Funtonal metagenomic of salt resistance. Functional metagenomics study of salt resistance genes within a hyper saline environment

Hypersaline environments are considered some 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 involved in salt resistance from the microbial communities of brines and the rhizosphere of the halophyte Arthrocnemum from the Es Trenc saltern (Mallorca, Spain). The bacterial and archaeal diversity assessed by pyrosequencing of 16S rRNA gene libraries revealed the presence of microbial communities that are typical in such environments. Metagenomic libraries were constructed with DNA from brine and rhizosphere samples, they were transferred to the osmosensitive strain Escherichia coli MKH13, and screened for salt-resistant clones. As a result, a total of eleven genes that confer salt resistance were identified, some of which encode for well known proteins previously related to osmoadaptation as a glycerol and a proton pump, whereas other genes encode for proteins not previously related to this function as RNA and DNA 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 interestingly, three of them exhibited also salt resistance in this bacterium, broadening the spectrum of bacterial species where these genes can operate. This is the first report of salt resistance genes recovered from different metagenomes of a hypersaline environment, which will help to further elucidate novel molecular mechanisms of salt resistance.