Micrococcus sodonensis is a biotin-requiring strict aerobe that cannot utilize carbohydrates as sole sources of carbon and energy. However, addition of mannose, glucose, sucrose, or maltose to a medium on which the organism can grow resulted in an increase in total growth. M. sodonensis oxidized these sugars without induction, thus indicating the presence of constitutive enzymes for their transport, activation, and metabolism. Under appropriate nonproliferating cell conditions, glucose was readily incorporated into essential constituents of the cell. When glucose-i-C'4 and glucose-6-C'4 were oxidized by nonproliferating cells, the label was found in both the protein and nucleic acid fractions of the cell. The respiratory quotients of cells oxidizing glucose in saline and in phosphate buffer indicated assimilation of sugar carbon in buffer and virtually no assimilation in saline. The ability of M. sodonensis to completely oxidize glucose and to grow on intermediates of glucose oxidation but not on glucose suggests that glucose may suppress or repress some reaction(s) necessary for growth, and that growth substrates either derepress or circumvent this block. Micrococcus sodonensis is an obligate aerobe that can grow on a biotin-containing synthetic medium with lactate, succinate, pyruvate, or acetate as the carbon and energy source. In the original description of the organism, the inability to produce acid or gas from carbohydrates was noted (1). Subsequent research (14) demonstrated that M. sodonensis does not grow when glucose or other carbohydrates are the sole source of carbon and energy. Recently, we observed, however, that the addition of glucose to a medium containing lactate as substrate increased the rate and amount of growth of M. sodonensis (Perry and Evans, Bacteriol. Proc., p. 77, 1965). This increase in rate of growth and total cell yield also occurred with other substrates. Experiments with nonproliferating cells indicated that glucose is readily oxidized by this organism without prior induction. This observation has been extended,
