title: Algal species and light microenvironment in a low-pH, geothermal microbial mat community.
abstract: Unicellular algae are the predominant microbial mat-forming phototrophs in the extreme environments of acidic geothermal springs. The ecology of these algae is not well known because concepts of species composition are inferred from cultivated isolates and microscopic observations, methods known to provide incomplete and inaccurate assessments of species in situ. We used sequence analysis of 18S rRNA genes PCR amplified from mat samples from different seasons and different temperatures along a thermal gradient to identify algae in an often-studied acidic (pH 2.7) geothermal creek in Yellowstone National Park. Fiber-optic microprobes were used to show that light for algal photosynthesis is attenuated to < 1% over the 1-mm surface interval of the mat. Three algal sequences were detected, and each was present year-round. A Cyanidioschyzon merolae sequence was predominant at temperatures of > or = 49 degrees C. A Chlorella protothecoides var. acidicola sequence and a Paradoxia multisita-like sequence were predominant at temperatures of < or = 39 degrees C.
authors.affiliation: Microbiology Department and Thermal Biology Institute, Montana State University, Bozeman 59717, USA. mferris@chnola-research.org
authors.forename: M J
authors.initials: MJ
authors.lastname: Ferris
authors.forename: K B
authors.initials: KB
authors.lastname: Sheehan
authors.forename: M
authors.initials: M
authors.lastname: Kühl
authors.forename: K
authors.initials: K
authors.lastname: Cooksey
authors.forename: B
authors.initials: B
authors.lastname: Wigglesworth-Cooksey
authors.forename: R
authors.initials: R
authors.lastname: Harvey
authors.forename: J M
authors.initials: JM
authors.lastname: Henson
mesh_terms: D002708:Chlorella / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D017753:Ecosystem; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008027:Light; D008969:Molecular Sequence Data; D010788:Photosynthesis; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D000461:Rhodophyta / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D045483:Rivers / Q000382:microbiology*; D012621:Seasons; D017422:Sequence Analysis, DNA; D013696:Temperature
chemical_list: D012337:RNA, Ribosomal, 18S