Isolation, Characterization, and Antibacterial Activity of Actinomycetes from Sheep Feces

Actinomycetes are a vital group of Gram-positive bacteria known for producing a wide range of bioactive secondary metabolites, including important antibiotics. These microorganisms play an essential role in the degradation of organic matter and nutrient cycling, contributing significantly to soil health and fertility. Their capacity to synthesize diverse compounds and the presence of key biosynthetic pathways involving polyketide synthases and non-ribosomal peptide synthetases highlights their potential in antibiotic discovery, particularly against antibiotic-resistant pathogens. This study aimed to isolate and characterize Actinomycetes from fresh sheep feces collected in Ilam Province, Iran, focusing on their antibacterial activity and biosynthetic potential. A total of 86 actinomycete isolates were obtained from fecal samples collected from sheep in 2021. Morphological characterization confirmed all isolates as Gram-positive and filamentous. Molecular identification through PCR amplification of the 16S rRNA gene yielded a product of approximately 640 base pairs for all isolates. Antibacterial screening revealed that 17 isolates exhibited activity against various pathogens, with the highest efficacy observed against Bacillus cereus (62.1%). Molecular analysis also indicated the presence of biosynthetic gene clusters, with 31 isolates (36.05%) bearing non-ribosomal peptide synthetase (NRPS) gene, 15 isolates (17.44%) containing polyketide synthase I (PKS-I), and 16 isolates (18.6%) with polyketide synthase II (PKS-II) genes. This study highlights the significant antibacterial properties and biosynthetic capabilities of actinomycetes from sheep feces, suggesting their potential use in therapeutic, agriculture, and biotechnological applications.