Question: how fast does bacteria grow ?

Alison Graham answered on 18 Jun 2012:

This is a great question. There is no one final answer as there are lots and lots of different types of bacteria that all grow at different rates. It also really depends on the conditions they are in. When we talk about bacteria growing, we are talking about a single cell getting bigger and then dividing into two cells (check out this Youtube clip: http://www.youtube.com/watch?v=gEwzDydciWc).

What we do know is how fast they can grow given perfect conditions! The bacteria we know most about is E. coli. This has been studied for a long time. The conditions that allow a bacterium to grow best are called the “optimum conditions”. When E. coli is growing in optimum conditions (nice and warm, lots of nutrients), each individual cell can divide into two cells every 20 minutes! This means that if you start off with one E. coli cell, if the conditions are right, 20 minutes later you will have 2 cells. After another 20 minutes each of these will have divided into 2 cells giving a total of 4 cells. After another 20 mins (1 hour from the start), these four will have divided again giving a total of 8. After one day, there would be more bacteria than there are grains of sand in all of the world’s beaches!

So, why do we not have beaches made of bacteria then? This is basically because E.coli, in the real world, cannot divide this fast because conditions are usually not optimal and they run out of food before they take over the world. Lucky for us! 🙂

Although E. coli likes growing at 37 oC (body temperature!), some bacteria like really cold or really hot temperatures. There is a species of bacteria that can grow at 122 oC!