title: A cryptoendolithic community in volcanic glass.
abstract: Fluorescent in situ hybridization (FISH) and 16S rDNA analysis were used to characterize the endolithic colonization of silica-rich rhyolitic glass (obsidian) in a barren terrestrial volcanic environment in Iceland. The rocks were inhabited by a diverse eubacterial assemblage. In the interior of the rock, we identified cyanobacterial and algal 16S (plastid) sequences and visualized phototrophs by FISH, which demonstrates that molecular methods can be used to characterize phototrophs at the limits of photosynthetically active radiation (PAR). Temperatures on the surface of the dark rocks can exceed 40 degrees C but are below freezing for much of the winter. The rocks effectively shield the organisms within from ultraviolet radiation. Although PAR sufficient for photosynthesis cannot penetrate more than approximately 250 mum into the solid rock, the phototrophs inhabit cavities; and we hypothesize that by weathering the rock they may contribute to the formation of cavities in a feedback process, which allows them to acquire sufficient PAR at greater depths. These observations show how pioneer phototrophs can colonize the interior of volcanic glasses and rocks, despite the opaque nature of these materials. The data show that protected microhabitats in volcanic rocky environments would have been available for phototrophs on early Earth.
authors.affiliation: Geomicrobiology Research Group, Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR), The Open University , Milton Keynes, UK.
authors.forename: Aude
authors.initials: A
authors.lastname: Herrera
authors.forename: Charles S
authors.initials: CS
authors.lastname: Cockell
authors.forename: Stephen
authors.initials: S
authors.lastname: Self
authors.forename: Mark
authors.initials: M
authors.lastname: Blaxter
authors.forename: Joachim
authors.initials: J
authors.lastname: Reitner
authors.forename: Thorsteinn
authors.initials: T
authors.lastname: Thorsteinsson
authors.forename: Gernot
authors.initials: G
authors.lastname: Arp
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Dröse
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Tindle
mesh_terms: D000458:Cyanobacteria / Q000235:genetics / Q000254:growth & development*; D004275:DNA, Ribosomal / Q000737:chemistry; D004783:Environmental Microbiology; D056890:Eukaryota / Q000235:genetics / Q000254:growth & development*; D005898:Glass; D007055:Iceland; D017404:In Situ Hybridization, Fluorescence; D008027:Light; D008834:Microclimate; D008853:Microscopy; D052817:Phototrophic Processes; D012336:RNA, Ribosomal, 16S / Q000235:genetics*
chemical_list: D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; C036485:obsidian