# But how long is a generation?

Imagine a single bacterial cell. You might think a cell that is not actively dividing is sitting around, twiddling its non-opposable
thumbs or knitting or something. However, this is not actually true. For a while (anywhere from 20 minutes to a few days) the cell
spends its time gathering nutrients and synthesizing extra cellular structures. Once that is done, it can divide into two.
**Any given strain of bacteria requires, on average, a certain amount of time to gather nutrients and organize itself to divide** (of course the time required depends a lot on the amount of nutrients available, the temperature, and so on).
Nevertheless, if you know what the environment is like, you can make some educated guess about how long it will
take a bacterial cell to divide.

So this is our first and most straightforward way of measuring growth rate:

g = generation time = average time for cell to divide

Can you match these five bacteria with their doubling time under ideal conditions?

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