Microbial Diversity: Eukarya

Question 1

domain Eukarya is morphologically the most diverse of the 3 domains

Question 2

Eukaryotes are a very diverse group, how are they classified?

Answer 2

• All have a nucleus and membrane enclosed organelles but few are amitochondiate (lack mitochondria) and have few organelles

*believed they lost it, degenerative evolution

• All descended from an ancestral cell that ungulfed a Protobacterium (Gram neg) bacterial endosymbiont - became a mitochondrion
• Mitochondria conduct oxygenic respiration
• all phototrophic eukaryotes arose from an acestral eukaryote cell that engulfed an ancestral photosynthetic bacteria (cyanobacteria) that became a chloroplast
• chloroplasts condust oxygenic photosynthesis

Question 3

Eukaryotes are classified into…

Answer 3

• 8 different calsed; unicellular/microscopic forms dominate
• based on DNA sequence comparisions and protein trees
• sequence based calssification of eukaryotes has many challenges

*genomes are much larger (than prok) so many cases of reductive/degenerative evolution, convergent evolution

• 50-90% of DNA sequences are non-coding
• eukaryote evolution involved in serial endosymbiosis

*NO mitochondria in metamonada clade

Question 4

describe the Opisthokont clade

Answer 4

• animals, true fungi and microsporidia

Question 6

what are choanoflagellates?

Answer 6

• in the opisthokont clade
• considered the mixxing link between animals and microbial eukaryotes
• diverged most recently from animals (600 mya)
• while genome seq reveleaed interesting similarities to modern eukaryotes:

*Five immunoglobulin/antibody genes - yet choanoflagellates have no immune systems

*Collagen, cadherin & integrin domains - yet choanoflagellates ahve no cytoskeleton, or matrix binding cells together

*tyrosine kinase genes - yet they are not knwon to communicate or signal intracellularly or intercellularly with each other

Question 7

what does presence of a flagella differentiate

Answer 7

sets apart animals from protists and eukaryotes from prokaryotes

• Prokaryotic flagellum has a basl body, hook and rigid filament, the hollow filament is composed of flagellin protein
• eukaryotic flagellum has a basal body and flexible filament. the filament is packed with microtubes arranged in a 9+2 pattern

Question 8

How do funig play essential roles in a diverse ecosystem

Answer 8

• different species show vastly different forms - ex mushrooms (caps = fruting bodies that can weigh several pounds) to the mycelia of pathogens and the symbiotic partners of algae in lichens
• fungi provide essential support for all communities of multicellular organisms
• are natures recyclers: saprophytes
• some fungi are pathogenic to animals and plants - others produce antibiotics and food products like wine and cheese

Question 9

explain how fungi are natures recylers

Answer 9

• ex: saprophytes
• break down dead and decayng organic matter to release for other living thigns to suce
• fungi recycle the biomas of wood and leaves which other orgnaisms may be unable to digest (ex: ligins, pectins)

*they are chemoorganoheterotrophs: draw energy from organic material

• underground fungal filaments called mycorrhizae (plant symbionts) extend the root systems of most plants
• within the ruminant digestive tract, fungi (and bacteria) ferment plant materials

Question 10

what traits are common to most fungi

Answer 10

• most fungi grow by extending hyphae into the substrate/food source

*hyphae grow at the tips forcing thier way into the substrate

• hyphae: multinucleate ell filaments which branch extensively generating a mycelium

- cell walls contain chitin polymers of immense tensile strength, stronger than steel

• membranes contain phospholipids and ergosterol an analog of cholesterol not found in animals or plants
• absorptive nutrition: secretion of degradative enzymes into the extracellular environment and then absoroption of the broken down/simpler products/nutrients

Question 11

describe fungal mycelium

Answer 11

• a mass of extending braching hyphae
• mycelia are the vegetative part of the gunfi; largest body mass - extend into and are hidden in the food substrate
• spores are aerially displayed to allow for optimal dispersal, they are the reproductive part

(like the mold on an organe, thats the spore)

Question 12

fungi can be unicellular or multicellular, give examples of uniellualr

Answer 12

• unicellular fungi = yeast
• reproduce asexually by budding
• yeasts have no hyphae and mycelia
• ex: Saccharomyces cerevisiae, Baker’s yeast, and Schizosaccharomyces pombe (and other species) Brewer’s yeast

*Canadida albicans is a unicellualr fungi - an opportunistic pathogen and can grow also as mycelia

Question 13

describe sexual and asexual reproduction in yeast

Answer 13

• some yeastas are asexual - never amte
• others like Saccharomyces cerevisiae have a life cycle that alternates between haploid (1n) and diploid (2n) forms
• haploids develop gametes (1n) for fertilization producing a 2n diploid zygote
• dilpoids undergo meiosis, restoring the haplid form

Question 14

why are unicellular fungi model organisms for study of eukaryote cell biology

Answer 14

• have haploid genome
• they are eukaryotes so can be used as a proxy to study mammalian cell process
• saccharomyces cerevisae is used as a model organism, there are libraries where there genes have been mutated so you can do study for specific gene functin
• use to study protein folding, vesicle trafficking, lipid biology

Question 15

what is mycorrhizae

Answer 15

• fungi involved in mutually beneficial and essential symbiotic relationships with plant roots
• some species (armillaria) can spreaf for thousands of acres within forests and some are suspected to be over 8000 years old

Question 16

how do plants communicate

Answer 16

• using an ‘internet’ of fungus

Question 17

some fungi are pathogens, give examples of opportunistic fungi pathogens

Answer 17

• Candida albicans – thrush, candida in humans
• Pneumocystis jirovecii (formerly P. carinii) causes pneumonia
• Chytridiomycota sp. – responsible for massive global frog die-off
• Nosema species in bee colony collapse disorder

Question 18

what is Ophiocordyceps unilateralis

Answer 18

• fungi that infects insects
• ’ mind controlling’ fungi pathogen
• fungal spores enter the ant’s bod through enzymatic damage to the chitin exoskeleton

Question 19

what are amoebas?

