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Secondary Metabolites of Fungi

1 Definitions
2 Introduction
3 Species types involved
4 Processes involved
5 History
6 References

Definitions

Primary metabolite: a metabolite synthesized in a step in primary metabolism (www.medilexicon.com)

Secondary metabolite: a metabolite synthesized in a step in secondary metabolism (www.medilexicon.com)

Primary metabolism: metabolic processes central to most cells, biosynthesis of macromolecules, energy production, turnover (www.medilexicon.com)

Secondary metabolism: metabolic processes in which substances (such as pigments, alkaloids, or terpenes) are only synthesized in certain types of tissues or cells or are only synthesized under certain conditions (www.medilexicon.com)

Intermediate: A metabolic intermediate is a sub product produced at a certain step in the pathway that is used at a later time in the same pathway or a different pathway (Moore et al 2011)

Transporter: A transporter is an molecule that binds to a substrate in order to move it to another location (Moore et al 2011)

Antibiotic: A soluble substance derived from a mold or bacterium that kills or inhibits the growth of other microorganisms (www.medilexicon.com)

Evolutionary advantage: having a trait/characteristic that competing species do not have that causes favoritism by selection (Bergstrom et al 2012)

Natural Pigment: A naturally occurring colored compound; absorbs light in the visible range of the electromagnetic spectrum (www.medilexicon.com)

Bacteriophage/phage:A virus with specific affinity for bacteria (www.medilexicon.com)

Introduction

Fungi produce two types of metabolites; those that are required for survival and those that are not required but have evolutionary advantages (Moore et al 2011). These are labeled primary metabolites and secondary metabolites and can occur at the same time using similar intermediates(Moore et al 2011). Secondary metabolites are often smaller molecules that are often present after food sources are depleted (Keller et al 2005 & Moore et al 2011). Few secondary metabolites are present during primary metabolism as additional transporters of intermediates, however many are bioactive(Keller et al 2005). Many secondary metabolites are used in medicine as antibiotics and industry (fungal biology 2004).

Species types involved

Pigments

Black or dark brown pigment in fungi is usually melanin or melanoprotein. In the Dematiaceae, both hyphae and conidia are heavily pigmented. Many Ascomycetes and imperfect fungi appear to produce melanin by the pentaketide pathway while Basidiomycetes employ a different route; special substrates are used for the phenoloxidase system that leads to the formation of melanin. Melanin is important for the resistance of damage from high environmental temperatures. A protective role in desiccation and irradiation has also been suggested, where melanin is deposited in the cell (Durán et al, 2002).

There are a variety of other pigments of fungi being studied for the use of natural dyes in foods (Durán et al, 2002).

Figure 1. Exidia glandulosa is a jelly fungus that has black pigmentation that usually grows on decaying wood.

Volatiles (odour)

Hey guys, I am going to complete this section on Volatiles. (This is Courtney)

Antibiotics

The ability of a fungus to produce antibiotics as a secondary metabolite allows for it to have an evolutionary advantage since it can inhibit the growth of competitors (Moore et al 2011).

Penicillin

Penicillin was the first broad spectra antibiotic to be identified (Keller et al 2005). It was first identified by Alexander Fleming in 1929 in the species Penicillium notatum(Díez et al 2001 & Keller et al 2005). However penicillin was not purified enough to fully determine its effects on microorganisms until 1939 (Díez et al 2001 & Keller et al 2005). Shortly after that methods for greater production were developed such as selecting for individuals with greater production of penicillin (Keller et al 2005). More recent methods of improving production include duplicating the genes that code for penicillin can using a phage to introduce them (Díez et al 2001).

Griseofulvin

Griseofulvin is an antifungal drug which is used both in animals and humans to treat fungal infections of the skin and nails and taken orally. The most common skin infection is the ringworm. It was first isolated from Penicillium griseofulvum in 1939.

The drug disrupts the mitotic spindle through interacting with polymerized microtubules where inhibiting the mitosis. The cells get resistant to fungal infections when it binds to keratin in keratin precursor cells. The drug reaches its site of action only when the hair or skin is replaced by the keratin griseofulvin complex. Then the drug will bind to fungal microtubules by entering the dermatophyte through energy dependent transport process. Therefore, the process of mitosis changes and the original information for deposition of fungal cell walls.

Griseofulvin can also be a potential treatment for cancer. They use an unusual mechanism to confirm the correct genetic material is present within each of the resulting tumor cells when cancer cells divide, undergo mitosis. The most common side effects are nausea, diarrhea, headache, skin eruptions and photosensitivity. Hepatotoxicity and neurological side effects hardly occur.

Immune-suppressants

Toxins

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Steroids

Processes involved

History

References

Atmosukarto I, Castillo U, Hess WM, Sears J, Strobel G. 2005.Isolation and characterization of Muscodor albus I-41.3s, a volatile antibiotic producing fungus. Plant Science 169 854-861

Bergstrom CT, Dugatkin LA. 2012. Evolution. New York: W. W. Norton & Company Inc.

Díez B, Marcos AT, Rodríguez M, de la Fuente JL, Barredo JL. 2001. Structural and Phylogenetic Analysis of the g-Actin Encoding Gene from the Penicillin-Producing Fungus Penicillium chrysogenum. Current Microbiology 42 117–121

Fungal Biology. 2004. University of Sydney: http://bugs.bio.usyd.edu.au/learning/resources/Mycology/Feeding/secndryMetabolites.shtml

Keller NP, Turner G, Bennett JW. 2005. Fungal Seconardy Metabolism - from Biochemistry to Genomics. Nature Reviews|Microbiology 3 937-947

Moore D, Robson G D, Trinci A P J. 2011. 21st Century Guidebook to Fungi . Cambridge UK: Cambridge University Press.

Durán, N., Teixeira, Maria., De Conti, R., Esposito, E. Ecological-friendly pigments from fungi. Critical Reviews in Food Science and Nutrition, 2002. 42:1, 53-66

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