Carl C. Lindegren

The nucleic acids in a polyploid series of Saccharomyces.

Abstract 1. 1. A polyploid series from haploid through tetraploid in yeasts has been analyzed for a number of cellular characters including dry weight, desoxyribonucleic acid (DNA), ribonucleic acid (RNA), and metaphosphate content. 2. 2. The DNA content per cell is found consistent with an integral ratio in the polyploid series, and this character has proved most reliable of those studied in estimating ploidy. 3. 3. Dry weight, RNA, and metaphosphate content per cell are also ploidy-dependent but vary over a wider experimental range. 4. 4. The reliable estimation of ploidy in yeast provides a critical tool for the analysis of irregular segregation in the yeasts.

The mechanics of budding and copulation in saccharomyces

Abstract The yeast cell contains a nucleus whose rigid centrosome carries a band of Feulgen-positive chromatin (centrochromatin) on its surface. The first step in budding is the formation of the bud by an extension of the centrosome over which the cell wall persists. Next the nuclear vacuole extends a process into the bud which contains the chromosomes. Finally the centrochromatin divides directly and the cells separate; a plug either of centrosome or cytoplasm sealing the bud pore. The cytoplasm, the centrosome, the centrochromatin and the nuclear wall are autonomous non genic organelles which never originate de novo . Copulation is the reverse of budding. The centrosomes fuse first; the cytoplasms mix; the nuclear vacuoles fuse by processes which travel along the fused centrosomes; and finally the centrochromatins fuse to form a single band. Figures 1–12. Drawings of budding yeast cells fixed in Schaudinns fluid and stained with iron alum hemotoxylin, mounted in balsam. The cell wall is not visible due to the clearing action of the balsam. Except for Figure 5, the chromosomes and the nucleolus in the nuclear vacuole have been completely destained. The bud scar described by Barton is shown clearly at the end of the cell distal from the centrosome. The nuclear vacuole is usually forced into the extrusion formed by the bud scar. Since the cell wall is not visible, the plug of material connecting bud and mother cell as shown in Figure 12, fits into the cell wall and probably corresponds to the plug in the bud scar described by Barton. The details of the budding process are described in the text. Figures 13–18. Copulating yeast cells stained with Barretts hemotoxylin and aceto-orcein and mounted in the stain. Chromosomes are visible in the nuclear vacuoles. The centrosome is usually visible and often appears to have a core which stains differentially. Except in Figure 16, the centrochromatin is visible as darkly stained material; in some cases surrounded by a clear zone. The “thick waisted” form of the cells identifies them as derived from recent copulations and distinguishes them from budding cells. The process of copulation is discussed in the text.

The distribution of chromatin in budding yeast cells.

Summary and conclusionsA critical examination of well fixed yeast cells killed at different states in the growth cycle shows that the distribution of chromatin in the yeast cell varies depending on the stage in the growth cycle. Our data support the view (1) that the spindle is intravacuolar, (2) that mitosis occurs on the spindle, (3) that the chromosomes spin out after mitosis to extend into the vacuole, (4) that a large nucleolus appears in the nuclear vacuole of rapidly growing wellnourshed cells, and (5) that in the presence of adequate amounts of phosphate and otherwise favorable conditions the chromosomes are covered with metaphosphate.

The genetics of melezitose fermentation in Saccharomyces

SummaryA multiple series of alleles of the gene MZ exist inSaccharomyces. The members of this series are differentiated from one another by their adaptive response to maltose, turanose, sucrose, melezitose and alpha-methyl glucoside. The more capable members of the series can ferment all five sugars while various multiple alleles are characterized by loss of ability to act on alpha-methyl glucoside, melezitose or sucrose. MZ is linked to the gene MA which controls the production of a specific maltase and to the gene MG which controls the production of a specific alpha-methyl glucosidase. All members of the series of multiple alleles produce the same enzyme showing that the gene and the enzyme are not identical. The enzyme is produced in three different steps, the initial one being a specific reaction of gene with substrate and the final one being a non-specific elicitation of enzyme.

