Presentation of the antigenic tags on gp9 of phage particles. (A) M13 phage (panel A) was applied onto nitrocellulose membrane and incubated with antibody to gp8, T7 tag and HA tag, respectively, at the indicated concentrations. To visualise the phage a peroxidase-linked secondary antibody was applied and analysed by chemoluminescence. (B) M13am9 phage grown in E. coli K38 cells bearing a plasmid encoding gp9-T7 or gp9-DT7, respectively, were incubated with antibody to T7 and treated as described above. (C) M13am9 phage propagated in E. coli K38 cells bearing a plasmid encoding gp9-HA or gp9-DHA, respectively, were incubated with antibody to HA and treated as described above. For controls (Ctr), uninfected cultures were tested under identical conditions.