A study of the nutritional requirements of the root-nodule bacteria has demonstrated the necessity of an accessory factor for their growth. Two species of Rhizobium were studied. They were not able to maintain growth when continuously cultivated in a synthetic medium containing only C. P. chemicals, including mineral salts, a nitrogen source of KNO3 , and sucrose. Upon replacing the C. P. sucrose with commercial cane sugar the organisms were able to grow. Presumably cane sugar contains a factor necessary for the growth of rhizobia. A concentrated preparation of the growth substance was prepared by extracting cane sugar with absolute alcohol. Yeast extract contains sufficient of the factor to initiate maximum growth of the organisms. The stimulative factor in yeast extract was concentrated by alcoholic extraction. These results confirm the report of Allison and Hoover of an accessory factor for Rhizobium.
Proceedings of the Iowa Academy of Science
©1935 Iowa Academy of Science, Inc.
Thorne, D. W. and Walker, R. H.
"A Growth Factor for Rhizobia,"
Proceedings of the Iowa Academy of Science, 42(1), 89-90.
Available at: https://scholarworks.uni.edu/pias/vol42/iss1/22