FIG. 4.

Effect of iron on production of CAS-reactive material. Strain 130b was grown in BYE to an OD₆₆₀ of 1.0, washed, and inoculated at an OD₆₆₀ of 0.1 into CDM containing 0 (●), 0.5 (■), or 2.0 (▴) μM ferric pyrophosphate. Over the next 2 days, the growth (top) and CAS reactivity (bottom) of the cultures were monitored. The CAS reactivity pattern is the same for CDM controls containing 0, 0.5, or 2.0 μM added iron. Thus, for simplicity, we have only depicted the CAS reactivity for the CDM blank with 0 μM added iron (◊). The values presented represent the means and standard deviations from duplicate cultures. The delay in peak growth and CAS reactivity for the culture with 0 μM iron was due to the small size of the inoculum used (Fig. 2). Another experiment determined that the CAS reactivity of Philadelphia-1 was also abolished by the inclusion of 2.0 μM iron in the assay medium (data not shown).