FIG. 1.

Aero tolerance provided by SOD enzymes and/or Mn-antioxidants that remove O₂^•−. (A) As is the case with SOD enzymes, certain manganese complexes to small metabolites (small ball attached to Mn) have the capacity to remove O₂^•−. Such metabolites include phosphate, carbonate, and organic acids (see text). (B) Lactobaccilus plantarum does not express SOD enzymes but is aero tolerant due to high accumulation of Mn antioxidants (small balls). Other organisms such as the Baker's yeast Saccharomyces cerevisiae largely remove O₂^•− by SOD enzymes, but can also use Mn-antioxidants as a secondary defense against O₂^•−. (C) In the absence of SOD enzymes, susceptibility to atmospheric oxygen is directly proportional to the level of Mn antioxidants that accumulate. O₂^•−, superoxide; SOD, superoxide dismutase.