Figure 4. TraA is the molecular determinant for specificity.

Schematic representations of cell-cell interactions are shown on the left, in which variant TraA receptors are color coded. On the right are merged micrographs from red and green fluorescence images after mixed cells were collected from an agar surface. The laboratory M. xanthus strain was labeled with a red lipophilic DiD membrane dye, which does not transfer to the M. fulvus cells, which were labeled with the green fluorescent tracer dye. In contrast, an isogenic M. xanthus traA allele replacement strain (DW1470), which encodes the traA^{M. fulvus} allele, enables recognition and transfer with M. fulvus (yellow/orange cells).