All compounds providing adequate protection to virions appeared to have at least one sulfonic group. Eosin Y did not contain a sulfonic group but offered much weaker protection than food dyes. To verify that this was also true in the case of bacteria, we compared the protective properties of BB and crystal violet (CV). CV stains bacterial cell walls in a protocol known as Gram staining (R. , but it does not possess any sulfonic group. CV presented no stabilizing properties towards examined bacteriophage (T4, Figure ) and bacteria (E. coli, S. aureus; Figure , Supporting Information). We went a step further and compared the behavior of sodium isatin-5sulfonate (ISA) and isatin. These two compounds differ only by a single sulfonic group. ISA (with sulfonic group) protected T4 virions, while isatin (without sulfonic group) did not (Figure ).