key findings are (1) much terrestrial deep subsurface metabolic activity relies on abiotic energy-yielding fluxes and in situ abiotic and biotic recycling of metabolic waste products rather than on buried organic products of photosynthesis; (2) subsurface microbial cell concentrations are highest at interfaces with pronounced chemical redox gradients or permeability variations and do not correlate with bulk host rock organic carbon; (3) metabolic pathways for chemolithoautotrophic microorganisms evolved earlier in Earth's history than those of surface-dwelling phototrophic microorganisms; (4) the emergence of the former occurred at a time when Mars was habitable, whereas the emergence of the latter occurred at a time when the martian surface was not continually habitable; (5) the terrestrial rock record has biomarkers of subsurface life at least back hundreds of millions of years and likely to 3.45 Ga with several examples of excellent preservation in rock types that are quite different from those preserving the photosphere-supported biosphere. These findings suggest that rock-hosted life would have been more likely to emerge and be preserved in a martian context. Consequently, we outline a Mars exploration strategy that targets subsurface life and scales spatially, focusing initially on identifying rocks with evidence for groundwater flow and low-temperature mineralization, then identifying redox and permeability interfaces preserved within rock outcrops, and finally focusing on finding minerals associated with redox reactions and associated traces of carbon and diagnostic chemical and isotopic biosignatures. Using this strategy on Earth yields ancient rock-hosted life, preserved in the fossil record and confirmable via a suite of morphologic, organic, mineralogical, and isotopic fingerprints at micrometer scale. We expect an emphasis on rock-hosted life and this scale-dependent strategy to be crucial in the search for life on Mars.
Collapse
Affiliation(s)
- T.C. Onstott
- Department of Geosciences, Princeton University, Princeton, New Jersey, USA
- Address correspondence to: T.C. Onstott, Department of Geosciences, Princeton University,, Princeton, NJ 008544
| | - B.L. Ehlmann
- Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- B.L. Ehlmann, Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
| | - H. Sapers
- Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, California, USA
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- Department of Earth Sciences, University of Southern California, Los Angeles, California, USA
| | - M. Coleman
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
- NASA Astrobiology Institute, Pasadena, California, USA
| | - M. Ivarsson
- Department of Biology, University of Southern Denmark, Odense, Denmark
| | - J.J. Marlow
- Department of Organismic & Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - A. Neubeck
- Department of Earth Sciences, Uppsala University, Uppsala, Sweden
| | - P. Niles
- Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, Texas, USA
| |
Collapse
|
7
|
Amend A, Burgaud G, Cunliffe M, Edgcomb VP, Ettinger CL, Gutiérrez MH, Heitman J, Hom EFY, Ianiri G, Jones AC, Kagami M, Picard KT, Quandt CA, Raghukumar S, Riquelme M, Stajich J, Vargas-Muñiz J, Walker AK, Yarden O, Gladfelter AS. Fungi in the Marine Environment: Open Questions and Unsolved Problems. mBio 2019; 10:e01189-18. [PMID: 30837337 PMCID: PMC6401481 DOI: 10.1128/mbio.01189-18] [Citation(s) in RCA: 134] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Terrestrial fungi play critical roles in nutrient cycling and food webs and can shape macroorganism communities as parasites and mutualists. Although estimates for the number of fungal species on the planet range from 1.5 to over 5 million, likely fewer than 10% of fungi have been identified so far. To date, a relatively small percentage of described species are associated with marine environments, with ∼1,100 species retrieved exclusively from the marine environment. Nevertheless, fungi have been found in nearly every marine habitat explored, from the surface of the ocean to kilometers below ocean sediments. Fungi are hypothesized to contribute to phytoplankton population cycles and the biological carbon pump and are active in the chemistry of marine sediments. Many fungi have been identified as commensals or pathogens of marine animals (e.g., corals and sponges), plants, and algae. Despite their varied roles, remarkably little is known about the diversity of this major branch of eukaryotic life in marine ecosystems or their ecological functions. This perspective emerges from a Marine Fungi Workshop held in May 2018 at the Marine Biological Laboratory in Woods Hole, MA. We present the state of knowledge as well as the multitude of open questions regarding the diversity and function of fungi in the marine biosphere and geochemical cycles.
