Mycology Flashcards
Describe the general characteristics of fungi.
Fungi are eukaryotes that can be unicellular or multicellular.
They are heterotrophs and most are obligate aerobes.
They stain gram positive and have cell walls composed of chitin, glucan polysaccharides and ergosterol (replaces cholesterol).
Describe the general characteristics of the Chytridiomycota phylum of fungi.
The Chytridiomycota phylum is found on aquatic habitats.
They reproduce asexually via Zoospores.
They only have one hyphae: rhizoides.
Describe the general characteristics of Zygomycota phylum of fungi.
The Zygomycota phylum is found on decaying matter.
They reproduce asexually through spores.
They have three hyphae: stolon, rhizoids and sporangiophore.
Describe the general characteristics of Basidiomycota phylum of fungi.
The Basidiomycota phylum includes jelly fungus and mushrooms.
They reproduce sexually via spores in Basidium.
hyphae makes up their club like body.
Describe the general characteristics of the phylum Ascomycota.
The Ascomycota phylum contains truffles and common yeasts.
They reproduce both sexually and asexually.
They have a sac like structure which is made from hyphae.
Describe the Saccharomycotina subdivision of Ascomycota.
Saccharomycotina contains unicellular yeasts that undergo asexual reproduction by budding.
First the parent nucleus splits and moves to the daughter cell.
The cytoplasm then divides to form a new yeast cell.
Pseudo-hyphae are formed when the yeast forms chains.
Describe the Taphrinomycotina subdivision of Ascomycotina phylum.
Taphrinomycotina includes multicellular hyphae that reproduce sexually by spores.
Describe the Pezizomycotina subdivision of Ascomycotina phylum.
Pezizomycotina include multicellular hyphae that either sexually reproduce by binary fission or asexually reproduce by spores which are released from the condiophore.
During sexual reproduction, the ascogonium releases pheromones which are recognised by antheridium (Wilson et al., 2021).
This causes growth of trichogyne towards the ascogonium (Wilson et al., 2021).
Fertilisation occurs which produces the protoascocarp (Wilson et al., 2021).
The ascocarp is formed as a result of mitosis and cell division.
Asci at the tip of the hyphae contain nuclei which fuse and form a diploid zygote.
Meiosis results in the formation of an ascus containing four haploid nuclei.
These undergo mitosis and cell division to form eight haploid ascospores.
The ascospores are then dispersed and germinated.
Reference: Wilson, A. M., Wilken, P. M., Wingfield, M. J., and Wingfield, B. D. (2021) ‘Genetic Networks That Govern Sexual Reproduction in the Pezizomycotina’, Microbiology and molecular biology reviews, 85(4), e0002021.
Describe an infection caused by Saccharomycotina.
An infection caused by Saccharomycotina is candidiasis, caused by C. albicans.
It is an opportunistic pathogen that affects immunocompromised patients, pregnant individuals and individuals on antibiotic therapy.
C. albican infection causes oral thrush, which is overgrowth of the pathogen on the tongue.
It commonly occurs in individuals with dentures.
C. albican infection causes vaginal thrush, which is overgrowth of the pathogen in the vaginal tract.
A symptom of this infection is a thick, cottage cheese like discharge and painful urination.
It commonly occurs in individuals with IUD’s (intron urinary device).
Candidaemia occurs when C. albicans enters the blood.
The infection is characterised by skin rash, muscle aches, fever and chills, headaches, abdominal pain, low lood pressure, fatigue, vision changes or eye infection and neurological deficits.
Describe some diagnostic tests for C. albicans.
C. albicans can be cultured on Sabouraud agar, which is porous to allow oxygen in.
A KOH test can be performed, where you add a few drops of KOH on a sample of scrapping of the infected area.
The KOH enters cell wall and allows visualisation of the cell.
A germ tube test can also be performed to differentiate C. albicans from other yeasts.
0.5ml of sheep or human blood is added to a tube and a colony of yeast is added to it.
It is then incubated for up to two to four hours at 37 degrees.
A drop of the serum is then added to a slide and cover slipped for examination by microscope.
What is the difference between the ascogonium and the antheridium?
The ascogonium are the male structures and the antheridium are the female structures.
Describe the infection Athlete’s foot.
An infection caused by Pezizomycotina is Athlete’s foot, a skin infection caused by T. rubrum.
It is characterised by white cracked painful skin in-between toes.
It can be treated by foot creams.
It can be tested in the lab using SAB agar and Lactophenol cotton blue staining.
Describe the infection Aspergillosis.
Another infection caused by Pezizomycotina is aspergillosis, a lung infection caused by A. fumigatus.
It occurs in immunocompromised patients.
It causes symptoms like shortness of breath and coughing up mucus.
It can be treated by antifungal tablets, or a surgery may be performed if the aspergilloma has grown.
Sputum can be cultured onto SAB agar for lab testing.
