Sulfite formation by wine yeasts

Eight different strains of wine yeasts were investigated phenomenologically with respect to their fermentation characteristics and sulfite production. It was established that the amount of produced sulfite is specific for each strain and proceeds parallel to the fermentation of sugar. A reduced production of biomass observed in the strongly sulfite-forming strains might be a result of an intracellular inhibition by the produced sulfite.     

Sulfite formation by wine yeasts

Four strains of wine yeasts of two different species (Saccharomyces cerevisiae var. ellipsoideus and Saccharomyces bayanus) were investigated with respect to the influence of various sulfur compounds on the formation of O-acetylserine sulfhydrylase, O-acetylhomoserine sulfhydrylase and serine sulfhydrase. The specific enzyme activities were followed over a growth period of 96 h.In the presence of sulfate, sulfite and djencolic acid during exponential growth, a moderate increase of O-acetylserine sulfhydrylase and O-acetylhomoserine sulfhydrylase activities was recognized. In three strains cysteine and methionine prevented this derepression. At the end of the exponential growth phase, biosynthesis of these two enzymes was suppressed again. Serine sulfhydrase showed a modified regulation which indicates that its synthesis and the synthesis of O-acetylserine and O-acetylhomoserine sulfhydrylases are not coordinated.Abbreviations OAS O-acetylserine - OAHS O-acetylhomoserine     

Sulfite formation by wine yeasts

Five different strains of wine yeasts were investigated with respect to active uptake of [³⁵S] sulfate and its regulation by methionine. Considerable differences exist between low and high sulfite-producing strains in the initial velocity of sulfate uptake. Further differences were established in repression of sulfate permease by l-methionine, most evident in a total lack of repression in one of the high sulfite producers. These findings explain in part variable sulfite and sulfide formation.List of Abbreviations CCMP carbonylcyanide-p-trifluormethoxyphenylhydrazone     

Sulfite formation by wine yeasts

The enzyme catalyzing the reduction of sulfite by reduced benzyl viologen (BVH) was partially purified and characterized from two strains of wine yeasts, a sulfite-producing strain and a non-producing strain.Both enzymes showed corresponding features in pH-optima, optima of buffer and benzyl viologen concentrations.The enzymes did not catalyze the reduction of nitrite by reduced viologen dyes, but the reduction of sulfite was uncompetitively inhibited by nitrite. Compounds of sulfur metabolism such as sulfate, thiosulfate, cysteine, serine and methionine did not influence the activity of either of the enzymes. The main differences between the two enzymes exist in the specific activities in crude extracts, the K _m -values for sulfite, substrate inhibition rates, and localization in different fractions during (NH₄)₂SO₄ precipitation. The specific activity in crude extracts of the sulfite-producing strain (0.052 moles S^2- x min^-1 x mg^-1) was about three fold higher than that of the non-producing strain (0.0179 moles S^2- x min^-1 x mg^-1). On the other hand the sulfite-producing strain had a higher K _m -value for sulfite (2×10^-3 M) and was more strongly inhibited by the substrate than the non-producing strain (6×10^-3 M).     

Sulfite formation by wine yeasts

Four strains of wine yeasts of two different species (Saccharomyces cerevisiae var. ellipsoideus and S. bayanus) were investigated with respect to regulation of NADPH- and benzyl viologen-dependent sulfite reductases by various sulfur sources. The enzyme activity was followed over a growth period of 96 h. The low sulfite-producing strains showed an increased biosynthesis of NADPH-dependent sulfite reductase during the exponential growth phase in the presence of sulfate, sulfite and djencolic-acid. This increase was not observed in the high sulfite-producing strains. Methionine and cysteine prevented this derepression. At the end of the exponential growth phase, enzyme biosynthesis was repressed again, presumably by sulfur-containing amino acids which were produced during growth. The regulatory influence of the various sulfur sources on benzyl viologen dependent sulfitereductase activity is obviously much weaker.Abbreviation BV benzyl viologen     

Damage of PSII by Sulfite

The photoreduction of DCIP by PSⅡ pasticles isolated from spinach leaves was inhibited by sulfite and the degree of inhibition was increased with the increase of sulfite concentration. The site of sulfite damage was on the oxidation side. In dark, electron flow from H2O to DCIP and from DPC to DCIP was not affected by sulfite. With certain concentrations of sulfite, the damage to PSⅡ particle varied with time of sulfite treatment and the mechanism of the damage might be related to the discretion of 33 kD polypeptide from thylakoid membrane and the leakage of Mn. Sulfite did not specifically damage the newly prepared thyla- koid, but this was the case with aged thylakoid. The rate of DCIP photoreduction decreased as the aging process was prolonged. Decrease in Mn content correlated with the decrease of DCIP photoreduction. Especially in the presence of EDTA, with the decrease of Mn, the rate of electron transport was severely reduced.     

