Table 4.

Effects of extracellular Zn2+ on growth, magnetite synthesis, and ferric reductase activitya

Zn in medium (μM)Growth (optical density at 660 nm)Avg no. of magnetosomes/ cellActivity (Ub)Zinc in cell (μg/g of protein)
  1 (control)0.08518.611.650.9
 200.08012.13.03559
 750.0806.41.681,726
2000.0655.31.42NDc
  • a Cells were grown for 72 h in the presence of various amounts of ZnSO4. The average numbers of magnetosomes in the given samples were obtained by counting of electron-dense particles in electron micrographs from a total of about 100 cells in each sample. Ferric iron reductase activity was determined by measuring the increase in the A 562(7). Zinc concentrations in the cells were determined with an induced coupled plasma atomic spectroscopy system as described in Materials and Methods.

  • b One unit is 1 nmol of Fe2+-ferrozine formed per min per mg of protein.

  • c ND, not determined.