A Growth Factor Required by Donovania granidomatis. ∗ †

Summary

The studies described indicate that the growth factor in egg yolk required by Donovania granulomatis is non-diffusible and was destroyed by hydrolysis with acid, alkali or a crude trypsin preparation. The activity was found in the protein fraction of the yolk, and on separation of the yolk proteins, the major portion of the activity was associated with the vitellin. The factor required for growth does not seem to be any one of a number of well known growth factors which were tested, and furthermore, several other materials considered to be good sources of growth factors when used to replace egg yolk in the medium would not support growth of D. granulomatis.