title: Salt resistance genes revealed by functional metagenomics from brines and moderate-salinity rhizosphere within a hypersaline environment.
abstract: Hypersaline environments are considered one of the most extreme habitats on earth and microorganisms have developed diverse molecular mechanisms of adaptation to withstand these conditions. The present study was aimed at identifying novel genes from the microbial communities of a moderate-salinity rhizosphere and brine from the Es Trenc saltern (Mallorca, Spain), which could confer increased salt resistance to Escherichia coli. The microbial diversity assessed by pyrosequencing of 16S rRNA gene libraries revealed the presence of communities that are typical in such environments and the remarkable presence of three bacterial groups never revealed as major components of salt brines. Metagenomic libraries from brine and rhizosphere samples, were transferred to the osmosensitive strain E. coli MKH13, and screened for salt resistance. Eleven genes that conferred salt resistance were identified, some encoding for well-known proteins previously related to osmoadaptation such as a glycerol transporter and a proton pump, whereas others encoded proteins not previously related to this function in microorganisms such as DNA/RNA helicases, an endonuclease III (Nth) and hypothetical proteins of unknown function. Furthermore, four of the retrieved genes were cloned and expressed in Bacillus subtilis and they also conferred salt resistance to this bacterium, broadening the spectrum of bacterial species in which these genes can function. This is the first report of salt resistance genes recovered from metagenomes of a hypersaline environment.
authors.affiliation: Laboratory of Molecular Adaptation, Department of Molecular Evolution, Centro de Astrobiología, Consejo Superior de Investigaciones Científicas - Instituto Nacional de Técnica Aeroespacial, Madrid Spain.
authors.forename: Salvador
authors.initials: S
authors.lastname: Mirete
authors.affiliation: Marine Microbiology Group, Department of Ecology and Marine Resources, Mediterranean Institute for Advanced Studies, Consejo Superior de Investigaciones Científicas - Universidad de las Islas Baleares, Esporles Spain.
authors.forename: Merit R
authors.initials: MR
authors.lastname: Mora-Ruiz
authors.affiliation: Laboratory of Molecular Adaptation, Department of Molecular Evolution, Centro de Astrobiología, Consejo Superior de Investigaciones Científicas - Instituto Nacional de Técnica Aeroespacial, Madrid Spain.
authors.forename: María
authors.initials: M
authors.lastname: Lamprecht-Grandío
authors.affiliation: Laboratory of Molecular Adaptation, Department of Molecular Evolution, Centro de Astrobiología, Consejo Superior de Investigaciones Científicas - Instituto Nacional de Técnica Aeroespacial, Madrid Spain.
authors.forename: Carolina G
authors.initials: CG
authors.lastname: de Figueras
authors.affiliation: Marine Microbiology Group, Department of Ecology and Marine Resources, Mediterranean Institute for Advanced Studies, Consejo Superior de Investigaciones Científicas - Universidad de las Islas Baleares, Esporles Spain.
authors.forename: Ramon
authors.initials: R
authors.lastname: Rosselló-Móra
authors.affiliation: Laboratory of Molecular Adaptation, Department of Molecular Evolution, Centro de Astrobiología, Consejo Superior de Investigaciones Científicas - Instituto Nacional de Técnica Aeroespacial, Madrid Spain.
authors.forename: José E
authors.initials: JE
authors.lastname: González-Pastor
keywords: DNA repair; brine; functional metagenomics; hypersaline; rhizosphere; salt resistance genes; saltern; stress response