Anaerobic organism

An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It may react negatively or even die if oxygen is present. An anaerobic organism may be unicellular (e.g. protozoans,bacteria) or multicellular.

First observation

In his letter of 14 June 1680 to The Royal Society, Antonie van Leeuwenhoek described an experiment he carried out by filling two identical glass tubes about halfway with crushed pepper powder, to which some clean rain water was added. Van Leeuwenhoek sealed one of the glass tubes by using a flame and left the other glass tube open. Several days later, he discovered in the open glass tube ‘a great many very little animalcules, of divers sort having its own particular motion.’ Not expecting to see any life in the sealed glass tube, Van Leeuwenhoek saw to his surprise ‘a kind of living animalcules that were round and bigger than the biggest sort that I have said were in the other water.’ The conditions in the sealed tube had become quite anaerobic owing to consumption of oxygen by aerobic microorganisms.