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Nitrifying bacteria
A
Reduce nitrates to free nitrogen
B
Oxidize ammonia to nitrates
C
Convert free nitrogen to nitrogen compounds
D
Convert proteins into ammonia
Detailed Solution
Nitrification is the oxidation of ammonia to nitrate in the soil; it takes place in two steps.
Step 1: ammonia is oxidised to nitrite by $Nitrosomonas$ and $Nitrococcus$: $2NH_3 + 3O_2 \rightarrow 2NO_2^- + 2H^+ + 2H_2O$
Step 2: nitrite is oxidised to nitrate by $Nitrobacter$: $2NO_2^- + O_2 \rightarrow 2NO_3^-$
These nitrifying bacteria are chemoautotrophs.
Reduction of nitrates to free nitrogen is denitrification ($Pseudomonas$, $Thiobacillus$); conversion of free nitrogen to nitrogen compounds is nitrogen fixation; conversion of proteins into ammonia is ammonification.
Hence nitrifying bacteria oxidise ammonia to nitrates.
Step 1: ammonia is oxidised to nitrite by $Nitrosomonas$ and $Nitrococcus$: $2NH_3 + 3O_2 \rightarrow 2NO_2^- + 2H^+ + 2H_2O$
Step 2: nitrite is oxidised to nitrate by $Nitrobacter$: $2NO_2^- + O_2 \rightarrow 2NO_3^-$
These nitrifying bacteria are chemoautotrophs.
Reduction of nitrates to free nitrogen is denitrification ($Pseudomonas$, $Thiobacillus$); conversion of free nitrogen to nitrogen compounds is nitrogen fixation; conversion of proteins into ammonia is ammonification.
Hence nitrifying bacteria oxidise ammonia to nitrates.