Question

A microbiologist hypothesized that Staphylococcus aureus is more susceptible to antibiotics than Escherichia coli. She tested her hypothesis by exposing the two species of bacteria to three different antibiotics. The closer the bacteria were able to grow to antibiotic-soaked disks, the more resistant they were to treatment by that antibiotic.

Which bacterium would you expect to be more responsive to antibiotic treatment?
Graph

Answer 1

Staphylococcus aureus.
If S. aureus is more susceptible than E. coli, you would see larger zones of inhibition (i.e., greater distance from the antibiotic disk to the edge of bacterial growth) for S. aureus than for E. coli.

How to graph it:
- X‑axis: antibiotic (three categories).
- Y‑axis: zone of inhibition (distance from disk edge to bacterial growth, in mm, or radius/diameter of clear zone). Larger values = more susceptible.
- For each antibiotic, plot two bars or points: one for S. aureus and one for E. coli (use different colors and include a legend).
- Include error bars (SD or SE) from replicates and note sample size.
- Expected pattern: S. aureus bars higher than E. coli bars for each antibiotic (or at least on average), indicating greater responsiveness to treatment.

(Optionally run t‑tests or ANOVA to test whether differences are statistically significant.)