Mucorales

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Mucorales
Pilobolus crystallinus (F.H. Wigg.) Tode 1013949.jpg
Pilobolus crystallinus sporangia
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Mucoromycota
Subdivision: Mucoromycotina
Order: Mucorales
Families

See text

The Mucorales is the largest and best-studied order of zygomycete fungi. Members of this order are sometimes called pin molds. The term mucormycosis is now preferred for infections caused by molds belonging to the order Mucorales.[ citation needed ]

Contents

Systematics

The order includes: 11 families, 56 genera, and approximately 300 species. Mucoralean classification has traditionally been based on morphological, developmental, and ecological characteristics. Recently, molecular data has revealed that some aspects of traditional classification are quite artificial. For example, the Mucoraceae is believed to be polyphyletic, as are the Thamnidiaceae, Chaetocladiaceae and Radiomycetaceae. Some of the genera, (including Mucor , Absidia and Backusella ) appear to be polyphyletic. Today, the traditional system is still largely in use, as further studies are needed to reconcile morphological and molecular concepts of families and genera.

Families

Micrograph of a mucoralean fungus, showing characteristic variation in thickness Zygomycosis.jpg
Micrograph of a mucoralean fungus, showing characteristic variation in thickness

The order consists of the following families:

Description

Mucoralean fungi are typically fast-growing, and their wide hyphae (long, filamentous structures) lack septa (multi-perforate septa are present only in sporangiophores and gametangia). The hyphae grow mostly within the substrate. Sporangiophores are upright (simple or ramified) hyphae, that support sac-like sporangia filled with asexual sporangiospores. Other structures include merospores, oidia, and sporangiola.

Many are known by the damage they do to stored food such as bread. Others can cause mucormycosis, generally in immunosuppressed patients, or patients already infected with other diseases.

Life cycle

The sporangiospores are asexual mitospores (formed via mitosis), produced inside sporangia (thousands of spores) or sporangioles (single or few spores). They are released when mature by the disintegration of the sporangium wall, or as a whole sporangiole that separates from the sporangiophore.

The sporangiospores germinate to form the haploid hyphae of a new mycelium. Asexual reproduction often occurs continuously.

In heterothallic species, sexual reproduction occurs when opposite mating types (designated + and -) come into close proximity, inducing the formation of specialized hyphae called gametangia. The gametangia grow toward each other, then fuse, forming a diploid zygote at the point of fusion. The zygote develops a resistant cell wall, forming a single-celled zygospore, the characteristic that gives its name to this group of fungi. Meiosis occurs within the zygospore (see article Phycomyces). Upon germination, a new haploid mycelium or sporangium is formed. Some species are homothallic.

The original report of sex in fungi, occurred two centuries ago, based on observations of the fungus Syzygites megalocarpus (Mucoromycotina) (reviewed by Idnurm [1] ). This species, was subsequently used in 1904, to represent self-fertile species when the concept of two major mating strategies were developed for the fungi. These strategies are homothallism for self-fertile fungi and heterothallism for self-incompatible, outcrossing fungi.

Ecology

Most Mucoralean species are saprotrophic, and grow on organic substrates (such as fruit, soil, and dung). Some species are parasites or pathogens of animals, plants and fungi. A few species cause human and animal disease.

Related Research Articles

<span class="mw-page-title-main">Sporangium</span> Enclosure in which spores are formed

A sporangium ; pl.: sporangia) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cycle. Sporangia can produce spores by mitosis, but in nearly all land plants and many fungi, sporangia are the site of meiosis and produce genetically distinct haploid spores.

<span class="mw-page-title-main">Zygomycota</span> Division or phylum of the kingdom Fungi

Zygomycota, or zygote fungi, is a former division or phylum of the kingdom Fungi. The members are now part of two phyla: the Mucoromycota and Zoopagomycota. Approximately 1060 species are known. They are mostly terrestrial in habitat, living in soil or on decaying plant or animal material. Some are parasites of plants, insects, and small animals, while others form symbiotic relationships with plants. Zygomycete hyphae may be coenocytic, forming septa only where gametes are formed or to wall off dead hyphae. Zygomycota is no longer recognised as it was not believed to be truly monophyletic.

