Which enzyme is essential for nitrogen fixation?

Free-living nitrogen-fixing aerobic microbes are ...... and .......

What is required for nitrogen fixation by $Rhizobium$?

The function of leghaemoglobin during $N_2$-fixation is

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

$A -$ The enzyme nitrogenase is highly sensitive to molecular oxygen.
$R -$ To protect nitrogenase enzymes,the nodule contains an oxygen scavenger called leghaemoglobin.