MIC2011 Week 3

what is the defining structural feature of a eukaryotic cell, and what major advantage does it provide?

a membrane-bound nucleus (and other organelles). this allows compartmentalization of cellular processes, enabling greater complexity than in prokaryotes.

describe the basic structure of the eukaryotic cell membrane. how does it compare to Bacteria and Archaea?

structure: phospholipid bilayer with ester-linked fatty acids, reinforced with sterols (cholesterol, ergosterol).

• comparison: same ester-linkage as Bacteria. archaea have ether-linked lipids and generally lack sterols

what are the key features of the eukaryotic nucleus?

• site of DNA replication & transcription

• linear DNA packaged with histones into nucleosomes

• enclosed by a double membrane (nuclear envelope) with pores

• contains nucleolus (rRNA synthesis & ribosome assembly)

compare eukaryotic and prokaryotic DNA form and packaging.

• eukaryotes: linear, multiple chromosomes, with histones.

• bacteria: circular, single chromosome, no histones.

• archaea: circular, single chromosome, histone-like proteins.

what are the functions of the Smooth ER and Rough ER?

• smooth ER: carbohydrate & lipid (including sterol) synthesis.

• rough ER: membrane protein synthesis (has bound ribosomes).

what is the role of the Golgi apparatus in the endomembrane system?

receives transport vesicles from the ER at its cis face, modifies them (glycosylation, phosphorylation), and buds vesicles from its trans face to send them to their final destinations.

how do lysosomes function in the endocytic pathway?

lysosomes contain hydrolytic enzymes and fuse with phagosomes (formed by engulfment) to perform intracellular digestion.

name the three types of endosymbiotic organelles involved in ATP/metabolism and their functions.

1. mitochondria: site of aerobic respiration.

2. hydrogenosomes: site of fermentation (H₂ production) in anaerobic parasites.

3. mitosomes: Iron-sulfur cluster synthesis (no ATP) in anaerobic parasites.

what evidence supports the endosymbiotic theory for mitochondria and chloroplasts?

both have their own circular DNA and prokaryotic-sized (70S) ribosomes.

describe the basic structure of eukaryotic flagella and cilia. how does their power source compare to bacterial flagella?

structure: same 9+2 axoneme (9 microtubule doublets around 2 central singlets). differ only in length.

• power source (Eukaryotes): ATP-powered

• power source (Bacteria): proton motive force

compare eukaryotic and archaeal flagella.

they are similar – both are ATP-powered. (bacterial flagella use proton motive force).

fill in the blanks: eukaryotic ribosomes are __S, while bacterial and archaeal ribosomes are __S.

eukaryotic = 80S (larger); Bacteria & Archaea = 70S (smaller).

how does the cell wall composition differ between eukaryotes, bacteria, and archaea?

• eukaryotes: variable (cellulose, chitin, agar, or absent)

• bacteria: peptidoglycan

• archaea: pseudopeptidoglycan or other

compare membrane sterols across the three domains.

• eukaryotes: yes (cholesterol, ergosterol)

• bacteria: generally no

• archaea: generally no

what are the four defining features that make a eukaryote a fungus?

1. nutrition: heterotrophic (chemo-organo-heterotrophs) – decomposers or parasites.

2. cell wall: composed of chitin.

3. cell membrane: contains ergosterol (unique fungal sterol).

4. relationship: more closely related to animals than plants (both store carbon as glycogen, lack chloroplasts, have chitin).

what does it mean that fungi are "osmotrophic"?

they secrete digestive enzymes and then absorb the released nutrients. this is a key feature of all fungi.

what is the single unifying feature of all protists? why are they considered polyphyletic?

unifying feature: they are eukaryotes that are NOT animals, plants, or fungi.
polyphyletic: they do not share a single unique common ancestor (unlike plants, animals, and fungi, which are monophyletic). protists are a "catch-all" group.

based on classification features, how would you distinguish a fungus from a protist in general?

• fungi: alll share unified features – heterotrophic, chitin cell wall, ergosterol membrane, osmotrophic.

• protists: no unified features – they are everything eukaryotic that isn't a fungus, plant, or animal. includes photosynthetic algae, heterotrophic protozoa, and slime molds.

