Lecture Set 2 : Part 4

Question 1

what are flagellum?

Answer 1

-hollow protein filaments
-provide motility

Question 2

how can we view flagellum under the microscope?

Answer 2

-specific stain (for bright-field, not usually visible without)
-dark-field microscopy
-TEM

Question 3

how do we identify flagellum?

Answer 3

-monotrichous (single)
-amphitrochous (at opposite ends)
-lophotrichous (multiple in a single tuft at 1 pole)
-perithrichous (distrubuted all around the cell)

Question 4

how can we further identify monotrichous flagellum?

Answer 4

-polar or subpolar
-polar = one-end
-subpolar = off center from the pole

Question 5

what are the 3 parts of the flagellar structure?

Answer 5

-filament
-hook
-basal body (motor)

Question 6

what makes up the filament of the flagellum?

Answer 6

-indentical protein subunits called flagellin
-forms a rigid helical protein (20 micrometers long)
-much longer than the bacteria itself

Question 7

what is the hook of the flagellum?

Answer 7

-flexible coupling of the filament and the basal body

Question 8

what makes up the basal body (motor) of the flagellum in a gram negative cell?

Answer 8

-L ring (in the LPS layer)
-P ring (in the peptidoglycan)
-MS ring (in the membrane)
-C ring (in the cytoplasm + associated with the membrane)

Question 9

what are the inner rings?

Answer 9

-MS ring
-C ring

Question 10

what are the outer rings?

Answer 10

-L ring
-P ring

Question 11

what differs in the basal body between the gram negative and gram positive cell?

Answer 11

-gram positive cell lacks the L ring and the P ring

Question 12

what is the general makeup of the basal body?

Answer 12

-central rod that passes through a series of rings

Question 13

do all cells have a flagella? why or why not?

Answer 13

-NO
-cells can have the ability to have one but they do not always express it
-this is because it is very energetically expensive due to its high complexity (takes energy to build and move)

Question 14

where does the energy to move the flagella come from?

Answer 14

-proton motive force
-high [] outside
-low [] inside
-protons will flow inside the cell through the Mot proteins of the stator (form a channel)

Question 15

how does the flagellum move? how does this differ from a eukaryotic flagellum?

Answer 15

-propellor movement
-eukarya flagella have a whip-like motion

Question 16

how is the flagella synthesized?

Answer 16

-basal body is made first by assembling in the cytoplasmic membrane and periplasm
-the hook is then added to the basal body
-flagellin proteins get synthesized in the cytoplasm and move up through a 3nm channel in the flagellum
-a cap protein puts the flagellin in the right location

Question 17

which direction does the flagellum grow?

Answer 17

-from its tip (opposite to hair)

Question 18

what type of process is flagellar synthesis?

Answer 18

-conserved process (sequence of proteins being added never changes)
-defined process
-many genes contribute to the synthesis

Question 19

how fast is the flagella’s movement?

Answer 19

-can rotate up to 1000 times per seconds
-propels the cell 60 cell lengths per second (2x as fast as a cheetah)

Question 20

what is the pattern of movement for a peritrichous flagella?

Answer 20

-series of runs and tumbles
-run = forward motion with all flagella rotating counter-clockwise in a bundle
-tumble = change of direction with all flagella rotating clockwise out of the bundle
-flagella cannot sustain a single direction
-new direction is not chosen (random)

Question 21

what is the flagella of archaea?

Answer 21

-archaellum

Question 22

how does archaellum differ from the bacterial flagellum?

Answer 22

-filament is thinner
-fewer protein types in the basal body
-rotation is driven by ATP

Question 23

is the archaellum related to the bacterial flagellum?

Answer 23

-NO
-looks similar and has the same function but is not related
-related instead to the type IV (4) pilus in terms of structure

Question 24

what is taxis?

Answer 24

-directed movement in response to chemical or physical gradients

Question 25

what are the different types of taxis?

Answer 25

-chemotaxis (chemicals) -phototaxis (light) -aerotaxis (oxygen) -osmotaxis (ionic strength) -hydrotaxis (water)

Question 26

how does chemotaxis work?

Answer 26

-directed movement toward an attractant (nutrient) or away from a repellent (antibiotic/not advantageous) -attractants and repellents are sensed by chemoreceptors

Question 27

how do chemoreceptors sense the attractants and repellents?

Answer 27

-senses temporally instead of spatially -sense [] over points in time -if the attractant [] is increasing over time they will sustain their path -if the attractant [] is decreasing over time they will change their path -opposite for a repellent

Question 28

how will bacteria move with their peritrichous flagella in the absence of a chemical attractant or repellent?

Answer 28

-move in a series of runs and tumbles -cells will all seem to move but there will be no net movement of the population -called a random walk

Question 29

how will bacteria move with their peritrichous flagella in the presence of a chemical attractant?

Answer 29

-still move in a series of runs and tumbles -if [] of the attractant is sensed to be increasing it will want to keep its path -does so by delaying the tumble and making the runs last longer (biased (directionality) random walk) -the net movement of cells will be toward the attractant (even tho some cells will be headed in the wrong direction) -if [] of the attractant is sensed to be decreasing it will want to change its path -does so by increasing its tumbles and making the runs shorter

Question 30

how will bacteria move with their peritrichous flagella in the presence of a chemical repellent?

Answer 30

-still move in a series of runs and tumbles -same reaction as the attractant, just reversed -tumbles delay and run lasts longer if [] of repellent is decreasing (biased random walk) -tumbles increase and run lasts short if [] of repellent is increasing -net movement of cells will be away from the repellent (some will be in the wrong direction)

Question 31

what is an experiment used to measure chemotaxis (see what is an attractant and what is a repellent to a bacteria)?

Answer 31

-insert a capillary tube containing a chemical into a medium containing motile bacteria -a chemical gradient will form surrounding the capillary tip -after time has passed you can count the # of bacteria in the capillary vs the number in the medium -cell # ^ in the capillary = attractant (if lower = repellent)

Question 32

what is an experiment using microscopy used to measure aerotaxis?

Answer 32

-coloured lines showing bacterial movement -large white spots of oxygen producing algae cells -coloured lines will surround the algae cells

Question 33

what term is only used to describe flagella motility?

Answer 33

-swimming

Question 34

what is surface motility of a bacteria?

Answer 34

-slower than flagellar motility -requires surface contact -several mechanisms to achieve

Question 35

what are the different mechanisms for surface motility?

Answer 35

-slime excretion -twitching motility -gliding

Question 36

what bacteria typically use the excretion of slime to achieve surface motility?

Answer 36

-filamentous cyanobacteria

Question 37

what is the twitching motility mechanism?

Answer 37

-requires the type IV (4) pili (extends from one pole of the cell) -allows cells to move together in groups -pilus is extended and then attached to a surface -ATP hydrolysis then causes the pilus to retract and drag the cell forward -done by many bacteria and some archaea

Question 38

what is the gliding mechanism?

Answer 38

-smooth (continuous) movement along the long axis of a cell -no aid by external propulsive structures -involves 3 sets of proteins -gliding motors use energy from the proton motive force to rotate (causes displacement of the helical tract which moves adhesion proteins) -cell will then rotate on its axis and get propelled forward -done by several bacteria (no archaea are known to) -ex: adventrous motility in myxobacteria

Question 39

what are the 3 sets of proteins used in the gliding mechanism?

Answer 39

-stationary "gliding motors" -helical protein track -extracellular adhesion proteins