Microbial Diversity: Eukarya Flashcards
domain Eukarya is morphologically the most diverse of the 3 domains
Eukaryotes are a very diverse group, how are they classified?
- 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
Eukaryotes are classified into…
- 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
describe the Opisthokont clade
- animals, true fungi and microsporidia
what are choanoflagellates?
- 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
what does presence of a flagella differentiate
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
How do funig play essential roles in a diverse ecosystem
- 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
explain how fungi are natures recylers
- 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
what traits are common to most fungi
- 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
describe fungal mycelium
- 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)
fungi can be unicellular or multicellular, give examples of uniellualr
- 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
describe sexual and asexual reproduction in yeast
- 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
why are unicellular fungi model organisms for study of eukaryote cell biology
- 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
what is mycorrhizae
- 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
how do plants communicate
- using an ‘internet’ of fungus
some fungi are pathogens, give examples of opportunistic fungi pathogens
- 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
what is Ophiocordyceps unilateralis
- fungi that infects insects
- ’ mind controlling’ fungi pathogen
- fungal spores enter the ant’s bod through enzymatic damage to the chitin exoskeleton
what are amoebas?
- 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)
some stories of amoeba in the news
-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
describe slime molds
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
describe algae
- 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
describe the concept of primary and secondary endosymbiosis
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
what is the rhodophyta clade
- 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
ex of alveolates
- Dinoflagellates – phototrophs & predators
- Apicomplexans – specialized parasites
what are diatoms
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’
what are dinoflagellates & Red tides
- 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
what are apicomplexans
- 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
what is Plasmodium falciparum
- 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
describe protozoa/protists
- 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
what are trypanosomes
- 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
what is Leishamia species
Ex f protezoa/protists
Leishmania species – cause leishmaniasis
- transmitted by sandflies vectors)
- affects skin, mucous tissues, cartilage, heart, decay of extremities, death
