Comparison of Legionella Biofilm Formations at Three Different Temperatures in Liquid Flow, in Static Liquid and on Agar Plate

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The biofilm formation of Legionella pneumophila on glass was examined under nutrient water flow condition at 37°C, 40°C, and 42°C. The three-dimensional structures of 8-days biofilm were analyzed using confocal laser scanning microscopy. It was revealed that the properties of the biofilms were influenced significantly by temperature changes. Equivalent outer diameters of the microcolonies were 39µm at 37°C, 189µm at 40°C and 359µm at 42°C, respectively. The most interesting observation was that the microcolonies show areas of hollowing. The hollowness or emptiness is 37% at 37°C, 52% at 40°C and 74% at 42°C, respectively. The average number of bacteria per single colony was c.a. 1 x 105 at 37°C. Also, bacteria lengths were compared among the biofilms in liquid flow, those in static liquid and those on BCYE-α agar plate. In the liquid flow, the average bacteria length was 4.4µm at 37°C, 2.9µm at 40°C and 3.5µm at 42°C, respectively, while in the static liquid and on agar plate the lengths increased with the rise of temperature. Our experiments results on the biofilm formation of L. pneumophila will provide the basis for a better understanding of the sessile mode of life of L. pneumophila.