Lecture 12 Flashcards
What are the two main types of movement exhibited by bacteria?
Bacteria exhibit random movement and directed movement.
What structures do most bacteria use for motility?
Most bacteria use flagella or pili for motility.
Define taxis in the context of bacterial motility.
Taxis refers to directed movement in response to a stimulus.
What is positive taxis?
Positive taxis is movement towards a stimulus, such as nutrients.
Provide an example of negative taxis.
Negative taxis is movement away from a stimulus, such as toxic substances.
What is chemotaxis?
Chemotaxis is the movement towards or away from attractants/repellents in response to chemical stimuli.
What are flagella?
Flagella are long helical surface structures used by bacteria for motility in liquid environments.
What are the dimensions of flagella?
Flagella typically have a diameter of 20 nanometers and can be up to 20 micrometers long.
How does flagellar swimming occur?
Flagellar swimming results from the rapid rotation of flagella.
Why is water considered viscous for microbes?
Water is considered viscous for microbes because it significantly impedes their movement.
What is the typical rotation speed of flagella?
Flagella can rotate at speeds ranging from 100 to 1000 times per second.
What is the maximum speed at which bacteria can swim using flagella?
Bacteria can swim at speeds of up to 100 micrometers per second using flagella.
How can flagella be different across different bacteria?
Bacteria exhibit variation in the number and distribution of flagella.
What does “atrichous” mean in terms of flagella?
Atrichous bacteria have no flagella.
Define “monotrichous” in the context of flagella.
Monotrichous bacteria have a single flagellum located at one pole.
What is the characteristic feature of lophotrichous bacteria?
Lophotrichous bacteria have a tuft of flagella at one or both poles. (looks like little hair on a cartoon characters head)
Describe the arrangement of flagella in amphitrichous bacteria.
Amphitrichous bacteria have a single flagellum at both poles.
What is the distribution pattern of flagella in peritrichous bacteria?
Peritrichous bacteria have flagella distributed over their surface.
What is the function of the basal body in flagellum structure?
The basal body attaches the flagellum to the cell envelope and contains the motor responsible for rotation.
Describe the filament of the flagellum.
The filament is a long helical structure that extends from the surface of the cell. Rotation of the filament moves the cell.
What is the function of the hook in flagellum structure?
The hook is a flexible, bent structure that transmits rotation from the basal body to the filament.
In which types of bacteria are basal bodies present? (Gram pos or Gram neg)
Basal bodies are present in both Gram-negative and Gram-positive bacteria.
Describe the protein structure of the basal body.
The basal body is composed of a central rod and several rings.
What rings are embedded in the cell envelope of most Gram-negative bacteria?
Most Gram-negative bacteria have L, P, and MS rings embedded in the cell envelope.
Where is the C ring located in bacteria?
The C ring is located in the cytoplasm of bacteria.
Do most gram-negatives have a C ring? If so, where?
Yes, most gram-negs have a C ring in the cytoplasm
What are the functions of the basal body in bacteria?
The basal body is responsible for transporting subunits during flagellum assembly and for motor functions, rotating the hook and filament.
What is the role of the basal body in the export functions of bacteria?
The basal body plays a role in exporting proteins necessary for various cellular functions.
What components make up the basal body as a motor?
The basal body as a motor consists of a rotor (including a rod and MS ring), bushings or bearings (P and L rings), and a stator (composed of MotA and MotB proteins).
How is rotation of the basal body typically powered?
Rotation of the basal body is typically powered by the proton motive force.
What is the function of the proton channel formed by MotA and MotB proteins?
The proton channel formed by MotA and MotB proteins facilitates the flow of protons, contributing to the proton motive force that powers rotation.
What role does the switch (C ring) play in flagellar motors?
The switch, represented by the C ring, determines the direction of rotation of the flagellar motor.
In what order does the assembly of the flagellum occur?
The assembly of the flagellum begins with the basal body, followed by the hook, and then the filament.
How are subunits added to the distal end of the flagellum during assembly?
Subunits are exported up the hollow core of the flagellum and added to the distal end during assembly.
What protein makes up the filament of the flagellum?
The filament of the flagellum is made of thousands of flagellin proteins.
How is the filament of the flagellum assembled?
The filament is assembled in a helical pattern, with flagellin proteins being incorporated under a cap protein.
Techoic acids are a type of microbe-associated molecular pattern (MAMP). How does the innate immune system recognize MAMPs?
a) using antibodies
b) using complement proteins
c) using dendritic cells
d) using pattern-recognition receptors
d)
using pattern-recognition receptors on surface of bacterial cells
Why are flagella considered major immune targets?
Flagella are considered major immune targets because they are exposed on the surface of bacteria.
How does the innate immune system recognize flagellin?
The innate immune system recognizes flagellin through Toll-like receptor 5 (TLR5).
What happens when flagellin binds to Toll-like receptor 5 (TLR5)?
When flagellin binds to Toll-like receptor 5 (TLR5), it activates NF-κB, a transcription factor.
What is the role of NF-κB in the immune response?
NF-κB activation leads to the production of pro-inflammatory cytokines, contributing to the immune response.
How are flagella targeted by the adaptive immune system?
Flagella are targeted by the adaptive immune system as they are recognized as major antigenic structures.
Provide an example of a bacterium where flagellar antigens are targeted by the adaptive immune system.
E. coli O157:H7 is an example of a bacterium where flagellar antigens, specifically H7, are targeted by the adaptive immune system.
What is the significance of the large number of protein subunits, such as flagellin, in flagella?
The large number of protein subunits in flagella increases the likelihood of antibody formation.
What is the consequence of antibody binding to flagellar antigens?
Antibody binding to flagellar antigens leads to phagocytosis, which is the process of engulfing and destroying the bacteria by immune cells.
What is observed in some bacteria once they enter the host environment regarding flagella production?
Some bacteria stop producing flagella once they enter the host environment.
How do some bacteria alternate between different flagellins?
Some bacteria alternate between different flagellins through phase variation, which involves a reversible change in phenotype.
Describe phase variation. Include key terms phenotype and genetic content.
Phase variation is a process through which some bacteria can alternate between different flagellins. This involves a reversible change in phenotype, but the genetic content stays roughly the same throughout this.
Provide an example of a bacterium that exhibits phase variation in flagellins.
Salmonella enterica is an example of a bacterium that exhibits phase variation in flagellins, specifically FljB and FliC.
What mechanism underlies phase variation in flagellins?
Phase variation in flagellins is often mediated by a reversible inversion of the promoter region, which involves recombination events.
What is the significance of phase variation in terms of immune evasion?
Phase variation allows bacteria to evade the host immune response by altering their surface antigens, making it difficult for the immune system to recognize and target them effectively.
