Differential effects of iron on the growth of Listeria monocytogenes: minimum requirements and mechanism of acquisition.

The differential effects of iron on the growth of virulent and avirulent Listeria monocytogenes were examined. We found that virulent strains exhibited faster rates of growth as a function of iron than did the avirulent strains. We also noted that serum was microbiostatic, but this microbiostasis was overcome either by saturating the serum transferrin with iron or by increasing the number of organisms initially inoculated into the serum. We were unable to identify any component of a high-affinity iron transport system. We did find, however, that this microorganism removes iron from Fe -transferrin-CO3-- by a reductive pathway, and we propose that this pathway is a nonspecific mechanism of iron acquisition.