The structure of the nucleus of saccharomyces bayanus

Abstract S. bayanus is an elongate cell whose cytoplasm appears homogeneous in the living state. The nuclear vacuole has the same shape as the cell and contains paired Feulgen-positive chromosomes and a Feulgen-negative nucleolus which is typical in its staining reaction and its relation to the chromosomes. A nuclear membrane is indicated by the definite, regular outline of the nuclear vacuole. When the nuclear vacuole is collapsed the wall lies in folds, establishing the presence of a definite membrane. Certain stains suggest that the centrosome may be within the boundaries of the nuclear membrane. The centrosome is closely associated with the chromosomes, characteristic of the typical fungal nucleus. The centrosome is Feulgen-positive. The chromosomes and centrosome are not Feulgen-positive simultaneously, suggesting a cyclic relationship. The Feulgen-positive substance of the centrosome when present varies in amount and pattern. It divides, part going into the bud, part remaining in the mother cell. The separating Feulgen-positive masses are connected by a Feulgen-negative strand. The proposal is made that the chromatin of the yeast cell be called chromosomal chromatin and centrosomal chromatin. A central clear sphere is present in the centrosome and is closely associated with the Feulgen-positive material. The cytoplasm contains mitochondria which are more densely aggregated in the area surrounding the nuclear vacuole, the centrosome and the region of the cytoplasmic clear area. The mitochondria are visible only in the living cell since the ordinary fixatives destroy them. A clear area is almost constantly present in the cytoplasm opposite the centrosome, apparently in contact with the nuclear vacuole.

Electron microscopy of mitochondria in Saccharomyces

The mitochondria in Saccharomyces , grown on glucose nutrient agar medium, have been revealed by electron microscopy. Specimens were fixed in 2% potassium permanganate, post-fixed in 1 % uranyl acetate, and embedded in a methacrylate mixture. The yeast mitochondrion is bounded by a continuous membrane consisting of two dense layers divided by a less dense osmiophobic interspace. The inner membranes also consist of two dense outer layers and a less dense central one. The dense layers of the inner membranes are continuous with the osmiophilic layers of the outer membranes; the clear layers are directly connected with the osmiophobic interspace of the outer membrane. Both the inner membranes and the outer surface membrane are about 150 A thick.

Carbohydrases in Saccharomyces haploid stocks of defined genotype. II. Gene-controlled induction of glucosidases by α-glucosides☆☆☆

Abstract 1. 1. Yeast containing the gene MA formed both maltase and glucosucrase when grown on maltose and lost these responses to maltose when MA was replaced by its recessive allele. 2. 2. Yeast containing the gene MG formed both α-methyl glucosidase and glucosucrase when grown on α-methyl glucoside and lost these responses to α-methyl glucoside when MG was replaced by the recessive allele. 3. 3. Yeast containing both MA and MG responded heterologously to growth on maltose with the appearance of the ability to ferment α-methyl glucoside as well as maltose, whereas yeast containing MA and lacking MG failed to ferment α-methyl glucoside after growth on maltose. 4. 4. Glucose inhibited the responses of the yeasts to maltose and α-methyl glucoside. 5. 5. α-Methyl glucoside inhibited the formation of maltase in response to maltose. 6. 6. The mode of the control of homologous and heterologous response to glucosides by genes MA and MG is discussed. 7. 7. It is noted that the inhibition of homologous response to glucosides by glucose provides the cells with a homeostatic mechanism for the regulation of their adaptive response.

Eight genes controlling the presence or absence of carbohydrate fermentation in Saccharomyces.

SUMMARY: Genes controlling carbohydrate fermentation in Saccharomyces often control the fermentation of more than one carbohydrate. The gene MZ has at least five different manifestations involving its ability to respond to five different carbohydrate inducers for the production of a single enzyme; a series of multiple alleles of MZ differ from one another in ability to respond to the different inducers. The gene DX controls the fermentation of dextrin and glycogen. The gene ST controls the fermentation of starch; some starch-positive cultures are Schardinger-dextrin-positive. The gene SU controls the production of a constitutive enzyme which splits both sucrose and raffinose.

Autolysis and Sporulation in the Yeast Colony

Yeast colonies contain an outer layer of autolyzed cells, and this layer is the region in which sporulation occurs. Autolysis of yeast cells probably provides a substrate favorable for sporulation. Legroux and Magrou showed that in bacterial colonies a similar structural (one might almost say histological) differentiation exists. The bacterial cells in the outer layer of the colonies produced tetrads, which may possibly be homologous to the ascospores of yeasts.

Concepts of gene-structure and gene-action derived from tetrad analysis of saccharomyces

Die mit Tetradenanalyse durchgeführten Untersuchungen fordern eine grundsätzliche Modifikation der Mendel-Theorie. Die Experimente führen zur Annahme, dass das Gen eine grosse Zahl übertragbarer Bestandteile trägt, die ringförmig um das Chromosom gelagert sind. Diese Teilchen können bei der Reduktion ungleichmässig auf die Allele verteilt werden. Gewisse Gene werden als « Enzym-Matrizen-Gene » (enzyme-template) bezeichnet, und ihre übertragbaren Bestandteile werden als Spiegelbilder des Substrats aufgefasst. Die Untersuchung einer multiplen Allelserie eines Enzyme-template-Gens ergab, dass das Gen nicht selbst das Enzym darstellt, sondern nur als eine Rezeptorstelle wirkt, die durch die Einwirkung des Substrats angeregt wird. Dies führt zur Bildung des Enzyms.