MICR221 MIDTERM TEST QUESTIONS WITH ALL ANSWERS VERIFIED
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Module
MICR221
Institution
MICR221
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...
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 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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