True or False? all protists are unicellular.

false. many protists are unicellular (the focus of the lectures), but the group includes multicellular forms (some algae). the key is they are not animals, plants, or fungi.

a eukaryotic microbe has a chitin cell wall and ergosterol in its membrane. is it a fungus or a protist?

fungus. chitin cell wall + ergosterol membrane are diagnostic for fungi. protists do not share these features.

a eukaryotic microbe is photosynthetic and has a cellulose cell wall. is it a fungus or a protist?

protist (specifically an alga). fungi are never photosynthetic and do not have cellulose cell walls (they have chitin).

what major taxonomic difference exists between the groups "Fungi" and "Protists"?

fungi are monophyletic (share a single common ancestor). protists are polyphyletic (no single common ancestor – they are defined by exclusion).

what is the fundamental structural difference between a yeast and a mold?

yeasts are unicellular (single cells). molds are multicellular, forming filaments called hyphae (collectively a mycelium).

how do the colony appearances of yeasts and molds differ?

yeasts produce colonies that appear smooth/creamy. molds produce fuzzy, filamentous colonies.

describe the two main types of asexual reproduction in yeasts vs. molds.

• yeasts: budding or fission.

• molds: produce conidia (asexual spores) on conidiophores, in sporangia, or via hyphal fragmentation.

do yeasts and molds have different processes for sexual reproduction?

no – they share the same conserved process: plasmogamy → dikaryon (n+n) → karyogamy → diploid (2n) → meiosis → haploid spores. in molds, this may occur within macroscopic fruiting bodies (mushrooms).

what are the two types of hyphae found in molds?

• septate: cross-walls with pores.

• aseptate/coenocytic: no cross-walls, multinucleate.

(note: yeasts do not have hyphae.)

what is a dimorphic fungus? give an example of a common trigger for dimorphism.

a fungus that can switch between yeast and mold forms. thermal dimorphism (temperature-dependent) is common in animal pathogens: mold at ambient temperature, yeast at 37°C.

what is the primary nutritional difference between protozoa and algae?

• protozoa: heterotrophic – engulf bacteria/other protists; some are decomposers or predators.

• algae: autotrophic (photosynthetic) – primary producers. some are mixotrophic (can also feed heterotrophically).

what key structural feature distinguishes protozoa from algae?

protozoa have no chloroplasts. algae contain chloroplasts (derived via endosymbiosis).

give two examples of protozoa and two examples of algae from your notes.

• protozoa: Paramecium (ciliated), Entamoeba, Trypanosoma (parasite), slime molds.

• algae: Chlorella (green microalgae), rhodophytes (red algae), zooxanthellae, diatoms.

how do the motility structures differ between protozoa and algae (general trend)?

protozoa commonly have flagella, cilia, or pseudopodia for motility. algae may have flagella in some motile stages, but many are non-motile; their key structures are chloroplasts and cell walls (cellulose, agarose) or pellicles/shells.

compare the ecological roles of protozoa vs. algae.

• protozoa: consumers, parasites, decomposers.

• algae: primary producers, carbon fixers, oxygen production.

what does "mixotrophic" mean, and how are such protists typically classified?

mixotrophic protists have chloroplasts (can photosynthesize) but can also feed heterotrophically. they are often classified as protozoa due to their heterotrophic capability.

describe Microsporidia and argue their importance.

key features: obligate intracellular parasites; lack mitochondria (have mitosomes); genome reduction; smallest eukaryotes (spores ~1 µm).
importance: infect immunocompromised individuals (SDG 3).

describe Chytridiomycetes (chytrids) and argue their importance.

key features: aquatic; flagellated zoospores (posterior flagellum).
importance: amphibian pathogens (Batrachochytrium dendrobatidis) – caused decline of 500+ amphibian species, including 7 extinctions in Australia. linked to SDG 15 (biodiversity loss driven by climate change).

describe Glomeromycetes and argue their importance.

key features: obligate mutualists; form endomycorrhizae (within plant roots); no known sexual reproduction.
importance: improve plant growth by providing phosphorus and nitrogen in exchange for carbohydrates. used to inoculate crops. supports SDG 2 (Zero Hunger) and SDG 15.

