FIG. 1.

Vanadate transport in wild-type strain FD. Strains were grown as previously described, in molybdate-free AA/8 medium (1, 50). The kinetics of vanadate transport was measured indirectly by the ability of vanadate to stimulate V-nitrogenase activity in Mo- and V-starved cells. Na₃VO₄ at various concentrations was added to starved cells 60 min before the measurement of acetylene reduction to ethylene and ethane. Ethane values were about 4% of the ethylene values at all concentrations of vanadate. The graph represents a nonlinear regression analysis with the 95% confidence interval shown by the dashed lines. chla, chlorophyll a.