Hyphae are comprised of hypha, which are the long filamentous branches found in fungi and actinobacteria (shown below). Hyphae are important structures required for growth in these species, and together, are referred to as mycelium.
Each hypha is comprised of at least one cell encapsulated by a protective cell wall typically made of chitin, and contain internal septa, which serve to divide the cells. Septa are important as they allow cellular organelles (e.g., ribosomes) to pass between cells via large pores. However, not all species of fungi contain septa. The average hyphae are approximately 4 to 6 microns in size.
Hyphae growth occurs by extending the cell walls and internal components from the tips. During tip growth, a specialized organelle called the spitzenkörper, assists in the formation of new cell wall and membrane structures by harboring vesicles derived from the golgi apparatus and releasing them along the apex of the hypha. As the spitzenkörper moves, the tip of the hypha is extended via the release of the vesicle contents, which form the cell wall, and the vesicle membranes, which create a new cell membrane. As the hypha extends, new septa can be created to internally divide the cells. The characteristic branching of hyphae is the result of the formation of a new tip from a hypha, or the division of a growing tip (see diagram below).
(1- Hyphal wall 2- Septum 3- Mitochondrion 4- Vacuole 5- Ergosterol crystal 6- Ribosome 7- Nucleus 8- Endoplasmic reticulum 9- Lipid body 10- Plasma membrane 11- Spitzenkörper/growth tip and vesicles 12- Golgi apparatus)
Hyphae are associated with multiple different functions, depending on the specific requirements of each fungal species. The following are a list of the most commonly known hyphae functions:
Nutrient Absorption from a Host
Some hyphae of parasitic fungi are specialized for nutrient absorption within a specific host. These hyphae have specialized tips called haustoria, which penetrate the cell walls of plants or tissues of other organisms in order to obtain nutrients.
Nutrient Absorption from Soil
Some fungal species (e.g., mycorrihizae) have developed a symbiotic relationship with vascular plant species. The fungi forms specialized hyphae called arbuscules, which can be found in the roots or phylum of vascular plants, and function to absorb nutrients and water from the soil. In this manner, the hyphae aid the plants by increasing its access to nutrients in the soil while facilitating its own growth.
In some fungal species, hyphae have evolved into specialized nematode-trapping structures, using nets and ring structures to trap nematode species.
Several fungal species exhibit hyphae composed of chord-like structures, termed mycelial chords, which are used by fungi (e.g., lichens and mushrooms) to transport nutrients across great distances.
In general, hyphae can be classified based on the following traits:
Hyphae characteristics are an important method of classifying various fungal species. There are three main hyphae characteristics:
- Binding: Binding hyphae have a thick cell wall and are highly branched.
- Generative: Generative hyphae have a thin cell wall, a large number of septa, and are typically less differentiated. Generative hyphae may also be contained within other materials (e.g., gelatin or mucilage) and can also develop structures used in reproduction. All fungal species typically contain generative hyphae.
- Skeletal: Skeletal hyphae contain a long and thick cell wall with few septa. Skeletal hyphae can also be of a fusiform subtype, with a swollen midsection surrounded by tapered ends.
Fungal species are also further classified based on the hyphal systems they contain. There are four general subtypes:
- Monomitic: While virtually all fungal species contain generative hyphae, those with only exhibit this type are referred to as monomitic (e.g., agaric mushrooms).
- Dimitic: A species that contains generative hyphae in addition to one other type of hyphae. The most common combination of dimitic fungi is generative and skeletal.
- Trimitic: Species which contain all three types of hyphae (generative, binding, and skeletal).
- Sarcodimitic and sarcotrimitic: Sarcodimitic hyphae are fusiform skeletal hyphae bound to generative hyphae. Sarcotrimitic species contain fusiform skeletal hyphae, as well as binding and generative hyphae.
Under a microscope, the appearance of oily or granular hyphae under a microscope is termed gloeoplerous. This term is also used to further classify the hyphae of various species.
Hyphae can be classified based on the presence of internal septa (septate versus aseptate species). Hyphae can also be distinguished from species which produce pseudohyphae via cell division . Pseudohyphae is a form of incomplete cell division, in which the dividing cells do not separate. There are several yeast species which produce such pseudohyphae.
1. Which of the following statements is TRUE regarding hyphae?
A. All fungi contain skeletal hyphae.
B. All hyphae contain septa.
C. Fungal species can exhibit both generative and binding hyphae.
D. Fusiform skeletal hyphae are a form of pseudohyphae.
2. Which of the following is NOT a primary function of hyphae:
A. Nutrient absorption from the soil
B. Nutrient transportation
C. Nutrient absorption from host tissues
D. All of the above
E. Only A and B are primary functions
- Fricker et al. (2017). The Mycelium as a Network. Microbiol Spectr. 5(3): doi: 10.1128/microbiolspec.FUNK-0033-2017.
