Trichosporon adeninovorans sp. nov., a yeast species utilizing adenine,xanthine, uric acid,putrescine and primary n-alkylamines as the sole source of carbon,nitrogen and energy

A new yeast species, Trichosporon adeninovorans, was isolated from soil by the enrichment culture method. Apart from adenine, the strain utilized uric acid, guanine, xanthine, hypoxanthine, 6,8-dihydroxypurine, putrescine, propylamine, butylamine, pentylamine, hexylamine and octylamine as sole source of carbon, nitrogen and energy.The structure of the cell wall of Tr. adeninovorans was ascomycetous. On the subcellular level growth on adenine or uric acid was accompanied with the development of microbodies in the cell. These cell organelles probably were the site of urate oxidase, an enzyme that, after growth on purine substrates, together with allantoinase was present at high activities. Low activities of adenine amidohydrolase and xanthine dehydrogenase were also demonstrated.     

Induction and repression of arginase and ornithine transaminase in baker's yeast

The arginase and the ornithine transaminase of baker's yeast are induced byl-arginine. Both enzymes have been shown to be repressed by nitrogen compounds. This is evidenced primarily by the decrease in specific enzyme activities caused by the addition of readily assimilable nitrogen compounds to a yeast culture with arginine, secondly by the derepression of both enzymes during nitrogen starvation of the yeast grown in various arginine-free media. This derepression equals both in rate and in amount the enzyme synthesis during the adaptation of the yeast to a medium withl-arginine as the sole nitrogen source. It is inhibited by various assimilable and non-assimilable amino acids. The derepression is the result of the nitrogen deficiency itself, since during the starvation of the yeast for sulphate, phosphate or magnesium, neither of the two enzymes is derepressed, and since it is independent of the nature of the carbon source in the nitrogen starvation medium, provided the latter is immediately assimilable.The enzymes are not subject to catabolite repression by glucose metabolites.It is concluded that the synthesis of arginase and ornithine transaminase in yeast is regulated by induction and repression. Arginine induces the enzymes; they are repressed by nitrogen compounds, probably in cooperation with one or more vitamins.Thanks are due to Professor E. G. Mulder for his frequent encouragement, to the Heineken's Brouwerij, Rotterdam and to the Landbouwhogeschoolfonds for research grants, and to Miss H. P. M. Klinkers, to Mr. P. J. Buysman and to Mr. G. J. K. Pesch for their skilful technical assistance.     

Induction of bacteriocin production in Lactobacillus sake by a secreted peptide.

Lactobacillus sake LTH673 is known to produce a bacteriocin called sakacin P. Production of and immunity to sakacin P were found to depend on the presence of a protease-sensitive component that is produced by L. sake LTH673 itself. This component (called inducing factor [IF]) was purified from culture supernatants and shown to be a basic, nonbacteriocin peptide consisting of 19 amino acids, which in principle is capable of forming a highly amphiphilic helical structure. Circular dichroism studies showed that IF indeed could adopt a helical structure, but only in membrane-mimicking environments. Both purified IF and chemically synthesized IF induced expression of the structural gene for sakacin P and concomitant secretion of the gene product. In addition, IF induced its own production and immunity to sakacin P and related bacteriocins. These results indicate that bacteriocin production by L. sake LTH673 is controlled by an autoinduction pathway in which IF may function as a cell density signal.     

Novel Pathway for Alcoholic Fermentation of δ-Gluconolactone in the Yeast Saccharomyces bulderi

Under anaerobic conditions, the yeast Saccharomyces bulderi rapidly ferments delta-gluconolactone to ethanol and carbon dioxide. We propose that a novel pathway for delta-gluconolactone fermentation operates in this yeast. In this pathway, delta-gluconolactone is first reduced to glucose via an NADPH-dependent glucose dehydrogenase (EC 1.1.1.47). After phosphorylation, half of the glucose is metabolized via the pentose phosphate pathway, yielding the NADPH required for the glucose-dehydrogenase reaction. The remaining half of the glucose is dissimilated via glycolysis. Involvement of this novel pathway in delta-gluconolactone fermentation in S. bulderi is supported by several experimental observations. (i) Fermentation of delta-gluconolactone and gluconate occurred only at low pH values, at which a substantial fraction of the substrate is present as delta-gluconolactone. Unlike gluconate, the latter compound is a substrate for glucose dehydrogenase. (ii) High activities of an NADP(+)-dependent glucose dehydrogenase were detected in cell extracts of anaerobic, delta-gluconolactone-grown cultures, but activity of this enzyme was not detected in glucose-grown cells. Gluconate kinase activity in cell extracts was negligible. (iii) During anaerobic growth on delta-gluconolactone, CO(2) production exceeded ethanol production by 35%, indicating that pyruvate decarboxylation was not the sole source of CO(2). (iv) Levels of the pentose phosphate pathway enzymes were 10-fold higher in delta-gluconolactone-grown anaerobic cultures than in glucose-grown cultures, consistent with the proposed involvement of this pathway as a primary dissimilatory route in delta-gluconolactone metabolism.     

