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Virulence determinants of the human pathogenic fungus A spergillus fumigatus protect against soil amoeba predation
Author(s) -
Hillmann Falk,
Novohradská Silvia,
Mattern Derek J.,
Forberger Tilmann,
Heinekamp Thorsten,
Westermann Martin,
Winckler Thomas,
Brakhage Axel A.
Publication year - 2015
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12808
Subject(s) - biology , microbiology and biotechnology , virulence , dictyostelium discoideum , amoeba (genus) , conidium , conidiation , appressorium , fungus , aspergillus fumigatus , innate immune system , secretion , fungal protein , phagocytosis , gliotoxin , hypha , immune system , botany , mutant , immunology , gene , biochemistry
Summary Filamentous fungi represent classical examples for environmentally acquired human pathogens whose major virulence mechanisms are likely to have emerged long before the appearance of innate immune systems. In natural habitats, amoeba predation could impose a major selection pressure towards the acquisition of virulence attributes. To test this hypothesis, we exploited the amoeba Dictyostelium discoideum to study its interaction with A spergillus fumigatus , two abundant soil inhabitants for which we found co‐occurrence in various sites. Fungal conidia were efficiently taken up by D . discoideum , but ingestion was higher when conidia were devoid of the green fungal spore pigment dihydroxynaphtalene melanin, in line with earlier results obtained for immune cells. Conidia were able to survive phagocytic processing, and intracellular germination was initiated only after several hours of co‐incubation which eventually led to a lethal disruption of the host cell. Besides phagocytic interactions, both amoeba and fungus secreted cross inhibitory factors which suppressed fungal growth or induced amoeba aggregation with subsequent cell lysis, respectively. On the fungal side, we identified gliotoxin as the major fungal factor killing D ictyostelium , supporting the idea that major virulence attributes, such as escape from phagocytosis and the secretion of mycotoxins are beneficial to escape from environmental predators.