Collapse
Affiliation(s)
- Anthony Amend
- Department of Botany, University of Hawai'i at Manoa, Honolulu, Hawaii, USA
| | - Gaetan Burgaud
- Université de Brest, EA 3882, Laboratoire Universitaire de Biodiversité et Ecologie Microbienne, ESIAB, Technopôle Brest-Iroise, Plouzané, France
| | - Michael Cunliffe
- Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth, United Kingdom
| | - Virginia P Edgcomb
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
| | | | - M H Gutiérrez
- Departamento de Oceanografía, Centro de Investigación Oceanográfica COPAS Sur-Austral, Universidad de Concepción, Concepción, Chile
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Erik F Y Hom
- Department of Biology, University of Mississippi, Oxford, Mississippi, USA
| | - Giuseppe Ianiri
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA
| | - Adam C Jones
- Gordon and Betty Moore Foundation, Palo Alto, California, USA
| | - Maiko Kagami
- Graduate School of Environment and Information Sciences, Yokohama National University, Yokohama, Japan
| | - Kathryn T Picard
- Department of Botany, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | - C Alisha Quandt
- Ecology and Evolutionary Biology Department, University of Colorado, Boulder, Colorado, USA
| | | | - Mertixell Riquelme
- Department of Microbiology, Centro de Investigación Científica y Educación Superior de Ensenada (CICESE), Ensenada, Baja California, Mexico
| | - Jason Stajich
- Department of Microbiology & Plant Pathology and Institute for Integrative Genome Biology, University of California-Riverside, Riverside, California, USA
| | - José Vargas-Muñiz
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Allison K Walker
- Department of Biology, Acadia University, Wolfville, Nova Scotia, Canada
| | - Oded Yarden
- Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Amy S Gladfelter
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Marine Biological Laboratory, Woods Hole, Massachusetts, USA
| |
Collapse
|
8
|
|
9
|
Ivarsson M, Bengtson S, Drake H, Francis W. Fungi in Deep Subsurface Environments. ADVANCES IN APPLIED MICROBIOLOGY 2018; 102:83-116. [PMID: 29680127 DOI: 10.1016/bs.aambs.2017.11.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The igneous crust of the oceans and the continents represents the major part of Earth's lithosphere and has recently been recognized as a substantial, yet underexplored, microbial habitat. While prokaryotes have been the focus of most investigations, microeukaryotes have been surprisingly neglected. However, recent work acknowledges eukaryotes, and in particular fungi, as common inhabitants of the deep biosphere, including the deep igneous provinces. The fossil record of the subseafloor igneous crust, and to some extent the continental bedrock, establishes fungi or fungus-like organisms as inhabitants of deep rock since at least the Paleoproterozoic, which challenges the present notion of early fungal evolution. Additionally, deep fungi have been shown to play an important ecological role engaging in symbiosis-like relationships with prokaryotes, decomposing organic matter, and being responsible for mineral weathering and formation, thus mediating mobilization of biogeochemically important elements. In this review, we aim at covering the abundance and diversity of fungi in the various igneous rock provinces on Earth as well as describing the ecological impact of deep fungi. We further discuss what consequences recent findings might have for the understanding of the fungal distribution in extensive anoxic environments and for early fungal evolution.
Collapse
Affiliation(s)
- Magnus Ivarsson
- Nordic Center for Earth Evolution, University of Southern Denmark, Odense, Denmark; Swedish Museum of Natural History, Stockholm, Sweden.
| | | | | | - Warren Francis
- Nordic Center for Earth Evolution, University of Southern Denmark, Odense, Denmark
| |
Collapse
|
10
|
Fungus-like mycelial fossils in 2.4-billion-year-old vesicular basalt. Nat Ecol Evol 2017; 1:141. [PMID: 28812648 DOI: 10.1038/s41559-017-0141] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Accepted: 03/15/2017] [Indexed: 11/09/2022]
Abstract
Fungi have recently been found to comprise a significant part of the deep biosphere in oceanic sediments and crustal rocks. Fossils occupying fractures and pores in Phanerozoic volcanics indicate that this habitat is at least 400 million years old, but its origin may be considerably older. A 2.4-billion-year-old basalt from the Palaeoproterozoic Ongeluk Formation in South Africa contains filamentous fossils in vesicles and fractures. The filaments form mycelium-like structures growing from a basal film attached to the internal rock surfaces. Filaments branch and anastomose, touch and entangle each other. They are indistinguishable from mycelial fossils found in similar deep-biosphere habitats in the Phanerozoic, where they are attributed to fungi on the basis of chemical and morphological similarities to living fungi. The Ongeluk fossils, however, are two to three times older than current age estimates of the fungal clade. Unless they represent an unknown branch of fungus-like organisms, the fossils imply that the fungal clade is considerably older than previously thought, and that fungal origin and early evolution may lie in the oceanic deep biosphere rather than on land. The Ongeluk discovery suggests that life has inhabited submarine volcanics for more than 2.4 billion years.
Collapse
|
11
|
Ivarsson M, Schnürer A, Bengtson S, Neubeck A. Anaerobic Fungi: A Potential Source of Biological H2 in the Oceanic Crust. Front Microbiol 2016; 7:674. [PMID: 27433154 PMCID: PMC4922220 DOI: 10.3389/fmicb.2016.00674] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 04/25/2016] [Indexed: 11/23/2022] Open
Abstract
The recent recognition of fungi in the oceanic igneous crust challenges the understanding of this environment as being exclusively prokaryotic and forces reconsiderations of the ecology of the deep biosphere. Anoxic provinces in the igneous crust are abundant and increase with age and depth of the crust. The presence of anaerobic fungi in deep-sea sediments and on the seafloor introduces a type of organism with attributes of geobiological significance not previously accounted for. Anaerobic fungi are best known from the rumen of herbivores where they produce molecular hydrogen, which in turn stimulates the growth of methanogens. The symbiotic cooperation between anaerobic fungi and methanogens in the rumen enhance the metabolic rate and growth of both. Methanogens and other hydrogen-consuming anaerobic archaea are known from subseafloor basalt; however, the abiotic production of hydrogen is questioned to be sufficient to support such communities. Alternatively, biologically produced hydrogen could serve as a continuous source. Here, we propose anaerobic fungi as a source of bioavailable hydrogen in the oceanic crust, and a close interplay between anaerobic fungi and hydrogen-driven prokaryotes.
Collapse
Affiliation(s)
- Magnus Ivarsson
- Department of Palaeobiology and Nordic Center for Earth Evolution, Swedish Museum of Natural History Stockholm, Sweden
| | - Anna Schnürer
- Department of Microbiology, Uppsala BioCenter, Swedish University of Agricultural Sciences Uppsala, Sweden
| | - Stefan Bengtson
- Department of Palaeobiology and Nordic Center for Earth Evolution, Swedish Museum of Natural History Stockholm, Sweden
| | - Anna Neubeck
- Department of Geological Sciences, Stockholm University Stockholm, Sweden
| |
Collapse
|
12
|
|