Studies made with respect to utilization of various N-containing compounds, use of various C sources, nitrate reduction in presence of certain sugars, and oxidation-reduction potentials produced in various media, showed that although P. tumefaciens and B. radiobacter utilized somewhat the same compounds in their growth, the final changes produced during growth differed markedly. P. rhizogenes, however, was limited in its utilization of inorganic and simpler organic N-containing compounds used by the other 2. Nitrates were reduced slightly by P. tumefaciens when certain C sources were used, and were reduced completely by B. radiobacter. With peptone added to the medium, nitrate reduction took place more quickly. Various carbohydrates, gluco-sides, alcohols and organic salts were utilized to about the same extent by P. tumefaciens and B. radiobacter, but with some differences in final reaction. Considerable differences were found with various media in the oxida-tion-reduction potentials induced by P. rhizogenes and by the other 2 organisms.