In viable plate counting, what is assumed about colonies on a plate?

In viable plate counting, what is assumed about colonies on a plate?

• A. Each colony arises from a single cell or a small group of attached identical cells that were not separated during plating.
• B. Each colony is formed by multiple cells and cannot be traced to a single parent.
• C. Colony size is always uniform across the plate.
• D. Colonies can only form on specific media.

Answer: (A)

In viable plate counting, you estimate how many viable organisms were in the original sample by counting the colonies that grow on a plate. The essential assumption is that each colony comes from a single viable cell (or from a very small group of attached cells that were not separated during plating). If you spread and dilute properly, most colonies originate from one cell, so counting colonies lets you infer colony-forming units per milliliter. This assumption is what makes the method workable; if colonies routinely came from many cells or from clumps that weren’t separated, the count wouldn’t reflect the true number of individual viable cells. Colder aspects like uniform colony size or requiring specific media aren’t what define the counting principle.

In viable plate counting, you estimate how many viable organisms were in the original sample by counting the colonies that grow on a plate. The essential assumption is that each colony comes from a single viable cell (or from a very small group of attached cells that were not separated during plating). If you spread and dilute properly, most colonies originate from one cell, so counting colonies lets you infer colony-forming units per milliliter. This assumption is what makes the method workable; if colonies routinely came from many cells or from clumps that weren’t separated, the count wouldn’t reflect the true number of individual viable cells. Colder aspects like uniform colony size or requiring specific media aren’t what define the counting principle.