Effects of Cocultivation of Lichenophilic Yeasts with Bacteria Escherichia coli and Staphylococcus aureus

Abstract— Lichens are complex systems, and the taxonomic structure of their microbial communities follows a number of patterns. Similar to bacteria, yeasts are integral components of the lichen symbioses. Their role in lichens is, however, presently unknown. Existence and nature of the interactions between yeasts and bacteria in lichens also remain unstudied. The goal of the present work was to assess in kinetic experiments the growth of eight yeast cultures previously isolated from lichens in the presence of two bacterial cultures, Escherichia coli and Staphylococcus aureus. Yeast growth was found to be suppressed in the presence of E. coli, while cocultivation with S. aureus did not result in antagonism. Assessment of two factors, the initial yeast population density and introduction of an additional carbon source (glucose), showed that adding an extra substrate to binary cultures with E. coli did not cause significant changes in their growth parameters. At the same time, initial concentration of yeast cells affected the parameters of growth kinetics in binary cultures. These data revealed relationships between the growth characteristics of the lichen-derived yeast cultures and the type of their bacterial partner. The effect of suppression of yeast growth activity after cultivation with bacteria was established.