In a microbiology experiment, why is one sterile broth inoculated with Escherichia coli while another sterile broth is left uninoculated?

• A. To determine the optimal temperature for E. coli growth
• B. To compare bacterial growth in the presence and absence of E. coli as a control for contamination
• C. To observe the effect of antibiotics on E. coli in broth culture
• D. To test the effect of different nutrient concentrations on E. coli growth

Answer: (B)

Verified step by step guidance

1. Understand the purpose of using controls in microbiology experiments: Controls help to ensure that the observed effects are due to the experimental variable and not other factors.
2. Recognize that inoculating one sterile broth with Escherichia coli introduces the bacteria to observe its growth under specific conditions.
3. Note that leaving another sterile broth uninoculated serves as a negative control to check for contamination; if growth occurs here, it indicates contamination.
4. By comparing the inoculated broth with the uninoculated broth, you can confirm that any bacterial growth is due to the intentional inoculation and not from external contamination.
5. This comparison validates the experiment's results by ensuring that the observed bacterial growth is specifically from Escherichia coli and not from other sources.