Fig. 1

Characterization of the lp_0640-41-42 operon. A Layout and genetic context of the lp_0640-41-42 operon. The numbers in parentheses indicate the genome locus. B Schematic diagram showing in-frame gnp deletion and marker elimination. Lp_0640-41-42 mediated allelic replacement resulted in disruption of the gnp gene and insertion of the cat marker, while Cre subsequently eliminated the marker. C dsDNA recombination assay with different protein combinations. 1 μg dsDNA substrate was electroporated into L. plantarum JDM1 expressing various combinations of proteins, and the respective resultant chloramphenicol resistant colony number were shown. pSIP411 was used as the control. Results are the averages from at least three independent experiments, with standard deviations indicated by error bars. D Inspection of potential Δgnp::cat mutants by PCR testing using primers gnp-testA (a) and gnp-testB (b), as shown in B. Lanes 1 and 24 show DNA ladders, lanes 2 and 23 the wild-type strains expected to generate amplicons of ∼3.9 kb. Lanes 3–22 were tested colonies, with correct mutants expected to generate amplicons of ∼4.3 kb