Effects of iron and manganese availability on growth and production of superoxide dismutase by Streptococcus suis

A complex medium supported good growth of the type strain of Streptococcus suis irrespective of the presence or absence of a high concentration (1 mM) of the iron chelating agent, ethylenediamine di-o-hydroxyphenylacetic acid . Good growth was also obtained using a complex medium that had been treate d with Chelex-100 to reduce the iron content, but only if this medium was s upplemented with manganese; supplementation with iron had little effect. Co llectively, these results indicate that S. suis requires manganese, but not iron, for growth. Polyacrylamide gel electrophoresis of cell extracts foll owed by activity staining revealed the presence of a single manganese-cofac tored superoxide dismutase; activity staining and enzyme assays revealed th at manganese availability during growth affected the activity of the supero xide dismutase in cell extracts. The results are discussed with respect to the capacity of S. suis to avoid damage by reactive oxygen species.