Ultrastructural cytochemistry of Bacillus subtilis

The ultrastructure of B. subtilis has been studied with a new procedure of fixation with glutaraldehyde and embedding in glycol-methacrylate (GMA) because cytochemical studies can be carried out directly on the ultrathin sections. The cell wall appears triple-layered with two dense layers enclosing a less dense one. The middle unstained layer of the cell membrane is wider than in classical preparations. Ribosomes have a high contrast when amino acids are present in the fixing and washing solutions, but are indistinct when amino acids are not employed. Frequent coagulation of the nucleoplasmic fibrils suggests that aldehydes are not adequate preservatives for hydrated DNA. Ribonuclease digestion of the sections destroys the ribosomes, and deoxyribonuclease attacks the nucleoplasmic fibrils.