FUNGAL
TANNING
Summer is coming and the temptation is to pack one’s bag and head to the
beach to get a tan. Your skin cells produce melanin in order to protect you from
the sun’s UV rays. But melanin is not unique to humans, in fact there are fungi
that produce it.
Melanin also protects against other types of
environmental stress such as oxidizing agents and
ionizing radiation. In the case of fungi, melanin allows
their survival in extreme environments such as
deserts, the Antarctica, the most contaminated areas
of Chernobyl, or the hot interior of a dishwasher full of
detergent.
In the case of pathogenic fungi such as Cryptococcus
neoformans species complex, melanin is a virulence
factor. Melanin protects against oxidative factors, one of
the main weapons used by immune system cells. It has
also been observed to inhibit melanin-producing fungi
macrophage phagocytosis and even interfere with the
production of cytokines.
Biochemically speaking, melanin is an amorphous
polymer whose detailed chemical structure is
unknown. Fungi can synthesize it in two different
ways. Granules are biosynthesized in some
intracellular vesicles similar to mammalian
melanosomes and from there are transported to the
cell wall. Once outside, the melanin granules are
located on the cell wall, where they cross
polysaccharides covalently forming melanin. In yeast,
the synthesis is extracellular-producing vesicles which
are secreted into the cell wall where enzymes use an
exogenous source as a substrate to produce melanin.
Melanin produced by fungi can have an interesting
biotechnological application as well. Melanin protects
against ionizing radiation so it was decided to use a
species of melanogens fungi in bioremediation of areas
contaminated with radioactive elements. Since it has
also been found that melanin protects against the
action of toxic substances and can efficiently absorb
heavy metals, using bio-immobilization processes of
such elements.
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BIBLIOGRAPHY
EisenmanHC,&Casadevall A (2012). Synthesis and assembly of fungal
melanin. Appliedmicrobiology and biotechnology, 93 (3), 931-40 PMID: 22173481 Tel. +34 91 761 02 00
Fax +34 91 656 82 28