Effect of Culture Conditions on the Biofilm of Proteus mirabilis

The effects of different initial bacteria concentration, culture environment (temperature, gas environment), medium composition (pH value, NaCl concentration, carbon source type and concentration), medium dosage and contact materials on biofilm formation of Proteus mirabilis were investigated. Microporous plate culture, the crystal violet staining, plate counting and scanning electron microscopy were used to evaluate the effects of different culture conditions on biofilm formation. After 24 h of culture, the amount of biofilm formation was relatively low at the initial bacterial concentration of 10 CFU/cm² whereas the amount of biofilm formation was dominant at the initial concentration of 10²~10⁸ CFU/cm².The aerobic condition at 37℃ was adaptable for the formation of Proteus mirabilis biofilm. The culture medium composition with 2.0% NaCl and 1.0% maltose at pH8.0 and double quantity of the medium promoted obviously the formation of Proteus mirabilis biofilm. Among the four contact materials, the surface with roughed wood chip was the easiest material to form biofilm of Proteus mirabilis, followed by silica gel. The surface with polypropylene plastic and cover glass plate were not easy to form Proteus mirabilis biofilm due to its smoothness to adhere. Scanning electron microscopy investigation showed that the structure of Proteus mirabilis biofilm formed was various with different contact materials. On the silica gel, the biofilm of Proteus mirabilis was a mushroom-like while on the cover glass plate it was a flat layer. These results provide a theoretical and technical basis for prevention and control of Proteus mirabilis contamination in the food production and processing line.