Microbodies und Diaminobenzidin-Reaktion in den Acetat-Flagellaten Polytomella caeca und Chlorogonium elongatum

Abstract

In two forms of acetate flagellates, the colourless Volvocale Polytomella caeca and the green Volvocale Chlorogonium elongatum, cell organelles can be demonstrated which are ultrastructurally similar to microbodies of higher organisms. The organelles do not have a close association with the endoplasmic reticulum and are located in the peripheral cytoplasm between the elongated mitochondria. In Polytomella they exhibit more or less spherical profiles in section and have a maximum diameter of approximately 0.2–0.25 μ. In Chlorogonium the organelles occasionally have an elongated shape and are larger than in Polytomella. Employing the electron microscopic cytochemical reagent diaminobenzidine (DAB)/H₂O₂ to localize the microbodial marker enzyme catalase in these organelles, it was found that no accumulation of the electron-opaque product occurs in the microbodies either at alkaline or neutral pH or at room temperature or 37° C. Only the cristae of mitochondria are stained with the DAB reaction caused by cytochrome oxidase and possibly by a cytochrome peroxidase. Organelles of Polytomella caeca containing catalase or cytochrome oxidase can be separated by rate centrifugation of a crude particulate fraction on a sucrose gradient (Gerhardt, 1971). The particles isolated from the peak of catalase activity show the same fine structural characteristics as the microbodies in situ do. But again, there is no detectable staining of these organelles by the DAB/H₂O₂ reaction. The identity of the microbody-like particles in Polytomella caeca and Chlorogonium elongatum with microbodies in general is deduced despite the negative results in cytochemical localization of catalase in these organelles.