Antagonistic interactions between black fungi and the parasite Escovopsis spp

Abstract

Black fungi, also called dematiaceous, form a heterogenic group characterized by a dark pigmentation due to the presence of Dihydroxynaphthalene (DHN) melanin in their micelial wall, which protects them from environmental stress conditions, such as lack of nutrients and water, toxic substances and acid pH.These microorganisms are opportunistic pathogens of humans, and chromoblastomycosis is an example of disease that may be caused by various fungal etiological agents belonging to Chaetothyriales order. Apart from their association with plants, black fungi also interact with insects, as the association between the black yeast Phialophora and Attini tribe ants. Attini ants maintain a compulsory association with basidiomicetous fungi, which are cultivated as food source. Occasionally, the cultivation is parasitized by a specialized pathogen of the genus Escovopsis, which destroys the mutualistic fungus biomass and can lead the nest to total collapse. It is known that Attini ants' nests hold a large microbial diversity, although the interactions among these microorganisms have not yet been totally elucidated. Actinobacteria from the genus Pseudonocardia produce antibiotics that inhibit the growth of Escovopsis, protecting the nests. These bacteria can be found on the cuticle of Attini ants and indirectly protect these insects. However, the actinobacteria growth is apparently compromised by the presence of black fungi (related to the genus Phialophora) also present in the ants' cuticle, which can indirectly benefit the survival of the parasite Escovopsis.Therefore, it is evident that many aspects involving the microbial interactions in Attini ants' nests require more attention from researchers due to the potential that they hold regarding discoveries of new antimicrobial drugs and possible natural enemies that could act as biological control for these insects.Studies about black fungi diversity in the Attini ants' environment are scarce and this work is going to be the first one to analyze the interactions between black fungi and other microorganisms involved in the Attini ants' symbiosis, as the parasite Escovopsis.