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A biologist is studying the effect of a new antibiotic on bacterial growth. They prepare agar plates with different concentrations of the antibiotic (0 µg/mL, 5 µg/mL, 10 µg/mL, 20 µg/mL). An equal amount of bacterial culture is spread on each plate. After 24 hours of incubation at 37°C, the number of bacterial colonies is counted. The data shows: - 0 µg/mL: 150 colonies - 5 µg/mL: 90 colonies - 10 µg/mL: 30 colonies - 20 µg/mL: 5 colonies Based on these results, what is the most appropriate conclusion regarding the antibiotic's effectiveness?
- AThe antibiotic is equally effective at all concentrations.
- BThe antibiotic inhibits bacterial growth, with greater inhibition at higher concentrations.
- CThe antibiotic is only effective at concentrations above 20 µg/mL.
- DHigher concentrations of the antibiotic lead to increased bacterial growth.
Show answer & explanationAnswer & explanation
Correct answer: B. The antibiotic inhibits bacterial growth, with greater inhibition at higher concentrations.
As the concentration of the antibiotic increases from 0 to 20 µg/mL, the number of bacterial colonies consistently decreases (150 to 5). This directly indicates that the antibiotic is inhibiting growth, and its effectiveness increases with concentration.
Why the other options are wrong
- A. The number of colonies varies significantly with concentration, indicating differing effectiveness.
- C. The antibiotic shows effectiveness even at 5 µg/mL (90 colonies vs. 150 without antibiotic), so it's effective below 20 µg/mL.
- D. Higher concentrations lead to fewer colonies, meaning decreased bacterial growth (inhibition), not increased growth.
Data Interpretation
The process of reviewing data and arriving at conclusions based on observed patterns and relationships.
- Involves identifying trends, correlations, and anomalies.
- Requires careful examination of numerical or observational data.
- Conclusions must be supported directly by the evidence.
Memory trick: Data speaks: listen to the numbers' story.