Studies to Determine if Antibiosis Occurs among Rhizobia: I. between Rhizobium Meliloti and Rhizobium Trifolii 1

A pure culture of each single strai1~ was inoculated into 25o cc of yeast-mannitol liquid medium on September I, I944. "One week later these liquid cultures were used to prepare single-strain humus cultures. Forty cc of each liquid suspension of bacteria were mixed with 50 grams of 2oo-mesh, dried and partially sterilized humus and 12.5 grams of finely ground limestone to neutralize the acidity. Combination alfalfa cultures were prepared by mixing 2o cc of a single-strain alfalfa culture with 2o cc of a composite liquid suspension of red clover bacteria. (This composite suspension was prepared by mixing together 5o cc of liquid culture from each one of the five single-strain cultures of red clover bacteria.) The combination red clover cultures were prepared by mixing 2o cc of a singlestrain red clover culture with 2o cc of a composite liquid suspension of alfalfa bacteria. (This composite culture was made by mixing together 5o ce of liquid culture from each one of the five alfalfa strains.) The 4o-cc mixture containing single-strain culture and the composite suspension was then mixed with 5° grams of humus and ~2.5 grams ground limestone. These humus cultures, both single strain and combination, were packed in closed containers and allowed to incubate at room temperature for I7 days.