The demonstration of the succinic dehydrogenase system in Bacillus subtilis using tetranitro--blue tetrazolium combined with techniques of electron microscopy.

Activity of the succinic dehydrogenase system was studied in Bacillus subtilis utilizing combined techniques of cytochemistry and electron microscopy. Organisms were incubated in a medium containing tetranitro-blue tetrazolium (TNBT) which served as an electron acceptor. Enzymatic activity, as evidenced by deposition of TNBT-formazan, was found on membranous organelles associated with the cytoplasmic membrane and septal plasma membrane, the nuclear area, and the plasma membrane. Flagella, approximately 190 A in diameter, with thorn-like projections protruded through the cell wall. Tangential-oblique sections of the cell wall showed many pores approximately 220 A in diameter with a center-to-center spacing of approximately 450 A.