IMIP Fungi

mycoses

diseases caused by fungi e.g. toxoplasmosis

what type of cells are fungi?

eukaryotic

3 major fungi groups

1. mould (filamentous)

2. yeast

3. mushrooms

what’re mould?

multicellular fungi that grow as hyphae e.g. dermatophytes

what causes malaria?

plasmodium falciparum (type of parasite → protozoa → sporozoa!!!)

what’re yeast?

unicellular microscopic organisms e.g. candida albicans

fungal cell wall

composed mainly of chitin (N-acetylglucosamine) as well as glucans (glucose polymers that cross-link chitin) and mannose-bound proteins which form the outer layer

fungal cell wall function

structural and protective barrier e.g. from UV rays

fungal plasma membrane

contain ergosterol (replaces cholesterol in animal membranes!)

how do anti-fungals work?

target ergosterol in the fungal plasma membrane so don’t harm human cells which contain cholesterol!

what type of nucleus do fungal cells have?

haploid (2n)

function of Golgi apparatus, ER and vesicles in fungal cells?

protein modification and secretion

function of vacuole in fungal cells?

pH regulation

mould (filamentous fungi) structure and size

consists of hyphae which intertwine to form mycelium

2 - 30 microm in diameter

how do yeast reproduce?

budding and/or spore formation (both asexual)

!!!Exam Q: describe any 4 features about the dimorphism of fungi

1. many fungi can switch between mould and yeast form

2. this switch occurs in response to environmental changes

3. animal pathogens are usually filamentous (mould-like) in their saprophytic phase (when they’re feeding off of dead/decaying material)

4. animal pathogens are usually yeast-like in the pathogenic phase (when they’re causing disease)

e.g. candida albicans is a dimorphic fungus

where do fungi get their food from?

fungi are heterotrophs (can’t synthesise their own food) so rely on organic substances. they acquire nutrients by absorption.

fungi are either 1. saprophytes (live off dead/decaying matter) 2. parasites (get food from host) 3. mutualists (benefit themselves and their host)

4 methods of fungal asexual reproduction

1. fragmentation: mycelium separates into pieces which each grow into a new colony (happens in moulds)

2. budding: bulge forms on cell, nucleus divides and bud detaches (happens in yeasts)

3. fission: cell undergoes nucleus division, producing 2 identical daughter cells

4. spore formation (most common): spores produced by one parent via mitosis and are genetically identical to that parent

2 types of fungi reproduction spores

1. conidiospores: released from tip/side of hyphae

2. sporangiospores: produced in a sporangium

sexual fungi reproduction

introduces genetic variation and often occurs in response to adverse environmental conditions

parasite

any organism that lives on or in a host organism and gets it’s food from or at the expense of the host

3 main parasite classes

1. protozoa: unicellular eukaryotes e.g. toxoplasma gondii from infected cat faeces

2. helminths: multicellular worms e.g. tapeworm

3. ectoparasites: arthropods e.g. lice and ticks

how can protozoa survive adverse conditions?

they form protective cysts and ingest food through their small mouth aka cytosome

ectoparasites

arthropods that live on/in skin; important as vectors e.g. lice and ticks

vectors

animals that transmit pathogens from one host to another

how are infectious protozoa classified?

based on movement

4 infectious protozoa movement classifications

1. amoeboids - form temporary “false feet” to move

2. flagellates - use 1+ flagellas to move and sense surroundings

3. ciliates - use short, hair-like structures (cilia) to move and gather food

4. sporozoa - organisms whose adult stage is not motile e.g. toxoplasma and plasmodium

helminths 3 main groups

1. flatworms e.g. tapeworms and flukes

2. roundworms e.g. threadworms aka pinworms

3. thorny-headed worms

how’re helminths (worms) transmitted?

1. contaminated food/water

2. soil

3. faecal-oral route (esp pinworms in children)

!!!Exam Q: what is a common cause of thrush?

candida albicans

!!!Exam Q: in mould, hyphae keep growing and intertwining until they form a network of threads called a…

…mycelium

!!!Exam Q: what is a common protozoal infection that can be caught from the faeces of infected cats?

toxoplasmosis (v dangerous for unborn babys)

!!!Exam Q: what disease is caused by the protozoal (sporozoa) parasite Plasmodium falciparum

malaria

!!!Exam Q: the 3 main groups of helminths that are human parasites are thorny-headed worms, flatworms and…

…roundworms e.g. pinworms

!!!Exam Q: which group of protozoa form temporary 'false feet' (pseudopods) to move?

amoeboid

!!!Exam Q: describe TWO similarities and TWO differences between bacterial and fungal cells

similarities: 1. both contain cell wall

2. both contain ribosomes

differences: 1. bacteria are prokaryotic cells while fungi are eukaryotic

2. bacterial cell wall mainly consists of peptidoglycan while fungi cell wall main consists of chitin