SUMMARYThe metabolic control of the protocatechuate branch of the 3-oxoadipate pathway in Rhodotorula mucilaginosa was examined and the specific inducers identified using appropriately blocked mutants. Three successive inductive events permitted the synthesis of the five enzymes converting p-hydroxybenzoate to 3-oxoadipyl-CoA: the independent induction of 4-hydroxybenzoate 3-monooxygenase by its own specific substrate, the independent induction of protocatechuate 3,4-dioxygenase by either protocatechuate or p-hydroxybenzoate, and finally the co-ordinate induction of 3-carboxymuconate cyclase, 3-carboxymuconolactone hydrolase and 3-oxoadipate CoA-transferase by either protocatechuate or p-hydroxybenzoate. Evidence is presented which suggests that R. mucilaginosa is unable to metabolize catechol or its usual precursors, and the significance of this is discussed in relation to control of the protocatechuate branch and the differing control mechanisms governing the synthesis of enzymes of the 3-oxoadipate pathway in other fungi and bacteria.
Three bacterial strains have been isolated that differ in their ability to degrade polyethylene glycols (PEGs). Strains R and O showed a marked preference for growth on the low and high molecular weight PEGs, respectively, while strain Z utilized mono‐ethylene glycol only. The partial degradation of PEG 200 by strains R and O was studied in some detail and the results suggested that those components of the mixture that were not utilized were converted into acidic derivatives which accumulated in the medium.
SUMMARYThe antifungal antibiotic nystatin has been successfully used to select mutants of the yeast Rhodotorula mucilaginosa from populations consisting largely of wildtype organisms. The most efficient selection technique has been found by a study of the duration of the nitrogen starvation period, the composition of the starvation medium, and the concentration of nystatin. Several mutants have been obtained which are unable to utilize either or both of the aromatic carbon sourcesp-hydroxybenzoate and protocatechuate.
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