Endophytic Symbionts Of Acacia Victoriae: Diversity And Potential For Antibiotic Production

The potential disease burden due to pathogenic microbes is increasing worldwide due to the evolution and spread of antibiotic resistance. Thus there is an urgent need to discover new antibiotics from diverse sources. One important source for new antibiotics is medicinal plants, some of which produce secondary compounds with antibiotic activity. Recently it has been shown that microbiomes of such plants may play a role in producing antimicrobials, some of which have been thought previously to be of plant origin. Here I examine the antibiotic potential of microbial endophytes of a focal medicinal plant, Acacia victoriae. In doing so I tested the hypothesis that endophytes from stems, a long-lived tissue, will have more potent antimicrobial activity than endophytes of shorter-lived leaves. I isolated over 70 endophytes from A. victoriae, including 32 from leaves and 39 from stem tissue. Isolates were organized to morphotypes, identified via DNA barcoding, and evaluated for antimicrobial activity against model strains of three pathogenic species (Escherichia coli, Bacillus subtilis, and Candida albicans). I did not find strong evidence of inhibition by focal endophytes under the culture conditions used here, but several endophytes overgrew the focal microbes, suggesting the potential for competitive interactions worthy of future exploration