Résumé:
Extreme ecosystems can be a source of untapped microorganisms to
produce new bioactive compounds of industrial interest. Actinobacteria are at the forefront due to their
versatile production of secondary metabolites that exhibit various biological activities. Algerian marine
and terrestrial environments remain largely unexplored and may represent an important source for the
discovery of bioactive molecules.
Objectives: The aim of this research is to study the identification and antimicrobial activity of
actinobacteria isolated from various samples of forest (Constantine) and thermal soils (Guelma), marine
sediments and seawater (Skikda and El-Kala).
Methods: Actinobacteria were isolated using the suspension-dilution method on different
culture media: Benett, CSPY-ME, SCA and ISP2. Morphological identification (macroscopic and
microscopic) of isolates was carried out on ISP2 medium by the slide culture technique. All isolates
were then subjected to antimicrobial screening using the agar plug technique against five bacteria and
three pathogenic fungi: Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus,
Bacillus subtilis, Aspergillus niger, Fusarium oxysporum and Candida albicans.
Results and discussion: Consequently, in this work, 18 phenotypically different actinobacterial
isolates were collected from the various ecosystems studied. On the basis of morphological
characteristics, the isolates were assigned to the genera Streptomycs, Saccharopolyspora, Nocardiopsis,
Oerskovia, Jonesia, Streptoalloteichus and Dactylosporangium. The antibacterial activity of
actinobacteria showed that around 61% of isolates possessed strong activity against at least one of the
test bacteria. Antifungal activity revealed that 55.55% of isolates were active on at least one of the test
fungi. In addition, three isolates from forest soil (SF22, SF62 et SF92) possess a broad spectrum of
inhibition against the majority of test microorganisms (Garm+ bacteria and fungi).
Conclusion: Most of actinobacterial isolates studied of marine and terrestrial origin are very
useful microorganisms for the production of bioactive natural products of industrial and
biotechnological interest
