Isolation and Antibacterial Properties of Actinomycetesfrom Licorice (Glycyrrhiza glabra).

Abstract

Introduction: Actinomycetes associated with the medicinal plant licorice (Glycyrrhiza glabra) were investigated for their potential to produce novel antibiotics, an area of growing importance in combating bacterial resistance.

Materials & methods: In this study, a total of 75 actinomycete isolates were obtained from licorice plant samples collected in Ilam Province, Iran. These samples were carefully selected due to licorice's traditional use in herbal medicine, suggesting a rich microbial diversity.

Results: Molecular identification through 16S rRNA gene amplification confirmed that 57 of the isolates belonged to the class Actinomycetia, within the phylum Actinomycetota. Further screening for biosynthetic gene clusters (BGCs) revealed that an impressive 96% of the isolates harbored genes for nonribosomal peptide synthetases (NRPS). In contrast, only 28% and 17% of the isolates contained genes associated with polyketide synthase type I (PKS-I) and type II (PKS-II), respectively. Utilizing agar well diffusion assays, the study demonstrated that 16 isolates (28%) exhibited significant antibacterial activity against both drug-resistant and drug-sensitive strains of Staphylococcus aureus and Pseudomonas aeruginosa. Among these, two isolates, S12 and S14, showcased remarkable broad-spectrum antibacterial properties by inhibiting three members of the ESKAPE pathogen group.

Conclusion: The strong correlation between the presence of NRPS genes and antibacterial activity underscores the potential of actinomycetes associated with licorice as a promising source of novel antimicrobial compounds. These findings emphasize the importance of bioprospecting medicinal plant-derived microbiomes as a strategic approach to address the escalating global challenge of antibiotic resistance, paving the way for future research and development in antimicrobial therapies. Future research should focus on elucidating the genetic and metabolic networks that underpin these interactions to fully exploit their pharmaceutical potential.