describe Mucoromycetes and argue their importance.

key features: mostly saprophytes (food spoilage); some opportunistic pathogens; produce sporangia with pigmented spores. example: Rhizopus stolonifer (black bread mold).
importance: cause mucormycosis ("black fungus") – high mortality (~50%), increased during COVID (diabetics, corticosteroid users). relevant to SDG 2 and SDG 3.

describe Ascomycetes and argue their importance.

key features: dikarya (septate hyphae, dikaryotic phase); includes yeasts and molds.
importance:

• Candida spp. (opportunistic pathogens, multidrug-resistant)

• Saccharomyces cerevisiae (model organism, bioethanol, biopharmaceuticals)

• Aspergillus (mycotoxins, allergens, bioremediation)
  Supports SDG 2, 3, 7, 12.

describe Basidiomycetes and argue their importance.

key features: dikarya; often produce macroscopic fruiting bodies (mushrooms).
importance:

• ectomycorrhizae (tree symbionts)

• plant pathogens (corn smut)

• bioremediation (oyster mushrooms clean oil spills)

• psilocybin for PTSD
  Supports SDG 2, 3, 12, 15.

what is the note about medically and industrially relevant fungi?

almost all medically and industrially relevant fungi are in Dikarya (Ascomycetes + Basidiomycetes).

describe Chlorella spp. (green algae) and argue their importance.

key features: highly efficient photosynthesis; high lipid accumulation. supergroup Archaeplastida.
importance:

• biofuel feedstock (biodiesel, bioethanol, biochar)

• wastewater bioremediation (absorbs N, P, heavy metals)

• livestock/human feed
  Supports SDG 2, 6, 7, 12.

describe Rhodophytes (red algae) and argue their importance.

key features: cell walls contain agar and agarose. some reduce methane in ruminants. native to Australia.
importance:

• agar for culture media; agarose for gel electrophoresis (microbiology labs)

• livestock feed – reduces methane burps (SDG 13)

describe Zooxanthellae and argue their importance.

key features: endosymbionts of coral; mutualistic (provide sugars to coral). supergroup SAR – Alveolates.
importance: warming oceans cause coral to eject them → coral bleaching. research into coral probiotics to save the Great Barrier Reef (SDG 14).

describe Cryptosporidium and argue its importance.

key features: parasite; causes diarrheal disease (cryptosporidiosis); forms chlorine-resistant cysts.
importance: current QLD outbreak; spreads via swimming pools; increasing due to climate change (warmer temperatures). relevant to SDG 3.

describe Foraminifera (forams) and argue their importance.

key features: produce CaCO₃ shells; form carbon sinks (sediment to ocean floor). supergroup SAR – Rhizaria.
importance:

• climate indicators: shell formation impaired by ocean acidity

• water quality surveillance – community composition correlates with water quality
  Supports SDG 13 and SDG 14.

describe Slime molds and argue their importance.

key features: unicellular amoebae that aggregate into fruiting bodies; no chitin. supergroup Amoebozoa.
importance: used as a template for urban design – slime mold growth efficiently connects nodes (road/public transport networks). supports SDG 9 (Industry, Innovation & Infrastructure).

describe Trypanosoma spp. and argue their importance.

key features: parasites spread by insect vectors (tsetse fly, kissing bug). cause African Sleeping Sickness & Chagas disease. supergroup excavates.
importance: on WHO Neglected Tropical Diseases (NTD) Roadmap. difficult to treat (late neuropsychiatric stage) and eradicate (pesticide resistance in vectors). supports SDG 3 and SDG 10 (Reduced Inequalities).

what lecture concept links climate change to fungal threats?

climate change is driving increased fungal threats (chytrids and amphibians, mucormycosis during COVID, Cryptosporidium with warming temps).

are fungi mostly harmful or helpful according to the lecture?

fungi are both friend and foe – but mostly friends (useful for achieving multiple SDGs).

what are fungal secondary metabolites, and why are they important?

fungal secondary metabolites (not needed for growth) are a rich source of bioactive compounds – including drugs (penicillin, psilocybin, cortisone) and pigments.

how do fungi contribute to SDG 2 (Zero Hunger)? give examples.

fungi improve crop yields, prevent crop loss, and provide food.

