Growth of an unknown bacterium on nutrient agar allows one to:

• A. identify the optimal temperature for bacterial growth
• B. observe colony morphology and estimate purity of the culture
• C. determine the exact species of the bacterium
• D. measure the bacterium's antibiotic resistance

Answer: (B)

Verified step by step guidance

1. Understand the purpose of growing bacteria on nutrient agar: it primarily allows observation of colony morphology and assessment of culture purity, rather than precise identification or measurement of resistance.
2. Recall that nutrient agar is a general-purpose medium that supports the growth of many bacteria but does not provide selective or differential properties needed for species identification or antibiotic resistance testing.
3. Recognize that observing colony morphology includes noting characteristics such as size, shape, color, texture, and edge of bacterial colonies, which helps in preliminary identification and checking for contamination.
4. Note that determining the optimal temperature for bacterial growth requires incubating cultures at various temperatures and measuring growth rates, which is not achieved simply by growing on nutrient agar at one temperature.
5. Understand that exact species identification typically requires additional biochemical, molecular, or serological tests beyond growth on nutrient agar, and antibiotic resistance is measured using specialized assays like disk diffusion or MIC tests.