Midterm 1-2 Flashcards
Bactoprenol
undecaprenol diphosphate
hydrophobic C55 alcohol that is bonded to N-acetylglucosamine and N-acteylmuramic acid
pentapeptide PG precursor
transports the PG precursors across the cytoplasmic membrane by rendering them sufficiently hydrophobic to cross through the membrane
Growth of the bacterial cell wall
- Autolysins hydrolyze (break) the B-1,4 linkages - creates gaps in the cell wall
- Flippase - flips single units of PG precursors across the cytoplasmic membrane
- Once the bactoprenol units are crossed the cytoplasmic membrane, the unit interacts with transglycosylases that insert the units into the cell wall and catalyze glycosidic bond formation. TRANSGLYCOSYLATION
transpeptidation
forms the peptide cross links between
- adjacent muramic acid residues in Gram+ cell walls
- DAP on one peptide and D-alanine on the adjacent strand in Gram- cell walls
exergonic - supplies the E required for the wall formation
Transpeptidation is inhibited by:
Vancomycin and penicillin (beta lactam antibiotic)
Transglycosylation inhibited by:
vancomycin
Agents that destroy PG
lysozyme - found in tears and egg whites - hydrolyzes PG
antibiotics like vancomycin and B-lactam antibiotics (penicillin)
- inhibit formation and/or cross linking of the glycan strands
B-lactamase
enzyme that breaks down B-lactam (ring) antibiotics
a common component of antibiotic resistance plasmids (R-plasmids) that are becoming increasingly prevalent in clinical settings
Divisome
Forms 3/4 through cell division and is made up of Fts proteins (filamentous temperature sensitive).
FtsZ
Part of the divisome
Forms a ring around the centre of the cell -
It has been found to have structural homology with tubulin in eukaryotes
COORDINATES THE CELL DIVISION PROCESS. the other components are less important
ZipA
Anchor that connects FtsZ ring to the cytoplasmic membrane
FtsL
A peptidoglycan biosynthesis proteiN
FtsK
assists in chromosome separaton
FtsA
ATPase
DNA replication and cell division events
Initially MinCD inhibits formation of FtsZ ring
Then MinE oscillates from pole to pole - sweeping MinCD aside
When the cell becomes very long, there is little MinCD in the middle of the cell - why the cell divides in the middle
crescentin
shape determining protein found in curved cells - causes curvature
organizes into filaments that localize on the concave face of curved cells
MreB
major shape determining factor in prokaryotes. Esp rod cells (not found in coccus shaped cells)
Forms simple cytoskeleton with patch-like filaments around the inside of the cell just below cytoplasmic membrane in Bacteria and some Archaea
coordinates the breakdown of PG
Recruits other proteins for cell wall growth to group into a specific pattern
polyhydroxyalkanoates (PHA)
Energy storage polymer that includes PHB
nitrification
lithotrophic oxidation of ammonia to nitrate
- done by ammonia oxidizerd
annamoxisome
A membrane-bound compartment packed with enzymes. Allows it to grow with NH3 under anoxic conditions
Endospores
Only found in Gram+ bacteria. Resting stage is able to survive all sorts of harsh conditions
Only formed in some Firmicutes
lophotrichous flagella
a tuft of flagella coming out from one region on the bacterium. Like a pony tail.
fimbriae
small hair-like structures coming off of the entire body of a bacterium. These are smaller than both flagella and pili
enable organisms to stick to surfaces or form pellicles (thin sheets of cells on a liquid surface) ie biofilms
pili
longer and fewer than fibriae
- conjunctive sex pili facilitate exchange between bacteria (conjugation)
- type lV pili adhere to host tissues and support twitching motility (Pseudomonas ex)
Archaeal cell membranes
- can form monolayers (rather than bilayers) which decrease the fluidity of the membrane)
- monolayers have tetraethers while bilayers have diether linkages
- ether linkages are more thermostable and more resistant to hydrolytic cleavage compared to ester bonds.
