Effect of iron on growth and toxin production byClostridium botulinum type A

Abstract

The kinetics of growth and toxin production by the Hall strain ofClostridium botulinum type A was examined in the presence of various concentrations of iron (0.1 to 10.1 μg/ml, 1.8 to 182 μM) in a chemically defined medium. At concentrations below 0.5 μg/ml, iron insufficiency limited the growth of the organism. The maximum amount of toxin produced varied by only twofold (6×105 to 1.2×106 mouse median lethal doses/ml per A540 unit) over the 100-fold range of iron concentrations used. High concentrations of iron did not reduce the elaboration of botulinum toxin, in contrast with its marked inhibitory effects on the production of many bacterial toxins. Iron is unlikely to be a regulatory effector for the formation of botulinum toxin by the Hall strain of type A.