A zygospore is a diploid reproductive stage in the life cycle of many fungi and protists. Zygospores are created by the nuclear fusion of haploid cells. In fungi, zygospores are formed in zygosporangia after the fusion of specialized budding structures, from mycelia of the same or different mating types, and may be chlamydospores. In many eukaryotic algae, including many species of the Chlorophyta, zygospores are formed by the fusion of unicellular gametes of different mating types.

<i>Rhizopus</i> Genus of fungi

Rhizopus is a genus of common saprophytic fungi on plants and specialized parasites on animals. They are found in a wide variety of organic substances, including "mature fruits and vegetables", jellies, syrups, leather, bread, peanuts, and tobacco. They are multicellular. Some Rhizopus species are opportunistic human pathogens that often cause fatal disease called mucormycosis. This widespread genus includes at least eight species.

<i>Phycomyces blakesleeanus</i> Species of fungus

Phycomyces blakesleeanus is a filamentous fungus in the Order Mucorales of the phylum Zygomycota or subphylum Mucoromycotina. The spore-bearing sporangiophores of Phycomyces are very sensitive to different environmental signals including light, gravity, wind, chemicals and adjacent objects. They exhibit phototropic growth: most Phycomyces research has focused on sporangiophore photobiology, such as phototropism and photomecism. Metabolic, developmental, and photoresponse mutants have been isolated, some of which have been genetically mapped. At least ten different genes are required for phototropism. The madA gene encodes a protein related to the White Collar-1 class of photoreceptors that are present in other fungi, while madB encodes a protein related to the White Collar-2 protein that physically bind to White collar 1 to participate in the responses to light.

<i>Phycomyces</i> Genus of fungi

Phycomyces is a genus of fungus in the Zygomycota phylum. They are known for their strong phototropism response and helical growth of the sporangium. The best studied species is Phycomyces blakesleeanus.

<i>Mucor</i> Genus of fungi

Mucor is a microbial genus of approximately 40 species of molds in the family Mucoraceae. Species are commonly found in soil, digestive systems, plant surfaces, some cheeses like Tomme de Savoie, rotten vegetable matter and iron oxide residue in the biosorption process.

Sporogenesis is the production of spores in biology. The term is also used to refer to the process of reproduction via spores. Reproductive spores were found to be formed in eukaryotic organisms, such as plants, algae and fungi, during their normal reproductive life cycle. Dormant spores are formed, for example by certain fungi and algae, primarily in response to unfavorable growing conditions. Most eukaryotic spores are haploid and form through cell division, though some types are diploid sor dikaryons and form through cell fusion.we can also say this type of reproduction as single pollination

<i>Mucor mucedo</i> Species of fungus

Mucor mucedo, commonly known as the common pinmould, is a fungal plant pathogen and member of the phylum Mucoromycota and the genus Mucor. Commonly found on soil, dung, water, plants and moist foods, Mucor mucedo is a saprotrophic fungus found world-wide with 85 known strains. It is often mistaken for Rhizopus rots on fruits due to similar mould growth shape and colour. Contrastingly, however, Mucor mucedo is found to grow on a wide range of stored grains and plants, including cucumber and tomato. Discovered in Italy in 1729 by P.A. Micheli and later noted by Carl Linnaeus in 1753 in the Species Plantarum, Mucor mucedo was originally classified as Mucor vulgaris by Micheli but later classified synonymous under name Mucor mucedo. The species was redescribed as Ascophora mucedo by H.J. Tode in 1790 but this type resided in a stoloniferous habitat and was later made the type of new genus Rhizopus.

<span class="mw-page-title-main">Cunninghamellaceae</span> Family of fungi

The Cunninghamellaceae are a family of fungi in the order Mucorales.

<span class="mw-page-title-main">Phycomycetes</span> Obsolete polyphyletic taxon for certain fungi with nonseptate hyphae

Phycomycetes is an obsolete polyphyletic taxon for certain fungi with aseptate hyphae. It is used in the Engler system. Asexual reproduction takes place by zoospores (motile) or by Aplanospores (non-motile). These spores are endogenously produced in sporangium. A zygospore is formed by fusion of two gametes. These gametes are similar in morphology (isogamous) or dissimilar.

