Figure 7.

Conserved amino acid residues of TagF are required for repressing type VI activity in A. tumefaciens. A, Western blot analysis of total (T) and secreted (S) proteins isolated from WT C58 harboring the vector pTrc200 (V) or various TagF-Strep–overexpressing plasmids grown in AB-MES (pH 5.5) liquid culture with specific antibodies. The nonsecreted protein ActC and RNA polymerase α subunit RpoA were internal controls. The proteins analyzed and molecular weight standards are shown on the left and right, respectively. B, A. tumefaciens antibacterial activity assay against E. coli. The A. tumefaciens WT C58 or ΔtssL or chromosomally encoded tagF-pppA variants, including tagF-pppA with substitutions in the tagF domain (tagF^GK-pppA, tagF^DW-pppA, and tagF^SDR-pppA), were co-cultured on LB agar with E. coli strain DH10B cells harboring the plasmid pRL662. Data are mean ± S.D. (error bars) of at least three biological replicates. Different letters above the bar indicate statistically significantly different groups of strains (p < 0.05) based on cfu of the surviving target cells.