Tetranitro-blue Tetrazolium Reduction in Proteus Vulgaris

In Bacillus subtilis the reduction of potassium tellurite and of tetranitro-blue tetrazolium (TNBT) give comparable results: reduced products appear deposited in particular membranous organelles. For this reason these specialized organelles are considered to be chondrioids (1-3). In the Gram-negative Proteus vulgaris similar membranous structures were never observed by us (4, 5). Therefore it is a challenging problem to investigate the location of the respiratory chain in this organism. With potassium tellurite applied to Proteus (2, 4, 5) in a manner similar to that for Bacillus subtilis (1, 2, 5), we observe deposition of reduced product in a rather restricted cytoplasmic area contiguous to the plasma membrane. In view of modern ideas that enzymes belonging to the oxidative phosphorylation process would be located in elementary particles forming part of the cristae mitochondriales, it was considered essential to determine upon what cell structures in this organism the products of tetranitro-blue tetrazolium reduction are deposited.