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. 2010 Aug;48(5):775-9.
doi: 10.3109/13693780903451810.

Paramecium species ingest and kill the cells of the human pathogenic fungus Cryptococcus neoformans

Shalom Z Frager  1 , Cara J Chrisman, Rachel Shakked, Arturo Casadevall
Affiliations

Paramecium species ingest and kill the cells of the human pathogenic fungus Cryptococcus neoformans

Shalom Z Frager et al. Med Mycol. 2010 Aug.

Abstract

A fundamental question in the field of medical mycology is the origin of virulence in those fungal pathogens acquired directly from the environment. In recent years, it was proposed that the virulence of certain environmental animal-pathogenic microbes, such as Cryptococcus neoformans, originated from selection pressures caused by species-specific predation. In this study, we analyzed the interaction of C. neoformans with three Paramecium spp., all of which are ciliated mobile protists. In contrast to the interaction with amoebae, some Paramecium spp. rapidly ingested C. neoformans and killed the fungus. This study establishes yet another type of protist-fungal interaction supporting the notion that animal-pathogenic fungi in the environment are under constant selection by predation.

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Figures

Fig. 1
Fig. 1
Incubation of Paramecium spp. with Cryptococcus neoformans strains 24067 and H99 results in the ingestion of fungal cells. (A) Light microscopy, 400× magnification. (C) Corresponding fluorescence microscopy showing 1% Uvitex 2B labeled 24067. (B) Merged light and fluorescent microscopy images showing 24067 present within P. mulitmicronucleatum (arrow). (D) Transmission electron micrograph of H99 infected Paramecium tetraurelia (arrow). 2000× magnification, V=vacuole. (E) Magnified view of image (D). After a 2 h incubation, P. tetraurelia begins to digest C. neoformans in a membrane-bound food vacuole. 5000× magnification, Cn=C. neoformans, M=mitochondria. (A–C) Bar=10 μm. (D) Bar=2 μm. (E) Bar=1 μm.
Fig. 2
Fig. 2
Twenty-four hour incubation of Cryptococcus neoformans strains H99, 24067 and NIH 112 with Paramecium tetraurelia, P. mulitmicronucleatum, and P. aurelia. The histograms show average CFU+95% CI at time 0 and 24 h (A) Incubation of C. neoformans strains with P. tetraurelia. (B) Incubation of C. neoformans strains with P. multimicronucleatum. (C) Incubation of C. neoformans strains with P. aurelia. A plus (+) sign indicates the presence of a Paramecium species, whereas a minus (−) sign indicates the absence of a Paramecium sp.s. *indicates statistical significance (P < 0.05). Numbers in parenthesis denote the P-value when comparing the 24 h control group and 24 h experimental group. P-values were obtained using the Student's t-test.
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