EXAM 3: Chapter 2- Part 3 Flashcards
Cell envelope
Plasma membrane and anything external
Gram Negative cell envelope
periplasmic space larger
periplasmic space contains peptidoglycan
also has outer membrane
Gram positive cell envelope
periplasmic space is narrower and do not find a ton of enzymes
Have teichoic and lipteichoic acids that extend into plasma membrane
Teichoic and lipteichoic acids
helps anchor the peptidoglycan into plasma membrane
contributes to net negative charge and shape
Where do you find LPS
ONLY in the outer membrane of Gram-negative
What is LPS composed of?
lipid A
core polysaccharide
O antigen
Lipid A
most internal and what anchors it to the inner leaflet of outer membrane
rigid
two fatty acid tails
Core polysaccharide
usually made up of about 10 unusual sugars
O antigen
longest and most external
may find up to 200 sugars
plays important role in evading immune response
How does O antigen evade immune response?
initial immune response recognizes sugars in O-antigen
but the bacteria can then change its sugars and go undetected
Why is LPS important
contributes negative charge on cell surface
helps stabilize outer membrane
- bcus of rigidity of Lipid A
contributes to attachment and biofilm formation
- sugar residues are sticky
creates permeability layer and protection from host defenses
can act as an endotoxin
- lipid A
Endotoxin
maintained within the cell and are not secreted
How does Lipid A work as an endotoxin
does not do anything when embedded
if lysis occurs Lipid A is released and causes a massive immune response
Gram-positive pores
peptidoglycan layer has large pores throughout its matrix
does not require much machinery
Gram-negative pores
has Porin and TonB proteins in outer membrane to transform molecules into periplasmic space
machinery for facilitated and active
Porin protein
last line of defense
more permeable than plasma membrane
Porin-based transport
Porin/channel used for facilitated diffusion in outer mem
active transport system embedded in PM
TonB- dependent transportant
active transport mechanism in the outer membrane
Autotransporters
move from the periplasm to outside environment directly
embedded part of themselves and use other part to move things across
passenger and translocator domains
Mechanis of Gram stain reaction- positive
large pores shrink
crystal violet cannot leave cell
pores seal shut when you add decolorizer
mechanism of Gram stain reaction- negative
outer membrane lipids stripped by decolorizer
flagella
spiral, hollow, rigid filaments extending from cells surface
monotrichous
one flagellum
polar flagellum
flagellum at end of cell (could be one or both)
amphitrichous
one flagellum at each end
lophotrichous
cluster of flagella at one or both ends
peritrichous
flagella spread over entire surface of cell
Flagella are composed of 3 parts
filament
hook protein
basal body
filament
most external
sits in hook protein
hook protein
smallest part
connects the basal body to the filament
basal body
anchors flagella into plasma membrane
Gram negative flagella
Rings are connected to a central sheath
L-ring in outer membrane
P-ring in peptidoglycan
MS-ring in plasma membrane
C-ring located in cytoplasm
Gram positive flagella
Outer ring is peptidoglycan
Inner ring is in plasma membrane
What is the difference between flagellar structure between Gram-stains?
basal body
How is flagella encoded
by operon
might need up to 20 different genes to build flagella
operon
transcribes all genes required at the same time
How is flagella built?
built starting from tip
Every protein is moved up through the hallow sheath and is assembled at the tip
Self assembly of flagella
subunits are able to organize themselves
do not need outside organization
How do flagella rotate
like a propeller
very rapidly
Counterclockwise rotation
causes forward motion (run)
direct movement towards something
Clockwise roation
disrupted run causing cell to stop and tumble
used to reorient themselves
Chemotaxis
movement toward a chemical attractant or away from a chemical repellant
Chemorecpetors
allow chemical attractants/ repellants to bind
Positive chemotaxis
Movement toward an attractant
Bacteria settles at center then expands outward
Negative chemotaxis
Movement away from a repellant
As concentration of repellant increases zone of clearance gets larger
In presence of attractant:
Tumbling frequency is intermittently reduced
Runs in direction of attractant are longer
In presence of a repellant
similar to that of an attractant but opposite
Chemotaxis system
Default direction is counterclockwise
CheW transmits signal that determines if CheY gets phosphorylated
If CheY is phosphorylated it tells to change direction to clockwise
Mechanism for flagellar movement
2 part motor that produces torque
- rotor
- stator
rotor
C-ring (FliG protein) and MS ring turn and interat with stator
Inner and outer ring in Gram-positive
stator
Mot A and Mot B proteins
Not embedded within rings
Form a channel and use energy stored in ion gradients
Protons flow down gradient and down channel and release energy which powers flagella
How do archaea flagella move
push me-pull me alternation with no tumbles
What time of organisms have internal flagella
spirochetes
where are internal flagella located and what type of motion?
