1-65 Microbiology Flashcards
1
Q
Eukaryotes vs. Prokaryotes
A
Eukaryotes: nucleaus with nuclear membrane, internal membrane network (golgi ER), introns, organelles Pro: chromosome in cytoplasm, cell wall, no introns, no internal membrane network, no classical organelles
2
Q
Size of bacteria
A
1-2 uM in size (RBC 7uM, smallest size visible to eye 40 uM)
3
Q
Cell envelope (bacteria)
A
- surounds the cytosol
- protection from environemental threats
- housing for factors important in cellular functions
- consists of cytoplasmic membrane and cell wall
- cytoplasmic membrane: “plasma membrane” lipid bilayer contianing integral and periphal proteins, do not contains “sterols” (except Mycoplasma)
- cell wall: gives shape, protects the cell against osmotic lysis, all medically important bacteria (except Mycoplasma) have cell walls
- made of peptidoglycan (aka murein), antibiotic target (cuz human cells dont make these)
4
Q
Peptidoglycan structure
A
- N-acetylglucosamide and N-acteylmuramic acid
- peptide of alternating L and D amino acids, dissachiride
- thrid AA of some peptides are cross linked to the terminal aa of other peptides
- penicillin-binding proteins (PBPs): responsible for making the peptidoglycan structure
- adds glycine cross bridge
- 2 major forms of cell walls:
- Thick: gram+
- Thin:gram-
5
Q
Penicillin mechanism
A
6
Q
Mech of bacterial resistance to penicillins
A
- beta-lactamase production
- alteration of PBPs
- prevention of access
7
Q
Vancomycin mechanism
A
- binds last 2 aa from side chain to prevent cross linking
- resistance mediated by altering the last of 2 AAs so vanco cannot recognize/bind
8
Q
Mech of bacterial resistance to vancomycin
A
9
Q
Lysozyme mechanism vs bacteria
A
10
Q
A
11
Q
Gram staining process & Limitations
A
- Limitations of gram-staining
- few medically important bacteria are poorly visulized by the Gram technique
-
mycobacteria: contain long-chain fatty acids are call acid-fast use Ziehl-Neelsen of Kinyoun stain
- Red: thick wall
- Blue: counterstain
- Some spirochetes: dark-field microscopy (becasue so smol!)
- Mycoplasma: have no cell wall
- Rickettzia, Legionella: unsure why!
-
mycobacteria: contain long-chain fatty acids are call acid-fast use Ziehl-Neelsen of Kinyoun stain
- few medically important bacteria are poorly visulized by the Gram technique
12
Q
Gram-positive bacteria
A
-
Teichoic acids: long polymers of either glycerol phosphate or ribitol phsopahte that also contain sugars and AAs
- atached to teither the ycytoplasmi membrane (alled lipoteichoic acid) or the cell walls
- adhesins
- exact sturcutre varies
13
Q
Gram-negative bacteria
A
- Additional outer membrane
- Contains porins
- The phospholipids in the outer leaflet are replaced by lipopolysaccharide (LPS).
- The space between the outer membrane and the cytoplasmic membrane, which contains the peptidoglycan layer, is called the periplasm or periplasmic space.
14
Q
Lipopolysaccaride structure
A
- LPS, with six (sometimes five or seven) saturated fatty acid side-chains, forms a tight barrier that prevents many molecules, including certain antibiotics, from reaching the underlying cell wall.
- 3 parts
- Lipid A: A diglucosamine molecule containing substituted fatty acids. Lipid A is the component of LPS that is embedded in the outer membrane.
- Core polysaccharide: A region attached to lipid A consisting of 7-9 sugar residues (including some
unusual ones such as ketodeoxyoctonate [KDO]
and heptose). - O antigen (O side-chain): A polysaccharide chain consisting of repeating units of 3-5 sugar residues, up to 40 units in length.
15
Q
o- antigen
A
- one component of LPS, used to categorize bacteria if they all have the same O antigen
- Serum resistance vs. serum sensitive.
- O-antigen resists complement deposition, thereby inhibiting complement-mediated killing
- Upon repeated exposures, O-antigen is recognized by specific antibodies, which mediates bacterial clearance.
- Antigenic and allows serotyping.
