A Fungal-Prokaryotic Consortium at the Basalt-Zeolite Interface in Subseafloor Igneous Crust.
We have after half a century of coordinated scientific drilling gained insight into Earth´s largest microbial habitat, the subseafloor igneous crust, but still lack substantial understanding regarding its abundance, diversity and ecology. Here we describe a fossilized microbial consortium of prokaryotes and fungi at the basalt-zeolite interface of fractured subseafloor basalts from a depth of 240 m below seafloor (mbsf). The microbial consortium and its relationship with the surrounding physical environment are revealed by synchrotron-based X-ray tomographic microscopy (SRXTM), environmental scanning electron microscopy (ESEM), and Raman spectroscopy. The base of the consortium is represented by microstromatolites-remains of bacterial communities that oxidized reduced iron directly from the basalt. The microstromatolites and the surrounding basalt were overlaid by fungal cells and hyphae. The consortium was overgrown by hydrothermally formed zeolites but remained alive and active during this event. After its formation, fungal hyphae bored in the zeolite, producing millimetre-long tunnels through the mineral substrate. The dissolution could either serve to extract metals like Ca, Na and K essential for fungal growth and metabolism, or be a response to environmental stress owing to the mineral overgrowth. Our results show how microbial life may be maintained in a nutrient-poor and extreme environment by close ecological interplay and reveal an effective strategy for nutrient extraction from minerals. The prokaryotic portion of the consortium served as a carbon source for the eukaryotic portion. Such an approach may be a prerequisite for prokaryotic-eukaryotic colonisation of, and persistence in, subseafloor igneous crust.
Department of Palaeobiology and Nordic Center for Earth Evolution, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden.
Magnus
M
Ivarsson
Department of Palaeobiology and Nordic Center for Earth Evolution, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden.
Stefan
S
Bengtson
Department of Geosciences, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden.
Henrik
H
Skogby
Department of Earth Sciences, Uppsala University, Villavägen 16, SE-752 36 Uppsala, Sweden.
Peter
P
Lazor
Department of Geological Sciences, Stockholm University, Svante Arrheniusväg 8, SE-106 91, Stockholm, Sweden.
Curt
C
Broman
Department of Palaeobiology, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden.
Veneta
V
Belivanova
Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
Federica
F
Marone
D001419:Bacteria / Q000378:metabolism*; D005580:Fossils; D005658:Fungi / Q000378:metabolism* / Q000648:ultrastructure; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology; D025301:Hyphae / Q000378:metabolism / Q000648:ultrastructure; D008670:Metals / Q000378:metabolism; D059013:Microbial Consortia; D008853:Microscopy / Q000379:methods; D008855:Microscopy, Electron, Scanning; D008903:Minerals / Q000378:metabolism; D012623:Seawater / Q000737:chemistry / Q000382:microbiology; D017640:Silicates / Q000032:analysis*; D013059:Spectrum Analysis, Raman; D017356:Synchrotrons; D014056:Tomography, X-Ray / Q000379:methods; D017641:Zeolites / Q000032:analysis*
D008670:Metals; D008903:Minerals; D017640:Silicates; C060346:basalt; D017641:Zeolites