In a streak plate technique, which plate(s) demonstrate successful isolation of colonies across most of the plate surface?

• A. A plate with well-separated, individual colonies throughout the surface
• B. A plate with isolated colonies only at the edge and dense growth elsewhere
• C. A plate with confluent growth and no distinct colonies
• D. A plate with no visible bacterial growth

Answer: (A)

Verified step by step guidance

1. Understand the purpose of the streak plate technique: it is used to isolate individual bacterial colonies from a mixed culture by spreading cells over the agar surface to obtain well-separated colonies.
2. Identify what successful isolation means: it requires distinct, individual colonies that are separated enough to be counted and studied, rather than dense or confluent growth.
3. Analyze each option based on the definition of successful isolation: a plate with well-separated, individual colonies across most of the surface indicates successful isolation.
4. Recognize that a plate with isolated colonies only at the edge and dense growth elsewhere shows partial isolation but not across most of the plate, so it is not fully successful.
5. Understand that plates with confluent growth or no visible growth do not demonstrate successful isolation because colonies are either merged or absent.