MID 2 - Genetics / Abx Intro Flashcards
(39 cards)
What is an insertion sequence?
Smallest transposable element known, only encodes genes for mobilization and insertion (has ability to disrupt genes when it jumps, 768 bp -> 5 kb in length).
Why are transposon events considered ‘high frequency, low diversity?’
High frequency because they happen a lot. Low diversity because they only effect the amount of a gene product that is produced (as opposed to point mutations, which effect the gene itself).
What is the difference between transformation and transduction?
Transformation - lysed cell DNA is taken up by host.
Transduction - viral protein with bacterial DNA load ‘infects,’ host cell, providing DNA that is taken up by host.
What is conjugative transposition?
Transposon larger than IS element with inverted repeats, transposases, genes for sex plus, can enter chromosome and can leave chromosome to become plasmid in order to conjugate.
What is the difference between generalized transduction and specialized transduction?
generalized: DNA fragment transferred by a lytic bacteriophage.
specialized: DNA gragment transferred by a temperate bacteriophage carrying donor bacterial DNA due to error in lysogenic life cycle.
Pseudomonas aeruginosa: What is its gram / shape stain, where is it found, who does it infect
gram negative bacillus; found on shower heads, salad bars, ubiquitous; causes disease in impaired hosts.
What are three critical gene products necessary for bacterial infection?
1) attachment proteins (pili)
2) siderophores (iron scavenging)
3) flagella (motility)
What ar the important extracellular virulence factor products of bacteria and what are their functions?
Proteases (to get proteins); hemolysins (to get iron); exotoxin A (inhibits protein synthesis); exoenzyme S (bacteria make their own anchoring proteins); pyocyanin (anti-oxidant)
How does pseudomonas aeruginosa cause disease at the cellular level?
Activates TLRs and NODS, inflammasome activation causes activation of caspase-1, leading to inflammation.
How does pseudomonas aeruginosa cause lung damage?
activates alveolar macrophages (which are usually anti-inflammatory), signaling the recruitment of PMNs, cellular debris, activated platelets, mass cells, we start to kill cells that make up the alveolar cell lining.
What recognizes the flagella?
TLR5 (NFkB signaling, proinflammatory),, ifound on the BL of the gut epithelium so that only causes response to invasive organisms.
What is the ‘inflammasome’, what causes its assembly, and what does it do?
Multiprotein oligomer whose assembly is activated by flagella and other bacterial factors. Expressed in myeloid cells and is a component of the innate immune system. The inflammasome promotes the maturation of the inflammatory cytokines Interleukin 1β Interleukin 18 via caspase-1.
What is the ‘Type III secretion system”
Found in gram neg bacteria, allows bacteria to infect host, creates the equivalent of a sex pilus called a translocate complex.
What are the 5 major mechanisms of actions of antibiotics?
1) inhibit cell wall synthesis
2) inhibit protein synthesis
3) alter nucleic acid metabolism
4) inhibit folate metabolism
5) other mechanisms
What are the 6 classes of antibiotics that inhibit cell wall synthesis?
1) penicillins
2) cephalosporins
3) monobactams
4) carbapenems
(above are all beta-lactams)
5) glycopeptides (vancomycin)
6) lipoglycopeptide (televancin)
What are the 8 classes of antibiotics that inhibit protein synthesis?
1) aminoglycosides
2) tetracyclines
3) Glycylcyclines
4) Macrolides
5) Lincosamides
6) Streptogramins
7) Oxazolidinones
8) Chloramphenicol
What are the 2 classes of antibiotics that alter nuclei acid metabolism?
1) Rifamycins (rifampin)
2) quinolones
What are the 2 classes of antibiotics that inhibit folate metabolism?
1) Trimethoprim
2) Sulfonamides
What is the mechanism of action for beta lactams?
Inhibit synthesis of peptidoglycan layer of cell wall by blocking action of transpeptidases (aka penicillin binding proteins)
For what illnesses is penicillin the treatment of choice?
Strep group A, syphilis;
What is vancomycin’s mode of action and what is it used for?
Prevents cross-linking of peptidoglycan chains; only active against gram+ bacteria (with rare exceptions); used for serious infections caused by methicillin-resistant Staph.
What classes of ABXs target the 30S ribosomal subunit?
aminoglycosides; tetracyclines
What classes of ABXs target the 50S ribosomal subunit?
Macrolides; chloramphenicol; lincosamides; oxazolidinones; streptogramins
What is the mode of action of quinolones?
Inhibit DNA synthesis by inhibiting topoisomerases responsible for DNA supercoiling / unsupercoiling.
