Species: Malassezia globosa
Description and Significance
M. globosa is a unicellular fungus species. It has the typical spherical shape associated with yeast spores. The spores are typically around 2 micrometers in diameter. The species naturally exhibits a cream/yellow color and a venose and furrowed appearance. A colony of M. globosa typically has a butyrous texture. In addition, this microbial species exhibits monopolar and sympodial budding. It is most known for causing dandruff in humans. A picture of M. globosa can be found here.
M. globosa’s genome contains 4,286 genes. Its total genome size is 8.9 Mb, which is relatively small for a free-living fungus. It has 6,377 exons and 2,092 introns. There are approximately 6.2 Mbp of nucleotides in the exons. This genome also includes mating genes, indicating the possibility of sexual reproduction for the species, although this is not typically observed. Interestingly, the genome does not encode the enzyme fatty acid synthase, even though the organism is dependent upon lipids for growth and survival. However, it does encode secreted lipases to break down external lipids. It also encodes the necessary enzymes for glycolysis, the Krebs cycle, the pentose phosphate pathway, and the synthesis of the typical amino acid and nucleic acid “building blocks.”
Cell Structure, Metabolism and Life Cycle
M. globosa has the typical features and organelles of a eukaryotic cell (nucleus, endoplasmic reticulum, cell membrane, etc.). This species, like many of its close Malassezia relatives, is dependent upon lipids for growth. However, because it is unable to synthesize lipids, it must acquire them from host organisms. It uses secreted lipases in order to break down the lipids it acquires from its host. It gains energy through aerobic respiration. In addition, it reproduces through asexual budding.
Ecology and Known Roles in Symbiosis
M. globosa have been found in a wide variety of habitats. They were first found on the surfaces of essentially all mammals and were presumed to live exclusively in the niche of the skin of warm-blooded animals. However, in recent years they have been found on a much wider variety of animals, including marine animals such as corals and sponges. They have been found in habitats ranging from warm tropical areas to soil in Antarctica. M. globosa is known to live on the skin of animals because it needs the lipids from the host to grow and survive. Therefore, it is most frequently found on more “oily” areas of the body.
M. globosa is most known for causing dandruff, which affects approximately 50% of the population at some point in their lifetime. Interestingly, much of the research on this species has been funded by Proctor & Gamble, makers of Head & Shoulders anti-dandruff shampoo.The symptoms of dandruff include dry, flaky skin on the scalp, along with redness and irritation. These symptoms are most likely the result of the non-metabolized oleic acid byproduct of the M. globosa lipase breaking down lipids from the skin surface. Human skin can react to the oleic acid by producing more skin cells, causing dead cells to “flake” off. Interestingly, it does not appear that people with dandruff have higher levels of the pathogen, but instead have different sensitivities to its metabolic byproducts. This condition is treated efficiently with antifungal shampoos and creams. M. globosa has also been implicated in other skin conditions, such as sweat allergy. It releases MGL_1304, a 17-kDa protein that acts as an antigen for the release of high levels of histamine. It also plays a role, along with other species of Malassezia, in pityriasis versicolor and atopic eczema.
2. Dawson, Thomas L. "Malassezia Globosa and Restricta: Breakthrough Understanding of the Etiology and Treatment of Dandruff and Seborrheic Dermatitis through Whole-Genome Analysis." Journal of Investigative Dermatology Symposium Proceedings, vol. 12, no. 2, 2007, pp. 15-19.
4. Gordon James, A., et al. "Metabolic Analysis of the Cutaneous Fungi Malassezia Globosa and M. restricta for Insights on Scalp Condition and Dandruff." International Journal of Cosmetic Science, vol. 35, no. 2, 2013, pp. 169-175.
6. Saunders, Charles W., Annika Scheynius, and Joseph Heitman. "Malassezia Fungi are Specialized to Live on Skin and Associated with Dandruff, Eczema, and Other Skin Diseases." PLoS Pathogens, vol. 8, no. 6, 2012, pp. e1002701.
9. Xu, Jun, et al. "Dandruff-Associated Malassezia Genomes Reveal Convergent and Divergent Virulence Traits Shared with Plant and Human Fungal Pathogens." Proceedings of the National Academy of Sciences of the United States of America, vol. 104, no. 47, 2007, pp. 18730-18735.
This page was authored by Nikki Sullivan, a student of Dr. Erik Hom at the University of Mississippi.