Résumé:
A combination of cultural and culture-independent (the latter is metagenomics by molecular cloning) techniques, was used to study the biodiversity of halophilic and halotolerant Actinobacteria, living in Ezzemoul sebkha, Chott Tinsilt and Djendli sebkha soils (located in northeastern Algeria). These ecosystems are mainly, extremely saline, alkaline, with low moisture content. According to the phylogenetic analysis of the 16S rDNA gene sequences: 40 isolates from the Ezzemoul site are assigned to species of the genera Nocardiopsis (dominant), Streptomyces and Rhodococcus; Another 42 isolates from the Tinsilt site are attributed to Streptomyces (dominant), Nocardiopsis, Actinopolyspora and Brevibacterium; and 22 isolates from the Djendli site belong to the same genera Streptomyces (dominant) and Nocardiopsis. Among all these isolates, there is a high probability of the presence of many new species. In addition, 24 clone sequences derived from the Ezzemoul site are affiliated with the genera Demequina (dominant), Plantactinospora, Friedmanniella and Mycobacterium. Also, 15 clone’s sequences from the Djendli site are related to the genera Marmoricola, Phytoactinopolyspora and Streptomyces; and to an unclassified actinobacterial clone. Some sequences (from both sites) are related to uncultured clones and/or not belonging to the class Actionbacteria (dominant in the site Djendli). Furthermore, the isolates obtained from the three study sites are: moderately halophilic and halotolerants, mesophilic, neutrophilic or acid-alkali-tolerant. Several of them can produce at the same time, extracellular hydrolytic enzymes such as cellulase, amylase, lipase, pectinase and proteases; as well as bioactive molecules against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and fungi (Candida albicans and Aspergillus niger). The results of this research show a wide taxonomic, physiological and metabolic diversity of Actinobacteria, from sebkhas and chott. These bacteria can therefore be excellent candidates for future biotechnological applications.
