Research in anoxic environments is a relatively new and rapidly growing branch of science that is of general interest to many students of diverse microbial communities. The term anoxia means absence of atmospheric oxygen, while the term hypoxia refers to O 2 depletion or to an extreme form of “low oxygen.” Both terms anoxia and hypoxia are used in various contexts. It is accepted that the initial microorganisms evolved anaerobically and thrived in an atmosphere without oxygen. The rise of atmospheric oxygen occurred ~ bya through the photosynthesis process of cyanobacteria which “poisoned” the environment by the release of toxic O 2 . Microorganisms that could adapt to the.
