TITLE:
Isolation, Examination and Characterization of Actinomycetes as a Source of Antimicrobial Agents from Libyan Soil
AUTHORS:
Galal S. Salem, Saleh H. Baiu, Ali A. Ali
KEYWORDS:
Actinomycetes, Antimicrobial Activity, Isolation, Streptomyces
JOURNAL NAME:
Advances in Bioscience and Biotechnology,
Vol.14 No.6,
June
30,
2023
ABSTRACT: The rapid increase of bacterial resistance strains to multiple antibiotics
has become a global public health concern. In the present study, actinomycetes from
different districts of Libyan soil were isolated and screened for their inhibitory
activity against pathogenic bacteria and fungi. Three hundred soil samples were
taken from 77 diverse ecosystems, including deserts, forests, pastureland, and cropland
located in different climatic regions in Libya. A total of 164 actinomycetes were
obtained. Of 164 isolates, 38 (23.2%) isolates were morphologically and microscopically
characterized by spore chain and surface morphology, aerial and substrate mycelia
and soluble pigments. The preliminary classification of the isolates illustrates
that all isolates belong to the genus Streptomyces. These isolates were further
examined for their antagonistic potential against nine pathogenic bacteria and fungi. Out of 38, 11 (28.9%)
isolates showed their capability to produce inhibitory substances against at least two tested strains. Among bacterial strains, Staphylococcus
aureus was susceptible to almost all eleven isolates (90.9%), while Streptococcus pyogenes was found to be resistant to most selected
isolates (18.2%). The isolate, 063 (Wadan soil-desert zone) was the only isolate
that exhibited broad spectrum antimicrobial activity against all tested pathogenic
microbes, and hence was selected for further
study. According to its cultural, morphological, physiological, and biochemical
characteristics, the isolate 063 was identified as Streptomyces rochei. The
results obtained indicate that the Libyan soil, particularly in extreme environments,
could be a potent source of bioactive metabolites with antimicrobial potency
against a wide variety of microbial pathogens. Thus, this investigation suggested
that exploring new habitats in unexplored and untapped regions of Libya could provide
a promising source of biologically active compounds for therapeutic applications.