Lecture 5 Flagella
What Makes an Endospore so Resistant?
-Calcium (complexed with dipicolinic acid) -Small, acid-soluble, DNA-binding proteins (SASPs) -Dehydrated core -Spore coat and exosporium protect
PROCESS WHEN MCP not bound by attractant-STEP 2
-CheA/CheW is active (phosphorylated)
PROCESS WHEN MCP not bound by attractant-STEP 3
-CheY is active -diffuses to flagellar motor and switches to clockwise (CW) rotation -tumbling occurs -concentration of attractant is measured every few seconds (receptors reset)
DESCRIPTION OF Bacterial Endospore
-Complex, dormant structure formed by some bacteria -Various locations within the cell
PROCESS WHEN MCP not bound by attractant-STEP 1
-MCP is methylated (CheR)
Twitching and Gliding Motility
-May involve Type IV pili and slime
Spirochete Motility
-Multiple flagella form axial fibril which winds around the cell -Flagella remain in periplasmic space inside outer sheath -Corkscrew shape exhibits flexing and spinning movements
Sporulation DESCRIPTION
-Process of endospore formation -Occurs in a hours (up to 10 hours) -Normally commences when growth ceases because of lack of nutrients or presence of harmful substances. -Complex multistage process
DESCRIPTION OF GLIDING
-SMOOTH MOVEMENTS
ENDOSPORE STRUCTURE
-Spore surrounded by thin covering called exosporium -Thick layers of protein form the spore coat -Cortex, beneath the coat, thick peptidoglycan -Core has nucleoid and ribosomes
Bacterial Flagella DESCRIPTION
-Thin, rigid protein structures -composed of three parts -Pattern of flagellation varies
FUNCTION OF MCPs
-binds environmental chemicals -initiates a series of interactions with cytoplasmic proteins that affects flagellar rotation
Flagellar Synthesis
-complex involving many genes/gene products -new flagellin transported through the hollow filament using Type III-like secretion system -filament subunits self-assemble with help of filament cap at tip, not base
Formation of Vegetative Cell-GERMINATION STEP
-environmental nutrients are detected -spore swelling and rupture of absorption of spore coat -increased metabolic activity
DESCRIBE THE FILAMENT
-extends from cell surface to the tip -hollow, rigid cylinder of flagellin protein -acts as a syringe to inject its protein into another cell
FLAGELLA FUNCTIONS
-motility and swarming behavior -attachment to surfaces -may be virulence factors
DEFINITION OF CHEMOTAXIS
-move toward chemical attractants such as nutrients -away from harmful substances
DESCRIPTION OF TWITCHING MOTILITY
-pili at ends of cell -short, intermittent, jerky motions -cells are in contact with each other and surface
Formation of Vegetative Cell-ACTIVATION STEP
-prepares spores for germination -often results from treatments like heating
FORMS OF DNA
A FORM B FORM Z FORM
WHAT DO FLAGELLA NEED TO DO IN ORDER TO REPLICATE?
ATTACH
Regulated by a two-component signal transduction pathway
Activates sensor kinase CheA (with help of CheW) which autophosphorylates -CheA phosphorylates the response regulator CheY
WHAT FORM OF BACTERIA ARE FLAGELLA USUALLY FOUND ON?
BACILLI
HOW CHEMOTAXIS WORKS
Changing concentrations of chemical attractants and chemical repellents bind chemoreceptors of chemosensing system
MCP bound by attractant-STEP 2
CheA is inactive (not phosphorylated) -CheY is inactive -flagellar rotation is counter- clockwise (CCW) and running o occurs
BEHAVIOR IN PRESENCE OF REPELLENT
Chemotaxis away from repellent involves similar but opposite responses
NAME Three Parts of Flagella
FILAMENT HOOK BASAL BODY
TYPES OF Motility
Flagellar movement Spirochete motility Twitching motility Gliding motility
Mechanism of Flagellar Movement
Flagellum is 2 part motor producing torque Rotor -C (FliG protein) ring and MS ring turn and interact with stator Stator - Mot A and Mot B proteins -form channel through plasma membrane -protons move through Mot A and Mot B channels using energy of proton motive force -torque powers rotation of the basal body and filament
Bacterial Flagellar Movement
Flagellum rotates like a propeller very rapid rotation up to 1100 revolutions/sec -counterclockwise (CCW) rotation -causes forward motion (run) -clockwise rotation (CW) disrupts run causing cell to stop and tumble
WHAT TO FLAGELLA STIMULATE IN THE BODY?
IMMUNE RESPONSE
DESCRIBE THE HOOK
LINKS FILAMENT TO BASAL BODY -THIS PORTION BUILDS UP FIRST
MCP bound by attractant-STEP 1
MCP is not methylated (CheB)
DEFINITION OF Chemotaxis
Movement toward a chemical attractant or away from a chemical repellent
WHAT GOVERNS ROTATION OF FLAGELLA
Response regulator CheY governs rotation of flagella
DESCRIBE THE BASAL BODY
SERIES OF RINGS THAT DRIVE FLAGELLAR MOTOR
WHY DOES IT STIMULATE AN IMMUNE RESPONSE?
TO BE TAKEN UP BY MACROPHAGES
FLAGELLA DESCRIPTION
Threadlike, locomotor appendages extending outward from plasma membrane and cell wall
CAN FLAGELLA LIVE IN MACROPHAGES?
YES!
DEFINITION OF Methyl-accepting chemotaxis proteins (MCPs)
chemoreceptors in membrane
Formation of Vegetative Cell-OUTGROWTH STEP
emergence of vegetative cell
ENDOSPORE Resistant to numerous environmental conditions
heat radiation chemicals desiccation
MCP bound by attractant-STEP 3
regulatory system allows E. coli to respond to and adapt to very small amounts of attractant
WHO DOES CheA phosporylate
response regulator CheY
TYPES OF STIMULANT FOR CHEMOTAXIS
temperature light oxygen osmotic pressure gravity
BEHAVIOR IN PRESENCE OF ATTRACTANT
tumbling frequency is intermittently reduced and runs in direction of attractant are longer -Behavior of bacterium is altered by temporal concentration of chemical
