Immunogold labelling of rSbpA/Bet v1 recrystallized on a solid support. After production in B. subtilis 1012, the S-layer/allergen fusion protein rSbpA/Bet v1 recrystallized on peptidoglycan-containing sacculi of Ly. sphaericus CCM 2177 was incubated with the monoclonal mouse antibody BIP1 raised against Bet v1. Bound BIP1 was detected by using colloidal gold-labelled anti-mouse IgG. Bar = 100 nm.