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Sem 2: Microbiology > Micro cell 2 > Flashcards

Micro cell 2 Flashcards

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1
Q

What is the function of FtsZ?

A

Recruits cell wall synthetic machinery for cell division
FtsZ controls cell division in bacteria

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2
Q

What happens to the FtsZ?

A

FtsZ polymerisation is GTP dependent
With the help of some accessory proteins, the FtsZ ring is formed

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3
Q

What are the stages of bacterial cell division?

A

Growth, extension
Chromosome replication
Chromosome segregation
Marking the division site, crosswall formation
Cell-cell separation

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4
Q

What is the function of the Ftsz ring?

A

Is a aring around the chromosome to help with the segregation of the chromosome and cell

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5
Q

How do spherical cells use Ftsz?

A

Cell wall extension only occurs at the middle of the dividing cell using FtsZ as a scaffold

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6
Q

How do rod shaped bacteria use Ftsz?

A

In addition to the lateral wall extension directed by MreB, cell wall extension also occurs at the middle of the dividing cells using FtsZ as a scaffold.

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7
Q

What is an overview of CreS?

A

CreS is a bacterial intermediate filament
CreS mutants have lost the curved shape
CreS forms a filament alongside the curved shape of Caulobacter cells

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8
Q

What is an example of a bacteria that uses CreS?

A

Caulobacter crescentus
aquatic bacterium
curved rod shape

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9
Q

What different shapes of bacteria and the cytoskeletal proteins used?

A

Spherical - S.aureus - FtsZ
Rod - E.coli - MreB and FtsZ
Vibrioid - C.crescentus - Mreb, FtsZ and crescentin

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10
Q

What is an overview of ParM?

A

ParM (actin homologue) mediated plasmid partitioning
A mechanism analogous to that used by microtubules during eukaryotic mitosis

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11
Q

What is the mechanism of ParM?

A

After plasmid replication, growth of a ParM polymeric filament pushes apart the two progeny R1 plasmids, moving them from midcell to the two poles

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12
Q

How does the ParM attach to the plasmid?

A

The ParM-ADP filament is capped by ParM-ATP subunits.
The capped end is attached to the parC centromeric region of the plasmid via the ParR protein.
ParM filament growth occurs by insertion of ParM-ATP subunits at the interface between the end of the ParM filament and the ParR/parC complex

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13
Q

What is an antibiotic?

A

Chemical produced by a microorganism that kills or inhibits the growth of another microorganism

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14
Q

What is an antimicrobial agent?

A

Chemical that kills or inhibits the growth of microorganisms

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15
Q

What are the different antibacterial actions done by antimicrobial and antibiotics?

A

Bactericidal : kills bacteria
Bacteriostatic: inhibit growth and reproduction of bacteria , but does not kill

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16
Q

What is an overview of Fleming?

A

Fleming and Penicillin (1929)
Alexander Fleming, Howard Florey and Ernst Chain – 1945 – Nobel Prize for Medicine

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17
Q

What is an overview of Beta-lactam antibiotics?

A

Contains a beta-lactam ring (peptide ring) in their molecular structure - side chains impact the biological activity
Penicillin

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18
Q

What are glycopeptide antibiotics?

A

Contains glucose or derivative in the structure - Vancomycin

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19
Q

What are tetracyclin antibiotics?

A

Are an aromatic macrolides - minocycline

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20
Q

What are aminoglycoside antibiotics?

A

Inhibit protein synthesis and contain as a portion of the molecule an amino-modified glycoside
Streptomycin

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21
Q

What are macrolide antibiotics?

A

Macrocyclic lactone of different ring sizes, to which one or more deoxy‐sugar or amino sugar residues are attached
Erythromycin A

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22
Q

What are examples of antibiotics and their target?

A

Cell Wall synthesis - Beta lactams
RNA polymerase transcription - Rifampicin
Cell membrane - Polymyxins
30S subunit - Tetracyclines

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23
Q

What are the mechanisms for antibiotic resistance?

A

1 - Impermeable barrier blocks antibiotics (blue spheres) because the bacterial cell envelope is now impermeable to the drug.
2 - Target modification alters the proteins inhibited by the antibiotic, so the drug cannot bind properly.
3 - Antibiotic modification produces an enzyme that inactivates the antibiotic.
4 - Efflux employs genes coding for enzymes that actively pump the antibiotic out of the cell.

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24
Q

What is the mechanism for cell wall expansion?

A

Autolysins cut the peptidoglycan
Transglycosidases build in new pentapeptide to build in new glycosidic bonds betweent the pentapeptide
Transpeptidases restore cross linkes betwen the peptidoglycan strands

