Cell Wall-Treated Lactococcus lactis Increases the Plasmid Transfer Efficiency of Internal Ribosome Entry Site-Incorporated Lactococcal Bicistronic Vector into DF1 Cells

This study demonstrates that cell wall treatment of Lactococcus lactis harbouring the internal ribosome entry site-incorporated lactococcal bicistronic vector pNZ:VIG mediated the delivery of genes into an eukaryotic cell line, DF1 cells, through bactofection. Bactofection analysis showed that the pNZ:VIG plasmid in L. lactis can be transferred into DF1 cells and that both the VP2 and gfp genes cloned in the plasmid can be transcribed and translated. The protein band relative to the Mr of VP2 protein (49 kDa) was successfully detected via Western blot analysis, while green fluorescence was successfully detected using a fluorescence microscope. The intensity of the bands detected increased for samples treated with both 1.5% (w/v) glycine and 10 μg/mL of lysozyme when compared to L. lactis treated with glycine alone and without treatment. Cell wall treatment of L. lactis with a combination of both glycine and lysozyme was not only shown to mediate plasmid transfer to DF1 cells, but also to increase the plasmid transfer efficiency.