Table of Contents

• Section 1. Frank's Story
• 1: Recap the story
• Section 2. How Could We Measure the Infection?
• 2: Count 'em all?
• 3: Direct count
• 4: Light scatter (using spec)
• 5: The dilemma of the dead cell
• 6: Viable plate count
• 7: Comparison of methods
• Section 3. How to Do a Viable Plate Count
• 8: Why we need to dilute
• 9: The dilution factor
• 10: Overall dilution
• 11: Interlude: Diluting Cold Press Coffee
• 12: How to scale back up
• 13: Why we plate more than one dilution
• 14: Picking the plate count
• Section 4. Practice Problems
• 15: Putting it all together
• 16: More dilution problems
• 17: Quickies
• Section 5. Back to Poor Frank
• 18: Is he dead yet?

Quickies

Below, you can practice a couple more times. I also included a few unusual situations ... things do go wrong, of course, and you should be able to recognize that. If you think the dilution series is not valid, click on "re-do the dilution". Oh, and "TNTC" means "too numerous to count".

 

dilution factor	1:100,000	1:1,000,000	1:10,000,000	1:100,000,000
count	TNTC	674	68	7
answer

 

dilution factor	1:100,000	1:1,000,000	1:10,000,000	1:100,000,000
count	375	105	11	1
answer

 

dilution factor	1:100	1:1000	1:10,000	1:100,000
count	TNTC	249	24	0
answer

 

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dilution factor	1:10	1:100	1:1000	1:10,000
count	954	96	10	0
answer

 

dilution factor	1:10,000	1:100,000	1:1,000,000	1:10,000,000	1:100,000,000
count	TNTC	567	58	12	1
answer