Wood-decay fungus
Encyclopedia
A wood-decay fungus is a variety of fungus
that digests moist wood
, causing it to rot
. Some wood-decay fungi attack dead wood, such as brown rot, and some, such as Armillaria (Honey fungus), are parasitic and colonize living trees. Fungi that not only grow on wood but actually cause it to decay, are called lignicolous fungi. They do not necessarily need to decay lignin
in the wood to be termed lignicolous.
Wood-decay fungi can be classified according to the type of decay that they cause: brown rot, soft rot, and white rot.
and cellulose
. Cellulose is broken down by hydrogen peroxide
(H2O2) that is produced during the break-down of hemicellulose. Because hydrogen peroxide is a small molecule, it can diffuse rapidly through the wood, leading to a decay that is not confined to the direct surroundings of the fungal hypha
e. As a result of this type of decay, the wood shrinks, shows a brown discoloration, and cracks into roughly cubical pieces; hence the name brown rot or cubical brown rot.
Brown rot in a dry crumbly condition is sometimes incorrectly referred to as dry rot in general. The term brown rot replaced the general use of the term dry rot, as wood must be damp to decay, although it may become dry later. Dry rot
is actually a generic name for certain species of brown-rot fungus that have water-conducting strands capable of carrying water (usually from soil) that enable it to decay normally dry wood. It is also called true dry rot.
Brown-rot fungi of particular economic importance include Serpula lacrymans
(true dry rot), Fibroporia vaillantii
(mine fungus), and Coniophora puteana (cellar fungus), which may attack timber in buildings. Other brown-rot fungi include the sulfur shelf
, Phaeolus schweinitzii
, and Fomitopsis pinicola
.
from their hypha
e, an enzyme
that breaks down cellulose
in the wood. This leads to the formation of microscopic cavities inside the wood, and sometimes to a discoloration and cracking pattern similar to brown rot. Soft-rot fungi need fixed nitrogen in order to synthesize enzymes, which they obtain either from the wood or from the environment.
Examples of soft-rot-causing fungi are Chaetomium
, Ceratocystis
, and Kretzschmaria deusta
.
in wood, leaving the lighter-colored cellulose behind; some of them break down both lignin and cellulose. Because white-rot fungi are able to produce enzymes, such as laccase
, needed to break down lignin and other complex organic molecules, they have been investigated for use in mycoremediation
applications.
Honey mushroom (Armillaria ssp.) is a white-rot fungus notorious for attacking living trees. Pleurotus ostreatus and other oyster mushroom
s are commonly cultivated white-rot fungi. Other white-rot fungi include the turkey tail
, artist's conk
, and tinder fungus
.
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
that digests moist wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
, causing it to rot
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...
. Some wood-decay fungi attack dead wood, such as brown rot, and some, such as Armillaria (Honey fungus), are parasitic and colonize living trees. Fungi that not only grow on wood but actually cause it to decay, are called lignicolous fungi. They do not necessarily need to decay lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
in the wood to be termed lignicolous.
Wood-decay fungi can be classified according to the type of decay that they cause: brown rot, soft rot, and white rot.
Brown rot
Brown-rot fungi break down hemicelluloseHemicellulose
A hemicellulose is any of several heteropolymers , such as arabinoxylans, present along with cellulose in almost all plant cell walls. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength...
and cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
. Cellulose is broken down by hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
(H2O2) that is produced during the break-down of hemicellulose. Because hydrogen peroxide is a small molecule, it can diffuse rapidly through the wood, leading to a decay that is not confined to the direct surroundings of the fungal hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e. As a result of this type of decay, the wood shrinks, shows a brown discoloration, and cracks into roughly cubical pieces; hence the name brown rot or cubical brown rot.
Brown rot in a dry crumbly condition is sometimes incorrectly referred to as dry rot in general. The term brown rot replaced the general use of the term dry rot, as wood must be damp to decay, although it may become dry later. Dry rot
Dry rot
Dry rot refers to a type of wood decay caused by certain types of fungi, also known as True Dry Rot, that digests parts of the wood which give the wood strength and stiffness...
is actually a generic name for certain species of brown-rot fungus that have water-conducting strands capable of carrying water (usually from soil) that enable it to decay normally dry wood. It is also called true dry rot.
Brown-rot fungi of particular economic importance include Serpula lacrymans
Serpula lacrymans
Serpula lacrymans is one of the fungi that are responsible for dry rot. It is a basidiomycete in the order Boletales.-Taxonomy:The species was first described under the name Boletus lacrymans by Franz Xavier von Wulfen in 1781...