located in periplasm
corkscrew-like motion
3 types of nonflagellar motility
gliding motility
twitching motility
polymerization of actin
Gliding motility
smooth sliding over a surface
Associated with organisms that secrete a slime layer
twitching motility
slow jerky process using pili
Extend pili and then retract it to move forward
Not all organisms with pili twitch- primary function is to adhere
polymerization of actin
for propulsion of bacteria into adjacent cells
Frequently used by intracellular bacteria
Use host cell actin to polymerize it and build a tail
Tail pushes the bacteria along
Example organism for gliding motility
Myxobacteria and cyanobacteria
example organism for twitching motiliity
N. meningitidis and P. aeruginosa
Adherence
ability to stick to surfaces
mediated by pili
How fo pili adhere
also called fimbriae
fibers of pilin protein possessother protein on their tips for sticking
sex pilus
different structure used for conjugation
Other method of adhesion
stalk
stalk
Use an extension of the cell envelope tipped by a “Holdfast” of polysaccharides
Made my organisms in low nutrient environments
- Stalk increases surface area
Components outside cell envelope
Glycocalyx
S-layers
Glycocalyx
made up of polysaccharides
aid in attachent to solid surfaces
capsules and slime layers
Capsules
well organized and not easily removed from cell
visible in light microscopes
have protected advantages
What are protective advantages of capsules?
high H2O content- protection from desiccation
protects organism from immune detection
T/F if you have capsules you are not virulent
false
Biofilms
Provide protection and enhanced survivability in harsh environments
Composed of polysaccharides
Can be single or mixed species
Slime layers
Usually composed of polysaccharides
Held onto the cell by covalent connectionH
How are slime layers similar to capsules
High in water content
Aid in attachment
Hide from host cell immune response
How are slime layers different to capsules
Diffuse
Are thinner
Unorganized
Easily removed
Need EM to see
Example organism with slime layer
Xanthamonas campestris
S- layers (surface arrays)
crystalline array of interlocking proteins
Found in both Gram-negative and Gram-positive
Regular structured layers of protein/glycoprotein that self-assemble
Highly organized and thinner
Where do S-layers adhere in Gram-negative
to outer membrane
Where do S-layers adhere in Gram-positive
associated with petidoglycan surface
How do S-layers adhere
via non-covalent interactions
T/F you can see S-layers under light microscope
TRUE
but hard to visualize because it is so thin
Functions of S-layer
Protects from ion and pH fluctuations, osmotic stress, enzymes, and predation
Maintains shape and rigidity
Promotes adhesion to surfaces
Protects from host defenses
Potential use in nanotechnology
- Because of the self-assembly of the S-layer
Endospore
complex, dormant (metabolically inactive) structure formed by some bacteria
Clostridium and bascillus species
vegetative state
metabolically active
non-spore forming
What are endospores resistant to?
Heat
Radiation
Chemicals
Desiccation
Spore forming organisms are typically found where?
soil
What do spore formers also produce
nasty toxins
Endospore locations
central
swollen sporangium- clostridium
terminal
subterminal- B.subtilis
What is endospore locations used for
characterize/identify species
- they do not ever change
Spore layers
core
core wall
inner membrane
cortex
outer membrane
inner/outer coat
(exosporium
Core
dehydrated
Contains only calcium diacid, NO WATER
core wall
turns into cell wall when converted to vegetative cell
inner membrane
germinate receptors
cortex
makes up most of spore volume
made up of specialized peptidoglycan that is not fully cross-linked- heat-resistant
outer membrane
semi-permeable
inner/outer coat
highly structured
Acts as a physical barrier
exosporium
only found in some species
similar to S-layer
adds another layer of protection
Sporulation
Process of endospore formation
All-or-nothing response: once it is triggered you cannot reverse
It is tightly regulated
Complex multistage process that occurs in up to 10 hours
Regulation of sporulation
Master regulator= SpO0A
If phosphorylated then sporulation will complete
Steps of sporulation
Actin filament formation:
- DNA stretches length; some will be degraded and some moved to spore
Septum formation and forespore development
Engulfment of forespore
- Septum membrane engulfs forespore
Cortex formation
Coat synthesis
Completion of coat syntheis
- Increase in refractility and heat resistance
Lysis of sporangium and spore liberation
- Kills mother spore
Germination
Reverse of sporulation
Triggered by nutrient-rich environments
- Nutrients bind to nutrient receptors
Transformation of endospore into vegetative cell
All-or-nothing response
Complex multistage process
Three stages of germination
Activation
Germination
Outgrowth
Activation stage
triggers a population of spores homogenously (at same time)
Prepares spore for germination
Often, results from heating
germination stage
“peeling back layers”
Environmental nutrients are detected
Spore swelling and rupture-spore coat is absorbed
- Water rushes in and calcium dicloacid rushes out- triggering metabolic activity
Loss of resistance
Increased metabolic activity
Outgrowth stage
the emergence of vegetative cell
lysis of spore coat
Species
a group of strains sharing common features while differing considerably from other strains
genus
group of closely related species
Hierarchy of taxonomy
phylum (broad)
class
order
family
genus
species (narrow
