Microbio MT 2 Flashcards
Average size of a bacteria cell compared to unicellular protist?
Bacteria: 1 - 3 uM
Protists 3 - 500 uM, typically between 10-100uM.
Size of an organism in relation to its Reynolds number
Smaller sizes = Smaller Reynolds number
Re = (Density * Speed * size of object) / Viscosity of liquid
What is the consequence of protists having low momentum?
They stop very quickly with no propulsion requiring a relatively large amount of energy to keep moving.
Cocci morphology
Oval
Don’t change shape
Why don’t morphological types always reflect relatedness?
Some protist species can match multiple morphological types and they are different from taxonomic groups.
Microtubule structure and functions (broad)
Tubulin
Structure, spindle, transport, flagella
Microfilament structure and functions (broad)
Actin
Structure, transport, cytokinesis (contractility)
Microtubule structure (specific)
Alpha and beta tubulin monomers come together to make tubulin dimers that stack to create protofiaments.
13 protofilaments make one complete microtubule.
Approximately 20 nM diameter
Microfilament structure (specific)
Motor protein?
Actin monomers join together to create microfilaments.
Myosin is motor protein
7nM diameter
Microtubule motor proteins
Kinesin and Dynein
Kinesin moves in the positive direction and dynein moves in the negative direction.
Microtubules grow and shrink at the positive side.
Flagellar roots purpose
Basal body alone not enough of an anchor for flagella to move. Flagellar roots anchor the basal body allowing necessary stability.
Axoneme structure
9 + 2
Central pair of microtubules is surrounded by 9 microtubule doublets.
The doublets are composed of one complete MT with 13 protofilaments fused with a second incomplete MT with 11 protofilaments.
What drives the beating of cilia and flagella?
two arms of dynein are attached to each A tubule, and it is the motor activity of these axonemal dyneins that drive the cilia and flagella.
Basal body function
Basal bodies serve to initiate the growth of axonemal microtubules, as well as anchoring cilia and flagella to the surface of the cell.
Basal body structure
9 x 3 - Nine triplets of microtubules
Each of the outer microtubule doublets of the axoneme is formed by extension of two of the microtubules present in the triplets of the basal body.
What is in between the axonemes and the basal body?
The transition zone
MTOC
Microtubule organizing centers
Areas of the cell from which microtubules emerge, assemble and are regulated.
Centrosome
Relatively large discrete, organelle-like MTOC involved in forming the spindle
Centrioles
Two of them form the basic structure of the animal centrosomes.
Homologous to basal bodies
Rare among other eukaryotes
What protists typically have only 1 flagells?
Opithokonts
What amount of flagella is the most common?
2
Stramenopile flagella
They have two, one with mastigonemes
Dinoflagellate flagella
Longitudinal flagella for propulsion, transverse for stability.
Mastigonemes
Extracellular hair like structures
When flagella have mastigonemes they pull the cell instead of pushing.
Undulating membrane
Extension of the cytoplasmic membrane or flagella helping movements.
Creates a fin for moving in thick liquid.
Typical in Parabasalians
Cilia used for crawling?
Cirri
Photoreceptor and stigma
Stigma blocks light to the photoreceptor.
As the organism rotates the stigma blocks light allowing for the detection of the direction of the light.
What groups don’t have flagella?
Red algae, fungi
Pseudopodia
Any cellular protrusion that changes it’s shape.
Pseudopodia used for locomotion:
Lobopodia and Filopodia
Pseudopodia used for feeding:
Detriculopodia, Axopodia,
Filopodia and Lobopodia shape
Filopodia are slender
Lobopodia are lobose and blunt, most having shells. Mostly amoebozoa, some excavates.
Both are microfilaments
Detriculopodia
Mostly foramiferans
Branching filaments that fuse together to form food traps.
Microtubules
Most have shell
Not flagella - change shape
Axopodia
Microtubules
Doesn’t change shape, only grows and shrinks
How do lobose amoeba produce enough force to propell cytoplasmic stream?
Actin squeeze the cell pushing cell content (in a ring).
Actin polymerizes (grows) pushing membrane.
