Protein Synthesis in the Induced Formation of Catalase in Rhodopseudomonas spheroides

Rhodopseudomona-s spheroides i a facultative photoheterotroph in which catalase synthesis can be induced by aeration (1). In cultures grown anaerobically in the light, catalase constitutes only about 0.002% of the dry cell mass. In contrast, the catalase content of cultures grown aerobically is as high as 0.3%. If an illuminated, anaerobic culture is exposed to air, a vigorous synthesis of catalase ensues. Under these conditions the utilieation of oxygen is slight; the energy for growth is provided mainly through photosynthesis (1). In terms of the range of catalase content attainable, R. spheroides is superior to other microbes in which inducible catalase has been observed. The catalase of R. spheroides i easily purified and has been characterized extensively (2) ; its assay in intact cells is simple and accurate (1). The metabolic versatility of R. spheroides makes it possible to study induced catalase synthesis under a variety of environmental conditions. For these reasons the present system holds promise for the study of induced enzyme synthesis and of the function of catalase. Further characterization of this system is therefore desirable. Induced synthesis of catalase in R. spheroides requires sources of carbon, nitrogen, and energy (1). Inhibitors, such as tetracycline, chloramphenicol, and ultraviolet irradiation, exert parallel effects on growth and induced catalase synthesis (1). These results suggest hat the protein of the newly formed catalase is synthesized de nova. This paper describes radiocarbon-incorporation experiments that support this conclusion. Similar experiments by Hogness et al. (3) and by Rotman and Spiegelman (4) have shown that, in the induced synthesis of P-galactosidase in Escherkhia co& the enzyme-protein is synthesized de TWVO.