Which of the following bacteria is free-living in the soil?

The important contribution of molybdenum is in:

Which of the following bacteria are free-living nitrogen fixers?
$(i)$ $Pseudomonas$ $(ii)$ $Azospirillum$
$(iii)$ $Azotobacter$ $(iv)$ $Nostoc$

Which mineral plays a vital role in nitrogen fixation?

Oxygen carrier red coloured Hemoprotein is sensitive for

Which of the following organisms fixes atmospheric nitrogen in a free-living state?