No abstract

Treatment of bacteria with silver yields intense and highly specific surface-enhanced Raman spectroscopy (SERS) spectra from various cellular chemical components located in the vicinity of the silver colloids. In particular, we demonstrate an extreme sensitivity to flavin components associated with the cell envelope and to their state of oxidation. Different spectra, possibly associated with DNA, carboxylates, and perhaps phosphates, are obtained from the soluble interior fraction of the cell.

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.