Glucose-Induced Production of Secondary Metabolites by Lasiodiplodia theobromae

Microbial chemodiversity of bioactive secondary metabolites remains largely unexplored for use as new antimicrobial agents. Current advances employed to exploit this plethora of bioactive compounds from microbes are focused on the stimulation of physiological processes that induce the expression of specific enzymes (gene clusters) that eventually regulate the production of secondary metabolites. In this work, we studied the impact of glucose optimized medium in the induction of specific-gene clusters within the genome of Lasiodiplodia theobromae. High-performance Liquid Chromatographic analysis was used to monitor and identify the metabolites in each crude extract. Agar well diffusion was used to assay the antimicrobial activities of each crude extract against selected isolates of vancomycin and oxacillin resistant-Staphylococcus aureus, Multidrug resistant-Pseudomonas aeruginosa, Candida albicans, and Dermatophytes. The induced secondary metabolites identified included Protocatechuic acid scopularide. None of these compounds were hitherto produced by the uninduced (wild type) L. theobromae strain when cultured under normal laboratory conditions. The resultant extracts demonstrated good microbial inhibitory activities and MIC which ranged between 2 to 8 mm and 31 to 500 µg / mL respectively. The broad-spectrum activities may be due to the presence of the glucose-induced structurally diverse secondary metabolites produced by L. theobromae.