Carbon Dioxide as a Growth Factor for Mutants of Escherichia coli

SUMMARY: This report shows that some auxotrophic mutants of Escherichia coli can grow on a minimal medium without growth factors when the gas phase is supplemented with carbon dioxide. Mutants which respond to CO2 are called CO2 mutants. The CO2 mutants of E. coli resemble those already known in Neurospora. When the gas phase is not supplemented with CO2 most of the mutants respond to other specific growth factors such as arginine, uracil, adenine, succinate or isoleucine+valine, depending upon the locus of their mutation. One mutant is an obligate CO2 mutant. The CO2 effects shown by these mutants are discussed in relation to the general problem of CO2 effects in micro-organisms.