Influence of Culture Conditions on Metabolite Diversity in Epichloë sinensis Strains

Epichloë sinensis, associated with Festuca sinensis, exhibits rich morphological, genetic and functional diversity across different strains. To comprehensively evaluate the categories and difference in the secondary metabolites of different E. sinensis strains and thereby reveal the functional diversity, the present study analyzed the metabolites of mycelia collected from potato dextrose agar (PDA) and potato dextrose broth (PDB) cultures and fermentation broths of three different E. sinensis strains. These strains (ID1, 2, and 84C) were isolated from F. sinensis seeds collected from different locations. These three strains of E. sinensis produced a total of 1029 compounds categorized into 14 major classes in the mycelia and fermentation which included a wide range of compound structure and types, revealing E. sinensis possesses abundant metabolites. The different strains shared the similar types of metabolites which only varied in concentrations of some metabolites, indicating the similarity in metabolic function. However, types, quantity and concentrations of secondary metabolites varied in different conditions, suggesting the metabolites changed with environmental variations, as 135 unique compounds were only detected in mycelia from PDA (solid medium), while 205 exclusive metabolites were identified in PDB fermentation broth (liquid environment). Comparing metabolites of hyphae in PDA and PDB, there were a total of 100 different compounds. Comparing metabolites of hyphae in PDB and fermentation broth, there were 136 different compounds. These metabolites were mainly involved in the citrate cycle (TCA cycle) and alanine, aspartate, and glutamate metabolism.