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Title: Biomarkers of Endolithic Communities within Gypsum Crusts (Southern Tunisia).

item STIVALETTA, NUNZIA - Universita Di Bologna
item LOPEZ-GARCIA, PURIFICACION - University Of Paris
item Boihem, Larry
item MILLIE, DAVID - University Of South Florida
item BARBIERI, ROBERTO - Universita Di Bologna

Submitted to: Geomicrobiology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2009
Publication Date: 1/18/2010
Citation: Stivaletta, N., Lopez-Garcia, P., Boihem, L.L., Millie, D.F., Barbieri, R. 2010. Biomarkers of Endolithic Communities within Gypsum Crusts (Southern Tunisia). Geomicrobiology Journal. 27(1):101-110.

Interpretive Summary: In this study gypsum crust from Southern Tunisia were examined using Small Subunit Ribosomal RNA (SSU rRNA) and High Performance Liquid Chromatography (HPLC). The data from SSU rRNA revealed microbial communities consisting of Flavobacteria, Actinobacteria, Deinococcales and Alpha- and Gamma- Proteobacteria. HPLC pigment analysis data indicated carotenoids and chlorophyll A and B. Overall results are typical of crusts samples found in arid/semiarid and hot desert environments.

Technical Abstract: Evaporite accumulations produced by artesian waters in the arid zones of southern Tunisia led to the formation of subrounded,gypsiferous mounds consisting of irregular alternations of mineral precipitates and aeolian sand. The joint occurrence of gypsum crusts and plant colonization determined the stabilization of their top surface. Careful examination of the pigmented (green-brown) crusts revealed endolithic microbial communities just below the surface. In previous optical and scanning electronmicroscope studies cyanobacteria were the dominant component of these communities. Molecular diversity studies based on small subunit ribosomal RNA (SSU rRNA) gene analysis revealed that Flavobacteria, Actinobacteria, Deinococcales, Alpha- and Gamma- Proteobacteria are also important components of the microbial assemblage. Their pigment analyses, determined by high performance liquid chromatography (HPLC), detected the presence of carotenoids and chlorophyll (chl) a and b. Microbial communities that produce pigmentation and display an endolithic lifestyle typify the extreme environments as those found in arid/semiarid and hot desert regions.