<span class="mw-page-title-main">Pilobolaceae</span> Family of fungi

The Pilobolaceae are a family of fungi in the Mucorales order. Generally, species in this family have a widespread distribution, although there are some that are restricted to tropical and subtropical regions. This family includes two genera: Pilobolus, and Utharomyces.

<i>Spinellus fusiger</i> Species of fungus

Spinellus fusiger, commonly known as bonnet mold, is a species of fungus in the phylum Zygomycota. It is a pin mold that is characterized by erect sporangiophores that are simple in structure, brown or yellowish-brown in color, and with branched aerial filaments that bear the zygospores. It grows as a parasitic mold on mushrooms, including several species from the genera Mycena, including M. haematopus, M. pura, M. epipterygia, M. leptocephala, and various Collybia species, such as C. alkalivirens, C. luteifolia, C. dryophila, and C. butyracea. It has also been found growing on agaric species in Amanita, Gymnopus, and Hygrophorus.

<i>Apophysomyces variabilis</i> Species of fungus

Apophysomyces variabilis is an emerging fungal pathogen that can cause serious and sometimes fatal infection in humans. This fungus is a soil-dwelling saprobe with tropical to subtropical distribution. It is a zygomycete that causes mucormycosis, an infection in humans brought about by fungi in the order Mucorales. Infectious cases have been reported globally in locations including the Americas, Southeast Asia, India, and Australia. Apophysomyces variabilis infections are not transmissible from person to person.

<i>Allomyces</i> Genus of fungi

Allomyces is a genus of fungi in the family Blastocladiaceae. It was circumscribed by British mycologist Edwin John Butler in 1911. Species in the genus have a polycentric thallus and reproduce sexually or asexually by zoospores that have a whiplash-like flagella. They are mostly isolated from soils in tropical countries, commonly in ponds, rice fields, and slow-moving rivers.

Cunninghamella bertholletiae is a species of zygomycetous fungi in the order Mucorales. It is found globally, with increased prevalence in Mediterranean and subtropical climates. It typically grows as a saprotroph and is found in a wide variety of substrates, including soil, fruits, vegetables, nuts, crops, and human and animal waste. Although infections are still rare, C. betholletiae is emerging as an opportunistic human pathogen, predominantly in immunocompromised people, leukemia patients, and people with uncontrolled diabetes. Cunninghamella bertholletiae infections are often highly invasive, and can be more difficult to treat with antifungal drugs than infections with other species of the Mucorales, making prompt and accurate recognition and diagnosis of mycoses caused by this fungus an important medical concern.

<i>Cunninghamella echinulata</i> Species of fungus

Cunninghamella echinulata is a fungal species in the genus Cunninghamella. It is an asexually reproducing fungus and a mesophile, preferring intermediate temperature ranges. C. echinulata is a common air contaminant, and is currently of interest to the biotechnology industry due to its ability to synthesize γ-linolenic acid as well as its capacity to bioconcentrate metals. This species is a soil saprotroph that forms rhizoids, preferring soils enriched in nitrogen, phosphorus and potassium. It has been reported occasionally an agent of mucormycosis following the inhalation of fungal spores. Czapek's agar is a suitable growth medium for the propagation of C. echinulata.

<i>Syzygites</i> Genus of fungi

Syzygites is a monotypic genus in Zygomycota. The sole described species is Syzygites megalocarpus, which was the first fungus for which sex was reported and the main homothallic representative in the research that allowed for the classification of fungi as homothallic or heterothallic. It is also the fungus from which the term "zygospore" was coined.

<span class="mw-page-title-main">Mucoromycota</span> Diverse group of molds

Mucoromycota is a division within the kingdom fungi. It includes a diverse group of various molds, including the common bread molds Mucor and Rhizopus. It is a sister phylum to Dikarya.

Lichtheimia ramosa is a saprotrophic zygomycete, typically found in soil or dead plant material. It is a thermotolerant fungus that has also been known to act as an opportunistic pathogen–infecting both humans and animals.

References

  1. Idnurm A (November 2011). "Sex determination in the first-described sexual fungus". Eukaryotic Cell. 10 (11): 1485–91. doi:10.1128/EC.05149-11. PMC   3209044 . PMID   21908600.
  • Voigt & Wöstemeyer, 2001
  • Mucorales in Bryce Kendrick's textbook, The Fifth Kingdom.
  • Mucorales at Zygomycetes.org