I believe they are not as important *never been on it only seen the ads on yt
Anaerobic organisms, those which do not perform the standard 'cellular respiration' or 'photosynthesis', do not require oxygen, nor sunlight to survive. Instead, they survive off of glycolysis which is a process also carried out in aerobic respirators, but it is one that does not <em>require </em>oxygen or sunlight. You can do this by using lactate, sulfate or even alcohol instead of the usual oxygen.