The function of the gene loiP in transformation efficiency and outer membrane permeability change of Escherichia coli treated by Ca2+ ions

The preparation of Escherichia coli competent cells by calcium chloride is a common method in molecular biology, but the mechanism is poorly understood. In a previous study, using transcriptomics and proteomics approaches, we found that the expression pattern of the gene loiP was upregulated by CaCl2. In order to investigate the function of the loiP gene in Ca2+- mediated formation of competent cells of E. coli DH5α, the loiP gene deletion strains were constructed by the lambda-derived Red homologous recombination technique. Then, the cell morphology, transformation efficiency, and cell membrane changes of the competent cells of the mutant strain were further explored. Compared with the wild-type E. coli DH5α, the mutant strains have no significant differences in the morphology, growth characteristics, and the permeability of the intracellular membrane. However, the transformation efficiencies of the mutant strains to plasmids of different sizes were significantly reduced, and the permeability of the outer membrane decreased by 2.94 times. These results indicate that the deletion of gene loiP may directly affect the transformation efficiency and outer membrane permeability of E. coli competent cells.