Ha Trang Phan, Hung Vuong Pham, Trung Hai Huynh, Xuan Truong Nguyen, Quoc Phong Truong, Thuy Hang Dam, Truong Giang Nguyen
https://doi.org/10.1016/j.jgeb.2026.100786, Journal of Genetic Engineering and Biotechnology
Abstract
The rise of antimicrobial resistance and emerging infectious diseases necessitates the discovery of novel anti
bacterial agents. Endophytic actinomycetes, especially Streptomyces species colonizing medicinal plant tissues,
constitute a reservoir of structurally diverse bioactive metabolites that remains insufficiently characterized. This
study reports the isolation and comprehensive characterization of an endophytic actinomycete, designated strain
YBRX0, recovered from the root tissues of the Vietnamese medicinal plant Croton tonkinensis Gagnep. Strain
identity was established through an integrated approach combining colony morphology, scanning electron mi
croscopy, physiological and biochemical profiling, and 16S rRNA gene phylogenetic analysis. Bioactivity
screening of the ethyl acetate fermentation extract employed agar well diffusion to assess antibacterial spectrum,
with inhibitory potency quantified by broth microdilution. Antioxidant capacity was measured via DPPH radical
scavenging, and secondary metabolite composition was profiled by GC–MS. The integrated characterization
placed strain YBRX0 unambiguously within the genus. At 1 mg/mL, the ethyl acetate extract demonstrated
broad-spectrum activity against both Gram-positive and Gram-negative pathogens, with MIC values ranging from
8 to 16μg/mL. Antioxidant screening yielded an IC₅₀ of 197.26 ± 8.87μg/mL. GC–MS tentatively identified
Pyrrolopyrazine diketopiperazines and Benzeneacetamide as principal constituents. Collectively, these findings
indicate that the crude extract of Streptomyces sp. YBRX0 exhibited notable antibacterial activity despite being
an unfractionated mixture, supporting its potential as a promising source of bioactive metabolites for further
bioprospecting and compound isolation efforts targeting drug-resistant pathogens.
