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''Sordaria fimicola'' is a species of
microscopic The microscopic scale () is the scale of objects and events smaller than those that can easily be seen by the naked eye, requiring a lens (optics), lens or microscope to see them clearly. In physics, the microscopic scale is sometimes regarded a ...
fungus A fungus ( : fungi or funguses) is any member of the 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, separately from th ...
. It is commonly found in the
feces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...
of
herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
s. ''Sordaria fimicola'' is often used in introductory
biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...
and
mycology Mycology is the branch of biology concerned with the study of fungi, including their genetic and biochemical properties, their taxonomy and their use to humans, including as a source for tinder, traditional medicine, food, and entheogens, as ...
labs because it is easy to grow on nutrient
agar Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from ogonori (''Gracilaria'') and "tengusa" (''Gelidiaceae''). As found in nature, agar is ...
in dish cultures. The genus ''Sordaria'', closely related to ''
Neurospora ''Neurospora'' is a genus of Ascomycete fungi. The genus name, meaning "nerve spore" refers to the characteristic striations on the spores that resemble axons. The best known species in this genus is ''Neurospora crassa'', a common model organi ...
and
Podospora ''Podospora'' is a genus of fungi in the family Podosporaceae. Fossils of ''Podospora'' have been reported from 12 million year old rocks from central England. Species *'' Podospora adelura'' *'' Podospora alexandri'' *'' Podospora ampullacea ...
'', is a member of the large class
Sordariomycetes Sordariomycetes is a class of fungi in the subdivision Pezizomycotina (Ascomycota), consisting of 28 orders, 90 families, 1344 genera. Sordariomycetes is from the Latin sordes (filth) because some species grow in animal feces, though growth habit ...
, or flask-fungi. The natural habitat of the three species of ''Sordaria'' that have been the principal subjects in genetic studies is dung of herbivorous animals. The species ''S. fimicola'' is common and worldwide in distribution. The species of ''Sordaria'' are similar morphologically, producing black perithecia containing asci with eight dark
ascospore An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or s ...
s in a linear arrangement. These species share a number of characteristics that are advantageous for genetic studies. They all have a short
life cycle Life cycle, life-cycle, or lifecycle may refer to: Science and academia *Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring *Life-cycle hypothesis, ...
, usually 7–12 days, and are easily grown in culture. Most species are self-fertile and each strain is isogenic. All kinds of mutants are easily induced and readily obtainable with particular ascospore color mutants. These visual mutants aid in
tetrad analysis The tetrad is the four spores produced after meiosis of a yeast or other Ascomycota, ''Chlamydomonas'' or other alga, or a plant. After parent haploids mate, they produce diploids. Under appropriate environmental conditions, diploids sporulate and ...
, especially in analysis of intragenic recombination. The most common form of ''S. fimicola'' is a dark brown. Certain mutants are grey or tan. A common experiment for an introductory biology lab class is to cross one of the mutant types with a wild type and observe the ratio of coloring in the offspring. This experiment illustrates the concepts of genetic inheritance in a
haploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...
organism. The eight ascospores are produced inside an
ascus An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or s ...
. Sordaria squashes can give us information about crossing over during meiosis. If no crossing over then there is a 4:4 pattern. 4 black spores, and 4 tan spores all lined up. If crossing over does occur there is a 2:2:2:2 pattern visible, or a 2:4:2 pattern. Another common lab use is to observe
meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately resu ...
and
mitosis In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...
in the fruit bodies, called perithecia. An interesting feature of ''S. fimicola'' is that its fruit body is phototrophic. Thus, as it grows the stalk will bend toward a light source and when the sac bursts, the
spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
s are shot towards the light.


Taxonomy

Research to update Sordariomycete fungal taxonomy is ongoing, and S. fimicola position within the taxonomy of the Sordariomycetes is being researched and updated. The sordariomycetes are known as the flask fungi because they are characterized by flask-shaped perithecia and unitunicate asci. Phylogenetic studies of partial 18s ribosomal DNA strands has illuminated the phylogeny of the Sordariomycetes. Morphological features that characterize the Sordariaceae include the differentiation of the hyphal envelope that surrounds the ascogonium into peripheral wall layers and a pseudoparenchymatous centrum. Broad paraphyses composed of delicate, multinucleate cells arise from the cells of the centrum and completely fill the perithecium, crushing the remaining pseudoparenchymatous cells against the perithecial wall. Sordaria fimicola differs from other species of Sordariaceae studied in the aggregation of the ascogenous cells to form a placenta‐like mass in the base of the centrum. Consequently, the asci arise in a cluster rather than in a uniform wall layer.


Fungal Morphology

Sordaria fimicola is an ascomycete fungus that grows well on nutrient agar, dung, and in decaying matter in soil. As an ascoymcete it has a sexual teleomorph form and an asexual anamorph form. S. fimicola typically follow the life cycle of an obligate dung fungi; sexual reproduction that is obligate to herbivore dung after passage through the herbivore’s gastrointestinal tract . Following meiosis on dung, ascospores are discharged and stick onto plant surfaces where they are thought to remain epiphyllous. S. fimicola grows septate hyphae which at the macro level look like small dark brown fibers forming a fluffy sheet over the substrate. Small black spots will form when sexual reproduction occurs, as these spots are the location of the ascii. Additionally, there are tan and grey mutant strains of S. fimicola. S. fimicola grows best in carbon rich substrates, but it also needs access to nitrogen. Research has shown that S. fimicola grows best with a carbon:nitrogen ratio between 5:1 and 10:1, S. fimicola grown under these conditions produce markedly more perithecium than those with higher carbon ratios or higher nitrogen ratios. S. fimicola grows well in a laboratory setting and because of that it is often used in introductory biology laboratories and also as a model organism for research. S. fimicola is also a good tool for teaching meiosis as it quickly produces diploid perithecium which undergoes meiosis to produce ascii with ordered linear tetrads of haploid ascospores.


