Abstract

Proteus mirabilis colonies exhibit striking geometric regularity, and swarm colony terraces correspond to one swarming-plus-consolidation cycle. Basic microbiological methods and imaging techniques were used to measure periodic macroscopic events in swarm colony morphogenesis. Here, adding a respiratory enzyme indicator, 2,3,5-triphenyltetra-zolium chloride (TTC) into the culture medium, the bacteria on the rings gradually changed into red and the change was not synchronous with the formation of ring. According to this phenomenon, we distinguished five phases as P. mirabilis colonize agar surfaces during swarming to investigate the bacteria swarm colony development mechanism by the methods of matrix assisted laser desorption/ionization (MALDI) mass spectrometry and real time fluorescence quantitative-polymerase chain reaction (RTFQ-PCR). Through these observations, we found that P. mirabilis swarm colony development was closely related to the gene fusA, fliC1, tufB, ahpC, icd and flaB. The research indicates that the functions of the genes fusA, filC1 and tufB in swarming phase significantly influence the P. mirabilis swarming behavior. In consolidation phase, expression of ahpC connected to oxidative stress decreased as compared to other phases. The gene icd which affected the metabolism had high expression in consolidation phase I and there were more expression from the bacteria on the ring than that from the bacteria between two rings. The increase of flaB was concomitant with the development of cell growth from swarming phase to turn red phase II. The morphology of P. mirabilis was obviously distinct in different growth phase, and periodically changed. The movement and metabolize way of P. mirabilis were diverse in different growth phase. In swarming phase, the swarm colony and antioxidant ability was enhanced, but the functions of respiratory and metabolism was down-regulated. In conclusion, the bacteria fertility ability and respiratory function were enhanced in consolidation phase. These genes related with motion and metabolism played a key role in regulating P. mirabilis swarm colony development.

Key words: Proteus mirabilis, real time fluorescence quantitative-polymerase chain reaction (RTFQ-PCR), matrix assisted laser desorption/ionization (MALDI)-TOF, swarm.