(true dry rot), Fibroporia vaillantii
Fibroporia vaillantii
Fibroporia vaillantii, also known as mine fungus, white pore fungus, Antrodia vaillantii, Polyporus vaillantii, and various other names is a wood-decaying fungus which can occur on timber in humid conditions...
(mine fungus), and Coniophora puteana (cellar fungus), which may attack timber in buildings. Other brown-rot fungi include the sulfur shelf
Laetiporus sulphureus
Laetiporus sulphureus is a species of bracket fungus found in Europe and North America. Its common names are sulphur polypore, sulphur shelf, and chicken mushroom. Its fruit bodies grow as striking golden-yellow shelf-like structures on tree trunks and branches...
, Phaeolus schweinitzii
Phaeolus schweinitzii
Phaeolus schweinitzii, commonly known as velvet-top fungus, dyer's polypore,Norway Chicken, or dyer's mazegill, is a fungal plant pathogen that causes butt rot on conifers such as Douglas-fir, spruce, fir, hemlock, pine, and larch. P...
, and Fomitopsis pinicola
Fomitopsis pinicola
Fomitopsis pinicola, in English sometimes known as Red Banded Polypore, is a polypore mushroom of the genus Fomitopsis. The species is common throughout the temperate Northern hemisphere. An alternative binomial name is Fomes pinicola....
.
Soft rot
Soft-rot fungi secrete cellulaseCellulase
400px|thumb|right|alt = Colored dice with checkered background|Ribbon representation of the Streptomyces lividans beta-1,4-endoglucanase catalytic domain - an example from the family 12 glycoside hydrolases...
from their hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e, an enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
that breaks down cellulose
Cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....
in the wood. This leads to the formation of microscopic cavities inside the wood, and sometimes to a discoloration and cracking pattern similar to brown rot. Soft-rot fungi need fixed nitrogen in order to synthesize enzymes, which they obtain either from the wood or from the environment.
Examples of soft-rot-causing fungi are Chaetomium
Chaetomium
Chaetomium is a genus of fungi in the Chaetomiaceae family. It is a dematiaceous mold normally found in soil, air, and plant debris. According to the Dictionary of the Fungi , there are about 95 species in the widespread genus.As well as being a contaminant, Chaetomium spp. are also encountered as...
, Ceratocystis
Ceratocystis
Ceratocystis is a genus of fungi within the Ceratocystidaceae family.-Species:*Ceratocystis acericola*Ceratocystis acoma*Ceratocystis adiposa*Ceratocystis aequivaginata*Ceratocystis albida*Ceratocystis albofundus...
, and Kretzschmaria deusta
Kretzschmaria deusta
Kretzschmaria deusta, commonly known as brittle cinder, is a fungus and plant pathogen found in temperate regions of the Northern Hemisphere. It is common on a wide range of broadleaved trees including beech , oak , lime , and maple...
.
White rot
White-rot fungi break down the ligninLignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
in wood, leaving the lighter-colored cellulose behind; some of them break down both lignin and cellulose. Because white-rot fungi are able to produce enzymes, such as laccase
Laccase
Laccases are copper-containing oxidase enzymes that are found in many plants, fungi, and microorganisms. The copper is bound in several sites; Type 1, Type 2, and/or Type 3. The ensemble of types 2 and 3 copper is called a trinuclear cluster . Type 1 copper is available to action of solvents,...
, needed to break down lignin and other complex organic molecules, they have been investigated for use in mycoremediation
Mycoremediation
Mycoremediation, a phrase coined by Paul Stamets, is a form of bioremediation, the process of using fungi to degrade or sequester contaminants in the environment. Stimulating microbial and enzyme activity, mycelium reduces toxins in-situ...
applications.
Honey mushroom (Armillaria ssp.) is a white-rot fungus notorious for attacking living trees. Pleurotus ostreatus and other oyster mushroom
Oyster mushroom
Pleurotus ostreatus, the oyster mushroom, is a common edible mushroom. It was first cultivated in Germany as a subsistence measure during World War I and is now grown commercially around the world for food. However, the first documented cultivation was by Kaufert There is some question about the...
s are commonly cultivated white-rot fungi. Other white-rot fungi include the turkey tail
Trametes versicolor
Trametes versicolor — formerly known as Coriolus versicolor and Polyporus versicolor — is an extremely common polypore mushroom which can be found throughout the world. Versicolor means 'of several colours' and it is true that this mushroom is found in a wide variety of different colours. T...
, artist's conk
Ganoderma applanatum
Ganoderma applanatum is a bracket fungus with a cosmopolitan distribution.The spore bodies are up to 30-40 cm across, hard, woody-textured, and...
, and tinder fungus
Fomes fomentarius
Fomes fomentarius is a species of fungal plant pathogen found in Europe, Asia, Africa and North America...
.