POSSIBILE RESPIRATORY SITES IN A BLUE-GREEN ALGA NOSTOC SPHAERICUM AS DEMONSTRATED BY POTASSIUM TELLURITE AND TETRANITRO-BLUE TETRAZOLIUM REDUCTION

Colonies of Nostoc sphaericum were incubated in potassium tellurite and tetranitro-blue tetrazolium solutions with and without succinate substrate in the presence and absence of light. In all cases there is evidence that the reduction products are associated with the photosynthetic lamellae. Deposition of reduced tellurite with succinate substrate in the absence of light would rule out the reduction caused by photosynthesis (redox reaction). It seems, therefore, that the so-called photosynthetic lamellae in blue-green algal cells also function as mitochondrial equivalents. There is indication that reduced tellurite is continuously removed from the reduction site while TNBT-formazan is relatively immobile. There is no evidence for the reduction of tellurite on the plasma membrane or any of the cytoplasmic granules. © 1969 Academic Press, Inc.