basic Flashcards
What is the ribosome size in prokaryotes?
70S – 50S and 30S
Which antibiotics act on ribosomes?
Aminoglycosides, erythromycin, tetracycline, chloramphenicol
What kind of properties do pili contain?
Antigenic and haem agglutination
What is the importance of a capsule?
Virulence factor, specific identification of an organism, antigenic properties (use in disease), adherence
By limiting ability of phagocytosis, capsule can increase the risk of which infection?
Meningitis
Which bacteria commonly adhere to teeth and cause caries?
S. mutans, S. aureus, P. aeruginosa
What tests can help to visualize the capsule?
India ink (background stained, not organism) and quellung reaction (swelling test
Which bacteria are spore forming?
Aerobic bacillus and anaerobic clostridium (both Gram +)
When does sporulation occur?
Under harsh conditions when nutrients (ie Nitrogen, alaine) are depleted
What is the spore?
Dehydrated, multi-shelled structure that protects and allows bacteria to exist in “suspending animation”, high concentration of calcium bound to dipicolinic acid
What is the function of the cell wall?
Provides cell rigidity and gives shape, keeps cell intact (IC osmolarity higher than EC), provides attachment sites for bacteriophages (teichoic acids on outer surface), rigid platform for things like pili, flagella, fimbrae
What is the structure of the inner cytoplasmic layer of the cell wall?
Double layer phospholipid, no cholesterol or other sterol
Peptidoglycan layer components?
Repeating disaccharides, N-acetylglucosamine and N-acetylmuramic acid (NAG and NAM)
4 AA side chains of adjacent peptidoglycans covalently bound
Stable cross-linked structure
What catalyzes the cross-linking reaction of the peptidoglycan layer? What inhibits it?
Transpeptidase enzymes (in cytoplasmic membrane), B lactam
What acts as an antigen determinant (epitope) in the cell wall of gram positive bacteria?
Teichoic acid
What do lipoteichoic acids regulate?
Autolytic wall enzymes (muramidases)
How many layers are in the gram negative cell wall?
3 – cytoplasmic membrane, peptidoglycan layer, lipid bilayer with LPS in the outer portion
What protein is found in the peptidoglycan layer?
Murein protein
What are the 3 covalently linked compounds that make up the LPS structure?
- Outer carbohydrate chain (O-units), antigen determinant
- Water soluble core polysaccharide
- Lipid A (endotoxin)
Structurally, what is lipid A?
Disaccharide with multiple fatty acid chains
What are porin proteins?
Transmembrane complexes along the outer membrane of gram-negative bacteria allowing passage of nutrients
What enzymes do bacteria contain to break down oxygen products?
Catalase, peroxidase, superoxide dismutase
What are the two main modes of gene transfer?
Horizontal – parent to offspring (sexual or asexual)
Vertical – gene transfer between organisms, not traditional reproductive method
What are the mechanisms of horizontal gene transfer?
Transformation – after cell lysis, DNA released as soluble pieces into environment and picked up by neighboring bacteria
Transduction – transfer of DNA from one bacteria to another using a bacteriophage, plasmid transfer
Transposons – piece of DNA that moves from one location of chromosome to another (can contribute to resistance)
Conjugation – direct plasmid transfer, often between F plasmid (ie. sex pili)
Which mechanism of gene transfer contributes most to multi-drug resistance?
Conjugation (due to resistance gene transfer)