Ecology

Although S. fimicola was traditionally understood to grow on the dung of herbivorous animals or in decaying plant matter, but it has also been discovered that it grows symbiotically with some plants. New research shows that S. fimicola is a facultative dung fungus and, S. fimicola has been found to grow among the roots of Rye-grass and wheat-grass. In sterilized and unsterilized soil, S. fimicola promoted host growth and prevented mortality. Research shows that S. fimicola in potato dextrose cultrues, the fungis is capable of producing triacontanol and indole-3-carboxaldehyde, both of which have antibacterial properties that may help prevent host disease. S. fimicola has also been shown to inhibit the growth of other species of fungi which are pathogenic to plants including Pestalotiopsis guepinii, Colletotrichum capsici, Curvularia lunata ochliobolus lunatus Alternaria alternata and Fusarium oxysporum. S. fimicola has also been shown to negatively affect the health of some plants that it can be found growing on. When S. fimicola was first isolated from maize researchers believed that it was most likely an opportunistic pathogen.. Healthy maize plants in the laboratory did not grow S. fimicola indicating that healthy maize plants may exclude it. S. fimicola did colonize healthy B. tectorum resulting in reduced fecundity and reduced growth. S. fimicola is also phototropic and the response is twofold: 1) the number of fruiting bodies produced by the fungus is influenced by light and 2) the direction which the fruiting bodies grow is also influenced. This response is likely mediated by a specific fungal receptor called the S. fimicola white collar-1 photoreceptor (SfWC-1). Other species of phototropic fungi have homologous receptors with similar receptor domains. S. fimicola with a non-functional mutant SfWC-1 receptor had delayed and less-pronounced fruiting-body formation, was defective in phototropism of the perithecial beaks, and lacked the fruiting-body zonation pattern compared with the wild type.


Gene conversion Gene conversion is the process by which one DNA sequence replaces a homologous sequence such that the sequences become identical after the conversion event. Gene conversion can be either allelic, meaning that one allele of the same gene replaces a ...

Each individual meiosis generates four haploid products, and after one further round of mitosis, eight products are formed and all retained as haploid spores within the sac-like
ascus An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or s ...
(pl. asci). The retention of the products of an individual
meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately resu ...
in an individual ascus has facilitated certain kinds of genetic analyses, particularly the analysis of the molecular mechanism of
genetic recombination Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryo ...
. When a
wild type The wild type (WT) is the phenotype of the typical form of a species as it occurs in nature. Originally, the wild type was conceptualized as a product of the standard "normal" allele at a locus, in contrast to that produced by a non-standard, "m ...
(+) strain is mated with a
mutant In biology, and especially in genetics, a mutant is an organism or a new genetic character arising or resulting from an instance of mutation, which is generally an alteration of the DNA sequence of the genome or chromosome of an organism. It ...
(m) strain, ordinarily each ascus will contain a pattern of four + and four m spores. However, it was found that, with low frequency, some asci had ratios that differed from the expected 4+ : 4m (e.g. 6+: 2m or 2+: 6m or even 5+: 3m or 3+: 5m). In these cases it appeared that the m gene had been converted to the + gene or vice versa. And so the phenomenon was termed "
gene conversion Gene conversion is the process by which one DNA sequence replaces a homologous sequence such that the sequences become identical after the conversion event. Gene conversion can be either allelic, meaning that one allele of the same gene replaces a ...
." Gene conversion was first detected in ''S. fimicola'' in 1951 by Lindsay Olive, and definitively characterized by him in 1959. Olive considered that these gene conversion events resulted from "trans replication, by which a locus is copied more than the normal number of times during replication at meiotic prophase." Since then many studies on the gene conversion phenomenon were carried out with ''S. fimicola'' and other organisms, particularly other
ascomycetes Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The defi ...
ee review by WhitehouseHarold L. K. Whitehouse. 1982. Genetic Recombination. New York: Wiley (1982) Efforts to understand gene conversion at the molecular level have provided important insights into the mechanism and adaptive function of meiotic recombination, which in turn bears on the adaptive function of sexual reproduction. These insights are discussed further in the article
Gene conversion Gene conversion is the process by which one DNA sequence replaces a homologous sequence such that the sequences become identical after the conversion event. Gene conversion can be either allelic, meaning that one allele of the same gene replaces a ...
.


Images

Image:Sordaria fimicola mating plate.png, A mating between wild-type (dark brown) and mutant (tan) ''Sordaria fimicola'' colonies Image:Sordaria fimicola perithecium (heterozygote) 40X.png, ''Sordaria fimicola'' perithecia with both mutant and wild-type ascospores Image:Sordaria fimicola ascus (heterozygote) 160X.png, A ''Sordaria fimicola'' ascus with an unusual 2:1:1:1:1:2 pattern


References

{{DEFAULTSORT:Sordaria Fimicola Sordariales Taxa named by John Baptiste Henri Joseph Desmazières