BMSC207 Lecture Notes - Lecture 9: Aspergillus, Zygomycota, Coenocyte
Fungal Structure and Replication:
Kingdom Fungi:
Eukaryotic, non-photosynthetic •
Unicellular (yeast) or multicellular•
No tissue○
Made of filaments of cell s (moulds, mushrooms)•
Cell walls made of a complex sugar Chitin
•
Decomposers○
Parasites○
A symbiotic relationshi p in which both participants benefit
Mutualists○
Fungi exhibit diverse lifestyles:•
Cells secrete enzymes to the exterior○
These break down organic matter into smaller compounds, which are then absorbed
through cell walls and plasma membranes into the cells
○
Extracellul ar digestion:•
Acidic, high salt, high sugar etc. Unlike bacteria ○
Fungi can grow in harsh environmental conditions•
Fungal physiology, structure and symbioses:
Most fungi are multicellular, forming a network of hyphae
•
Conidia are often pigmented and resistant to drying○
Hyphae that extend above the surface can produce asexual spores called conidi a •
Hyphae form compact tufts cal led mycelia which are underground•
Mycorrhizae help plant roots obtain phosphorous •
Some fungi produce macroscopic reproductive structures called •
fruiting bodies
The part above ground○
Mushrooms and puffballs are fruiting bodies •
Fruiting bodies are composed of tight mesh of hyphal strands•
Fruiting bodies produce spores•
Mycoses in humans range in severity from "athlete's foot" to○
histoplasmosis
Fungi can cause disease in plants and animals•
Major groups of disease-causing fungi:
There are more than 70 000 species of fungi but only about 300 are identified as
humans and animals
•
Fungal pathogens can be class ified on the basis of their growth forms or the type of
they cause
•
Fungal pathogens may exist as branched filamentous forms or as yeasts; some show both
growth forms in their cycle (dimorphic fungi)
•
Examples are tinea pedis (athlete's foot) and vaginal candidiasis (thrush).
Superficial mycoses where the fungus grows of body surface (skin, hair, nails,
vagina).
○
Examples are mycetoma (Madura foot) and sporotrichosis.
Subcutaneous mycoses where nails and deeper layers of the skin are involved.○
Examples are histoplasmosis and systemic candidiasis
Systemic or deep mycoses with involvement of internal organs. This category
fungi capable of infecting individuals with normal immunity and the opportunistic
that cause disease in patients with compromised immune systems.
○
3 types of infection (mycoses) are recognized:•
Cats and dogs○
The superficial mycoses are spread by person to person contact or from animal to human
contact
•
Following skin penetration in the case of mycetoma○
The subcutaneous mycoses infect humans via the skin•
The deep mycoses often result from the opportunistic growth of fungi in individuals with
impaired immune competence and are primari ly acquired via the respiratory tract, with
intravenous lines an important portal of entry for Candida.
•
Fungal Reproduction and Phylogeny:
Growth and spread of hyphal filaments○
Asexual production of spores○
Simple divisi on (budding)○
Most fungi reproduce by asexual means:•
Different daughter cells
Ascospores, basidiospores, zygospores
Sexual spored can originate from the fusion of 2 haploi d cells to from a diploid cell ○
spores are resistant to drying, heating, freezing and chemicals○
Some fungi produce spores as a result of sexual reproduction•
Fungi share a more recent common ancestor with animals than any other group of
organisms
•
Estimated that fungi and animals diverges 1.5 billion years ago•
Earliest fungal lineage is thought to be chytriiomycetes•
5 different phylum:
hyphae
Fruiting body
budding
Lecture 5 - 29/8/16
Tuesday, 23 August 2016
8:53 AM
Lectures Page 1