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25
What enzymes do penicillin target?
Penicillin and other betalactam antibiotics target transpeptidases
26
How does penicillin work?
Penicillin can bind to the active site of transpeptidases, because its structure resembles that of D-Ala-D-Ala Penicillin inhibits cell wall synthesis
27
What is a mechanism a bacteria can prevent itself from being targeted by penicillin?
Antibiotic modification/inactivation Penicillinase (b Lactamase) Converts penicillin to penicilloic acid by modifying the beta-lactam ring
28
How can penicillin be protected from beta lactamases?
Clavulanic acid
29
What is an overview of clavulanic acid?
Do not have significant antibacterial activity Bind to and inactivate Beta-lactamases - protects the antibiotics Formulated in combination with beta-lactamase sensitive antibiotics Clavulanic acid and amoxicillin (penicillin antibiotic)
30
How can antibiotic resistance be acquired?
In vertical transmission, a bacterium accumulates errors or mutations in its genome during replication; some of those changes give the ability to resist antibiotics and are passed on to subsequent generations. In horizontal transmission, resistant genes are swapped from one microbe to another.
31
What is an example of a gram positive bacteria used for antibiotic source?
Bacillus subtilis - Bacitracin
32
What are examples of actinomyctes that are sources of antibiotics?
Often streptomyces: Steptomyces nodosus - Amphotericin B Steptomyces fradiae - Neomycin
33
What are examples of fungi that are sources of antibiotics?
Penicullium notatum - pencillin Penicillium griseofulvum - griseofulvin
34
What is an overview of the genetic for Streptomyces coelicolor?
Complete genome sequence 8.4 Mb linear chromosome – very large ~7800 genes! (more than yeast) ~5% code for secondary metabolites Well developed genetic tools
35
What is an overview of gene clusters for antibiotic production?
Antibiotic biosynthetic pathways are complex Genes encoding the biosynthetic enzymes are clustered Resistance genes are located within the biosynthetic gene-cluster
36
What is important for developing new antibiotics for hosts?
Selective toxicity - greater harm to microbes than host, done by interfering with essential biological processes common in bacteria but not human cells.
37
What is the therapeutic index?
LD50 vs. MIC - Therapeutic index (the lowest dose toxic to the patient divided by the dose typically used for therapy). High TI are less toxic to the patient.
38
What are important traits needed to be investiagated for new antibiotics?
Bactericidal vs. bacteriostatic Spectrum of activity - wide or narrow and what bacteria Lack of “side effects” allergic, toxic side effects, suppress normal flora Little resistance development
39
What are the pharmokinetics for new antibiotics?
Drug interxns, how drug is distributed, metabolized and excreted in body (unstable in acid, can it cross the Blood-brain barrier, etc)
40
What is bacterial swarming?
Swarming is the multicellular movement of bacteria across a surface and is powered by rotating helical flagella.
41
What is bacterial swimming?
Swimming is the movement of individual bacteria in liquid, also powered by rotating flagella
42
What is bacterial twitching?
Twitching is surface movement of bacteria that is powered by the extension of pili, which then attach to the surface and subsequently retract, pulling the cell closer to the site of attachment.
43
What is bacterial gliding?
Gliding is active surface movement that does not require flagella or pili and involves focal-adhesion complexes.
44
What is bacterial sliding?
Sliding is passive surface translocation that is powered by growth and facilitated by a surfactant.
45
What is an overview of the method for twitching?
Pillus extends through polymerisation by adding pilin mononers Pillus retracts through depolymerisation by removing pilin mononers
46
What is an example of a bacteria thats moves by twitching?
Neisseria gonorrhoeae
47
What is needed for gliding in bacteria?
Large focal adhesion complexes extend from the cell and connect the extracellular surface to actin-like cytoskeletal filaments.
48
What happens during gliding?
Motor proteins attached to the intracellular portion of the focal adhesion push backwards and move the focal adhesion along the cytoskeletal filament to move the cell forward –whilst they stay fixed at fixed position with respect to the substratum
49
What is the protein structure of the flagella?
Basal body attached in the cell membrane and cell wall A hook anchored in the basal body Long fine filament helical protein made of subunits (flagellin)
50
How big is the flagella?
20nm and 1 to 70um in length
51
What is required for the rotation of the flagellum?
Energy required comes from proton motive force: H+ movement across membrane through Mot complex driven rotation of flagellum 1000 H+ must be translocated per rotation of flagellum
52
How did they show what direction the bacteria moves based off of body rotaion?
Antibodies against flagellar proteins tether flagella to the surface of a glass slide Showed counterclockwise rotation of tethered flagella caused body of cell to rotate counterclockwisw
53
What is universal about turning and movement?
CCW rotation – run CW rotation - tumble
54
What is chemotaxis?
Ability of a cell to sense external concentration of a chemical species and migrate (directed movement) towards/away from higher concentrations
55
What is phototaxis?
Movement toward light Phototrophic organism orients itself most sufficient for photosynthesis
56
What is the overview of chemotaxis when no gradient present?
Runs: cell swims forward in smooth fashion Tumbles: when cell stops and jiggles about Direction of next run is random Cell moves randomly, but can go anywhere
57
What is the overview of chemotaxis when gradient present?
Random movements become biased Runs longer, tumbles less frequent Organism moves up or down the concentration gradient
58
What is the organisation of the flagellar and chemotaxis sensory complex?
The flagellar switch and the chemotaxis sensory complex are seperated in space There must be a messanger to link the flagellar to the sensory complex
59
What is the messanger linking flagellar and sensory complex?
The protein CheY
60
How does the CheY state impact FliM?
In two different states CheY and CheY-P (phosphorylated) CheY wont be able to form a complex with FliM resulting in CCW rotation of flagella CheY-P will be able to form a complex with FliM resulting in CW rotation of flagella
61
What determines CheY phosphorylation?
Phosphorylation is done by the sensory complex by CheA and CheW. CheA passes the phosphose to CheY creating CheY-P. The sensory complex is embedded in the membrane away from the FliM
62
What is the function of CheZ?
CheZ dephosphorylates CheY-P to form CheY promoting running
63
What happens to the CheY-P after the production?
They diffuse through cell if they meet FliM it will causign CW rotation and tumbling. They may get caught by CheZ and be dephosphorylated into CheY casuing running

Sem 2: Microbiology (12 decks)

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