User:Thejkhanna/Malassezia globosa

Background
Malassezia globosa is a species of basidiomycetous yeast, lipid-dependent fungus that grows in human skin, mucosa, and other warm-blooded animals [1] [2]. Malassezia globosa, and its related species, also grow in the oral cavity, gastrointestinal tract, respiratory tract, brain, and breast milk [1]. Compared to other Malassezia species, Malassezia globosa is found most frequently on the chest and arms in comparison to other areas on the human body. Malassezia globosa is also the most common species found in subjects over 50 years of age [3]. Malassezia globosa, in conjunction with Malassezia restricta, is thought to be the most predominant species in Asia, although this could also be the cause of differences in diagnostic methods used in Asia versus other regions of the world such as Europe [4]

The skin rash of tinea versicolor (pityriasis versicolor), seborrheic dermatitis, dandruff, sebopsoriasis and facial or scalp psoriasis, steroid acne, and some forms of facial atopic dermatitis are some diseases that have been linked specifically to Malassezia globosa [5].

Some common predisposing factors for the growth of Malassezia globosa are as follows: humidity, sweating (which contributes to the higher rates of pityriasis versicolor in tropical locations), oily skin, acne, treatment of acne with oral antibiotics, immunodeficiency, systemic corticosteroids, or immunosuppression caused by medication [5].

Cause of dandruff and dermatitis
In 2007, it was discovered that the responsible agent is a scalp specific fungus, Malassezia globosa (previously thought to be Malassezia furfur), that metabolizes triglycerides present in sebum by the expression of lipase, resulting in a lipid byproduct: oleic acid.

Identification of Malassezia on skin has been aided by the application of molecular or DNA-based techniques. These investigations show that the Malassezia species causing most skin disease in humans, including the most common cause of dandruff and seborrhoeic dermatitis, is M. globosa (though M. restricta is also involved). The skin rash of tinea versicolor (pityriasis versicolor) is also due to infection by this fungus.

As the fungus requires fat to grow, it is most common in areas with many sebaceous glands: on the scalp, face, and upper part of the body. When the fungus grows too rapidly, the natural renewal of cells is disturbed, and dandruff appears with itching (a similar process may also occur with other fungi or bacteria).

A project in 2007 has sequenced the genome of dandruff-causing Malassezia globosa and found it to have 4,285 genes. M. globosa uses eight different types of lipase, along with three phospholipases, to break down the oils on the scalp. Any of these 11 proteins would be a suitable target for dandruff medications.

Through this research on the Malassezia globosa genome new methods of treatment for dandruff and dermatitis have become visible. The Malassezia globosa genome is 9 Mb, the smallest genome of any known free-living fungi, and encodes for glycolysis, the tricarboxylic acid cycle, synthesis of all 20 amino acids and the five nucleic acid bases. The Malassezia globosa genome lacks the encoding data for a fatty acid synthase, which contributes to the need for Malassezia species to feed on fatty acids [6]. Furthermore, complete knowledge of the Malassezia globosa genome lends itself to epidemiological studies, kinetics knowledge of the colonization-to-infection process, and studies of the broader genotype’s susceptibility to antifungal therapies [7].

The number of specimens of M. globosa on a human head can be up to ten million.

Malassezia globosa has been predicted to have the ability to reproduce sexually, but this has not been observed.

Treatment of Malassezia globosa
While Malassezia species are affected by a large variety of antifungal medications, Malassezia globosa has specific tolerances and susceptibilities to specific therapies. For example, fluconazole is inactive against Malassezia globosa whereas itraconazole is highly effective [3]. Recent studies have also found that the use of pyrithione shampoo treatment on skin commensal Malassezia, including Malassezia globosa, is an efficacious treatment for dandruff by inhibiting Malassezia growth [8].