Antibiotic inhibition of protein synthesis by mitochondria of higher plants and animals

The antibiotic sensitivity of protein synthesis by mitochondria isolated from chick brain, trout liver, potato tuber and corn root has been investigated. Like mitochondria isolated from rat liver, organelles from these sources show a much reduced antibiotic sensitivity spectrum when compared to mitochondria derived from yeast, being sensitive to chloramphenicol, carbomycin, spiramycin and mikamycin but resistant to erythromycin, lincomycin, paromomycin, neomycin C and viridiogrisein. In addition spectinomycin inhibited protein synthesis by both types of plant mitochondria but not those from chick brain, rat liver or yeast.     

Chemocommunication between bacteria and the higher vertebrate animals

Between bacteria and the higher vertebrate animals there are close chemocommunicational connections that are realized via signal molecules secreted by bacteria, on the hand, and vertebrate hormones and hormone-like substances, on the other hand. The review presents data on regulatory effects of biogenic amines (catecholamines and serotonin), peptide hormones, and immunoregulator of the higher vertebrates on the vitally important functions of bacterial cells, their virulence and survivability. It has been shown that some bacterial signal molecules, such as N-acylated derivatives of homoserine lactones, also are able to regulate fundamental cellular processes in the higher vertebrates. Deciphering of molecular mechanisms of information exchange between bacteria and the higher vertebrates is both of theoretical significance for studies on pathways of evolution of chemosignal systems in proand eukaryote organism and of practical significance for development of new approaches for treatment of bacterial infections.     

Sulfite Additives

The CMA recommends that sulfites be banned as food preservatives when satisfactory and safe alternatives are available. When there is no suitable substitute strict labelling requirements on foods should be imposed for sulfite additives. The association supports the efforts of the Health Protection Branch of the Department of National Health and Welfare to regulate sulfites in the food and drug industry to prevent adverse reactions in people sensitive to sulfites. The CMA recommends that the Department of National Health and Welfare establish a federal-provincial liaison group that has the authority to introduce additive standards for food producers, distributors and restaurants and to monitor foods at the consumer level for the presence of allergenic additives.     

Mitochondrial DNA and the evolutionary genetics of higher animals

Mitochondrial DNA (mtDNA) in higher animals is rapidly becoming a well characterized genetic system at the molecular level. In this paper, I shift the focus to consider questions in organismal evolution that can be addressed by mtDNA assay. For the first time, it is possible to estimate empirically matriarchal phylogeny; to determine directionality in crosses producing hybrids; and to study the population genetic consequences of varying female demographies and life histories. The data obtainable from mtDNA may be especially well suited for studies of population genetic structure, dispersal, and historical zoogeography. The female-mediated, clonal transmission of mtDNA is also stimulating new ways of thinking about times to common ancestry of asexual lineages within otherwise sexually reproducing populations; about the possible relevance of mtDNA-nuclear DNA interactions to reproductive isolation; and about the very meaning of the phylogenetic status of related species with respect to particular kinds of genetic characters. These and other topics are reviewed.     

Characteristics of Sulfite Transport by Chlorella vulgaris

The rate of short-term accumulation of [³⁵S]sulfite in Chlorellavulgaris cells was found to be strongly dependent on the pHof the medium. The rate increased with decreased pH, and theincrease in rate closely paralleled the increase in the concentrationof the un-ionized form of sulfite. When the pH of the mediumwas increased, fast accumulation ceased immediately. The rateof accumulation showed a strong temperature dependence, withan apparent temperature coefficient of 1.93 per 10°C rise,between 10 and 25°C. Because pK_a values of sulfite shiftwith temperature, the rates were corrected by dividing by theconcentration of the un-ionized form of sulfite present at therespective temperatures. The temperature coefficient was thenfound to decrease to 1.45. When cells which had been allowedto accumulate [³⁵S]sulfite for 20 min were transferred to amedium containing no sulfite, more than 50% of the accumulated[³⁵S] was released into the medium in 20 min. Our results arecompatible with a simple diffusion model of SO₂ transport intoChlorella cells. (Received September 26, 1996; Accepted January 20, 1997)