Bioluminescence in Fungi


What is Bioluminescence?

The current paper main focus is on bioluminescent Fungi but the basic features
of bioluminescence discussed are common to all bioluminescent organisms.
Bioluminescence is simply light created by living organisms. Probably the most
commonly known example of bioluminescence by North Americans is the firefly,
which lights its abdomen during its mating season to communicate with potential
mates. This bioluminescent ability occurs in 25 different phyla many of which
are totally unrelated and diverse with the phylum Fungi included in this list
(an illustration of a bioluminescent fungi is displayed in figure 1). One of the
features of biological light that distinguishes it from other forms of light is
that it is cold light. Unlike the light of a candle, a lightbulb, bioluminescent
light is produced with very little heat radiation. This aspect of
bioluminescence especially interested early scientists who explored it. The
light is the result of a biochemical reaction in which the oxidation of a
compound called "Luciferin" and the reaction was catalyzed by an enzyme called
"Luciferase". The light generated by this biochemical reaction has been
utilized by scientists as a bioindicator for Tuberculosis as well as heavy
metals. On going research involving bioluminescence is currently underway in
the areas of evolution, ecology, histology, physiology, biochemistry, and
biomedical applications.

History of Bioluminescent Fungi
The light of luminous wood was first noted in the early writings of
Aristotle which occurred in 382 B.C.(Johnson and Yata 1966 and Newton 1952) The
next mention of luminous wood in the literature occurred in 1667 by Robert
Boyle who noticed glowing earth and noted that heat was absent from the light.
Many early scientists such as Conrad Gesner, Francis Bacon, and Thomas Bartolin
all observed and made notation of luminous earth(Johnson and Yata 1966 and
Newton 1952 ). These early observers thought that the light was due to small
insects or animal interactions. The first mention that the light of luminous
wood was due to fungi occurred from a study of luminous timbers used as supports
in mines by Bishoff in 1823. This opened the way for further study by many other
scientists and by 1855 modern experimental work began by Fabre ( Newton 1952).
Fabre established the basic parameters of bioluminescent fungi, those being:

- The light without heat - The light ceased in a vacuum, in hydrogen, and
carbon dioxide - The light was independent of humidity, temperature, light,
and did not burn any
brighter in pure oxygen

The work by Herring (1978) found that the luminescent parts of the included
pileus(cap), hymenium(gills) and the mycelial threads in combination or
separately(figure 2) also the individual spores were also seen to be luminescent.
Herring also stated that if the fruiting body (mushroom) was bioluminescent
then the mycelial threads were always luminescent as well but not vice versa.
From the 1850ís to the early part of the 20th century the
identification of the majority of fungal species exhibiting bioluminescent
traits was completed. The research of bioluminescent fungi stagnated from the
1920ís till 1950ís (Newton 1952 and Herring 1978 ). After which extensive
research began involving the mechanisms of bioluminescence and is still carried
out to the present.

The Process of Bioluminescence

Bioluminescence results because of a certain Biochemical reaction. This can be
described as a chemiluminescent reaction which involves a direct conversion of
chemical energy transformed to light energy( Burr 1985, Patel 1997 and
Herring1978). The reaction involves the following elements:

- Enzymes (Luciferase) - biological catalysts that accelerate and control the
rate of chemical reactions in cells. - Photons - packs of light energy. - ATP -
adenosine triphosphate, the energy storing molecule of all living organisms. -
Substrate (Luciferin) - a specific molecule that undergoes a chemical charge
when affixed by an enzyme. - Oxygen - as a catalyst

A simplified formula of the bioluminescent reaction:

ATP(energy) + Luciferin (substrate)+ Luciferase(enzyme) + O2(oxidizer) ==
== light (protons)

The bioluminescent reaction occurs in two basic stages:

1) The reaction involves a substrate (D-Luciferin), combining with ATP, and
oxygen which is controlled by the enzyme(Luciferase). Luciferins and Luciferase
differ chemically in different organisms but they all require molecular energy
(ATP) for the reaction. 2) The chemical energy in stage one excites a specific
molecule (The Luminescent Molecule: the combining of Luciferase and Luciferin).
The excitement is caused by the increased energy level of the luminescent
molecule. The result of this excitement is decay which is manifested in the form
of photon emissions, which produces the light. The light given off does not
depend on light or other energy taken in by the organism and is just the
byproduct of the chemical reaction and is therefore cold light. The