TOPIC I - Cell Wall Synthesis, Antibiotics, and Human Microbiota Flashcards
Where did antibiotics come from?
nature (ex: soil bacteria, fungi, etc.)
Does a bacteriocidal antibiotic kill bacteria?
yes
Does a bacteriostatic antibiotic kill bacteria?
no, it inhibits bacterial growth
What are the cellular targets for bacteria?
- cell wall synthesis (inhibited)
- cell membrane (function disrupted)
- translation (inhibited)
- metabolism (inhibited)
- transcription (inhibited)
- DNA replication (inhibited)
Why did microbes in nature produce antibiotics?
they lived in dense communities with lots of competition –> used antibiotics to kill each other
List the antibiotics (learned in class) that inhibit murein (peptidoglycan) synthesis.
- penicillin G
- methicillin
- ampicillin
- penicillin V
- vancomycin
- bactitracin
Penicillin G
- natural/semi-synthetic/synthetic/biosynthetic
- narrow spectrum/broad spectrum
- other info:
- natural (from fungi)
- narrow spectrum –> only affects gram + ; cannot penetrate gram -
- penicillin treatment –> osmotic lysis
Methicillin
- natural/synthetic/semi-synthetic/biosynthetic
- other info:
- semi-synthetic
- resistant to b-lactamase (an enzyme that some bacteria can produce to be resistant to penicillin)
What is b-lactamase?
an enzyme that some bacteria can produce to be resistant to penicillin
Ampicillin
- natural/synthetic/semi-synthetic/biosynthetic
- narrow spectrum/broad spectrum
- other info:
- semi-synthetic
- broad spectrum
Penicillin V
- natural/synthetic/semi-synthetic/biosynthetic
- narrow spectrum/broad spectrum
- other info:
- semi-synthetic
- acid-resistant
- FRIST orally administered penicillin
Vancomycin
- natural/synthetic/semi-synthetic/biosynthetic
- narrow spectrum/broad spectrum
- other info:
- blocks transglycosylase linkage of disaccharides NAG-NAM
- cannot penetrate gram -
- hard to administer
- expensive
- relatively toxic
- LAST RESORT antibiotic
What does bacitracin do?
bacitracin blocks the release of NAG-NAM peptide from its lipid carrier
Why is the folate biosynthesis pathway a good target for antibiotics?
- folate is an essential vitamin for all organisms
- bacteria rely on their ability to synthesis folate (via folate biosynthesis pathway)
- humans cannot synthesize folate (no folate biosynthesis pathway) –> must ingest folate in their food
- antibiotics that target pathway will not affect human cells
Are there different microbiome communities at different body sites?
yes, because of different environments (ex: pH, light, oxygen, etc.)
Are microbiomes highly variable between individuals?
yes
What are diurnal fluctuations?
refers to how gut microbiota will differ during morning and nighttime due to variations in:
1. body temp
2. nutrient availability
3. concentration of gastrointestinal hormones
4. levels of host-delivered antimicrobial peptides
5. levels of gut mucosal antibodies
What are some ways to re-stock beneficial species in the gut microbiome?
- probiotics (ex: fermented food, yogurt)
- prebiotics (ex: onions, flaxseed, leeks)
- fecal transplant
Where does antibiotic resistance come from?
- microbes that are producing antibiotics need to be resistant to it so that they don’t harm themselves
- large horizontal gene transfer (between the same generation)
What are some mechanisms of antibiotic resistance?
- reduced influx of antibiotics (reduced expression of porins)
- active efflux of antibiotics
- antibiotics degradation or modification
- target modification (ex: reduce binding) or protection
- bypass the target
- increased production of target (titration)
List the steps in murein (peptidoglycan) synthesis.
- pentapeptide added to N-acetyl muramic acid
- peptide-M and N-acetyl glucosamine are linked, creating peptidoglycan subunit
- peptide-MG is transported (flipped) across cell membrane by a lipid carrier
- peptide-MG is added to growing polysaccharide chain by transglycosylases
- peptides are covalently linked by a transpeptidase
