Estimation of Cell Numbers

What's the purpose of plate count?

Counting the number of colonies provides a measure of the number of viable cells or colony-forming units (cfu) per ml

What's the limitation of plate count?

Only works on colonies grown on a agar medoim

What is a direct microscopic count?

Used to determine the total number of cells within a suspension without cultivating them but can't distinguish between dead and living cells

What is culture turbidity or "optical density"?

Used to count the number of microorganisms in a pure culture by measuring the degree a light beam can pass through a pure culture placed in a spectrophotometer.