CatMase induction in Rhodopseudomonas spheroides and three locally isolated strains of l~hodopseudomonas (TL-1, TL-4 and Rps. D) was studied. A correlation between the rate of excretion of porphyrin and the inducibility of the culture was observed. 8-hydroxyquinoline at 4โข 10 -5 M had no effect on Bchl synthesis but it inhibited porphyrin excretion and catalase induction in Rhodopseudomonas spheroides. 8-OHQ at this concentration paldially inhibited Bchl synthesis and catMase induction in strain TL-1. The data indicate that the amount of catalase produced is dependent on the pool size of porphyrins.
When either O z or It~O~ was added to a photosynthetically growing culture of Rhodopseuclomonas spheroides, induction of the enzyme catalase (Hydrogen-peroxide : Itydrogen-peroxide oxidoreductase, EC 1.11.1.6) can be demonstrated (Clayton, 1960a, b). The induced synthesis of catalase requires "de novo" protein synthesis. The amount of catalase synthesized following induction is greater in a stationary phase culture than in an exponentially growing culture. Clayton observed that removal of acetate and gtutdmate from an acetate, glutamate, and malate medium abolishes this difference and the "exponential-phase" value for catalase induction is comparable to that of stationary-phase. This has been interpreted that, acetate and glutamate lead to the production of some metabolic intermediate which acts as an internal repressor for catalase. Although it is possible, it is unlikely that a metabolic intermediate represses the induction of an enzyme like catalase. A similar increase in auto-induced catalase synthesis during stationary-phase * This work is part of a thesis submitted by K. T. Shanmugam in partial fulfillment of the requirements for the Ph.D. degree.