Candida Infection Biology – fungal armoury, battlefields ... - FINSysB

Poster number: 06
Impact of non-fermentative growth on the C. albicans cell
wall and dynamic responses to osmotic stress
Iuliana V. Ene, Alistair J. P. Brown
Aberdeen Fungal Group, School of Medical Sciences, University of Aberdeen, Foresterhill,
Aberdeen AB25 2ZD, UK
Candida albicans displays considerable metabolic flexibility and robust stress
responses in vivo. Both contribute to the virulence of this pathogen. C. albicans
assimilates both fermentative and non-fermentative carbon sources in vivo, often
occupying poor glucose niches in its mammalian host. We reasoned that changes
in carbon source might influence stress adaptation, but stress responses are
generally studied during growth on glucose.
We found that the C. albicans cell wall is extremely dynamic and susceptible to
variations in carbon source. Growth on lactate rather than glucose has a major
impact on cell wall structure and flexibility. Although the relative proportions of
chitin, -glucan and mannan are similar within the wall of lactate-grown cells, they
display increased porosity and decreased cell wall biomass. TEM confirmed major
differences in cell wall architecture, underlying the importance of the carbon source
in the cell biology of this pathogen. This in turn influences the responses of this
pathogen to stresses as these differences were reflected in the cell wall-related
phenotypes. Lactate-grown cells displayed higher resistance to Congo Red and
Calcofluor White and showed significantly increased resistance to various doses
of osmotic stress. This change was independent of Hog1 and Mkc1, but correlated
with large changes in cell volume following exposure to NaCl. Growth on lactate
also increased resistance to antifungals such as Caspofungin, Tunicamycin and
Amphotericin B, which is likely to have a major impact upon the behavior of C.
albicans during infection.
The impact of carbon source on stress and drug resistance was confirmed in other
pathogenic Candida species and for other carbon sources, resulting in variations
in resistance when compared to a glucose-grown control. Clearly carbon source
strongly influences cell wall architecture and the resistance of C. albicans to certain
stresses, which is likely to have a major impact on its in vivo behavior.
We are grateful to the European Commission for funding the FINSysB Marie Curie Initial
Training Network (PITN-GA-2008-214004).
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