Candida albicans (PLS 527)
Classification
Fungi; Dikarya; Ascomycota; saccharomyceta; Saccharomycotina; Pichiomycetes; Serinales; Debaryomycetaceae; Candida/Lodderomyces clade; Candida
Species
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NCBI: [1] |
Candida Albicans
Description and Significance
Candida albicans is a polymorphic fungus that commonly lives on human skin and in the human gut microbiome (1). It can also be an opportunistic pathogen, typically causing disease in already immunocompromised patients, such as those with HIV or AIDS. It is one of the most common causes of candidiasis. Hospital cases of candidiasis cause between 2,800 and 11,200 deaths per year in the United States. It is a common model organism for fungal pathogens. It has many morphological phenotypes that C. albicans can switch between spontaneously and due to environmental conditions (1, 2, 3) .
Life Cycle and Cell Structure
When grown in standard laboratory medium, C. albicans grows as a yeast. However, when grown in a medium that mimics the environment of a human host, it grows hyphae and pseudohyphae (3). Changes in environmental conditions, such as temperature, pH, and nutrient concentrations, can drive the shift from yeast growth to hyphal growth, but not always (2, 3). C. albicans can produce chlamydospores which can survive hot, dry conditions.
C. albicans can also undergo a type of morphological switching called white-opaque switching (2). The white phase consists of round cells that form smooth, white colonies while the opaque phase consists of rodlike cells that form flat, grey colonies (3). This shift is reversible, meaning 'C. albicans can switch back and forth between the two phases. There is also a third phase called the grey phase which is difficult to distinguish from the opaque phase and has the highest capacity to cause cutaneous infections.
Genome Structure
C. albicans has a haploid genome size of 16Mb in length and 28Mb in length for the diploid stage. It has 8 sets of chromosome pairs and over 6000 open reading frames, of which 65% are not characterized. The C. albicans genome is highly heterozygous which contributes to its genetic diversity and adaptability (4).
Many members of the genus Candida, including C. albicans, have an uncommon feature in their genetic code in that the CUG codon specifies serine instead of leucine (4). This makes studying C. albicans more difficult, as other model organisms do not have this feature.
Ecology and Pathogenesis
C. albicans is a species found around the world. It is known for causing infections in hospitals, especially in immunocompromised patients. Most often, these infections are superficial, infecting the mucous membranes of the mouth or vagina (1). Candidiasis can also affect the gastrointestinal tract. In severe cases, infections by C. albicans can become systemic. Once this occurs, the mortality rate of the infection is between 40 and 60%. C. albicans infect their hosts by growing hyphae or pseudohyphae that are able to penetrate the tissue of the host (1). Very few drugs treat candidiasis so hospitals primarily focus on prevention via hygiene and cleanliness (5).
References
Mayer, F. L., Wilson, D., & Hube, B. (2013). Candida albicans pathogenicity mechanisms. Virulence, 4(2), 119-128. Sudbery, P. E. (2011). Growth of Candida albicans hyphae. Nature Reviews Microbiology, 9(10), 737-748. https://doi.org/10.1038/nrmicro2636 Sudbery, P., Gow, N., & Berman, J. (2004). The distinct morphogenic states of Candida albicans. Trends in microbiology, 12(7), 317-324. Scherer, S., & Magee, P. T. (1990). Genetics of Candida albicans. Microbiological Reviews, 54(3), 226-241. Moudgal, V., & Sobel, J. (2010). Antifungals to treat Candida albicans. Expert opinion on pharmacotherapy, 11(12), 2037-2048.
Author
Page authored by Favianna Cubello, student of Dr. Marc Orbach, University of Arizona .
