There are four categories of aerobes:
Obligate aerobes - need oxygen to grow. In a process known as cellular respiration, these organisms use oxygen to oxidize substrates (for example sugars and fats) and generate energy.
Facultative anaerobes - use oxygen if it is available, but also have anaerobic methods of energy production.
Microaerophiles - require oxygen for energy production, but are harmed by atmospheric concentrations of oxygen (21% O2).
Aerotolerant anaerobes - do not use oxygen but are not harmed by it.
Aerobic bacteria is crucial for live organic horticulture. Though respiration is crucial to life, the precise function that oxygen plays to maintain life is not readily understood. Essentially, in a microorganism that is capable of using it, oxygen enables food compounds to be totally digested. This ensures that every possible amount of energy will be used for maintaining the cell. So the aerobic bacteria have the advantage of metabolic efficiency. Aerobic bacteria can create twenty times more energy, with the equivalent amount of organic compounds, than anaerobic bacteria. What is more, aerobic bacteria aren’t generally known to produce horrible odors. One bacteria in the order of Actinomycetales, genus Streptomyces called actinomycetes, generate enzymes with volatile compounds which gives earth a fresh, clean smell. This is the good quality soil we smell when we instinctively hold a fist full of substrate up to our nose. Interesting how harmonious bacteria agree with us instinctively.