Growth of Candida famata and Trichosporon cutaneum on uric acid as the sole source of carbon and energy,a hitherto unknown property of yeasts

Yeast strains capable of utilizing uric acid as the sole source of carbon and energy were isolated from soil by the enrichment culture method. The strains were identified as Candida famata (Harrison) Meyer et Yarrow and Trichosporon cutaneum (De Beurm., Gougerot et Vaucher) Ota. On the subcellular level growth of yeasts on uric acid was accompanied with the development of a number of large microbodies in the cells.     

The effect of growth conditions on production and excretion of extracellular antigens by three ascomycetous yeasts

Ascomycetous yeasts produce extracellular antigens that are almost specific for the species. The antigen production by Hansenula wickerhamii and Stephanoascus ciferrii was independent of the carbon source and was proportional to the final cell density of the cultures. The same was true of chemostat cultures of Stephanoascus ciferrii, irrespective of the dilution rate and whether glucose or ammonia was the limiting nutrient. In cultures of Saccharomyces cerevisiae, however, antigen excretion mainly took place in the late exponential growth phase. Large amounts of antigen were extracted from the cell wall of Saccharomyces cerevisiae. A small amount was detected in the cytoplasm.     

Enzyme repression in the arginine pathway ofSaccharomyces cerevisiae

Enzyme repression in the arginine pathway ofSaccharomyces cerevisiae was demonstrated by comparison of specific enzyme activities in yeast grown with and without arginine in various mineral salts media. Of the enzymes tested only ornithine transcarbamoylase was found to be repressed by exogenous arginine. Acetylornithine-glutamate transacetylase and argininosuccinate lyase were not affected. No relationship between specific enzyme activities and intracellular arginine concentration was observed.During the adaptation of yeast grown in a medium supplemented with amino acids to a mineral salts medium, the enzymes ornithine transcarbamoylase and argininosuccinate lyase were not derepressed beyond their specific activities normally present in yeast grown in mineral salts media. Neither were the arginine-degrading enzymes arginase and ornithine transaminase broken down during this adaptation.Thanks are due to Professor E. G. Mulder and to Professor H. Veldkamp for stimulatory discussions; to the Heineken's Brouwerij, Rotterdam, and to the Landbouwhogeschoolfonds for research grants.     

The substrate constant for the ammonium ion of growing

The relation between ammonium concentration and growth rate was studied in steady state continuous cultures of Saccharomyces cerevisiae in nitrogenlimited glucose ammonium medium. This relation could be described by the Monod equation. A maximum specific growth rate of 0.41 h^-1 and a substrate constant for ammonium of 5–11 M were calculated. Ammonium was determined by a modification of the phenol hypochlorite method. A discussion of the results in view of literature data on the substrate constants for other nutrients is given.     

Carbon assimilation and extracellular antigens of some yeast-like fungi

Many yeast-like fungi assimilated n-hexadecane, butylamine and putrescine as sole carbon sources. Methanol was not assimilated. This points to a physiological similarity to endomycetous, hydrocarbon-utilizing yeasts. Stephanoascus ciferrii assimilated uric acid, adenine and allantoin as sole source of carbon and nitrogen. All strains of Geotrichum candidum and many other yeast-like fungi assimilated acetoin and butan-2,3-diol. Assimilation tests for adenine, uric acid, allantoin, acetoin and butan-2,3-diol were found to be suitable for taxonomic purposes.Extracellular antigens immunologically related to those produced by Geotrichum candidum were detected in the cell-free culture liquids of several yeast-like fungi. The extracellular antigen excreted by Stephanoascus ciferrii was species-specific.     

Biogenesis and metabolic significance of microbodies in urate-utilizing yeasts

Growth of Candida famata and Trichosporon cutaneum on uric acid as the sole source of carbon and nitrogen was associated with the development of a number of microbodies in the cells. Cytochemical staining experiments showed that the organelles contained urate oxidase, a key enzyme of uric acid metabolism, and catalase. Transfer of cells, precultured on glucose or glycerol, into uric acid-containing media indicated that these microbodies originated from the organelles, originally present in the inoculum cells, by growth and division. In urate-grown C. famata the microbodies were frequently observed in large clusters; in both organisms they existed in close association with mitochondria and strands of ER. The organelles lacked crystalline inclusions. In freeze-fractured cells their surrounding membranes showed smooth fracture faces.Exposure of urate-grown cells to glucose-excess conditions led to a rapid inactivation of urate oxidase activity but catalase was only slightly inactivated. Glucose-induced enzyme inactivation was not associated with the degradation of the microbodies present in the cells. Similarly, repression of urate oxidase synthesis by ammonium ions also did not lead to the degradation of peroxisomes.