Diversity of Actinobacteria Isolated from Date Palms Rhizosphere and Saline Environments: Isolation, Identification and Biological Activity Evaluation

The diversity of cultural Actinobacteria in two types of Algerian Sahara environments, including saline environments and date palms rhizosphere, was investigated. In this study, a total of 40 strains of actinomycetes was isolated from different soil samples, using a rehydration and centrifugation method. Molecular identification, based on 16S rRNA gene sequence analysis, revealed that these isolates were affiliated to six clusters corresponding to eight genera, including Streptomyces, Nocardiopsis, Saccharopolyspora, Actinomadura, Actinocorallia, Micromonospora, Couchioplanes, and Planomonospora. A taxonomic analysis, based on the morphological, physiological, biochemical, and molecular investigation, of selected strains, which belong to the rare Actinobacteria, was undertaken. Four strains (CG3, A111, A93, and A79) were found to form distinct phyletic lines and represent new actinobacterial taxa. An assessment of antimicrobial proprieties of the 40 obtained actinomycetes strains, showed moderate to strong antimicrobial activities against fungi and bacteria. This study demonstrated the richness of Algerian Sahara with rare Actinobacteria, which can provide novel bioactive metabolites, to solving some of the most challenging problems of the day, such as multi-drug resistance.

Diversity Analysis of an Extremely Acidic Soil in a Layer of Coal Mine Detected the Occurrence of Rare Actinobacteria

Studies that explore the diversity of microorganisms in unusual (extreme) environments have become more common. Our research aims to predict the diversity of bacteria that inhabit an extreme environment, a coal mine’s soil with pH of 2.93. Soil samples were collected from the soil at a depth of 12 meters from the surface, which is a clay layer adjacent to a coal seam in Tanjung Enim, South Sumatera, Indonesia. A culture-independent method, the polymerase chain reaction based denaturing gradient gel electrophoresis, was used to amplify the 16S rRNA gene to detect the viable-but-unculturable bacteria. Results showed that some OTUs that have never been found in the coal environment and which have phylogenetic relationships to the rare actinobacteria Actinomadura, Actinoallomurus, Actinospica, Streptacidiphilus, Aciditerrimonas, and Ferrimicrobium. Accordingly, the highly acidic soil in the coal mine is a source of rare actinobacteria that can be explored further to obtain bioactive compounds for the benefit of biotechnology.

Actinobacteria Derived from Algerian Ecosystems as a Prominent Source of Antimicrobial Molecules

Actinobacteria, in particular “rare actinobacteria” isolated from extreme ecosystems, remain the most inexhaustible source of novel antimicrobials, offering a chance to discover new bioactive metabolites. This is the first overview on actinobacteria isolated in Algeria since 2002 to date with the aim to present their potential in producing bioactive secondary metabolites. Twenty-nine new species and one novel genus have been isolated, mainly from the Saharan soil and palm groves, where 37.93% of the most abundant genera belong to Saccharothrix and Actinopolyspora. Several of these strains were found to produce antibiotics and antifungal metabolites, including 17 new molecules among the 50 structures reported, and some of these antibacterial metabolites have shown interesting antitumor activities. A series of approaches used to enhance the production of bioactive compounds is also presented as the manipulation of culture media by both classical methods and modeling designs through statistical strategies and the associations with diverse organisms and strains. Focusing on the Algerian natural sources of antimicrobial metabolites, this work is a representative example of the potential of a closely combined study on biology and chemistry of natural products.