Exopolysaccharide related gene bcsG affects biofilm formation of Cronobacter spp.

Cronobacter spp. is a conditioned pathogen found mainly in milk powder; it can seriously harm infant health. We investigated biofilm formation in eight strains of Cronobacter spp. and found that DSM 18707 had the strongest capacity to form biofilm. Biofilm-related genes bcsA, bcsG, flgJ, and flhE were selected for qRT-PCR detection. Expression of bcsG in Cronobacter spp. was associated with the ability to form biofilm. Knockout of bcsG in DSM 18707 was associated with markedly reduced biofilm formation and exopolysaccharide content relative to the wild type. Moreover, fluorescence microscopy revealed that the knockout mutants had comparatively lower biofilm density. In the knockout mutants, bcsA, flgJ, and flhE were up-regulated in the first three days but down-regulated by days 4 and 5. Hence, the expression levels of bacterial biofilm-related genes may change with biofilm production; moreover, bcsG positively regulates the formation of exopolysaccharides and biofilm in Cronobacter spp.