Abstract
Endophytic actinobacteria, known for symbiotic relationships with plants and production of bioactive compounds, occur in diverse environments, including deserts. The Sahara's nutrient scarcity, high temperatures, and salinity drive unique microbial adaptations, making it a promising reservoir of novel taxa. This study reports, for the first time, the isolation and characterization of endophytic actinobacteria from Artemisia judaica L. ssp. sahariensis, a medicinal plant of the Algerian desert. Forty-two actinobacterial isolates were obtained from root and leaf tissues and identified through 16 S rRNA gene sequencing, revealing their affiliation with five genera: Micromonospora, Nonomuraea, Nocardiopsis, Gordonia, and predominantly Streptomyces. These isolates were characterized for morphological, physiological, and bioactive traits, including stress tolerance, phosphate solubilization, extracellular enzyme production, and antibacterial activity. More than 93% exhibited antagonistic effects against at least one tested pathogen. The most active strains showed minimum inhibitory concentration values between 4 and 8 µg/mL, highlighting their strong antibacterial potential. All isolates tolerated up to 5% NaCl, and several, including AJR36, AJR38, and AJR16, grew at 15%. Phosphate solubilization was observed in 36% of isolates, while 38% displayed diverse enzymatic activities. Although this study focused on a single plant species, the observed functional diversity underscores the biotechnological potential of these desert-associated endophytes. These findings suggest that unexplored desert ecosystems harbor valuable Actinomycetota resources, supporting further investigations for the discovery of novel species and their potential applications in agriculture and medicine.