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Cryptococcus neoformans: pseudohyphal forms surviving culture with Acanthamoeba polyphaga
Abstract:
During experiments on the gastrointestinal tract as a possible portal of entry for Cryptococcus neoformans, we occasionally observed the free-living amoeba, Acanthamoeba polyphaga, growing in the presence of C. neoformans cultured from mouse feces. Examination of the amoebic trophozoites revealed that they were engorged with yeast cells. Over a period of 2 to 3 weeks of incubation, the amoebae apparently killed most of the yeast cells. Some of the surviving C. neoformans cells formed atypical colonies which contained pseudohyphae. Seven other strains have since been cultured with this amoeba. Pseudohyphal forms were found among the surviving colonies in all strains tested. Virulence studies were performed on one randomly selected pseudohyphal isolate from each of the eight strains of C. neoformans. Pseudohyphal isolates from seven of the eight strains failed to kill mice 30 days after intracranial inoculation. The potential role of soil amoebae in the control of C. neoformans in nature is discussed.
Insights
Free-living amoebae, Acanthamoeba polyphaga, were observed to consume Cryptococcus neoformans. Surviving yeast developed into less virulent pseudohyphal forms, suggesting amoebae may control fungal populations in nature.
Area of Science:
- Microbiology
- Mycology
- Environmental Science
Background:
- Cryptococcus neoformans is a significant human pathogen.
- The gastrointestinal tract is a potential entry route for C. neoformans.
- The interaction between C. neoformans and environmental microorganisms is not fully understood.
Purpose of the Study:
- To investigate the interaction between Acanthamoeba polyphaga and Cryptococcus neoformans.
- To determine the effect of amoebic predation on C. neoformans morphology and virulence.
Main Methods:
- Co-culturing C. neoformans with Acanthamoeba polyphaga.
- Microscopic examination of amoebic trophozoites for yeast cells.
- Incubation and observation of surviving C. neoformans for morphological changes.
- Virulence studies of C. neoformans isolates in mice after intracranial inoculation.
Main Results:
- Acanthamoeba polyphaga ingested and killed a significant number of Cryptococcus neoformans cells.
- Surviving C. neoformans developed atypical pseudohyphal forms.
- Pseudohyphal isolates from seven of eight strains showed reduced virulence in mice.
- Amoebic predation led to the emergence of less virulent C. neoformans strains.
Conclusions:
- Acanthamoeba polyphaga can significantly reduce C. neoformans populations.
- Amoebic interaction induces morphological changes in C. neoformans, leading to decreased virulence.
- Soil amoebae may play a role in regulating environmental C. neoformans populations.