FIG. 6.

Effect of divalent cations on M. xanthus fruiting-body formation. Wild-type M. xanthus cells (DK1622) were tested for the formation of fruiting bodies in MOPS buffer without a divalent cation (None) or with 4 mM CaCl₂, MgCl₂, or SrCl₂. The cells were suspended in buffer at an initial density of 4 × 10⁸ cells/ml. Large spore-filled fruiting bodies were formed in the presence of Ca²⁺ and Sr²⁺. The cultures were photographed with an inverted microscope after 96 h of incubation at 30°C.