While CsgD is suggested to activate biosynthesis of curli fimbriae directly by binding to the promoter of the csgBA operon , activation of cellulose biosynthesis by CsgD is indirect .
Therefore , in the next step the level of the CsgD protein , the proposed transcriptional activator of the csgBA promoter was investigated .
csgBA is positively regulated by the global regulator CsgD
However , we discovered that c-di-GMP , an integral part of the regulatory network promoting CsgD expression in S. Typhimurium , is not required for binding of CsgD to the csgBA and adrA promoters or for CsgD-activated transcription .
CsgD positively regulates the transcription of the csgBA operon .
In this study , we dem-onstrated for the first time that CsgD activates transcription of the promoter regions of csgBA .