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Possible relationship of morphogenesis in pathogenic fungus, Histoplasma capsulatum, to heat shock response

A M Lambowitz, G S Kobayashi, A Painter

    Nature
    |June 30, 1983
    PubMed

    Insights

    Histoplasma capsulatum

    Area of Science:

    • Medical Mycology
    • Fungal Pathogenesis
    • Cellular Biology

    Background:

    • Histoplasma capsulatum is a dimorphic fungus, existing as mycelia in soil and yeast in hosts.
    • The yeast phase is parasitic, making dimorphism crucial for pathogenicity.
    • Understanding factors influencing this transition is key to controlling H. capsulatum infections.

    Purpose of the Study:

    • To identify the triggering event for the mycelial-to-yeast transition in Histoplasma capsulatum.
    • To elucidate the biochemical and morphological changes associated with temperature-induced dimorphism.
    • To understand the role of cellular energy and respiration in fungal adaptation.

    Main Methods:

    • Inducing mycelial-to-yeast transition by shifting cultures from 25°C to 37°C.
    • Measuring intracellular ATP levels and assessing oxidative phosphorylation.
    • Analyzing respiration patterns in both mycelial and yeast phases at different temperatures.

    Main Results:

    • A rapid decline in intracellular ATP levels, caused by uncoupled oxidative phosphorylation, triggers the transition.
    • Respiration remains coupled at 37°C in the yeast phase, indicating adaptation.
    • Metabolic shifts, including changes in respiration and cysteine metabolism, accompany the morphological change.

    Conclusions:

    • The triggering event for H. capsulatum dimorphism is a drop in intracellular ATP due to oxidative phosphorylation uncoupling at higher temperatures.
    • The morphological transition can be viewed as a heat shock response followed by cellular adaptation.
    • This finding provides insights into controlling fungal pathogenicity by targeting energy metabolism.

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