A reconsideration of the swarming of Proteus vulgaris

SUMMARY: Studies by cinemicrography confirm that the long forms of Proteus vulgaris (Hauser) seen during the swarming stage are morphologically indistinguish-able from those induced by penicillin and other toxic agents. They appear only in cultures which are growing freely and when a threshold concentration of population has been reached; thereafter the organisms at the growing edge of t,he colony become more abnormal with each swarming. The normal small bacilli may begin to move before any long forms are present. In later swarmings, movement may be seen in small as well as in long organisms. It is suggested that the long forms are induced by a non-specific volatile agent which can not be detected when growth has been cleared from the medium. Its action is enhanced in cultures which are confined under a coverslip. Though it is partially neutralized by the action of catalase, conclusive proof of its nature is still lacking. When different strains are grown together long forms are soon produced. The agents causing this are specific and stable, producing their effect immediately, and are detectable in the medium after the primary culture has been cleared from it