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MICR221 MIDTERM TEST QUESTIONS WITH ALL ANSWERS VERIFIED

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MICR221 MIDTERM TEST QUESTIONS WITH ALL ANSWERS VERIFIED Extracellular Polysaccharide - Answer-Capsule! - not every bacteria -often lost in lab - ex. slime found in lungs of CF patients (pseudomonas aerginosa) is due to capsule - this is why antibiotics don't really work - can't get through c...

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  • August 29, 2024
  • 11
  • 2024/2025
  • Exam (elaborations)
  • Questions & answers

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  • micr221
  • micr221 midterm test questions with all answers
  • extracellular polysaccharide

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  • MICR221
  • MICR221

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MICR221 MIDTERM TEST QUESTIONS
WITH ALL ANSWERS VERIFIED
Extracellular Polysaccharide - Answer-Capsule!
- not every bacteria
-often lost in lab
- ex. slime found in lungs of CF patients (pseudomonas aerginosa) is due to capsule -
this is why antibiotics don't really work - can't get through capsule
- protects from desiccation (98% water)
- protects from predation
- helps cell adhere to surfaces - but bio fouling is bad!

Capsule gene organization - Answer-Region 1 - (5 genes) - transport across the outer
membrane
Region 2 - (variable) - actual biosynthesis of capsule
Region 3 - (T and M) - transport across cytoplasmic membrane

Pilus genes - Answer-PapA: bulk of pilus fiber
PapE: major component of fibrillum
PapF: needed to couple PapG to pilus fibrillum
PapG: Adhesin!
PapK: connects fibrillum to rest of pilus
PapC: removes proteins from Pap D and forms hole in membrane
PapD: acts as chaperone - directs proteins to Pap C
PapH: anchor

Amphitrichous - Answer-one flagellum at each end of cell

Lophotrichous - Answer-cluster of flagella at one or both ends

Peritrichous - Answer-spread over entire surface of cell

Flagella Hook Associated Proteins - Answer-HAP2: caps filament - critical for assembly
HAP 1 & 3 at junction of filament and hook

Flagella Structure - Answer-Filament: 95% of the flagella
- flagellin gene deficient in cys, trp
- capped by Hap2 - critical for assembly
Hook:
- defined length of 80nm
- HAP 1 & HAP 3 at jungtion of filament and hook
Basal Body
- LPSM rings, LS only in gram +ve

, Flagella Motor Proteins - Answer-MotA and MotB: form proton channel (for energy)
MotB: connects to peptidoglycan layer

Switch proteins : FliN, FliG, FliM

Flagella Basal body rings - Answer-L: in place of outer membrane
P: in plane of peptidoglycan layer
S: above the cytoplasmic membrane
M: in plane of cytoplasmic membrane

- Gram +ve only have L and S rings
- ring proteins have signal peptides
- flagella grows body then hook then filament

Chemotaxis proteins - Answer-CheW: receives chemical signal. Passes on to CheA
CheA: Phosphorylated when repellent present. Transfers P to CheY
CheY: when phosphorylated, binds to switch, rotating flagella
CheZ: dephosphorylates allowing to travel straight
CheR: methylase
CheB: demethylase (methylesterase)

Gram Positive Bacteria - Answer-- thick peptidoglycan layer containing teichoic acids
- Periplasm
- cytoplasmic membrane

Gram Negative Bacteria - Answer-- Outer membrane
- thin peptidoglycan layer
- periplasm
- cytoplasmic membrane
- lipopolysaccharides, proteins, phospholipids
- 2 chemically distinct lipid containing membranes

Gram Staining Protocol - Answer-1. Flood slide of heat fixed cells with violet dye for 1
min
2. flood slide with iodine for 1 min
3. wash slide with alcohol 20 sec.
4. Counterstain with safranin red
Gram -ve are stained red.
Gram +ve are stained violet (because colour got stuck in thick peptidoglycan layer)
RED means DEAD for gram +ve because their peptidoglycan layer is degraded

Periplasm - Answer-space between cytoplasmic membrane and outer membrane

Peptidoglycan - Answer-- peptide side chains important for attaching to adjacent chains
via cross links (Nag to Nam)
- important for cell shape maintenance - rigidity

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