Lab 11 - Motility Flashcards
what is brownian motion?
small, random movements exhibited by bacterial cells due to collisions with water molecules or other cells in their vicinity
how do the cells look during brownian motion?
they look like their vibrating, or moving slow in a floating type of motion
what is motility?
purposeful movement of bacterial cells using structures like flagella
define chemotaxis
motility in response to a chemical concentration gradient
what is an example of how chemotaxis happens?
when the cells are moving towards a nutrient or moving away from a toxin
what are two examples of chemotaxis sub examples?
chemoattractant - towards something (nutrients)
chemorepellent - away from something (a toxin)
what are four types of motility?
-twitching
-gliding
-flagella
-axial filaments
what does twitching use to move?
it uses its pili
how does twitching work?
the pili attach to a solid surface; as some pili extend at one edge, other pili retract from another edge causing the cell to crawl on the surface
what is an example of bacteria that use twitching to move?
Pseudomonas aeruginosa
what is gliding?
it is similar to twitching, except no pili are involved
what is an example of a bacteria that uses gliding to move?
Flavobacterium psychrophilum
what are the 3 parts of the flagella?
-Basal body: PMF-driven motor (proton-motor force).
-Hook: hinge, changes position with respect to the rotation of flagella; it is either perpendicular or parallel to the cell surface.
-Filament: the corkscrew-like structure made of flagellin protein subunits (also called H-antigen)
what are the H-antigens?
the flagellin protein subunits within the filament of the flagella
what do the proteins in the basal body act as?
they act as a motor, rotating when energy is supplied. The source of energy for the basal body is the proton motive force
what do the proteins in the basal body act as?
they act as a motor, rotating when energy is supplied. The source of energy for the basal body is the proton motive force
how does the flagellar movement happen?
??
what is the run-and-tumble?
it is a biased random walk
what is the run part of the run-and-tumble?
when the basal bodies all run in one direction - all filaments get flexed to form a superflagellum; the cells move in a straight line
what is the tumble part of the run-and-tumble?
when the basal body reverses directions - the filaments point in different directions - the cell moves randomly in all directions
T/F: the bacteria swims using run and tumbles sequentially
true
how long does the bacteria swim during run-and-tumble if they’re running in the direction of the nutrients?
runs long if it’s swimming in the right direction (like towards the nutrients)
If during the run, nutrient concentration is increasing, what will happen?
If during the run, nutrient concentration is increasing, it will be a long run (4-6 seconds)
If during the run, nutrient concentration is decreasing, what will happen?
If during the run, nutrient concentration is decreasing, it will be a short run (1-2
seconds)
where is the overall movement toward for run-and-tumbles?
towards the nutrients
what happens in axial filaments?
The whole cell rotates like a microscopic drill helping the bacterium to drill through human tissues
what are examples of bacteria that perform axial filaments and the disease they cause?
Spirochetes:
like Treponema pallidum (syphilis)
and Borrelia burgdorfi (Lyme disease)
??
Endoflagella or periplasmic flagella
what is the purpose of viewing motility?
Motility is viewed to help identify unknown organisms; it
helps to narrow down the possibilities, since not all
organisms are motile
what is the procedure for viewing motility?
-Make a hanging drop slide that suspends bacteria upside-down from a cover slip into a depression slide
-Using the 40X objective, focus on bacteria at the edge
of the drop to assess for motility
motility usually involves flagella, but can we see flagella under the microscope?
No, flagella are too small to
be seen with a light microscope (without staining)
are all bacteria in a culture alive?
No, not all bacteria in a culture are alive, so if you see any
motility at all, the culture is motile
is brownian motion motility?
Brownian motion is NOT motility, but represents water
molecules colliding with cells, making them rock back-and
-forth
