Chaetomiaceae
The Chaetomiaceae are a family of fungi in the Ascomycota, order Sordariales, class Sordariomycetes. Chaetomiaceae are usually saprobic or parasitic. Cheatomiaceae are a great source of enzymes with diverse biotechnological and industrial applic ...
. It is able to decay in manufactured cellulosic materials, and is known to antagonize a wide range of soil microorganisms. This species is a component of the biocontrol agent, Ketomium, a commercial biofungicide. It has also been investigated for use in the production of natural dyes. ''Chaetomium cupreum'' is
mesophilic
A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from . The optimum growth temperature for these organisms is 37 °C (about 99 °F). The term is mainly applied ...
and known to occur in harsh environments and can rapidly colonize organic substrates in soil. Laboratory cultures of ''C. cupreum'' can be propagated on a range of common growth media including potato dextrose at ambient or higher than ambient temperature producing cottony white colonies with a reddish reverse.
History
''Chaetomium cupreum'' was described by Lawrence Marion Ames in 1949 as part of a military effort to identify the organisms responsible for the biodeterioration. During this project, Ames documented 9 novel ''Chaetomium'' species including the culture Ames described as ''C. cupreum'' which was sent to him by Paul Marsh of the U.S Department of Agriculture from deteriorating material collected in the
Panama Canal Zone
The Panama Canal Zone (), also known as just the Canal Zone, was a International zone#Concessions, concession of the United States located in the Isthmus of Panama that existed from 1903 to 1979. It consisted of the Panama Canal and an area gene ...
. Ames selected the species epithet "cupreum" based on the copper coloration of the pigments produced by the fungus. A second sample was obtained by G.W Martin in
Guadalcanal
Guadalcanal (; indigenous name: ''Isatabu'') is the principal island in Guadalcanal Province of Solomon Islands, located in the southwestern Pacific Ocean, northeast of Australia. It is the largest island in the Solomons by area and the second- ...
. Both strains were isolated from rotting clothing, tenting, mattresses and equipment.
Description
The cell wall of ''C. cupreum'' is largely composed of
chitin
Chitin (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cell ...
and
glucan
A glucan is a polysaccharide derived from D-glucose, linked by glycosidic bonds. Glucans are noted in two forms: alpha glucans and beta glucans. Many beta-glucans are medically important. They represent a drug target for antifungal medications of ...
, which is reflected in the large number of acquired genes encoding class V chitin synthase and glucan synthase found in the ''C. cupreum'' cDNA. The vegetative mycelium is profusely branched, septate and multicellular; the mycelial cells are
multinucleate
Multinucleate cells (also known as multinucleated cells or polynuclear cells) are eukaryotic cells that have more than one nucleus, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coordinate ...
. The species is distinguished from other ''Chaetomium'' species by a high frequency of boat-shaped
ascospores
In fungi, an ascospore is the sexual spore formed inside an ascus—the sac-like cell that defines the division Ascomycota, the largest and most diverse division of fungi. After two parental nuclei fuse, the ascus undergoes meiosis (halving of ...
and copper coloured terminal hairs. The fruiting bodies occur on the surface of the substratum and are attached by undifferentiated rhizoids. The perithecia of ''C. cupreum'' are ovate in shape and copper colored with dimensions of 110–120 x 120–130 μm. The presence of long, thin hairs on the outer surface of the perithecium is a characteristic feature of ''Chaetomium'' (Gr. ''χαίτη'' = long hair). In ''C. cupreum'', these hairs are numerous, thin, septate lateral hairs with a base 3.0–3.5 μm in diameter. Hairs at the apex of the perithecium are rigid, septate, 4.5–6.0 μm in diameter with 1–2 spirals. The apical hairs are covered with small copper coloured granules whose pigment is soluble in alcohol, ether, cellosolve, xylol but insoluble in water. Club-shaped asci measuring 38 × 13 μm develop in clusters n the interior, basal part of the perithecium. Each ascus contains 8 reddish ascospores that are boat shaped with dimensions of 10.0 × 5.5μm. The walls of the asci are mucilaginous and disintegrate, causing the ascospores to remain inside the perithecium at maturity, embedded in mucilaginous jelly. The ascospores and the mucilaginous matrix form a paste that is extruded through the apical opening in the perithecium producing "cirrhi" resembling toothpaste squeezed out from a toothpaste tube. ''Chaetomium cupreum'' is intermediate between the species: ''C. trilaterale'' Chivers and ''C. aureum'' Chivers. ''C. aureum'' and ''C. cupreum'' both produce conspicuous cirrhi while ''C. trilaterale'' does not. The ascospores of ''C. cupreum'' are similar shape but larger than ''C. aureum''. The pigment produced by ''C. trilaterale'' in agar cultures is water-soluble while the granules produced on ''C. cupreum'' are insoluble.
Reproduction
''Chaetomium cupreum'' is known only as a sexually reproducing species and no asexual form has been reported. Ames originally reported ''C. cupreum'' to possess a homothallic mating system but this was later contradicted by Tveit in 1955 who determined the species to be heterothallic. Sexual reproduction in ''C. cupreum'' involves the formation of ascogonia arising as lateral outgrowths of the vegetative mycelium. In early developmental stages, the ascogonia are coiled and coenocytic with septa forming as the ascogonia mature. The terminal cell of each