Figure 1.

Quantitation of the capsule produced by Streptococcus pyogenes strains. The capsule produced by strains was quantitated and compared to that of the background strain CovRIFD incubated at 25 °C. Strains used: CovRIFD (covR in-frame deletion strain), the background strain showing capsule thermoregulation; spontaneous mutants, spontaneously-generated capsule thermoregulation-negative mutants; Tpn-generated L897_07695 mutant, a mutant with a transposon insertion in the L897_07695 gene in CovRIFD; and ΩL897_07695, a strain with a targeted disruption of the L897_07695 gene in CovRIFD. The data are the means and standard deviations of at least three independent experiments. * indicates significance (p < 0.01) for the difference between the amount of capsule production by strains at a given conditions and that by CovRIFD at 37 °C as calculated by the two-tailed paired Student’s t-test.