Cell wall assembly in Bacillus subtilis: visualization of old and new wall material by electron microscopic examination of samples stained selectively for teichoic acid and teichuronic acid.

Uranyl acetate staining of thin sections allowed a distinction to be made between cell wall material that contains teichoic acid and that which contains teichuronic acid. The stain was used to study the pattern of wall assembly in Bacillus subtilis undergoing transitions between growth conditions leading to incorporation of the different anionic polymers. The results showed that new material is incorporated along the inner surface of the cylindrical region of the wall confirming, by a more direct method, results obtained earlier with teichoic acid specific phages. New material appears to be evenly distributed along the inner surface and no evidence was obtained for the presence of specific zones of incorporation.