Dispersal of a RIFR strain of P. vortex within extended colonies of the RIFS strain. All graphs plot the average migration distance of the RIFR strain against time (± SD) on MH agar (0.3% w/v in panels A-C or 1.5% w/v agar in panels D-F) when inoculated into a RIFS colony and incubated at 37°C. A. Inoculation of the RIFR strain at the edge of the initial ring, 0.5 mm from center of the dish at the same time as the RIFS strain (■) and 5 h after (□). B. Inoculation of actively swarming 30 mm radius RIFS colonies at the outer edge of the colony with the RIFR strain. (■) Outwards migration of RIFR subsequently tracked and limited to 22.5 mm by the edge of the Petri dish. (□) Inwards migration. C. Inoculation of Petri-dish-wide RIFS colonies at one edge with RIFR strain. (□) Immediately after swarming RIFS cells reached edge of Petri dish, (■) 12 h later (▲) 36 h later. D. As (A) except on1.5% (w/v) agar. E. As (B) but on 1.5% (w/v) agar. F. As (C) but on 1.5% (w/v) agar.