Sequences used in the current study. The SD sequences and enhancers were inserted in front of the ORF coding for green fluorescent protein (GFP). Different SD variants were constructed by mutating the sequence into complementary nucleotides. The enhancers used were the "A/U-rich enhancer" (the boxA sequence of rrnB [19, 33]) and its mutant with decreased activity ("weak enhancer") . All SD variants in combination with the enhancers were inserted under control of the tac promoter regulated by IPTG.