Cellular plasticity of pathogenic fungi during infection

Abstract

A widespread trait amongst fungi is their ability to alter their morphology in response to environmental stimuli. The type and degree of alteration, which commonly includes changes in cell size and shape, can vary between strains and even between individual cells within genetically uniform populations, providing many levels of variation within species. As well as enhancing their ability to survive in different environmental niches, this variation plays an important role in the ability of human fungal pathogens to survive and cause disease in the host. Some well-known examples are the thermally dimorphic fungi, which grow as moulds at 22 °C-25 °C in the soil and covert into yeasts at 37 °C when in a mammalian host [1]. Some fungi, rather than switching between 2 distinct forms in different niches, produce a variety of forms in the host that appear to have roles in the infection process. This phenomenon has not been as extensively studied as thermal dimorphism but may be important for understanding disease progression and outcome. Here, we review selected examples of pathogenic fungi that produce distinct morphological forms when living in and on host tissues that may be linked to infection and virulence. Two genera, Candida and Malassezia, are highly adapted to the commensal lifestyle and can also become pathogenic, and 2 others, Coccidioides and Cryptococcus, have environmental components to their life cycle but show evidence of adaptation to life inside a host.