Fig. 2.

Growth of B. burgdorferi in serum- and calcium-free minimal medium. B. burgdorferi was cultured in complete BSK-II medium and in various modifications of serum-free (SF) medium. Serum-free incomplete or basal BSK medium (BSK-SF) (60) was supplemented with lipids (+ lip), treated with Chelex-100 (CH), or supplemented with essential cations (+Mg/Mn/Zn). Cells were counted under phase-contrast microscopy using a Petroff-Hausser counting chamber. Representative growth curves are shown. Note that the 1-day lag phase for cells grown in BSK-SFcc persisted even when bacteria had been passed in BSK-SFcc previously (data not shown).