Showing papers by "Thomas D. Brock published in 1958"

Mating reaction in the yeast Hansenula wingei; preliminary observations and quantitation.

Abstract: Wickerham (1956) has described a new species, Hansenula wingei, which exhibits a rather unusual mating reaction. When vegetative haploid cells of the two mating types are mixed, a strong agglutination reaction may occur. On agar, the cells set to a solid mass which resists further mixing and adheres tenaciously to the instrument used for mixing the cells. When the mass of cells is placed in water, they do not disperse but remain tightly clumped. After fusion of haploids has occurred, the agglutinability disappears and the diploids show no agglutination. This process markedly increases the frequency of zygote formation in this yeast, even though sporulation occurs only weakly in most diploids. Since agglutination is usually considered to be a surface reaction (Mudd, 1933), and since cells with such a tremendous attraction for one another should exhibit some large differences in surface components, a detailed study of the mechanism of this reaction was undertaken. The present paper outlines a method for quantitating the reaction and indicates the effects of certain factors on agglutination. Future papers will attempt to define the differences in surface properties which are responsible for the attraction.

The effect of salmine on bacteria.

Abstract: The bacteriostatic and bactericidal effects of salmine on various bacteria have been studied. Salmine has more bacteriostatic activity against Gram-positive than against Gram-negative bacteria. It is bactericidal in water but not in broth, and this bactericidal action occurs against both Gram-positive and Gram-negative bacteria. It has been shown that salmine causes agglutination of washed suspensions of certain bacteria and this agglutination is not correlated directly with the Gram stain. Salmine causes an increase in the turbidity of washed cells of all bacteria, Gram-positive and Gram-negative, and differs in this respect from the solutes sodium chloride and glucose, which affect only Gram-negative species.A comparison has been made of the effects of salmine and polymyxin and it has been concluded that salmine may also act by attachment to the bacterial surface.

Protein as a specific cell surface component in the mating reaction of Hansenula wingei.

Abstract: a hydrophobic cell mass. This phenomenon has been developed into a quantitative assay for agglutinability which has made it possible to study the mechanism of this attraction (Brock, J. Bacteriol., 75, 697, 1958). Work to be published elsewhere has shown that the two mating types do not differ in electrostatic charge or degree of hydration. Rather, the agglutination seems to be related to the presence of specific cell components on the two strains which are complementary to each other, and the reaction may be analogous to an antibody-antigen reaction. In the work to be reported here, it will be shown that one of the mating types (strain 21) requires a specific protein for agglutination, whereas the other mating type (strain 5) does not require such a protein. This is the first demonstration of a molecular basis for mating type compatibility in a fungus. The components responsible for agglutination exist on the cell wall. Cell walls isolated by mechanical disintegration with glass beads exhibit strong agglutination, even after extensive washing. However, since this yeast is difficult to disintegrate quantitatively, the work to be reported here is with whole cells prepared as described previously, and killed by heating to 100 C for 5 min. This heating intensifies the agglutination and eliminates autolysis during storage. When cell suspensions containing about 500 mg wet weight per ml were incubated with 1000 ,ug per ml of trypsin in 0.02 M tris(hydroxymethyl)aminomethane (Tris) buffer, a rapid removal of protein from the cell surfaces occurred. After 1 hr at 37 C, the cells were removed by centrifugation, washed, and assayed for agglutinability. The supernatant fluids were assayed for protein with the Folin phenol reagent. The results in table 1 demonstrate that onlv the agglutinability of strain 21 is affected, although almost identical amounts of protein are removed from both strains. Further tests with lower concentrations of trypsin have resulted in essentially the same amount of protein being removed in a longer period of time. Anthrone tests indicate that the trypsin is also removing carbohydrate material. Eddy (J. Inst. Brewing, 64, 19-21, 1958) has shown that trypsin and other proteolytic enzymes are able to remove a protein-mannan complex from the surface of flocculant brewer's yeasts which is apparently necessary for flocculation (agglutination) to occur. The conclusion seems reasonable that trypsin is removing a carbohydrate-protein complex from the surface of cells of H. uingei. Although almost identical amounts of protein are removed from both cell types, only the agglutination of one of these cell types is affected. Thus it is possible to differentiate between the two mating types of this yeast. If a protein is not responsible for the be-

Inhibition of growth of yeasts by 2.3.5-triphenyl tetrazolium chloride

Abstract: falls erforderlich, durch Ents~iuern n i t Calciumcarbonat auf einen p~-Wer t yon mehr als 3,1 gebracht wurde. Auch bet Abwesenhei t yon Hefen kamen die s~ureabbauenden Bak-\" terien in einem steril filtrierten T r a u b e n m o s t zur Entwiek lung und decarboxylier ten die Apfels~iure vollst~indig zu Milchsiiure und CO 2. Die Bildung und Ausscheidung yon Wachs tumsfaktoren oder N~hrstoffen yon der Here erscheint somit n icht als eine unbedingte Vorausse tzung fiir den biologischen S~iureabbau im Wein. Die Gegenwar t yon Trnbs to f fen war fiir die Entwick lung der Bakter ien ebenfalls nicht erforderlich. I m Gegensatz zu vorangegangenen Versuchen2) wurden die ]Bakterien durch Ku l tu r in saurem Tomatensa f t an niedrige pHWerte adaptiert , so dab die Bakterien un te r den wenig grinstigen Bedingungen des Mostes nicht abstarben, sondern sich vermehr ten . Dutch die vorliegenden Untersnchungen, die an anderer Stelle 5) ausffihrlich dargestellt werden sollen, wurden die Bed ingungen aufgezeigt, bet denen die s~tureabbauenden Bakterien des Weines gedeihen und der Siiureabbau erfolgen kann, und dami t wurde die bakterielle Grundlage des biologischen S~iureabbaus im Wein zweifelsfrei erwiesen.

Reversal of thymine xyloside inhibition in Escherichia coli by glutathione.

Abstract: AN unexpected competitive relationship between thymine xyloside and glutathione has been found. Thymine xyloside inhibits the growth of Escherichia coli in a synthetic medium. This inhibition is competitively reversed by glutathione.