Introduction. Enterohemorrhagic Escherichia coli (EHEC) O157:H7, an important zoonotic foodborne pathogen, is able to cause serious diseases in humans and animals such as haemorrhagic colitis and haemolytic uremic syndrome. Previously, it is well known that cyclic diguanylic acid (c-di-GMP) is a common second messenger in many bacterial species, which regulates various cellular functions including bacterial adhesion, biofilm formation, motility and/or virulence. Although the correlation of c-di-GMP with biological functions in non-pathogenic E. coli K-12 has been systematically studied, its functional roles in EHEC O157:H7 remain to be fully understood.
Materials and Methods. To investigate the effect of c-di-GMP in the pathophysiology of EHEC O157:H7, we firstly constructed an arabinose-inducible plasmid, pBAD/z2219, which carried the yddV gene encoding a diguanylate cyclase with the c-di-GMP synthetase activity, but not hydrolase activity. Secondly, we compared the pathophysiological differences between the overexpressed and the control (carrying the empty vector only) strains.
Results. Overexpression of YddV in EHEC O157:H7 EDL933 resulted in (i) a significant decrease in flagellar motility, partially due to the repression of the fliC gene in the overexpressed strain, (ii) an enhanced secretion of EHEC O157:H7 proteins compared to the control strain carrying the empty vector, and (iii) an increase in the expression of the rcsA gene, which is known to involve in biofilm development and capsular polysaccharide synthesis.
Conclusions. These results indicate that c-di-GMP signaling plays an important role in bacterial pathophysiology of EHEC O157:H7.