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Drawing of bats in an attic. Fungal body is shown in the guano. A micrograph of the fungus shows hyphae (long strands) withc spheres labeled conidia. The life cycle shows a person inhaling spores which then travel to the lungs and divide into a yeast form. They then travel to the lymph and blood.
Histoplasma capsulatum is a dimorphic fungus that grows in soil exposed to bird feces or bat feces (guano) (top left). It can change forms to survive at different temperatures. In the outdoors, it typically grows as a mycelium (as shown in the micrograph, bottom left), but when the spores are inhaled (right), it responds to the high internal temperature of the body (37 °C [98.6 °F]) by turning into a yeast that can multiply in the lungs, causing the chronic lung disease histoplasmosis. (credit: modification of work by Centers for Disease Control and Prevention)

There are notable unique features in fungal cell walls and membranes. Fungal cell walls contain chitin , as opposed to the cellulose found in the cell walls of plants and many protists. Additionally, whereas animals have cholesterol in their cell membranes, fungal cell membranes have different sterols called ergosterols . Ergosterols are often exploited as targets for antifungal drugs.

Fungal life cycles are unique and complex. Fungi reproduce sexually either through cross- or self-fertilization. Haploid fungi form hyphae that have gametes at the tips. Two different mating types (represented as “+ type” and “– type”) are involved. The cytoplasms of the + and – type gametes fuse (in an event called plasmogamy), producing a cell with two distinct nuclei (a dikaryotic cell). Later, the nuclei fuse (in an event called karyogamy ) to create a diploid zygote. The zygote undergoes meiosis to form spores that germinate to start the haploid stage, which eventually creates more haploid mycelia ( [link] ). Depending on the taxonomic group, these sexually produced spores are known as zygospores (in Zygomycota), ascospores (in Ascomycota), or basidiospores (in Basidiomycota) ( [link] ).

Fungi may also exhibit asexual reproduction by mitosis, mitosis with budding, fragmentation of hyphae, and formation of asexual spores by mitosis. These spores are specialized cells that, depending on the organism, may have unique characteristics for survival, reproduction, and dispersal. Fungi exhibit several types of asexual spores and these can be important in classification.

Zygomycete life cycle. The mycelia can undergo asexual reproduction by forming spores via mitosis. The spores then form mycelia by germination. The haploid spores can also undergo sexual reproduction. The first step is germination when mycelia form. If the two mating types (+ and -) are in close proximity, extensions called gametangia form between them. Next is plasmogamy. This is the fusion between the + and – mating types resulting in a zygosporangium with multiple haploid nucei. The zygosporangiom forms a thick, protective coat. Next the nuclei fuse to form a zygote with multiple diploid nuclei in karyogamy. This forms a diploid zygote. Next is mitosis and germination where the sporangium grows on a  short stalk and the haploid spores are formed inside. The spores are released in germination and we are back to the spore stage of the life cycle.
Zygomycetes have sexual and asexual life cycles. In the sexual life cycle, + and – mating types conjugate to form a zygosporangium.
a) A micrograph of long strands labeled hyphae and a sphere (labeled sporangium) on the end of one of the long strands. B) A photograph of bread mold. The white fuzz has black dots labeled sporangia.
These images show asexually produced spores. (a) This brightfield micrograph shows the release of spores from a sporangium at the end of a hypha called a sporangiophore. The organism is a Mucor sp. fungus, a mold often found indoors. (b) Sporangia grow at the ends of stalks, which appear as the white fuzz seen on this bread mold, Rhizopus stolonifer . The tips of bread mold are the dark, spore-containing sporangia. (credit a: modification of work by Centers for Disease Control and Prevention; credit b right: modification of work by “Andrew”/Flickr)
  • Is a dimorphic fungus a yeast or a mold? Explain.

Fungal diversity

The fungi are very diverse, comprising seven major groups. Not all of the seven groups contain pathogens. Some of these groups are generally associated with plants and include plant pathogens. For example, Urediniomycetes and Ustilagomycetes include the plant rusts and smuts , respectively. These form reddish or dark masses, respectively, on plants as rusts (red) or smuts (dark). Some species have substantial economic impact because of their ability to reduce crop yields. Glomeromycota includes the mycorrhizal fungi , important symbionts with plant roots that can promote plant growth by acting like an extended root system. The Glomeromycota are obligate symbionts, meaning that they can only survive when associated with plant roots; the fungi receive carbohydrates from the plant and the plant benefits from the increased ability to take up nutrients and minerals from the soil. The Chytridiomycetes ( chytrids ) are small fungi, but are extremely ecologically important. Chytrids are generally aquatic and have flagellated, motile gametes; specific types are implicated in amphibian declines around the world. Because of their medical importance, we will focus on Zygomycota, Ascomycota, Basidiomycota, and Microsporidia. [link] summarizes the characteristics of these medically important groups of fungi.

Questions & Answers

what are ways of handling sharps
namugenyi Reply
never recap or bend a sharp objects
describe the process of platelet formation
Joy Reply
what is parasitic helminths
Sadiya Reply
list three categories of symbiotic relationships.
mary Reply
what's the difference between microbial intoxication and infectious diseases
dranimva Reply
microbial intoxication results when a person ingests a toxin or a poisonous substance that has been produced by a microbe while infectious disease results when a pathogen colonize the body and subsequently cause disease.
weighing balance is needed in lab of microbiology for weighing?
amna Reply
It is mainly used for media preparation and product testing purpose.
thank you for your joining
what is microbiology
Shamsuddeen Reply
study of living organisms that are too small to be visible with naked eye
microbiology is the study of microscopic organisms, either unicellular(single cell), multicellular( cell colony), or acellular (lacking cell).
is the word Atypical or a typical bacteria. .am confused pliz help
typical bacteria
okay thank you what does that mean
atypical means that it has some characters from bacteria not all characters ...but tybical means that it has all the characters that bacteria have
thank you Zulpha
some examples please
thank you Reham
1) typical bacteria contain a cell wall whereas atypical bacteria usually do not contain a cell . 2) typical bacteria can be either Gram-positive or Gram-negative while atypical bacteria remain colorless with Gram staining. 3) cells of typical bacteria are large ,while cells of the atypical small
Example of atypical : Mycoplasma pneumoniae , chlamydophila pneumoniae , legionella
what is micro biology
Jauharah Reply
is the study of organisms which can't be viewed by our necked eyes
Because it preexisting causing secondary infection after collateral damage of normal microbota
Rafaa Reply
combinations of drugs that can't be taken together and why
Grace Reply
Antagonism: the combined action is less than that of the more effective agent when used alone). All these effects may be observed in vitro (particularly in terms of bactericidal rate) and in vivo والله اعلم
....fermentros have 1-15litre capacity
AMAR Reply
which of the following microorganisms are classified as eukaryotic?
Semugab Reply
how do I see the list?
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what are the new discoveries of microorganisms
Ezibon Reply
understanding of contributed to attempts to treat contain disease
james Reply

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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