Anthranilate-promoted iron uptake in Rhizobium leguminosarum

Anthranilate promoted the uptake of ferric iron into iron-starved cells of Rhizobium leguminosarum GF160. The uptake system was a saturable function of the concentration of ferric anthranilate. It was characterized by an apparent Km of 6 microM and a Vmax of 1.6 nmol/min/mg cell protein. Uptake was temperature dependent and inhibited by the metabolic poisons arsenate and iodoacetate. The proton motive force may not be involved since no effect was demonstrated by the respiratory inhibitor sodium azide and by various uncouplers. The anthranilate-promoted iron uptake was lower for cells grown in increasing levels of available iron and the addition of anthranilic acid to low-iron cultures resulted in a stimulation of bacterial growth. During growth under iron deficiency, anthranilic acid was not assimilated by the cells.