A bab_RS27735 deletion mutant was successfully constructed without phenotype changes. Genetic organization of the bab_RS27735 locus and position of the primers designed to identify the Δ27735 mutant (A). Identification of the Δ27735 mutant by polymerase chain reaction (PCR) using the outer primers P1/P3 (left panel) and the crossover primers P2/P3 (right panel). Lane 1 and 3 refer to the wild-type (WT) strain; lane 2 and 4 refer to the Δ27735 mutant (B). Extraction and silver staining of lipopolysaccharide (C). Determination of the transcriptional levels of the flanking genes by quantitative real-time PCR (D). Determination of growth curve in tryptic soy broth (E). Statistical significance was determined using the unpaired Student’s t test. ***p < 0.001.