Abstract

---

A new synthetic medium was developed for growth of rhizobia. The medium consisted of mineral salts amended with 0.5% mannitol and one or two growth factors. The vitamins calcium pantothenate, thiamine mononitrate, inositol, and biotin stimulated rhizobial growth. In particular, calcium pantothenate was found to be almost as effective as a combination of all the other vitamins in promoting growth of the root nodule bacteria studied. Three strains of Rhizobium proliferated readily in this simple medium. For instance, a cowpea Rhizobium strain K04SRPR grew in this medium with a generation time of 4.5 hours compared to a generation time of 4.1 in the conventional yeast extract mannitol broth. Therefore, this yeast extract-free, synthetic medium would be useful for the study of the metabolism and the physiology of the root nodule bacteria.

Keywords: rhizobial