Isolation of microorganisms from non-conventional environments and screening of their biotechnological traits

Non-conventional environments such as hot arid deserts or inland saline systems ‘Chott’ are characterized by dryness, high salinity, temperature extremes, very intense irradiation and oligotrophic conditions. These hostile setting for life make such environments invaluable resources for the selection and identification of microorganisms of great interest for biotechnological applications (Nicolaus et al., 2010; Schiraldi and De Rosa, 2002). In this work an investigation of the microbial diversity of two non-conventional extreme environments, inland saline system and desert sand soil located in the south of Tunisia, was performed through the application of a multiassay cultivation-based approach. In specific, the selection of extremophilic and extremotolerant bacteria that withstand intense environmental stresses was carried out by challenging the collected samples with pH (pH 3.0 and 9.5) and temperature extremes (4°c and 50 °C), exposure to high salt concentrations (300 g/l NaCl), irradiation and nutrient limitations. Under the different cultivation conditions applied, a total of 167 isolates were selected and clustered into 75 different haplotypes by internal transcribed 16S-23S rRNA gene spacer (ITS) typing. Partial 16S rRNA gene sequencing resulted in the affiliation of the isolates to four bacterial phyla including Firmicutes, Actinobacteria, Proteobacteria and Bacteroidetes. Moreover the isolates were screened for the production of pigments, biosurfactants, extracellular hydrolytic enzymes and biopolymers (exopolysaccharides). The obtained results showed that inland saline systems and desert sand are key ‘reservoirs’ of microbial diversity, of different microbially derived compounds and molecules with interesting biotechnological properties. In particular, the microbiota inhabiting these niches are important resources of pigments that can be used as natural colorants, biosurfactants useful for the stimulation of the bioremediation of oil-contaminated areas, extracellular enzymes and compounds, like for example exopolysaccharides, very important biopolymers with high potential for application in food and cosmetics industries.