SUMMARY:Forty‐six strains ofAcetobacter, representing twenty species, have been compared on the basis of their respective abilities to proliferate in two defined inorganic media, in which either glucose or ethanol was the sole source of carbon and energy. Twenty‐three strains, representing eleven species, grew in either inorganic medium when glucose was present and nine of these strains, representing five species, could grow also in either inorganic medium when ethanol was present. The remaining twenty‐three strains, representing eleven species, failed to grow in either medium with either glucose or ethanol. Three organisms grew better with ethanol than with glucose and three were inhibited by ethanol in the presence of gl