A. In vivo genetic complementation of the E. coli MC4100 wild-type (WT) and secB or/and tig knock-out derivatives by either an empty vector or one carrying the secB or tig (encoding TF) genes or derivatives (see "Plasmid" table in Appendix), as indicated. Serial dilutions of a culture (OD600= 0.5) were spotted (12μl) on LB-Ampicillin plates containing or not anhydrotetracycline (AHT; 5 ng/ml) and grown at 16°C or 30°C (as indicated). n= 3-7 biological replicates. 