Endophytic Fungi from Cathranthus roseus: A Potential Resource for the Discovery of Antimicrobial Polyketides

Abstract

Endophytic fungi from the stems, roots, leaves and flowers of Catharanthus roseus were isolated using routine isolation methods, yielding 25 strains. The crude ethyl acetate extracts of endophyte culture broths were assayed for antimicrobial properties against seven bacterial and two fungal test strains. Thirteen strains producing antimicrobial compounds were taxonomically characterized by 18S rRNA gene sequencing. The majority of these fungi were distributed among the orders Pleosporales, Botryosphaeriales and Capnodiales (class Dothideomycetes). Degenerate PCR-based screening was used to target polyketide synthase (PKS) biosynthesis genes in these bioactive strains, resulting in detection of 12 PKS gene fragments from eight strains. The differential antimicrobial activities and unique PKS gene sequences detected in the isolates reflected the potential for these endophytes to produce a range of chemically diverse compounds. Also, this can prove to be another useful dereplication tool for natural product discovery.