- Lew, R. (2011). How does a hypha grow? The biophysics of pressurized growth in fungi. Nat Rev Microbiol. 9(7): 509-18.
- Steinberg et al. (2017). Cell Biology of Hyphal Growth. Microbiol Spectr. 5(3): doi: 10.1128/microbiolspec.FUNK-0034-2016.
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Zygomycota: The Conjugation Fungi
Zygomycota: The Conjugation Fungi
The Zygomycota, or conjugation fungi, include molds, such as those that invade
breads and other food products. The identifying characteristics of the
Zygomycota are the formation of a zygospore during sexual reproduction and
the lack of hyphal cell walls except in reproductive structures. Many (~100
species) are known plant root symbionts.
The mycelia of Zygomycota are divided into three types of hyphae. The
rhizoids reach below the surface and function in food absorbtion. Above
surface, sporangiophores bear the spore-producing sporangia. Groups of
rhizoids and sporangiophores are connected above the surface by stolons.
Cell walls separating individual cells are absent in all but reproductive
structures, allowing cytoplasm and even nuclei to move between cells.
Like all fungi, Basidiomycota can undergo both asexual and sexual reproduction.
Asexual reproduction in Zygomycota is similar to that in other types of fungi,
while sexual reproduction bears some similarity to that in Ascomycota.
Asexual reproduction in Zygomycota varies greatly among orders and species.
Spores may be formed by the separation and thickening of hyphal cells. They may
also be produced in specialized organs, whose structure is also widely varied.
Like Ascomycota, some Zygomycota have two mating types, though individual
species may only have one mating type. When hyphae from opposite mating types
meet, they produce structures called progametangia that are dense and
multinucleate. Cell walls form to separate the tips of the progametangia into
gametangia, which continue to be attached to the mating hyphae by the
remaining suspensors. Plasmogamy then occurs between the two gametangia to
form a zygote. Next, karyogamy takes place within the zygote. The cell
walls of the zygote are thin at first, but later thicken into a zygospore.
Germination begins when the diploid nucleus undergoes meiosis and a
sporangium develops at the end of a germ tube. Spores are produced within
From the SparkNotes Blog
Elodie and Chelsea Dagger
- Melissa Petruzzello
Rhizopus, cosmopolitan genus of some 10 species of filamentous fungi in the family Rhizopodaceae (formerly Mucoraceae), in the order Mucorales. Several species, including Rhizopus stolonifer (the common bread mold ), have industrial importance, and a number are responsible for diseases in plants and animals.
The majority of Rhizopus species are saprobic (decomposers) and feed on a variety of dead organic matter, though some species are parasitic or pathogenic. Rhizopus fungi are characterized by a body of branching mycelia composed of three types of hyphae: stolons , rhizoids , and usually unbranching sporangiophores. The black sporangia at the tips of the sporangiophores are rounded and produce numerous nonmotile multinucleate spores for asexual reproduction . Rhizopus can reproduce sexually when two compatible and physiologically distinct mycelia are present. The rapidly growing colonies fade from white to dark as they produce spores and are similar to cotton candy (also called candy floss or fairy floss) in texture.
Many members of Rhizopus are commonly used in industrial processes. R. arrhizus (R. oryzae) is useful for the production of lactic acid and cortisone , for alcoholic fermentation , and for the biosorption (passive adsorption of chemical contaminants by an organism) of heavy metals. R. stolonifer is used to produce fumaric acid , lactic acid, and cortisone, and R. delemar produces fumaric acid and biotin . In Asia several species are important in some foods, such as tempeh, and in many traditional alcoholic beverages .
Mucormycosis (also called zygomycosis) is a rare and serious disease caused primarily by R. arrhizus in burn victims, individuals suffering from severe malnutrition , patients with diabetic ketoacidosis, or immunocompromised individuals, such as those with HIV / AIDS or certain cancers. The infection invades blood vessels in humans and other animals and can progress to other areas of the body, including the brain and lungs . The disease has an overall mortality rate of 50 percent, though outcomes can vary widely and are strongly affected by preexisting conditions.
A number of postharvest plant diseases , collectively known as storage rot, are caused by R. stolonifer and R. arrhizus. In warm conditions, these fungi can affect the soft tissues of harvested fruits , often causing a watery leakage and rendering them inedible. Leak disease in strawberries and tomatoes , soft rot and ring rot in sweet potatoes , pole rot in tobacco leaves, and fruit rot in papayas and stone fruits are all storage rot diseases caused by these Rhizopus species. Preventive fungicides are often sprayed postharvest to avoid crop losses from these diseases, and cold storage during transport can prevent or slow their spread.
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More About Rhizopus
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