Effect of Isolation Conditions on Diversity of Endolichenic Fungal Communities from a Foliose Lichen, Parmotrema tinctorum

Abstract

Endolichenic fungi (ELF) are emerging novel bioresources because their diverse secondary metabolites have a wide range of biological activities. Metagenomic analysis of lichen thalli demonstrated that the conventional isolation method of ELF covers a very limited range of ELF, and the development of an advanced isolation method is needed. The influence of four variables were investigated in this study to determine the suitable conditions for the isolation of more diverse ELF from a radially growing foliose lichen, Parmotrema tinctorum. Four variables were tested: age of the thallus, severity of surface-sterilization of the thallus, size of a thallus fragment for the inoculation, and nutrient requirement. In total, 104 species (1885 strains) of ELF were isolated from the five individual thalli of P. tinctorum collected at five different places. Most of the ELF isolates belong to Sordariomycetes. Because each part of lichen thallus (of different age) has unique ELF species, the whole thallus of the foliose lichen is needed to isolate diverse ELF. Moderate sterilization is appropriate for the isolation of diverse ELF. Inoculation of small fragment (1 mm2) of lichen thallus resulted in the isolation of highest diversity of ELF species compared to larger fragments (100 and 25 mm2). Moreover, ELF species isolated from the small thallus fragments covered all ELF taxa detected from the medium and the large fragments in this study. The use of two media—Bold’s basal medium (nutrient poor) and potato dextrose agar (nutrient rich)—supported the isolation of diverse ELF. Among the tested variables, size of thallus fragment more significantly influenced the isolation of diverse ELF than other three factors. Species composition and richness of ELF communities from different lichen thalli differed from each other in this study.