Fig. 3.

Fig. 3. Effect of nitrogen sources on Xoo biofilm formation and cell growth. (A) Effect of nitrogen source on Xoo biofilm formation (solid bars) and cell growth (hatched bars). Cells were incubated in 96-well polyvinyl chloride microplates for 24 h with XOM2 medium in which L-methionine and sodium L-(+)-glutamate monohydrate were replaced with the indicated nitrogen sources. N-210: 8 g/l casein hydrolysate and 4 g/l yeast extract, N-NB: 3 g/l beef extract and 5 g/ l peptone, N-PS: 10 g/l bacto-peptone, N-SOC: 20 g/l tryptone and 5 g/l yeast extract, XOM2: XOM2 medium alone, None: XOM medium without nitrogen sources. The cell growth was measured independently by culturing cells in test tubes (hatched bars). After measuring Abs₆₀₀, the number of colony-forming units (CFU) was calculated using a conversion factor of 1.12 × 10⁹ CFU/Abs₆₀₀. The mean values showing a statistically significant difference in comparison with the control value of ‘None’ were denoted by * (p < 0.05). (B) Effect of peptone on Xoo biofilm formation (■) and cell growth (▲). L-methionine and sodium L-(+)-glutamate monohydrate in XOM2 medium were replaced with peptone at the same concentration. Data represent mean ± standard deviation from at least 5 independent experiments for biofilm and from 2 independent experiments for cell density. The mean values showing a statistically significant difference in comparison with the control value at 0 g/l were denoted by * (p < 0.05).

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