Identification and validation of novel chromosomal integration and expression loci in Escherichia coli flagellar region 1

Escherichia coli is used as a chassis for a number of Synthetic Biology applications. The lack of suitable chromosomal integration and expression loci is among the main hurdles of the E. coli engineering efforts. We identified and validated chromosomal integration and expression target sites within E. coli K12 MG1655 flagellar region 1. We analyzed five open reading frames of the flagellar region 1, flgA, flgF, flgG, flgI, and flgJ, that are well-conserved among commonly-used E. coli strains, such as MG1655, W3110, DH10B and BL21-DE3. The efficiency of the integration into the E. coli chromosome and the expression of the introduced genetic circuit at the investigated loci varied significantly. The integrations did not have a negative impact on growth; however, they completely abolished motility. From the investigated E. coli K12 MG1655 flagellar region 1, flgA and flgG are the most suitable chromosomal integration and expression loci.