User:Rachel Oakes- Malassezia Globosa

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Revision as of 05:10, 29 January 2020 by Rloakes (talk | contribs) (Classification)
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Classification

Phylum: Basidiomycota
  • Class: Hymenomycetes
    • Order: Tremellales
      • Family: Filobasidiaceae
        • Genus: Malassezia
          • Species: Globosa
[Others may be used. Use NCBI link to find]

Description and Significance

Malassezia globosa is typically found in human skin and is known to cause dandruff. M. globosa thrives in the human scalp since it requires lots of lipid as a carbon source, so sebum satisfies the fungus. Usually, the fungus looks like small islands, with a greenish appearance and separated groups of the microbe. [] If it acts as dermatitis, it will appear as small white patchy flakes on the human scalp or small, light, discolored patches on the skin as tinea versicolor. Studying the chemistry and genome of M. Globosa is important to understand the stronger treatment for these fungal infections since M. Globosa is a common part of the skin flora. Malassezia globosa is also important because it is so common since it causes 50% of the world’s population to be affected by dermatitis and tinea versicolor.

Genome

The sequenced size of M. Globosa was 9 Mb. Twenty - seven percent of the genes were introns, which is a smaller percentage than most basidiomycete fungi. There are 9 chromosomes in the fungi and has 4,285 genes. The genome resembles the organization of a fungal polypeptide synthase. M. Globosa’s genome also codes for a lot of lipases, which shows the role of its’ genome to use fatty acids from other sources, with 6 phospholipases and 13 lipases encoded. This release of fatty acid occurs on the human scalp, where it typically resides. The genome when compared using DNA region sequences that revealed M. Globosa’s genome is most similar in sequence to a pathogen U. Maydis, despite the fact that U. Maydis prefers a plant leaf as its’ preferred host compared to the M. globosa’s human host. The genome is very small and is considered one of the smallest genomes of free-living fungi.

Cell Structure, Metabolism and Life Cycle

Through research published by PNAS, M. globosa is understood to partake in glycolysis, the glyoxylate cycle, pentose phosphate shunt, tricarboxylic acid cycle for metabolism. The fungus also synthesizes 20 Amino acids and 5 nucleic acids. It was previously believed that there was no possibility for globosa to perform metabolism properly because of the lack of a fatty acid synthase. Genome analysis released a synthase to exist, but have a different function, as a polyketide synthase. M. globosa was found to have two forms, an SMG1 and LIP1 form. Researchers studied the SMG1 model of the fungus and saw that two bulky hydrophobic residues are adjacent to catalytic and N- terminal of the lid. This could show that the hydrophobic residues cause steric hindrance with triacylglycerol binding for the lipase involved with M. globosa. [] The genome is haploid since polymorphisms within the genome were rare. No sexual cycles have been found for M. globosa or any of its sister groups. It is believed, however, that the fungus completes its sexual cycle while growing on human skin, due to the fact that its close relative, U. maydis does just that when growing on a plant. A mating-type locus was discovered when the genome of Malassezia globosa was studied.

Ecology and Known Roles in Symbiosis

This microbe is found in the vertebrate microbiome, specifically on the skin. When Malassezia globosa participates in symbiosis with humans, the fungus plays a commensal role, unless it is causing an infection, where it would act parasitically. Conditions associated with this symbiosis include seborrheic dermatitis (commonly known as dandruff) and pityriasis versicolor. Seborrheic dermatitis causes scalp flaking caused by the presence of M. globosa. Fatty acids like non-sebaceous lauric acid and sapienic acids can affect the microbiome of the scalp. Some of the etiology of how M. Globosa causes seborrheic dermatitis is unknown. Pityriasis versicolor is the disorder in where patches appear on the back and chest of humans that are discolored and flaky. Due to its abundance of lipase within the genome, Malassezia globosa can live on human skin and sometimes can cause an allergic reaction in humans due to dysfunctional skin barrier and genetics. Likewise, IgG and IgM antibodies are found in healthy humans with allergen reactions, since M. Globosa will be continually exposed to the skin.

Fun Facts

When compared in shotgun sequencing, the M. Globosa and M. restricta, another microbe associated with dandruff, shared all the same genomes except for three. Procter and Gamble, the parent company of Head and Shoulders, published the genomic results of the genome of Malassezia globosa in attempts to beat competitors by creating a better dandruff shampoo that works against the fungal infection. Dandruff is not contagious or infectious but can encourage the growth of fungus without treatment.

The microbe plays a role in a significant role in society as the fungus encourages research and marketing. Procter & Gamble working to better their products by sequence M. globosa’s genome benefits scientific research. This is because in some situations research will not be performed due to costs. M. globosa will also promote the marketing of hair products to consumers, due to the prevalence and concern of seborrheic dermatitis. Hopefully, companies like Procter and Gamble will continue striving to beat their competitors and fund more important scientific research into the widely unresearched kingdom of fungi.

References

[Sample reference] Bosch TCG, Guillemin K, McFall-Ngai M (2019) Evolutionary "Experiments" in Symbiosis: The Study of Model Animals Provides Insights into the Mechanisms Underlying the Diversity of Host-Microbe Interactions. BioEssays 41:1800256


Author

This page was written by Rachel Oakes as part of the 2020 UM Study USA led by Dr. Erik Hom at the University of Mississippi.