LAB 5 - Antimicrobial Compounds from Bacteria Flashcards
When was penicillin discovered
1928
Most antibiotics in use today
- Derived from Streptomyces genus
- e.g. Tetracycline, vancomycin, neomycin
- Key organisms in soil habitats
Method used to discover antimicrobial agents
- Microorganisms of interest are obtained from natural environments and cultured to ensure purity
- The isolate is then grown on agar and excretes the antimicrobial compound into the agar medium.
- When test microorganisms are cross-streaked onto the agar and incubated, their growth may be inhibited
Streptomyces species used in experiment
- S. diastaticus
- S. lavendulae
- S. venezuelae
Which Streptomyces species demonstrated highest overall growth inhibition
- S. venezuelae
- Inhibit Aeromonas hydrophila and Moraxella catarrhalis the most
Bacteria that were only inhibited by S. venezuelae
- A. hydrophila
- E. coli
- Klebsiella pneumonia
Least effective Streptomyces species
S. lavendulae, only inhibited M. catarrhalis
What bacteria did S. diastaticus inhibit
- Bacillus cereus
- M. catarrhalis
- Staphylococcus aureus
- Staphylococcus epidermidis
What bacteria was unaffected by all Streptomyces species
Pseudomonas aeruginosa
What was the most susceptible test bacteria
M. catarrhalis
Was there any observable trend related to whether the test bacteria were Gram positive or Gram negative? If you did observe that only Gram positive bacteria were affected, what might you conclude about the site of action of the inhibitor, and why it might not be affecting the Gram negative organisms?
- S. venezuelae affects both Gram-negative and Gram-positive bacteria.
- Its antimicrobial compounds may target sites other than the cell wall (e.g., ribosomes, DNA synthesis pathways).
- These compounds could penetrate the outer membrane of Gram-negative bacteria.
- S. venezuelae compounds may have broad-spectrum activity, potentially overcoming the protective barriers of Gram-negative bacteria.
