Lecture 2 Flashcards
What mechanism do bacteria use for uptake?
Rocker-switch mechanism
No endocytosis
What system do bacteria use to transport sugars?
Phosphotransferase system (PTS) If glucose is low, somethign stays phosphorylated, cAMP is produced, alternate carbon sources are used
What are energy sources for rocker-switch mechanism?
Membrane potential
Gradient of another solute
ATP hydrolysis
Type I SecMech
3 linked proteins form pore through IM, peri, OM ATP powers secretion E. coli hemolysin Pseudomonas proteases Pasturella leukotoxin
Type II SecMech
Sec B recognizes leader peptide Sec A is ATPase SecYEG is translocon Periplasmic leader protease Specific or semi-specific OM porin MOST SECRETED PROTEINS IN BACTERIA AND MITOCHONDRIA USE THIS MECHANISM
Type III SecMech
Virulence secretory pathway One step mechanism Shigella (Ipas) Salmonella (Sips) Yersinia (Yops)
Type IV SecMech
Transport DNA and proteins Two paradigm systems 1. Agrobacterium tumifaciens VirB/TraF 2. Dot/Icm sytstem in many pathogens a. Legionella pneumophila b. Helicobacter pylori c. Bordetella pertussis
Type V SecMech
Autosecretion
Sec B leader on N term through IM
Beta domain on C term spontaneously forms channel through OM
Brucella, E. Coli and others
Type VI SecMech
Genes usually located in pathogenicity islands
Structurally similar to bacteriophage tail fiber
Very common
What forms peptidoglycan backbone
N-acetylglucosamine
N-acetylmuramic acid
Linked beta 1-4
Which type of bacteria has pentapeptide cross bridge of peptidoglycan?
GramPos
What is the pentapeptide side chain added to?
UDP N-acetylmuramic acid
What is the MurNAc with pentapeptide added to?
Bactoprenol
What happens after MurNAc PP is added bactoprenol?
Flips to other side of membrane when BP is phosphorylated. It is then added into a hole in the membrane. Finally crosslinking occurs. BP is dephosphorylated and it flips back in
What blocks UDP addition to MurNAc?
Fosfomycin
What inhibits flipping of bactoprenol?
Bacitracin
What CLASS blocks transpeptidases?
Beta-lactams
What blocks transglycosidase?
Glycopeptides
What are the special wall components of GramPos?
Teichoic acid (Mg+ reserve, phosphate)
Teichuronic acid
Lipoteichoic acid
What is one function of lipoteichoic acid?
Links PG to membrane
What are holes in the OM?
Porins (three proteins)
Non-Allow MW less than 600
semi, specific
What links OM to PG layer?
Lipoprotein (Brauns protein)
Linked to DAP in PG
What is another name for LPS?
Endotoxin
What binds LPS?
LBP after the bacteria has been lysed
LBP then binds to CD14 and TLR4
Induces secretion of lymphokines
What are major effects of lymphokines?
Increase synthesis of WBC
Increase capillary permeability
What is the repeating unit in LPS
O-antigen
Why is LOS more virulent than LPS?
Resemble mammalian sphingolipids and evade host defense
How is LPS synthesized?
- Core is added as monosaccharide to lipid A on cyto side
- Flips to peri side
- Repeat unit is synthesized on cyto side, added to bactoprenol and flips
- Finished LPS translocates to OM by bridging proteins
What is mycolic acid used for?
Waxy protective coating
What is function of arabinogalactan and arabinomannan
Anchors waxy part of wall to to PG
Activates HIV-1 expression
What is the purpose of the capsule or glycocalyx?
Adhesions to surface
Anti-phagocytic
Immune mimic
What are pili and fimbriae
Short hollow cylinders of pilin and fimbrin
What are functions of pili and fimbriae?
Hold cells together
Attach cells to surface
Antigenic (cells can vary this to evade hosts)
Motility (twitching)
What are flagella composed of?
Flagellin
How does a flagella move?
Protons move through Mot A/B which causes a repulsion
What are the three stages of germination?
I-activation. Permeabilizes coat
II-initiation-binding of germinant releases autolysin and DPA is released
III-outgrowth-until first division of new cell
CCW rotation of flagella causes what?
Swimming
CW rotation of flagella causes what?
Cell tumbles randomly
What is S-layer?
A layer that surrounds some cells
Acts as a sieve
Might have anti-complement properties
When do endospores form?
Only under starvation conditions
This triggers membrane kinases that start a phosphorylation cascade ending with SpooA-P
What is a spore?
A metabolically inactive bacteria with a double membrane around its genetic material
What event reactivates a spore?
Germination
What can trigger germination of a spore?
Binding of nutrients
What is the difference in peptidoglycan residues between GramNeg and Pos?
Neg = DAP at #3 Pos = Lysine at #3
What are all capsules?
Polysaccharides except for B. anthracis
