Cytochemical Electron Microscopic Localization of Esterase Activity in Lactobacillus casei

Enzymes capable of hydrolyzing thiolacetic acid in two strains of Lactobacillus casei were localized by the formation of electron-opaque PbS deposits in vivo in the presence of Pb(NO(3))(2). By electron microscopy, the deposition of PbS appeared primarily at the plasma membrane and at the outer surface of the cell wall.