Further enzymic studies and electron microscopy of the microbodies of a mutant of Chlorella vulgaris.

Abstract

1. The presence of microbodies in the yellow mutant Chlorella vulgaris 211-2-11 h/20 has been demonstrated by means of electron microscopy. 2. A microbody preparation, obtained from the algae by cell disruption and subsequent sucrose density gradient centrifugation, contained an enzyme pattern which suggests that the microbodies from glucose-grown cells are of the peroxisomal rather than of the glyoxysomal type. No malate synthetase and no isocitrate lyase were found. 3. Microbodies of acetate-grown cells also did not contain isocitrate lyase or malate synthetase activities. In contrast to glucose-grown cells a supernatant fraction of acetate-grown cells exhibited low isocitrate lyase activity, but just as in the case of glucose-grown cells activity of malate synthetase was not detectable even if assayed for with a variety of methods, including the use of 14C-1-acetate. 4. In acetate-grown cells malate was the major product of acetate assimilation as evidenced by the characterization of short-term products of 14C-acetate assimilation. Malate was not a primary product of 14C-acetate assimilation in glucose-grown cells. 5. Since on the one hand the presence of malate synthetase could not be demonstrated in acetate-grown cells as well as in glucose-grown cells, on the other hand malate was the primary product of 14C-acetate assimilation in acetate-grown cells it must be concluded, either that the enzyme is so sensitive that it does not survive isolation, or that the mutant utilizes a pathway other than the glyoxylate by-pass for acetate assimilation when dependent upon acetate for growth. 6. As previously demonstrated (Codd et. al., 1972) the isolated microbodies from glucose-grown cells contain high amounts of catalase. An attempt to localize catalase cytochemically by the diaminobenzidine technique failed: diaminobenzidine plus H2O2 stained the microbodies, the mitochondria, Golgi apparatus, and even the lamellar system of the chlorophyll-free plastid. Staining of both the microbodies and mitochondria was relieved by aminotriazole.