Fungi 1 (Jeanette)

Question 1

Describe the general characteristics, mode of nutrition, and importance of fungi

Answer 1

General characteristics

• Kingdom of organisms within the domain eukaryotes.
• Both microscopic e.g. yeasts, and macroscopic e.g. mushrooms.
• Can have more than one nuclei.
• The human microbiome contains multiple fungal species which exist as commensals. These are referred to as the human mycobiota.

Mode of nutrition

• Can’t photosynthesise because they lack chlorophyll.
• Heterotrophic.
• Saprophytic (feed on dead or decomposing organic matter) by absorptive nutrition. They secrete digestive enzymes to break down complex molecules in their environment for subsequent absorption.

Importance of fungi

• Due to their saprophytic lifestyle they are major decomposers of organic material. This allows carbon, nitrogen, and phosphorous to be recycled for other living organisms.
• Their ability to ferment has been exploited in the production of food such as bread and cheese.
• Produce organic acids such as citric acid which is used as a food preservative.
• Produce certain drugs such as cortisone which is used to treat inflammation.
• Penicillin is secreted by the Penicillium mould.

Question 2

Name the six fungal phyla and describe a characteristic of each

Answer 2

Ascomycota - ascospores bourne internally in sacs called asci.
Basidiomycota - forms an elaborate fruiting body that contains basidia where basidiospores are formed.
Chytridiomycota - flagellated, motile spores.
Glomeromycota - most are endomycorrhizal fungi (penetrates the roots of plants.
Microsporidia - obligate intracellular parasites.
Zygomycota - highly resistant zygospore with suspensors.

Question 3

Describe the general structure of a fungus

Answer 3

• Can be unicellular (yeast) or multicellular (mould).
• Cell wall made of chitin as well as a cell membrane.
• The body of a fungus is called the thallus which consists of long, branched hyphae filaments tangled into a mycelium mass.
• Hyphae filaments can be separated into unicellular compartments with one nucleus via a septum. They can also be aseptate and therefore contain multiple nuclei.
• Hyphae provide moulds with a large surface area relative to the volume of cytoplasm, meaning that they can effectively absorb nutrients from their environment.

Question 4

What is a fungal spore and how is it important in fungal survival

Answer 4

• They are unicellular biological entities produced by fungi which allow them to survive.
• They can be part of the main lifecycle of a given species, or only produced under adverse conditions in other species to allow them to survive.
• They are very stress tolerant.
• They are often light and small and are therefore good for dispersal purposes.
• They are typically haploid and are generated through a process called sporulation.
• They are very characteristic and are used to identify different species of yeasts and moulds.

Sporangiospore - spores produced inside a sac called a sporangium. Asexual sporangia are commonly produced by the phyla Chytridiomycota and Zygomycota.
Condiospore - spores are mounted on the tip of a mould hypha. Multicellular fungi from the phylum Ascomycota produce condiospores.
Blastospore - produced by budding of a dividing mother cell. Fungi from the phylum Glomeromycota produce blastospores.