Which of the following must happen prior to attempting to identify a bacterial species?

• A. A pure culture of the bacterium must be obtained.
• B. The bacterium must be stained with Gram stain.
• C. The bacterium must be tested for antibiotic resistance.
• D. The bacterium must be observed under an electron microscope.

Answer: (A)

Verified step by step guidance

1. Understand that identifying a bacterial species requires analyzing characteristics that are specific and consistent for that species.
2. Recognize that a pure culture contains only one type of bacterium, which is essential to avoid confusion from mixed populations when identifying species.
3. Note that obtaining a pure culture is the foundational step before performing any staining, testing, or microscopic observation, as these techniques rely on examining a single bacterial type.
4. After obtaining a pure culture, staining methods such as the Gram stain can be applied to classify bacteria based on cell wall properties, aiding identification.
5. Additional tests, like antibiotic resistance profiling or microscopic examination, are performed after ensuring purity to further characterize and confirm the bacterial species.