Rhizobium lives symbiotically with root nodules and fixes atmospheric nitrogen. It provides nitrogenous compounds to the host and in turn takes food from the host. This food taken by the bacterium is:

Which of the following is a recently discovered Gram-positive,non-leguminous,nitrogen-fixing bacterium?

Identify the $A$ to $D$ correctly in the given diagram of root nodule development and choose the correct option accordingly.

In which of the following are root nodules found?

We find that $Rhizobium$ forms nodules on the roots of leguminous plants. Also,$Frankia$,another microbe,forms nitrogen-fixing nodules on the roots of the non-leguminous plant $Alnus$. Is it necessary for a microbe to be in close association with a plant to provide mineral nutrition? Explain with the help of one example.

Nitrogen fixation in root nodules of $Alnus$ is brought about by