Diversity and antagonistic properties of culturable halophilic actinobacteria in soils of two arid regions of septentrional Sahara: M’zab and Zibans

Abstract

The diversity of culturable halophilic actinobacteria in two Algerian arid ecosystems (M’zab and Zibans) of septentrional Sahara was investigated. A total of 69 halophilic strains were isolated from 19 soil samples. Taxonomy was determined using a polyphasic approach based on morphological, physiological (with the application of numerical taxonomy), chemotaxonomic and molecular investigations. Sequencing of the 16S rRNA gene revealed that the strains belonged to six clusters corresponding to six genera: Actinopolyspora, Nocardiopsis, Prauserella, Saccharomonospora, Saccharopolyspora and Streptomonospora. Some strains were found to represent known species, but others formed distinct phyletic lines. Interestingly, cluster VII, which contained four strains, represents an unknown actinobacterial genus. An assessment of the biological properties of the actinobacterial strains showed moderate to strong antimicrobial activities against fungi and bacteria, including methicillin-resistant Staphylococcus aureus. The bioactive potential of strains which did not show any antimicrobial activity on yeast extract-malt extract agar was analyzed based on the genetic background of these strains using polyketide synthase (type I, II and PKSE) and non-ribosomal peptide synthetase (NRPS) gene sequences. Most of the strains harbored NRPS and PKS-II genes, indicating that they might have a great potential to produce bioactive compounds if the laboratory culture conditions were changed.