Figure 1.

Schematic presentation of plasmid pBPES and its derivatives. Plasmid pBPES was the backbone used for screening promoters. The vector was an Escherichia coli – Bifidobacterium longum shuttle plasmid based on pUC57 using pMB1 cloned from pTB60 as a replicon, Cm^r as a selection marker, SP as a signal peptide. Chloramphenicol was used for selection of the plasmid at a concentration of 25 μg/mL in both E. coli and B. longum. P_tu, P_gap, and P_groEL were predicted promoters of gene BLLJ_0515, BLLJ_1241, and BLLJ_1448, respectively. They were cloned into pBPES between restriction sites of Hind III and EcoR I. The resulted three derivative plasmids were named as pBPES-tu, pBPES-gap, and pBPES-groEL, respectively.