The correlation of cellular changes with succinic dehydrogenase and cytochrome oxidase activities in the development of the cellular slime molds

Abstract

1. 1. The activities of succinic dehydrogenase and cytochrome oxidase were studied in different developmental stages of the slime mold, D. mucoroides, in particular, the transition from the active feeding to the morphogenetic stages. Cytochrome oxidase activity decreased during the interphase between the vegetative and the aggregation stages, and remained low in the migrating pseudoplasmodium. By contrast, succinic dehydrogenase activity remained low during the early part of the growth period but increased in activity 4–5 hours before the initiation of aggregation. 2. 2. The time of this sudden increase corresponded with the time of transition from the logarithmic to the stationary phase in the growth curve of the amebas, and it was further shown that this was the period of depletion of bacterial food supply and the cessation of feeding. 3. 3. Also at this time, the small dotlike form of the mitochondria seen in the earlier feeding stages became superseded by new filamentlike structures, and the amebas showed more active pseudopod formation and greater rate of movement. 4. 4. Histochemical studies were made to examine the possibility of differential distribution of these enzymes in the migrating pseudoplasmodia of D. mucoroides and D. discoideum. In the case of D. mucoroides the posterior, prespore region showed higher enzyme activities than the anterior, prestalk region. The migrating pseudoplasmodia of D. discoideum did not show clear differential staining between the two regions for either reaction, although experiments with phenylurethane seem to indicate that in older migrating pseudoplasmodia, there is a similar, but latent, differential pattern of cytochrome oxidase. 5. 5. In addition two reactions for peroxidase were tried on the migrating pseudoplasmodia of D. mucoroides, but both failed to show any positive result.