Answer 19

• protists
• look like amorphous blobs of jelly
• able to move trhough production of pseudopods (false feet)

*cytoplamc motility is complex, involved actin polymerization/depolymerization (more oslid-more liquid form)

• a few species are parasites of human/animals
• most are free-living in soil and water - engluf prey (microbes) using phagocytosis
• also act as environmental hosts for bacterial pathogens
  ex: listeria monoctogenes, mycobacterium
• used as a model organism for study of animal phagocyte/macrophage cells (interaction with microbial pathogens, motility)

Question 20

some stories of amoeba in the news

Answer 20

-Naegleria fowlerii - brain eating amoeba, feed on environmental bacteria/microbes. If inhaled in water aerosoles they establish infection in the repsiratory tract, from there can cross the bbb and feed on brain tissues

Question 21

describe slime molds

Answer 21

protists

• were thought of as fungi - hene mold

*instead have ccellulose not chitin in cell walls, aggregate to form multicelular structues

• two kinds:

cellular slime molds:

• E.g Dictyostelium discoideum
• Individual cells remain single/cellular, but in a swarm (work as community, move together)
• when unfavourable condiitons an come together in response to a signal, then aggregate to form a complex fruiting body (Fig 20.31)

Plasmodial slime molds

• E.g Fuligo septica (Dog’s vomit mold),
• The mass/swarm of cells comes together in response to a signal, but then fuse into a giant cell of full of many nuclei

Question 22

describe algae

Answer 22

• all have chlorplasts
• primary producers, most crucially aquatic and marine habitats
• in aquatic and marine ecology the algae and photosynthetic bacteria are known as phytoplankton
• have diverse lifestyles and morphologies - inlcude lichen symbionts
• two major types: primary and secondary endosymbiotic algae

Question 23

describe the concept of primary and secondary endosymbiosis

Answer 23

primary

• ancestral pre-eukaryote cell engulfed either
  
  • an acestral proteobacterium which became a mitochondrion (ancestor of modern protozoa, fungi, animal cells)
  • an ancestral phototrophic bacterium/cyanobacterium which became the chloroplast
  • all are phototrophs

Secondary

• eglufment of a primary phtototrophic endosymbioent (ex algae) has been englufed by a mitochondrion containing eukaryote
• distinguishing feature - the chloroplast is surrounded be 2 membranes from each event

Question 24

what is the rhodophyta clade

Answer 24

• some algae grow in large sheets but are only 2 cells thick
• red algae
• contain commercially valuable polymers ex: sulfated polygalactans (include agar and agarose)

several kinds are human food sources (ex Phorphyra) - mori used to wrap sushi

Question 25

ex of alveolates

Answer 25

* Dinoflagellates – phototrophs & predators * Apicomplexans – specialized parasites

Question 27

what are diatoms

Answer 27

Secondary endosymbiotic algae * Unicellular algae with unique, protective bipartite shells / Frustules * made of silica (glass) * Frustules form some of the most beautiful forms found in nature * Cell division is interesting! * Dead diatoms sink to the sediment and form ‘diatomaceous earth’

Question 28

what are dinoflagellates & Red tides

Answer 28

- part of alveolate clade - major group of marine phytoplankton - algal symbionts and critical endosymbionts of reef-building corals (provide organic components to other organisms) - Characteristic feature: possess 2 flagella, one is wrapped around the cell in a specialized groove - some supplement photosynthesis through prodation (heterotrophy) - some possess carotenoid pigments that confer a red colour, blooms cause red tise that releases toxins causing shellfish posioning and death

Question 29

what are apicomplexans

Answer 29

- alveolates - animal parasitesex Plasmodium falciparum * spore (oocyst)-forming Cryptosporidium gondii and Toxoplasma sp. * Malaria causing, insect-vector transmitted Plasmodium sp. -Have undergone extensive reductive evolution Possess two important/characteristic organelles: * ‘Apical Complex’ which the parasites use to attach to & gain entry into host cells. * Apicoplast – for lipid metabolism \*\*Toxoplasma gondii, a mind-controlling parasite, oocysts are transmitted in cat feces; parasite cells can cross placenta barrier and harm fetus

Question 30

what is Plasmodium falciparum

Answer 30

- best known apicoplexans - requires both the insect vector and animal host for completion of the life cycle - causative agent of human malaria - transmitted via saliva of the blood-feeding *Anopheles* sp. mosquitoes \*undergoes different development stages in the vector's gut and salivary glands - effective control must involve target both the parasites and vectors - in the human host the parasite has a complex lifecycle with several different stages in the liver and RBC \*can breach the placenta and brain barriers

Question 31

describe protozoa/protists

Answer 31

- most are harmless free-living protists and commensalas in guts of animals - are voracious feeders of other microbes including bacteria - few species cause serious/ deadly animal diseases - ex: * Cyst-forming Entamoeba histolytica – amoebic dysentery, liver abscesses, etc * Giardia sp – feces contaminated water, cause severe diarrhoea, cramps

Question 32

what are trypanosomes

Answer 32

- cause some of the most gruesome and debilitating condiitons - They are obligate parasites; are transmitted by insect vectors - They consist of an elongated cell with a single flagellum. - The trypanosome has a unique organelle called the “kinetoplast” - Specialized ‘part’ of the parasite mitochondria

Question 33

what is Leishamia species

Answer 33

Ex f protezoa/protists Leishmania species – cause leishmaniasis - transmitted by sandflies vectors) - affects skin, mucous tissues, cartilage, heart, decay of extremities, death