The Interrelationship of Iron and Certain Accessory Factors in the Growth of Rhizobium trifolii , Strain 205

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Abstract
Thiamine, pantothenic acid, inositol, pyri-doxine, nicotinic acid, riboflavin and p-aminobenzoic acid were shown to be accessory factors only under certain conditions. The greatest effect was shown in media low in iron in cultures incubated at 25[degree] C and agitated. The vitamins singly had no significant effect on cultures incubated at 25[degree] C when the media contained 500 [gamma] of added iron; in cultures incubated at 30[degree] C the increase in growth was greater in the presence of added Fe than in its absence. By increasing the time of incubation from 6 to 10 days, the effect of accessory factors was clearly shown even under favorable conditions of temp. and Fe content. In the absence of accessory factors the amt. of growth was proportional to the Fe content of the medium; the pH of the medium after growth was shown to be a function of the Fe content of the medium.