Iron content ofStreptococcus suisand evidence for adprhomologue

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Abstract
The type strain of Streptococcus suis was investigated for features that might help the organism to tolerate the H2O2that is produced during growth. Enzyme assays, using soluble extracts, revealed that the type strain, which lacks catalase, lacks NADH peroxidase in both the mid-exponential and stationary phases of the growth cycle. Although iron could not be detected colourimetrically in dense cell suspensions, determination of the cellular iron content following growth to early stationary phase in the presence of55FeCl3demonstrated that S. suis does contain iron and hence is incapable of iron exclusion. Gene amplification, using oligonucleotide primers based on dpr of Streptococcus mutans, followed by nucleotide sequencing, revealed in S. suis, the presence of a gene that encodes a Dpr homologue. It is concluded that in S. suis, tolerance of H2O2is due to iron sequestration by Dpr and the consequent effect of this process on the extent of Fenton chemistry.Key words: Streptococcus suis, iron, NADH peroxidase, Dpr.