The K. pneumoniae K2044, K2044-8Xyl-60G, K2044-ΔXylA and K2044-ΔXylB isolates were cultured overnight in MRS medium, then 1:200 diluted in MRS medium with 8% xylose to reach the exponential growth phase. The control group was K2044 treated with 8% xylose. The experiment was performed in triplicate.