Isolation, screening and biological activity Of Ocotea bullata and Aloe lettyae`s endophytes and metabolites

Abstract

This study investigated the potential of endophytes from endangered plants to support sustainable agriculture, species conservation efforts, and human health applications, focusing on Ocotea bullata (O. bullata) and Aloe lettyae (A. lettyae). Endophytes, known for synthesizing medicinal, agricultural, and biotechnological metabolites, may provide sustainable solutions for conservation efforts. In addition to the primary focus on the endangered A. lettyae, the study included Aloe longibracteata (A. longibracteata), a closely related non-endangered species, as a comparative model to identify traits beneficial for conservation and stress resilience. Comparative analysis revealed a diverse array of plant growth-promoting metabolites, such as indole-3-acetic acid (IAA) and 5-hydroxy indole-3-acetic acid, with significant implications for species conservation and agricultural applications. Endophytes from both Aloe species, predominantly belonging to the Bacillusmand Enterobacter genera, exhibited key plant growth-promoting traits including: 100% of isolates that fixed nitrogen, 35% that solubilised phosphate, 76% that produced siderophores, and IAA production ranging from 10 to 75 μg/mL. These traits collectively contribute to plant health and stress tolerance. This study also emphasized the importance of sustainable resource utilization, particularly by demonstrating the feasibility of harvesting metabolites from the leaves of the endangered O. bullata. The results showed that the leaves contain a diverse range of metabolites with potential human health applications, including ascorbate, gentisic acid, gallic acid, and chlorogenic acid, providing a sustainable alternative to harvesting the bark and thereby contributing to the protection of the species. Additionally, the endophytes isolated from O. bullata exhibited strong plant growth-promoting properties, including enhancing germination in tomato seeds and exhibiting antimicrobial activity, which could support the plant's health and resilience. The inclusion of A. longibracteata also allowed for the assessment of its potential as a donor of beneficial endophytes for transfer to A. lettyae, offering a novel conservation strategy for the endangered species. Future research should leverage the optimised metabolite extraction methods to explore additional applications while ensuring that the safety of using these Aloe species is thoroughly evaluated. The findings highlight the potential of metabolites derived from these plant species for biofertilizer and biocontrol applications, offering opportunities to develop eco-friendly agricultural solutions while contributing to the preservation of biodiversity.