Table of Contents

• 1: Recap the story
• 2: Count them all?
• 3: Direct count
• 4: Light scatter (spectrophotometer)
• 5: The dilemma of the dead cell
• 6: Viable plate count
• 7: Comparison of methods
• 8: Summary

Summary

In this module you have learnt some of the techniques that can be used for counting bacterial cells.

• The direct count, which uses a microscope to detect and count bacterial cells that have been loaded on a slide or a counting chamber
• The spectrophotometric method, which uses a spectrophotometer.  This method doesn't exactly count the bacteria, but it does measure how much light is absorbed by bacterial cells in suspension, and based on that, a standard curve can be used to decide how many bacteria there are.
• The viable plate count, which unlike the other two techniques, allows you to determine how many bacterial cells are alive in a bacterial population.

The next module “Viable Plate Count, or How to Count to a Million“ will show you all the steps and calculations involved in performing a viable plate count by using a serial dilution technique.