In the nitrogen cycle, what is the role of nitrifying bacteria?

Nitrifying bacteria play a crucial role in the nitrogen cycle by converting ammonia, which is typically produced from the decomposition of organic matter or from livestock waste, into nitrates. This process is vital because it transforms ammonia, which in high concentrations can be toxic to plants and aquatic life, into nitrates, a form of nitrogen that is easily absorbed by plants and utilized for growth. The conversion occurs in two main steps: first, ammonia is oxidized to nitrite by specific types of nitrifying bacteria, and then other nitrifying bacteria oxidize nitrite to nitrate. This conversion is essential in maintaining soil fertility and promoting healthy plant growth, demonstrating the important relationship between soil microbiota and agricultural productivity.

The other options represent different processes related to the nitrogen cycle but do not accurately describe the function of nitrifying bacteria. Decomposing organic material is primarily the role of decomposers like fungi and some bacteria. Fixating atmospheric nitrogen is the job of nitrogen-fixing bacteria, which convert nitrogen gas from the atmosphere into ammonia. Enriching soil with oxygen does not reflect a role in the nitrogen cycle; rather, nitrifying bacteria play a more targeted role in transforming nitrogen compounds.