Unique developmental characteristics of the swarm and short cells of Proteus vulgaris and Proteus mirabilis

Swarming cells of Proteus mirabilis and Proteus vulgaris could be distinguished from their short-cell counterparts by virtue of their synthesis (or lack of synthesis) of certain enzymes and outer membrane proteins. Urease synthesis was constitutive in swarm cells and uninducible in short cells. In contrast, phenylalanine deaminase was inducible in both short and swarm cells, demonstrating that transcriptional and translational processes were functional. During swarm cell development, the amount of one outer membrane protein (45 kilodaltons) fell and the amounts of two others (50 and 28.3 kilodaltons) rose significantly, the level of cytochrome b decreased, and the synthesis of cytochromes a and d were repressed. Respiratory activities of swarm cells were greatly diminished, suggesting that energy for swarming came from fermentation rather than from respiration. Widespread changes in the pattern of enzyme activities, in cytochrome composition, and in the composition and type of outer membrane proteins suggest that they are due to transcriptional regulation.