Question: What type of bacteria have you discovered inside pea-plant's roots? What do they do?

Isabel Webb answered on 17 Mar 2014:

The bacteria I look at inside pea roots are called Rhizobia leguminosarum. Related bacteria are found inside plants related to peas like broad beans or peanuts.

All living things need nitrogen-containing compounds to make lots of things inside them – including proteins and DNA. Most plants take up nitrogen as ‘nitrates’, which are found in the soil. Not enough nitrates are found in the soil for our crop plants though – and this is why farmers use fertilisers.

Rhizobia, my bacteria, is able to carry out a reaction called ‘nitrogen fixation’. This converts nitrogen from the air into nitrates. They live inside pea plants, and so can provide peas with nitrates immediately. The plant takes these nitrates, and in return provides the sugar for bacteria which gives them the energy they need for the reaction. This means that we don’t have to use fertilisers on peas.

Making chemical fertilisers for farmers is very expensive, and uses up a lot of energy. If we understood the action of these Rhizobia better, we could use it to make a biological version of these fertilisers – which would be really exciting and save everyone lots of money. Some other researchers are trying to encourage other species, such as wheat, to take up Rhizobia and ‘fix’ nitrogen for them.