Cytoskeleton
Precise term
Ancestral, super system conserved in eukaryotes
Microfilaments, microtubules
Skeleton
Vague term
Refers to endo (below PM) and exoskeleton (above PM)
Siliceous skeletons
Diatoms extracellular wall (frustule)
Polycistine Radiolarians - silica
Calcareous skeletons
Haptophytes –> Coccolithophorids
Foramiferans –> Amoeba with reticulapodia
Abundance of organisms with natural skeletons
All very abundant organisms - Huge biomass controls recycling of organisms
Sediment at bottom of ocean
Silica doesn’t dissolve in water and CaCO3 only dissolves very deep leading to lots of sediment.
How do salt water organisms control their buoyancy?
The skeleton and cytoplasm is more dense than water.
They can pump ions and salts out of their large aqueous vacuole lowering their density below that of seawater.
How come freshwater protists don’t swim?
They can’t pump ions and salts out of aqueous vacuoles to allow them to float.
No aqueous vacuoles.
Where does phagocytosis occur in Acontharea?
In the ectoplasm
What opens the plate of cortex by contracting to allow Acontharea to eat?
Myonemes contract to allow pseudopod to go through the hole to eat prey.
Organisms that use light for energy? Chemical bonds?
Phototrophs and chemotrophs
Organisms that fix carbon vs consume organic molecules
Autotrophs can fix CO2.
Heterotrophs consume organic molecules
Organisms that get electrons from inorganic vs organic molecules?
Lithotrophs from inorganic, organotrophs from organic molecules.
Electron acceptors (not a trophic strategy)
O2 - Aerobes
Anything else - Anaerobes
Eukaryote trophic strategies
Chemoorganoheterotrophs or photolithoautotrophs
What organisms are good at osmotrophy
Bacteria (only form of heterotrophy in bacteria and archaea) and fungi (hyphae).
Oomycetes
Unicellular eukaryotes not good at osmotrophy, lower SA to volume ratio.
Phagocytosis exclusivity
Exclusive to eukaryotes
One of the most important events in the history of life that allowed eukaryotes to grow by consuming other organisms.
How do protists sense their environment?
Mechanoreception –> Contact
Chemoreception
How do protists catch their prey?
Diffusion feeding –> Stay still and wait for prey
Raptorial feeding –> Capturing prey
Filter feeding
Filter feeding
Most common
Flagella used to create a water current.
Some excavates have a feeding groove where water is forced through the groove. Phagocytosis occurs when prey concentrated.
What do phagotrophic protists need?
Cytosome
Pallium feeding
Dinoflagellates extrude a feeding veil called a pallium. The pallium envelops the prey. The dinoflagellate then secretes digestive enzymes into the sac and breaks down the prey. Once complete, the dinoflagellate retracts the pallium and leaves behind any indigestible material.
Myzocytosis
Extends a penduncle that attaches and pierces prey then sucks out cellular content
Vampyrellids
Rhizaria with filose amoeba that pierce the cell wall of prey and suck out cellular content.
Digestion process
Food vacuole detaches from cytosome (mouth)
Acidosomes fuse to food vacuole and lower pH. Food vacuole becomes digestive vacuole.
Lysosomes fuse with acidified digestive vacuole and release lytic enzymes.
Vesicle with digested compounds and enzymes pinch off digestive vacuole. Enzymes are recycled.
Waste is defecated when digestive vacuole fuses with the cryptoproct (anus).
Other vesicles fuse and pinch off digestive vacuole to optimize each step.
Pre-defined path of digestive vacuole within the cytoplasm
Cyclosis
Shapeshifting as defence
Euplotes; a cilliate, change shape when predators are near into a defensive phenotype with a wing/fin that makes them harder to phagocytosize.
Extrosomes
Defense mechanism paramecium use.
Stuns incoming predators by shooting cloud of trichocysts
Trophic strategies of extra vs intracellular parasites
Intracellular parasites are typically osmotrophs due to most food already being broken down.
Extracellular parasites are typically phagotrophs
What protist steals ATP directly from hosts?
Microsporidians
Algae that are voracious predators
Most are photosynthetic dinoflagellates with plastids from red alga.
Green algae mixotrophy
Most abundant photosynthetic organism.
Also predators
Haptophyte specialized feeding structure
Haptonema
Heterotrophic organisms with algal symbionts
Ciliates, rhizarians
