Microbiology Lecture Notes September 4

Archaea – prokaryotes; more similar to eukaryotes; they have a distinct RNA polymerase that is similar to eukaryotes and ours more so that bacteria

Could you use rifampin to treat a hypothetical infection with archaea? ON EXAM
- Rifimpin destroys RNA polymerase and would be noneffective on acheae because their RNA polymerase is different from bacteria
- Archaea have the same RNA polymerase as us; it is different from the RNA polymerase in bacteria that rifampin targets
- If an antibiotic would be made to kill archaea it would also kill us because our RNA polymerase’s are very similar

We do not become immune to antibiotics; the bacteria become immune to them; we already are immune to them because they don’t kill us

Gram negative bacteria
- Plasma membrane: phospholipid bilayer
- Peptidoglycan cell wall: NO LTA; much thinner than in gram positive bacteria; ~5 layers thick; no cross linking so its not as tough
- Periplasmic space: space between cell wall and outer membrane
- Outer membrane contains lipopolysaccharide; contains an inside and outside leaflet; similar to phospholipid bilayer but contains lipopolysaccharide;
- inner leaflet: regular phospholipid bilayer
- outer leaflet: is made of a lipid (hydrophobic) inner part and a polysaccharide outer part(hydrophillic)
- Lipopolysaccharide is unique to gram-negative bacteria only

Other points on LPS and LTA:
- Inflammatory response reacts very violently to them
- If you had a lot of LPS or LTA in your body your inflammatory response will react very violently against it because it is a part of gram-negative bacteria ONLY not part of us

Acid Fast
- Plasma membrane
- Cell wall containing LTA like gram positive bacteria but not as thick
- Outer membrane (like an additional cell wall) contains mycolic acid which is a very dense waxy substance; makes the bacteria very resistant to drying out; can survive in a lot of environments
- Many of the bacteria found in the soil are Acid Fast bacteria
- Gram staining does not work on this type of bacteria because the mycolic acid outer membrane prevents the stain from penetrating the cell

Consequences of Rigid Cell Wall
- Bacteria that have cell walls containing peptidoglycan have clearly defined shapes; round shapes/spherical = cocci; tubes/cylindrical = bacilli; spiral/corkscrew = spirochetes

Amy Blass

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