JAMB Biology 2019 Paper

Concept:Nitrifying bacteria are soil chemoautotrophs that convert ammonia to nitrate, making nitrogen available to plants.Explanation:Nitrification occurs in two oxidative steps.First, bacteria such as $\textit{Nitrosomonas}$ oxidize ammonium ions ($\mathrm{NH}_4^+$) into nitrite ions ($\mathrm{NO}_2^-$).Second, $\textit{Nitrobacter}$ oxidizes nitrite ions ($\mathrm{NO}_2^-$) into nitrate ions ($\mathrm{NO}_3^-$).$\textit{Rhizobium}$ and $\textit{Azotobacter}$ are nitrogen-fixing bacteria, not nitrifying bacteria.$\textit{Pseudomonas}$ species are often denitrifying, so they do not perform nitrification.Therefore, the nitrifying bacterium among the options is $\textit{Nitrobacter}$. The correct choice is option B.Answer:B. Nitrobacter