• examples: Glomeromycetes (mycorrhizae inoculants), biopesticides (Cordyceps), Quorn (mycoprotein), mushrooms/truffles, soy sauce, cheese.

how do fungi contribute to SDG 3 (Good Health & Well-being)? give examples.

fungi provide drugs, treatments, and help us understand pathogens.

• examples: penicillin (from Penicillium), cortisone, psilocybin for PTSD (TGA-approved in Australia), Candida auris (MDR pathogen on WHO priority list), microsporidia (infect immunocompromised), mucormycosis.

how do fungi contribute to SDG 7 (Affordable & Clean Energy)? give an example.

fungi are used for bioethanol production.

• example: Saccharomyces cerevisiae ferments agricultural waste (sugarcane, woody biomass) to ethanol.

how do fungi contribute to SDG 12 (Responsible Consumption & Production)? give examples.

fungi perform bioremediation and enable sustainable industrial processes.

• examples: Aspergillus degrades plastics (UV-pretreated polypropylene); oyster mushrooms clean oil spills; fungal pigments for textile industry.

how do fungi contribute to SDG 15 (Life on Land)? give examples.

fungi maintain biodiversity and form symbiotic relationships.

• examples: chytrids (amphibian decline – need to understand to protect); mycorrhizae (plant health, land plant establishment).

how do protists contribute to SDG 2 (Zero Hunger)? give examples.

protists serve as food source, livestock feed, and fertilizers.

• examples: seaweed (nori); Chlorella as feed; rhodophytes reduce methane in livestock; algal fertilizers improve crop yields.

how do protists contribute to SDG 3 (Good Health & Well-being)? give examples.

understanding/treating parasitic diseases and monitoring toxic blooms.

• examples: Cryptosporidium (outbreaks), Trypanosoma (NTDs), Leishmania, malaria. Toxic algal blooms (climate-driven).

how do protists contribute to SDG 6 (Clean Water & Sanitation)? give an example.

bioremediation of wastewater.

• example: Chlorella removes nitrogen, phosphorus, and heavy metals from wastewater.

how do protists contribute to SDG 7 (Affordable & Clean Energy)? give an example.

biofuel production.

• example: Chlorella lipids → biodiesel, bioethanol, and biochar from waste.

how do protists contribute to SDG 9 (Industry, Innovation & Infrastructure)? give an example.

urban planning templates.

• example: slime mold growth models for efficient road/public transport networks.

how do protists contribute to SDG 12 (Responsible Consumption & Production)? give examples.

waste remediation and sustainable products.

• examples: wastewater-grown algae for biofuel; agar from red algae for labs.

how do protists contribute to SDG 13 (Climate Action)? give examples.

carbon sinks, reducing methane emissions, monitoring climate impact.

• examples: foraminifera sequester carbon; rhodophytes in livestock feed reduce methane; mixotrophic algae switching from carbon fixers to emitters due to warming.

how do protists contribute to SDG 14 (Life Below Water)? give examples.

coral reef health and marine biodiversity.

• examples: zooxanthellae and coral probiotics for the Great Barrier Reef; forams as water quality indicators.

how do protists contribute to SDG 10 (Reduced Inequalities)? give an example.

addressing neglected tropical diseases (NTDs) that disproportionately affect impoverished regions.

• examples: NTDs like trypanosomiasis (African Sleeping Sickness, Chagas disease), leishmania.

which protist group is linked to SDG 15 (Life on Land) and how?

slime molds (on land) are mentioned in the context of general protist diversity, though the link is less direct than for other SDGs.

according to the lecture, are eukaryotic microbes (especially fungi) mostly harmful or helpful for achieving the SDGs?

mostly friends – they are useful for achieving multiple SDGs (Zero Hunger, Good Health, Clean Energy, Climate Action).

what role does climate change play in eukaryotic microbe-related SDG challenges?

climate change is driving increased threats:

• chytrids causing amphibian extinctions (SDG 15)

• Cryptosporidium outbreaks increasing with warmer temps (SDG 3)

• coral bleaching from loss of zooxanthellae (SDG 14)

• mixotrophic algae switching from carbon sinks to carbon emitters (SDG 13)