Discovering antimicrobial properties from Ganoderma applanatum & Lentinula edodes

Abstract

This project involves the exploration of antimicrobial effects for the fungi Ganoderma applanatum and Lentinula edodes against the Gram-negative bacteria, Pseudomonas aeruginosa. Under stress, the cell wall of this bacteria is stabilized by the polycationic amine spermidine. The synthesis of spermidine is regulated by the PA3553 and PA4774 genes, both of which are controlled by two distinct pathways. Previously prepared PA3553::lux and PA4774::lux mutant strains of P. aeruginosa, which were programmed to illuminate upon gene activation via cell wall damage, were used for this study. Gene expression (determined via luminescence) and growth (optical density) was recorded weekly on the Wallace Victor luminescence plate reader for eight weeks to determine the period of greatest cell wall damage by the fungi. Data suggested highest amount of damage at week four and week eight for G. applanatum and L. edodes, respectively. In comparison to the control, G. applanatum showed a 22 fold PA3553::lux induction and a five fold PA4774::lux induction at a 20%v/v concentration during week four. Similarly, on week eight of growth L. edodes induced the PA3553 pathway 116 times more than the control when it was added at a 20%v/v concentration. Additionally, the fungal supernatants were also treated with trypsin. Significant reduction in gene induction was observed for both species after the trypsin digestion, suggesting the role of peptides as potential antimicrobial agents in G. applanatum and L. edodes. Future experiments will involve supernatant fractionation via column chromatography, followed by more screenings with the mutants to specify the antimicrobial compounds.

* Indicates faculty mentor.