Tom Volk's Fungus of the Month for November 2004

Trichoderma viride, the dark green parasitic mold and maker of fungal-digested jeans..         

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Trichoderma viride, dark green mold

Trichoderma is a very versatile mold: a nuisance for people, a useful fungus for industry and biocontrol, and a bane to other fungi.

Trichoderma viride is one of many species of mold. Most molds are innocuous saprophytes, living off of dead organic materials, although a number of them are plant pathogens. Remember that all molds are fungi, but not all fungi are molds. Some people argue that the correct spelling should be "mould," but I think this argument is not that interesting. You can read for a dissenting viewpoint. Can't we all just get along...?
(In truth, I recommend you read for lots of interesting and useful information on human-pathogenic fungi.)

dark green Trichoderma culture"Mold" is a name for any fungus that produces spores asexually, by mitosis. This is known as the anamorph state. Some of these molds are classified with the "deuteromycetes," a category reserved for fungi for which there is no known sexual state. However many molds are the asexual states of members of the Ascomycota, all of which have a known sexual (meiotic, teleomorph) state in which ascospores are produced internally in asci. In order for mycologists to change the classification of a fungus from the deuteromycetes to the Ascomycota, it's really just a matter of finding the sexual state and linking the two together. However, it's likely that many of these deuteromycetes completely lack a sexual state and have not had sex for many millennia. In addition many species for which we know the teleomorph probably lack a sexual state in nature, although they can be "forced" to have sex in the lab. It can get very confusing, especially when the anamorph and teleomorph have separate names! If you know the teleomorph name, that has precedence over the anamorph name. For example the anamorph Trichoderma usually has a teleomorph state Hypocrea. You can think about this in terms of a maiden name and a married name:. the maiden name (anamorph) is changed to the married name (teleomorph) when sex is "discovered." It can get very confusing at times, but it's easy once you get the hang of it. There are many kinds of molds, some of which have been Fungus of the Month, including Aspergillus, an important industrial and pathogenic mold, Penicillium chrysogenum, source of penicillin, and Stachybotrys chartarum, the alleged cause of "sick building syndrome."

Trichoderma growing on the fruiting body of the tooth fungus Hydnochaete The mycelium of Trichoderma can produce a wide variety of enzymes, including cellulases (degrading cellulose) and chitinases (degrading chitin) . Because of its cellulases, Trichoderma can grow directly on wood (shown above), which is primarily composed of cellulose, a polymer of glucose. Because of its chitinases, Trichoderma can be a parasite of other fungi. Remember that the cell walls of fungi are primarily composed of chitin, a polymer of n-acetyl-glucosamine. (Can you name the other major group of organisms that contain chitin?) In nature one can often find Trichoderma parasitizing the fruiting bodies and mycelia of other fungi, such as the fruiting body of Hydnochaete to the left. Trichoderma is a particular problem in the mushroom cultivation industry, where it can parasitize the mycelium and fruiting bodies of the fungus. This is known as green mold disease of mushrooms. When the mushroom is parasitized, it develops a green mold over the surface, making the mushroom ugly and deformed. When the mycelium is parasitized, the ability of the cultivated mushroom to grow is severely compromised because the mold saps it strength, benefiting from the hard work of the mushroom's exoenzymes to degrade the substrate. See this link at Penn State for more information on this disease and its impact on the mushroom industry.

However, this tenacity can be put to good use for us. Trichoderma also can be used as a biological control against plant pathogenic fungi. Trichoderma has shown promise against such plant pathogens as Rhizoctonia, Pythium, and even Armillaria. Even though its effectiveness and safety has yet to be proven, you can even buy Trichoderma inoculum!

rugged stone washed jeansSurprisingly, another industry that benefits from the enzymes of Trichoderma is the blue jean industry. You probably have heard of stone-washed jeans, or you may even own a pair or two. So you're probably thinking, "hmmmm, stone-washed jeans-- that must mean they hire little old ladies with babushkasTM to beat the jeans against the rocks in the nearby stream." In fact nothing could be farther from the truth. They dump the regular jeans into a large vat of water and add Trichoderma reesii cultures to the mix. The cellulases of the fungus partially (but irregularly) digest the cotton of the jeans, making them soft and appearing that they were washed using stones. In reality, "stone-washed jeans" should be called "fungal-digested jeans." Mycologists may be the only people who would buy jeans called by such a name. However, you probably know that it's all about the marketing. Interestingly, T. reesii was isolated from a decaying tent on the south Pacific island of Samoa. (Thanks to Gary Samuels for this information.)

There are actually several dozen Trichoderma species, most of which are rather difficult to distinguish from one another. Fortunately there is an excellent site at the National Fungus Collection in Beltsville, Maryland. In fact the whole website is devoted to Trichoderma. Congratulations and thanks to Gary Samuels, Priscila Chaverri, David Farr, & E.B. McCray .of the Systematic Botany & Mycology Laboratory, ARS, USDA, for "Trichoderma Online"

Mold Tech, a fine universityI hope you enjoyed learning something about the mold Trichoderma and how it is both beneficial and detrimental for humans. To learn more, maybe someday you can enroll at Mold Tech, as shown to the left. Anyway I hope this page will give you something to talk about the next time you see someone in "fungal-digested jeans."

If you have anything to add, or if you have corrections, comments, or recommendations for future FotM's (or maybe you'd like to be co-author of a FotM?), please write to me at

This page and other pages are © Copyright 2004 by Thomas J. Volk, University of Wisconsin-La Crosse.

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