Which of the following is NOT a phenotypic method of microbial identification?

• A. Colony morphology observation
• B. Biochemical testing
• C. 16S rRNA gene sequencing
• D. Gram staining

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the difference between phenotypic and genotypic methods of microbial identification. Phenotypic methods rely on observable characteristics of the microorganism, such as morphology, staining properties, and biochemical activities.
2. Step 2: Review each option to classify it as phenotypic or genotypic. Colony morphology observation involves looking at the physical appearance of microbial colonies, which is a phenotypic method.
3. Step 3: Biochemical testing assesses the metabolic and enzymatic activities of microbes, which are also phenotypic traits.
4. Step 4: Gram staining is a differential staining technique that categorizes bacteria based on cell wall properties, another phenotypic method.
5. Step 5: 16S rRNA gene sequencing analyzes the genetic sequence of the ribosomal RNA gene, which is a genotypic method, not phenotypic. Therefore, it is the correct answer as the method that is NOT phenotypic.