The bacteria and bacteriophages from a Mesquite Flats site of the Death Valley desert
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Arid zones cover over 30 % of the Earth’s continental surface. In order to better understand the role of microbes in this type of harsh environment, we isolated and characterized the bacteriophages from samples of the surface sand of the Mesquite Flats region via electron microscopy and DNA sequencing of a select number of cloned phage DNAs. An electron microscopic analysis of the recovered virus-like particles revealed at least 11 apparently different morphotypes sharing structural characteristics of the Caudoviridae family of tailed phages. We found that 36 % of the sequences contained no significant identity (e-value >10−3) with sequences in the databases. Pilot sequencing of cloned 16S rRNA genes identified Bacteroidetes and Proteobacteria as the major bacterial groups present in this severe environment. The majority of the 16S rDNA sequences from the total (uncultured) bacterial population displayed ≤96 % identity to 16S rRNA genes in the database, suggesting an unexplored bacterial population likely adapted to a desert environment. In addition, we also isolated and identified 38 cultivable bacterial strains, the majority of which belonged to the genus Bacillus. Mitomycin-C treatment of the cultivable bacteria demonstrated that the vast majority (84 %) contained at least one SOS-inducible prophage.
KeywordsDesert Electron microscopy 16S rDNA Bacteria Bacteriophages
The authors would like to thank Jeril Degrouard and Danielle Jaillard for their help with the electron microscopy, Evelyne Marguet and Patrick Forterre (Université Paris-Sud, Orsay, France) for their generosity in providing the sand samples from the Mesquite Flats site of Death Valley, and the Editor and Reviewers for their terrific comments, criticisms and suggestions. This work was supported by the AQUAPHAGE program of the Agence Nationale de la Recherche (ANR), France, and the Centre National de la Recherche Scientifique (CNRS, France).
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