Vancomycinis an antibiotic that has become critical for controlling penicillin-resistant bacteria. This large glycopeptide (molecularwt. = 1449) binds to cellwall precursors and interferes with peptidoglycansynthesis.
The polymyxinsare a group of antibiotics that are particularly effective as atopical antibiotic against skin infections. These largepolypeptides (molecular wt. = 1202) can disrupt some bacterialmembranesby binding preferentially tolipid Amolecules. In the experiments below, different prokaryoticcells were grown in broth cultures in the presence orabsence of anantibiotic (either vancomycin or polymixin). After 1 hour, cellswere rinsed, and the percent of bacteria that survived wasdetermined.
Graph Awas...
Bacillus E.Coli Methanoge n(archaea)
With Antibiotic----- 80%CellSurvival 20%CellSurvive 90%Cell Survive
Without Antibiotic--- 100% CellSurvive 100%CellSurvive 100%Cell Survive
Graph B was...
Bacillus E.Coli Methanoge n(archaea)
With Antibiotic----- 30% CellSurvival 80%CellSurvive 100%Cell Survive
Without Antibiotic--- 100% CellSurvive 100%CellSurvive 100%Cell Survive
QUESTION IS:
Using the dataabove, predict which experiment (A or B) was done using vancomycin andwhich experiment was doneusing polymyxin, and explain yourrationale.
NOTE: Bacillushas a Gram (+) type envelope; E.coli has a Gram (-) type envelopeand
Methanobacteriumisan Archaea. (Hint: think about cell envelopestructure).