Table of Contents

• Section 1. How the Vibrio population grows
• 1: What causes cholera?
• 2: Build the basic growth equation
• 3: Draw exponential growth
• Section 2. So why isn't Frank dead already?
• 4: How long until 1 million bacteria?
• 5: All we need now is data
• 6: Looking at data
• 7: Log transform straightens out exponential growth
• 8: Do ALL curves get "straightened" by taking the log?
• 9: Phases of bacterial growth
• Section 3. How can we tell when the population is growing exponentially?
• 10: A test for exponential growth
• 11: And the answer is...
• 12: To recap
• 13: Some more practice
• 14: Extended problem: Exponential growth ends
• Review
• 15: Summary

How long until 1 million bacteria?

The bacteria may have multiplied in either the water, if it was polluted, or in the oysters during storage.  If the starting number was one cell of Vibrio, how many doublings (or generations) does the cell have to go through to get to 1 million? (Remember, 1 million is the infective dose).

Here's a likely but vague answer: probably not as many as you think. Let's try some numbers. You can play along at home using a calculator, or just click the buttons to see the answer:

10 generations:

15 generations:

20 generations:

The magic number is  1 million, and although the number is well below this after 15 generations, after 20 generations, the numbers have reached the million mark.