Thin sections of E. coli strains labelled with an anti-his antibody and then with a secondary antibody conjugated to 10 nm gold particles viewed under TEM (A) strain that lacks shell proteins and 1,2-propanediol producing enzymes (control strain) (B) strain producing shell proteins only (control strain) (C) 1,2-propanediol producing enzymes tagged with targeting peptides (D) 1,2-propanediol producing enzymes tagged with targeting peptides and shell proteins (E) untagged 1,2-propanediol producing enzymes (F) untagged 1,2-propanediol producing enzymes and shell proteins. White pointers indicate gold particles.