Two novel halophilic actinomycetes, strains AH35 and AH10, isolated from saline soils obtained from the Algerian Sahara, were subjected to polyphasic taxonomic characterization. The strains showed good growth in medium containing 7, 10 and 15% NaCl with growth at temperatures of 28-42°C. The organism produced light grey-green aerial mycelium with reddish-brown or yellowbrown diffusible pigment. Micromorphology and chemotaxonomic characteristics were consistent with its assignment to the genus Saccharomonospora. Analysis of 16S rDNA gene sequences showed that AH35 and AH10 formed a robust clade with "Actinopolyspora iraqiensis", Saccharomonospora halophila and Saccharomonospora paurometabolica. However, a number of phenotypic characteristics readily distinguished strains AH35 and AH10 from these three species. The two strains showed antibacterial activity against Gram-negative bacteria such as Klebsiella pneumoniae, Salmonella enterica, Pseudomonas syringae and Agrobacterium tumefaciens.
A moderately halophilic actinomycete strain designated AH97 was isolated from a saline Saharan soil, and selected for its antimicrobial activities against bacteria and fungi. The AH97 strain was identified by morphological, chemotaxonomic and phylogenetic analyses to the genus Actinoalloteichus. Analysis of the 16S rDNA sequence of strain AH97 showed a similarity level ranging between 95.8% and 98.4% within Actinoalloteichus species, with A. hymeniacidonis the most closely related. The comparison of the physiological characteristics of AH97 with those of known species of Actinoalloteichus showed significant differences. Strain AH97 showed an antibacterial and antifungal activity against broad spectrum of microorganisms known to be human and plant pathogens. The bioactive compounds were extracted from the filtrate culture with n-butanol and purified using thin layer chromatography and high pressure liquid chromatography procedures. Two active products were isolated, one hydrophilic fraction (F1) and another hydrophobic (F2). Ultraviolet-visible, infrared, mass and 1H and 13C nuclear magnetic resonance spectroscopy studies suggested that these molecules were the dioctyl phthalate (F2) and an aminoglycosidic compound (F1).
A moderately halophilic actinomycete strain, designated AH97T , was isolated from Saharan soil in the Hoggar region (south Algeria) and was subjected to polyphasic taxonomic characterization. The morphological and chemotaxonomic characteristics of the strain were consistent with those of the genus Actinoalloteichus.
The Sahara Desert, one of the most extreme ecosystems in the planet, constitutes an unexplored source of microorganisms such as mycelial bacteria. In this study, we investigated the diversity of halophilic actinobacteria in soils collected from five regions of the Algerian Sahara. A total of 23 halophilic actinobacterial strains were isolated by using a humic-vitamin agar medium supplemented with 10% NaCl. The isolated halophilic strains were subjected to taxonomic analysis using a polyphasic approach, which included morphological, chemotaxonomic, physiological (numerical taxonomy), and phylogenetic analyses. The isolates showed abundant growth in CMA (complex medium agar) and TSA (tryptic soy agar) media containing 10% NaCl, and chemotaxonomic characteristics were consistent with their assignment to the genus Nocardiopsis. Analysis of the 16S rRNA sequence of 23 isolates showed five distinct clusters and a similarity level ranging between 98.4% and 99.8% within the Nocardiopsis species. Comparison of their physiological characteristics with the nearest species showed significant differences with the closely related species. Halophilic Nocardiopsis isolated from Algerian Sahara soil represents a distinct phyletic line suggesting a potential new species. Furthermore, the isolated strains of halophilic Nocardiopsis were screened for their antagonistic properties against a broad spectrum of microorganisms by the conventional agar method (agar cylinders method) and found to have the capacity to produce bioactive secondary metabolites. Except one isolate (AH37), all isolated Nocardiopsis showed moderate to high biological activities against Pseudomonas syringae and Salmonella enterica, and some isolates showed activities against Agrobacterium tumefaciens, Serratia marcescens, and Klebsiella pneumoniae. However, no isolates were active against Bacillus subtilis, Aspergillus flavus, or Aspergillus niger. The obtained finding implies that the unexplored extreme environments such as the Sahara contain many new bacterial species as a novel drug source for medical and industrial applications.
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