Which of the following can be used as an aid to count the number of colonies on a pour plate?

• A. Colony counter
• B. Autoclave
• C. Spectrophotometer
• D. Incubator

Answer: (A)

Verified step by step guidance

1. Understand the purpose of each item listed: an autoclave is used for sterilization, a spectrophotometer measures optical density of liquid cultures, an incubator provides controlled temperature for microbial growth, and a colony counter is a device designed to assist in counting colonies on agar plates.
2. Recognize that counting colonies on a pour plate requires a tool that can help visually or electronically count discrete colonies formed on the agar surface.
3. Eliminate options that do not directly assist in counting colonies: autoclave (sterilization), spectrophotometer (measures turbidity, not colony count), and incubator (growth environment).
4. Identify that a colony counter is specifically designed to aid in counting colonies by providing magnification and sometimes digital counting features, making it the appropriate tool for this task.
5. Conclude that the colony counter is the correct answer because it directly facilitates accurate and efficient counting of colonies on a pour plate.