title: Characterization of functional bacterial groups in a hypersaline microbial mat community (Salins-de-Giraud, Camargue, France).
abstract: A photosynthetic microbial mat was investigated in a large pond of a Mediterranean saltern (Salins-de-Giraud, Camargue, France) having water salinity from 70 per thousand to 150 per thousand (w/v). Analysis of characteristic biomarkers (e.g., major microbial fatty acids, hydrocarbons, alcohols and alkenones) revealed that cyanobacteria were the major component of the pond, in addition to diatoms and other algae. Functional bacterial groups involved in the sulfur cycle could be correlated to these biomarkers, i.e. sulfate-reducing, sulfur-oxidizing and anoxygenic phototrophic bacteria. In the first 0.5 mm of the mat, a high rate of photosynthesis showed the activity of oxygenic phototrophs in the surface layer. Ten different cyanobacterial populations were detected with confocal laser scanning microscopy: six filamentous species, with Microcoleus chthonoplastes and Halomicronema excentricum as dominant (73% of total counts); and four unicellular types affiliated to Microcystis, Chroococcus, Gloeocapsa, and Synechocystis (27% of total counts). Denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA gene fragments confirmed the presence of Microcoleus, Oscillatoria, and Leptolyngbya strains (Halomicronema was not detected here) and revealed additional presence of Phormidium, Pleurocapsa and Calotrix types. Spectral scalar irradiance measurements did not reveal a particular zonation of cyanobacteria, purple or green bacteria in the first millimeter of the mat. Terminal-restriction fragment length polymorphism analysis of PCR-amplified 16S rRNA gene fragments of bacteria depicted the community composition and a fine-scale depth-distribution of at least five different populations of anoxygenic phototrophs and at least three types of sulfate-reducing bacteria along the microgradients of oxygen and light inside the microbial mat.
authors.affiliation: Laboratoire d'Ecologie Moléculaire EA 3525, Université de Pau et des Pays de l'Adour, avenue de l'Université, BP 1155, F-64013 Pau Cedex, France.
authors.forename: Aude
authors.initials: A
authors.lastname: Fourçans
authors.forename: Tirso García
authors.initials: TG
authors.lastname: de Oteyza
authors.forename: Andrea
authors.initials: A
authors.lastname: Wieland
authors.forename: Antoni
authors.initials: A
authors.lastname: Solé
authors.forename: Elia
authors.initials: E
authors.lastname: Diestra
authors.forename: Judith
authors.initials: J
authors.lastname: van Bleijswijk
authors.forename: Joan O
authors.initials: JO
authors.lastname: Grimalt
authors.forename: Michael
authors.initials: M
authors.lastname: Kühl
authors.forename: Isabel
authors.initials: I
authors.lastname: Esteve
authors.forename: Gerard
authors.initials: G
authors.lastname: Muyzer
authors.forename: Pierre
authors.initials: P
authors.lastname: Caumette
authors.forename: Robert
authors.initials: R
authors.lastname: Duran
mesh_terms: D018441:Biofilms; D015415:Biomarkers / Q000032:analysis; D000458:Cyanobacteria / Q000235:genetics* / Q000502:physiology*; D004269:DNA, Bacterial / Q000032:analysis; D017753:Ecosystem; D005602:France; D055593:Geological Phenomena; D005844:Geology; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology*; D016133:Polymerase Chain Reaction; D011157:Population Dynamics; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D012965:Sodium Chloride; D014881:Water Supply
chemical_list: D015415:Biomarkers; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012965:Sodium Chloride; D010100:Oxygen