Silver Colloids Impregnating or Coating Bacteria

We produce silver nanocolloids selectively within and on Escherichia coli bacteria. Silver preferentially concentrates in the bacteria, distributes uniformly within them, or, alternatively, forms a rough coating over them. Oscillations in polarized light scattering vs scattering angle are more pronounced and shift to larger angles, compared to a control that has no silver. Very intense surface-enhanced Raman signals are observed for E. coli with a “wall colloid”. The main bands can be associated with peptides and polysaccharides in the cell wall and its membrane. This work was extended to Gram-positive Bacillus megaterium.