Which of the following statements is true about nitrifiers?

Nitrifiers play a crucial role in the nitrogen cycle by converting ammonia into nitrites and then into nitrates, which are forms of nitrogen that plants can utilize. The statement that they are sensitive to dissolved oxygen levels is true because nitrifying bacteria, such as Nitrosomonas and Nitrobacter, are aerobic organisms. This means that they require oxygen to carry out their metabolic processes effectively.

When oxygen levels are low, the efficiency of the nitrification process decreases, which can lead to the accumulation of ammonia in wastewater. In healthy wastewater treatment systems, maintaining adequate oxygen levels is essential for the nitrifying bacteria to thrive and perform their function. This sensitivity to dissolved oxygen levels is a key characteristic that distinguishes them from other types of bacteria that may be capable of thriving in anaerobic (oxygen-free) environments. Understanding this sensitivity is vital in managing and optimizing wastewater treatment systems to ensure effective nitrogen removal.