Factors influencing the early phases of growth of Aerobacter aerogenes.

The method used in maintaining cultures of Aerobacter m o g m s affects the relationship between duration of lag phase and age of inoculum in a gludose ammonium salt medium. Organisms kept in broth may show pronounced early lag whilst those from agar slopes do not. Previous subcultivation with aeration decreases the lag. Bacteria showing no lag may do so when they have been washed ; glutamate, a-ketoglutarate and succinate partially remove the lag so produced, whilst malate, Fumarate and aspartate do not. The initial growth rate of light inocula showing no lag is increased by the addition of glutamate, asparlate, a-ketoglutarate, succinate and oxalacetate; but pyruvate, fumarate and malate have no action or are slightly inhibitory. The effect of these compounds over a concentration range of 0 to 1*6xlO-ag. mol./l. was studied quantitatively. Filtrates from growing cultures have a similar effect on initial growth rate; those taken during the late logarithmic phase are more effective than those taken earlier. The effects of both filtrates and added compounds are confined to initial growth; the rate of growth in the later phase, when turbidity becomes visible, remains unaltered. This behaviour is dependent on the amount of 0, available in the medium., Early lag is a phase of greatly reduced rate of growth rather than complete absence of cell division. Glutamate and other effective compounds increase the rate to values approaching normal.