One of the useful activities of several bacteria is

One of the useful activites of several bacteria is :

Some bacteria live symbiotically inside root nodules of higher plants. The basic activity of these bacteria is associated with :

The stain used to observe bacteria is -

In biogas, methane is produced due to the activities of nitrogen-fixing bacteria.

Which of the following is mainly formed by the activity of anaerobic bacteria on sewage?

Which of the following is mainly produced by the activity of anaerobic bacteria on sewage ?