Heritable and Non-heritable Loss of Ability by Aerobacter aerogenes to Grow Adaptively on Single Carbon Sources

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Abstract
Mutants of A. aerogenes incapable of utilizing citrate were discovered in glucose cultures by a modification of the mutant-concentrating penicillin technic. These C- mutants utilize glucose as efficiently as does the wild-type, despite their inability to utilize a wide range of other metabolites as C sources for growth, including compounds that would be oxidized if glucose were aerobically dissimilated via the Krebs cycle. The compounds that the C- mutants cannot utilize are citrate, alpha-ketoglutarate, glutamate, succinate, fumarate, aspartate and acetate, which are all substrates to which glucose-grown C+ cells slowly adapt. A non-genetic loss of ability to grow in media containing these substrates also occurs in glucose-grown populations under certain conditions. The C- mutant can revert to the prototrophic condition directly, or indirectly by first mutating to a stable state in which fumarate and aspartate can be utilized whereas the other compounds cannot.