On culturing Escherichia coli on a mineral salts medium during anaerobic conditions

Abstract

The substrate and products of the hydrogenlyase complex, formic acid, carbon dioxide, and molecular hydrogen, are co-operatively implicated in maintaining growth of E. coli under anaerobic conditions. Growth is observed in the presence of a combination of carbon dioxide + molecular hydrogen, or carbon dioxide + formic acid in the medium. The study shows that it is possible to culture E. coli under anaerobic conditions while sparging with nitrogen, without supplementing exogenous carbon dioxide, formic acid or molecular hydrogen. This condition occurs when the strain is allowed an appropriate induction period and is present at a sufficiently high cell density, since the cell density affects the rate of e.g. CO2 production. In a system sparged with nitrogen gas, the removal of CO2 due to this sparging must be balanced with a cell density dependent production rate of CO2. It is concluded that the “formic hydrogenlyase complex” should be considered as an integral part of the general maintenance of the anabolism of E. coli during anaerobic conditions on a mineral salts medium, as well as being a net producer of end products in E. coli metabolism.