Which of the following microorganisms is associated with denitrification?

Denitrification is a crucial process in the nitrogen cycle, where nitrogen oxides are reduced to nitrogen gas (N2) or, less frequently, to nitrous oxide (N2O). This process helps to remove excess nitrogen from the ecosystem, which can otherwise lead to problems such as eutrophication.

Pseudomonas is a genus of bacteria that includes species known to be effective denitrifiers. These bacteria possess the necessary enzymes that facilitate the reduction of nitrates and nitrites to nitrogen gas, thus playing a vital role in returning nitrogen to the atmosphere and maintaining soil health.

The other microorganisms listed do not primarily engage in denitrification. For instance, Nitrosomonas is involved in nitrification, where ammonia is oxidized to nitrite. Rhizobium is known for fixing atmospheric nitrogen in symbiosis with legumes rather than denitrification. Bacillus, while it includes some species that may participate in various nitrogen transformations, is not specifically associated with the denitrification pathway in the same capacity as Pseudomonas is.

Understanding the specific roles of these microorganisms is essential for grasping nitrogen cycling processes and managing soil ecosystems effectively.