| Abstract: | From the effective and prototrophic Rhizobium meliloti strain L5-30 two auxotrophic mutants were isolated: RM4 and RM221. These two mutants required adenine and adenine with thiamine for their growth, respectively. Both mutants nodulated lucerne plants ineffectively. Electron microscopic observations of the nodule tissue showed that its cells were not occupied by bacteria. Prototrophic revertants and transductants of these mutants showed high symbiotic effectiveness. It is assumed that adenine or adenine and thiamine requirements made impossible release of bacteria from the infection thread. |
