Effect of trace metals on production of exoprotein and beta-lactamase by Staphylococcus aureus.

A minimum concentration of 0.01 mM of Mg2+ was essential for any growth of S. aureus. Of the trace metals, Mg2+ and Ca2+ were highly stimulatory for growth. All trace metals except Ni2+ in small concentrations were stimulatory for growth and exoprotein production. Amounts of exoprotein and beta-lactamase produced relative to the number of viable cells were maximum during the period of suboptimal proliferation of bacteria. Trace metals did not significantly influence the amount of beta-lactamase produced relative to exoprotein.