The Zonation Phenomenon And Structure Of The Swarm Colony In Proteus Mirabilis

Zonation of the swarm colonies of six strains of Proteus mirabilis did not appear to be caused by an alternationof swarming and sessile phases. The margin was constantly composed of active swarmers; and, although a thickened ring could be caused by a check, it was more often due to the rapid advance of the edge, leaving a thinner area which permitted a new, interior edge to form behind it. Motility ceased when the bacteria became crowded; the change to the non-swarming phase took place later. The structure of the swarm colonies was lobate, and the zonation of the separate lobes was synchronised. Reduction of nutrients in the medium reduced the speed of advance of the swarm, but the timing of the zone formation was unaltered. Lobes, at the edges of old colonies, in which swarming had ceased, also showed synchronised zonation. These appearances are suggestive of genetic programming.