Archaeal cell walls
NO PG, but have PG-like polymers like pseudomurin and methanochondroitin
HAVE S-LAYERS which function like PG does in bacterial cell walls
- consists of protein or glycoprotein
- paracrystallin structure
A sheath is an S-layer that covers multiple cells
S-LAYERS
function like PG does in bacterial cell walls
- consists of protein or glycoprotein
- paracrystallin structure
A sheath is an S-layer that covers multiple cells
Found mostly in Archaea, sometimes in Bacteria
Act as structural support, molecular sieves, and to form a pseudoperiplasmic space.
whICH shaPES of bacteria are flagella found on?
Found on rod-shaped or curved bacteria
wHAt protein are flagella made out of?
flagellin - repeated in a helical pattern along the flagellum
What is the function of the L and P rings in flagellar movement?
Sleeves in the peptidoglycan and outer membrane - anchors
What is the function of the Mot proteins in flagellar movement?
form the slater which is where protons come through. They do not move but instead form the framework for where the flagella rotates
What forms the rotor?
The MS ring and the Rod.
Within the slater, the rotor rotates using the energy from the proton motive force. (protons moving from the periplasm into the cytoplasm)
flagella biosynthesis
basal structures are formed first and then the filament grows from the TIP via the transport of flagellin proteins up through the hollow core of the growing structure.
What is going on when the flagella is rotating counter clockwise?
THE SAME DIRECTION AS THE HELIX OF THE FLAGELLA
the bacterium is in run mode and swimming STRAIGHT forward
The flagella form a trailing bundle.
What is going on when the flagella is rotating clockwise?
The bacterium is in tumble mode and the flagella are spread a part
rotation is the opposite of the direction of the helices of the flagella.
What does having a low Renolds number mean?
Bacteria have a low Renolds number and this means that the friction of water is massive compared to the momentum. Stops very quickly once it stops moving its flagellum (momentum ceases)
What are two component-regulatory systems composed of?
A sensor kinase and a response regulator
Sensor kinase
Usually found spanning the cytoplasmic membrane
Detects the environmental signal with a chemical signal and autophosphorylates itself on a histidine residue. It transmits the signal via the phosphorylation of a response regulator which activates the RR
CheA
Response regulator
in the cytoplasm. Usually a DNA binding protein that regulates transcription
- Has a negative feedback loops that terminates the signal
The RR can also sometimes interact directly with the flagellum
biased random walk
allows for directed movement
Bacteria respond to temporal, not spatial, difference in concentration.
length of runs changes respond to if things get better or worse
CheA
Sensor kinase. Associated with MCP (transmembrane component) and CheW
Phosphorylates CheY and indirectly CheB to mAKE THem active
MCPs
methyl-accepting chemotaxis proteins
Bind to the attractants or repellents in the environmment
interact with the sensor kinase ie CheA
Binding to attracting makes MCPs LESS active which promotes a longer run.
CheW
the link between MCP and CheA
CheY
primary response regulator. Signals the flagellar rotation to change direction and TUMBLE
Interacts with Fli proteins to reverse flagellar rotation
CheZ
the off switch for CheY (dephosphorylates CheY to an INACTIVE state)
Reset!
CheB
secondary response regulator that acts as an off switch for MCPs (making them INACTIVE)
removes the methyl groups from MCPs to make them inactive
meaning the promotion of RUNNING (not signalling a tumble)
regulates the negative feedback
CheB is activated during the signal promoting tumble. During the reset, CheB-P is removing methyl groups from MCPs so that MCPs come less active and CheY is no longer phosphorylated.
time-delay switch
CheR
On switch for MCPs. It methylates MCPs to make them ACTIVE/sensitive
Activity of CheR promotes the signal transduction pathway - ie promotes tumbling
This is what causes the tumble to happen even when the MCPs are binding attract that decreases their sensitivity
What is happening during a ‘run’
The response regulators are inactive (not phosphorylated) and the flagella rotate counterclockwise
- however CheR is constantly adding methyl groups to MCPs (making more sensitive/active and thus more likely to signal a tumble)
Tumble
Signal begins when MCP signals to CheA to be autophosphorylated
CheA-P then activates CheY to CheY-P and CheB to CheB-P
CheY-P interacts with Fli proteins to reverse the flagellar rotation of the motor.
Cell tumbles
Equations you need to know.
Nt = N0 * 2^n
n = t/g
Nt = population of bacteria at time T
N0= population of bacteria at time 0
n = number of generations
t = time passed
g = generation time (amount of time required for the population to double)
