Trace-Metal Requirements of NCTC Clone 929 Strain L Cells2

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Abstract
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 µM FeS04 was added. Cells grew faster in the presence of FeS04 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 z:inc. lhe iron requirement in this medium varied between 0.6 and 1.4 µM, depending on the concentrations of other cations added to the medium. A copper concentration of at least 0.4 µM 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 µM zinc was required for maximum cell growth in resin-treated medium.