Denitrifying bacteria
Denitrifying bacteria form a necessary part of the process known as denitrification as part of the nitrogen cycle which consists of the ongoing processes that Nitrogen has to undertake as it is the largest gas compound in the atmosphere. Their primary purpose being to metabolise nitrogenous compounds, with the assistance of the nitrate reductase enzyme, to turn oxides back to nitrogen gas or nitrous oxides for energy generation. Aerobic respiration yields more energy than denitrification, so denitrification generally takes place in the absence of oxygen. This is the main reason why denitrification mostly occurs in the deep substrata of the soil, or in areas of stagnant water. Most denitrifying bacteria are facultative aerobes (prefers to use oxygen as their terminal electron acceptors).