title: Ignimbrite textural properties as determinants of endolithic colonization patterns from hyper-arid Atacama Desert.
abstract: This study explores the photosynthetic microbial colonization of rhyolitic ignimbrites in Lomas de Tilocalar, a hyper-arid region of the Atacama Desert, Chile. Colonization appeared in the form of a green layer a few millimeters beneath the ignimbrite surface. Some ignimbrite rocks revealed two distinct micromorphological areas of identical mineralogical and chemical composition but different textural properties. According to texture, colonization patterns varied in terms of the extension and depth of colonization. The diversity of photosynthetic microorganisms was assessed by denaturing gradient gel electrophoresis (DGGE) of the 23S rRNA gene and by generating clone libraries of the 16S rRNA gene. We observed a low diversity of photosynthetic microorganisms colonizing the ignimbrite microhabitat. Most rRNA gene sequences recovered greatly resembled those of Chroococcidiopsis hypolith clones from arid deserts. These results point to highly restrictive conditions of the hyper-arid Atacama Desert conditioning the diversity of cyanobacteria, and suggest that microbial colonization and composition patterns might be determined by the microscale physico-chemical properties of the ignimbrite rocks.
authors.affiliation: National Museum of Natural Sciences-CSIC, Madrid, Spain.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Cámara
authors.affiliation: J. Craig Venter Institute, La Jolla, CA, USA.
authors.forename: Shino
authors.initials: S
authors.lastname: Suzuki
authors.affiliation: J. Craig Venter Institute, La Jolla, CA, USA.|University of Southern California, Los Angeles, CA, USA.
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Nealson
authors.affiliation: National Museum of Natural Sciences-CSIC, Madrid, Spain.
authors.forename: Jacek
authors.initials: J
authors.lastname: Wierzchos
authors.affiliation: National Museum of Natural Sciences-CSIC, Madrid, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Ascaso
authors.affiliation: Department of Plant Biology, Ecology and Earth Sciences. University of Extremadura, Plasencia, Spain.
authors.forename: Octavio
authors.initials: O
authors.lastname: Artieda
authors.affiliation: National Museum of Natural Sciences-CSIC, Madrid, Spain.
authors.forename: Asunción
authors.initials: A
authors.lastname: de los Ríos
mesh_terms: D000458:Cyanobacteria / Q000145:classification / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D003889:Desert Climate; D019015:Geologic Sediments / Q000737:chemistry* / Q000382:microbiology*; D008969:Molecular Sequence Data; D010788:Photosynthesis; D010802:Phylogeny; D012988:Soil Microbiology
keywords: Atacama Desert; Chroococcidiopsis sp.; endoliths; ignimbrite; rock porosity; volcanic rock