Microbiology - Outcome 2 - Fungi Flashcards
Describe and Explain Aspects of Eukaryotic Micro-organisms
what are fungi?
eukaryotic micro-organisms
what 2 broad groups can fungi be divided into?
- unicellular fungi or yeasts
- multicellular higher fungi or moulds
are all fungi heterotrophic?
yes - means they require organic foodstuffs
What type of organism is mould and how does it obtain nutrients?
- mould is a saprophytic organism
- obtains nutrients by decomposing dead or decaying organic matter
how can most fungi be described in terms of their oxygen levels?
aerobes
however yeast - are facultative anaerobes
where can fungi grow?
- wood
- paint
- paper
- synthetic plastics
what organelles do ALL fungi contain?
usual complement of internal organelles eg. nucleus, cell membrane, cell wall, rough ER
what external structure do fungi lack?
flagella
what are yeast?
single celled organisms which possess a single nucleus
how do yeast reproduce?
- asexually by budding
- sexually by spore formation
what is mould?
- multicellular organisms
- possesses long, thread-like filaments of cells called hyphae
what is it called when mould has a large mass of hyphae present?
mycelium
what are fungal hyphae?
tubular structures which have an outer cell wall and a hollow lumen - contains cytoplasm and organelles
what is the hyphen tube separated by?
- septum/ cross walls
- which forms barriers across a filament
what are the hyphae called that possess cross walls?
septate
what is cytoplasmic streaming?
where pores in the cross walls of septate allow movement of cytoplasm, nutrients and organelles between adjacent compartments.
what are the hyphae called that do NOT possess cross walls?
aseptate
what are vegetative hyphae?
- form mycelia
- anchor fungus in its substrate
- enable fungus to obtain nutrients from environment
what is reproductive hyphae/aerial hyphae?
- hyphae that stick up into air
- reproductive spores are formed
what is a characteristic of asexual reproduction on yeast?
bud scars
how do moulds reproduce?
- by fungal spores
- specialised cells that can function as resting or dispersal structures
what are the two types of fungal spores produced when moulds reproduce?
- asexual spores
- sexual spores
what is an asexual spore?
- genetically similar to its parent
- formed by asexual division
what is the most common type of mould that develops spores inside a sack and what are they called?
- mucor
- sporangium moulds
what is the sac called that contains sporangium?
sporangiospore
what type of variation of aerial hyphae is seen on penicillium mould?
- chains of spores known as condida that forms on end of aerial hyphae
what does sexual reproduction in moulds allow?
genetic variation - occurs less frequently than asexual reproduction
what does the production of sexual spores allow?
- mixing of genotypes
- can be used as a means of classifying fungi
describe what happens in zygomycetes in terms of sexual reproduction
- zygomycetes are a group of fungi
- sexual spore - zygospore - formed between hyphae opposite mating types
- haploid nuclei from each mating type fuse to form single (diploid) nucleus
describe what happens in ascus in terms of sexual reproduction?
- sexual spores ascomycetes form inside an ascus
- ascus can contain 8 ascospores
what is the structure called where fungi house their sexual spores?
fruiting body
what are moulds classed as In terms of pH?
acidophiles
what are fungi classed as in terms on temperature?
mesophiles
what mould has thermophilic properties?
penicillum dupontii
what process do fungi carry out in order to digest decaying plant material?
exodigestion
describe what happens during exodigestion
- secreting enzymes to digest cellulose in plant cell walls in order to gain access to cellular components
- small/simple (simple sugars, amino acids) molecules in solution can then be absorbed directly across fungal wall and cell membrane
- larger/complex molecules (polymers - polysaccharides and proteins) must be first broken down into smaller molecules which can then be absorbed
- this degradation takes place outside fungal cell and is achieved by enzymes which are either released through or are bound to fungal wall - extracellular enzymes
- once absorbed, nutrients distributed throughout mycelium by process of cytoplasmic streaming
what are moulds described as in terms of oxygen?
- obligate aerobes
- carry out aerobic respiration to produce energy
what are yeasts described as in terms of oxygen?
- obligate aerobes or facultative anaerobes
- use glucose in respiration
what do yeast produce when they respire anaerobically?
ethanol and less energy
what are the two antimicrobial chemicals that target fungi?
fungicidal chemicals and fungistatic chemicals
give an example of an item that contains a fungicide?
paints
how do fungicidal agents work?
by targeting specific enzymes within the fungus (sterol synthesis) and others inhibit mitochondrial function
give an example of a fungistatic item and how does it work?
-anti-fungal medicines
- fluconazole
- treat Candida
- interferes with synthesis of fungal cell membrane
what family of yeast mostly dominates the skin?
malassezia - feed on fatty secretions
give an example of a commensal relationship between fungi and humans?
- pneumocytosis
- lost genes for building some essential compounds so takes human
- can become an opportunistic pathogen and spread throughout the lungs if immune system is distrupted
what can be a result of the immune system attacking malassezia?
- eczema
- dandruff
describe what happens in soil regarding fungi?
- live on dead organic matter - decomposing them and returning nutrients to soil to improve soil fertility
what are mycorrhizae?
- mutualistic partnerships between between plant roots and fungi
- occurs when various species of mould attach themselves to roots of plants
why is the relationship between mycorrhizal fungi and plants considered mutualistic?
- plant feeds itself by photosynthesis and supplies carbohydrates to the fungus
- fungus sustains relationship by extending mycelium into soil - anchors plant and increases surface area for capturing water from dry soils and minerals from poor soils
what surfaces do moulds thrive in?
- surfaces on damp homes
- humid air in bathrooms and kitchens provides temperatures for mould to flourish
what industries use fungi as a basis and which fungi do they use?
- baking and brewing (Saccharomyces)
- preparation of cheese (penicillin roqueforti)
what fungus was the antibiotic penicillin derived from?
penicillin notatum
what fungus is mevinolin derived from?
Aspergillus terreus
what role does mevinolin play in terms of medicines?
basis for a number of statin medications that are used to treat high cholesterol
what role do fungi play in nature?
decomposers in carbon cycle - recycle nutrients from dead plants and animals back into soil
what are other indirect effects on humans caused by fungi?
- spoil fruits, vegetables and other fruit stuff - economic impact
- cause dry rot (merilus lacrymans)
- wet rot (coniophora cerebella)
describe the detrimental effect of aspergillus flavus
- grows on stored nuts and grains
- produces chemical called aflatoxin which is poisonous and causes liver cancer in humans - lethal if larger dose
how does aspergillum flavus enter the body?
consume nuts or grains that are contaminated
what fungi induce animal and human diseases?
- mycoses
- superficial mycoses (surface of body)
- systematic mycoses (within body)
what are examples of superficial mycoses?
- hair and nail fungal infections
- ringworm and athletes foot (trichophyton mould)
- thrush (candida)
