Trace-metal requirements of NCTC clone 929 strain L cells.

The effects of iron, zinc, copper, manganese, and Methocel on the growth of L cells in a synthetic medium were studied. The medium was iron-deficient unless a supplement of 1.0 g/liter Methocel HG (4,000 centipoises), Methocel ash equivalent to 1.0 g/liter Methocel, or 1.0 microM FeSO4 was added. Cells grew faster in the presence of FeSO4 or Methocel ash (generation time = 40 hours) than of Methocel (generation time = 110 hours), but Methocel was needed to protect cells from mechanical destruction. Treating the growth medium with Dowex A-1 chelating resin produced a medium deficient in both iron and zinc. The iron requirement in this medium varied between 0.6 and 1.4 microM, depending on the concentrations of other cations added to the medium. A copper concentration of at least 0.4 microM was beneficial as it reduced the amount of iron necessary for cell growth. No manganese was required in this medium; any added manganese produced an inhibition of cell growth. Additional iron could reverse this inhibition. The minimum iron requirement for the production of L cells was 3 nmoles/mg cell nitrogen produced. Approximately 0.6 microM zinc was required for maximum cell growth in resin-treated medium.