Divalent metal cations potentiate the predatory capacity of amoeba forCryptococcus neoformans

Abstract

19Among the best studied interaction between soil phagocytic predators and a human pathogenic fungus 20 is that of Acanthamoeba castellanii and Cryptococcus neoformans. The experimental conditions used in 21 amoeba-fungal confrontation assays can have major effects on whether the fungus or the protozoan is 22 ascendant in the interaction. . Cations enhanced A. castellanii activity against C. 29 neoformans through enhanced phagocytosis, which is the major mechanism for amoeba to kill fungal 30 cells. We found no evidence that amoeba uses extracellular killing mechanisms in their interactions with 31 C. neoformans. In summary, the presence of Mg 2+ and Ca 2+ enhanced cell adhesion on surface and 32 motility of amoeba, thus increasing the chance for contact of C. neoformans and the frequency of 33 phagocytosis. Our findings imply that divalent cation concentration in soils could be an important 34 variable for whether amoeba can control C. neoformans in the environment. 35Importance. Grazing of soil organisms by phagocytic predators such as amoeba is thought to select for 36 traits that allow some of them to acquire the capacity for virulence in animals. Consequently, 37 knowledge about the interactions between amoeba and soil microbes, such as pathogenic fungi, is 38 important for understanding how virulence can emerge. We show that the interaction between 39 amoeba and the pathogenic fungus C. neoformans is influenced by the presence of magnesium and 40 calcium in the assay, which potentiate amoeba. The results may also have practical applications since 41 enriching soils with divalent cations may reduce C. neoformans numbers in contaminated soils. 42 peer-reviewed)

A hidden battle in the dirt: soil amoebae interactions withParacoccidioidesspp

“…However, our results are in accordance with previously published studies of fungal-amoeba interactions, in which A. castellanii was shown to efficiently use C. neoformans as a food source and was considered an important factor controlling fungi in the environment [35, 36]. More recently, Fu and Casadevall reported that divalent cations have the ability to increase amoeba survival and potentiate their fungal killing abilities [37]. Their work points to one of the factors that might influence the outcome of fungal-amoeba interaction assays.…”

Unravelling the interactions of the environmental hostAcanthamoeba castellaniiwith fungi through the recognition by mannose‐binding proteins

“…Fungal viability within Ac was compared with viability in axenic culture medium alone. PYG was elected as the medium for the best growth of amoeba during the interactions, and the presence of divalent cations has shown to potentiate the predatory capacity of Ac (Fu & Casadevall, ). Upon interaction with Ac for 2 hr and washes, interacting fungi viability was followed for 48 hr.…”

The different morphologies of yeast and filamentous fungi trigger distinct killing and feeding mechanisms in a fungivorous amoeba

“…Whether these interactions reflect actual prey–predator relationships between fungi and amoebae is currently not known, as even for A. castellanii killing of Cr. neoformans was found to vary depending on the experimental conditions (Fu and Casadevall, ). Mycophagy is well documented for several species across the Amoebozoa and eponymous for Protostelium mycophaga , the first isolated species from the genus Protostelium (Olive and Stoianovitch, ).…”