The Experts below are selected from a list of 531 Experts worldwide ranked by ideXlab platform
Domingo Marquina - One of the best experts on this subject based on the ideXlab platform.
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the biology of Pichia membranifaciens killer toxins
Toxins, 2017Co-Authors: Ignacio Belda, Domingo Marquina, Javier Ruiz, Alejandro Alonso, Antonio SantosAbstract:The killer phenomenon is defined as the ability of some yeast to secrete toxins that are lethal to other sensitive yeasts and filamentous fungi. Since the discovery of strains of Saccharomyces cerevisiae capable of secreting killer toxins, much information has been gained regarding killer toxins and this fact has substantially contributed knowledge on fundamental aspects of cell biology and yeast genetics. The killer phenomenon has been studied in Pichia membranifaciens for several years, during which two toxins have been described. PMKT and PMKT2 are proteins of low molecular mass that bind to primary receptors located in the cell wall structure of sensitive yeast cells, linear (1→6)-β-d-glucans and mannoproteins for PMKT and PMKT2, respectively. Cwp2p also acts as a secondary receptor for PMKT. Killing of sensitive cells by PMKT is characterized by ionic movements across plasma membrane and an acidification of the intracellular pH triggering an activation of the High Osmolarity Glycerol (HOG) pathway. On the contrary, our investigations showed a mechanism of killing in which cells are arrested at an early S-phase by high concentrations of PMKT2. However, we concluded that induced mortality at low PMKT2 doses and also PMKT is indeed of an apoptotic nature. Killer yeasts and their toxins have found potential applications in several fields: in food and beverage production, as biocontrol agents, in yeast bio-typing, and as novel antimycotic agents. Accordingly, several applications have been found for P. membranifaciens killer toxins, ranging from pre- and post-harvest biocontrol of plant pathogens to applications during wine fermentation and ageing (inhibition of Botrytis cinerea, Brettanomyces bruxellensis, etc.).
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the transcriptional response of saccharomyces cerevisiae to proapoptotic concentrations of Pichia membranifaciens killer toxin
Fungal Genetics and Biology, 2011Co-Authors: Antonio Santos, Domingo MarquinaAbstract:abstract PMKT (Pichia membranifaciens killer toxin) reportedly has antimicrobial activity against yeasts and fila-mentous fungi. In previous research we posited that high PMKT concentrations pose a serious challengefor cell survival by disrupting plasma membrane electrochemical gradients, inducing a transcriptionalresponse similar to that of certain stimuli such as hyperosmotic shock. This response was related tothe HOG-pathway with Hog1p phosphorylation and a transitional increase in intracellular glycerol accu-mulation. Such a response was consistent with the notion that the effect induced by high PMKT concen-trations lies in an alteration to the ionic homeostasis of the sensitive cell.By contrast, the evidence presented here shows that low PMKT doses lead to a cell death process in Sac-charomyces cerevisiae accompanied by cytological and biochemical indicators of apoptotic programmedcell death, namely, the production of reactive oxygen species, DNA strand breaks, metacaspase activationand cytochrome c release. Furthermore, dying cells progressed from an apoptotic state to a secondarynecrotic state, and the rate at which this change occurred was proportional to the intensity of the stim-ulus. We have explored the global gene expression response of S. cerevisiae during that stimulus. Theresults obtained from DNA microarrays indicate that genes related with an oxidative stress responsewere induced in response to proapoptotic concentrations of PMKT, showing that the coordinated tran-scriptional response is not coincident with that obtained when ionophoric concentrations of PMKT areused. By contrast, cwp2D mutants showed no signs of apoptosis, indicating that the initial steps of thekiller mechanism coincide when proapoptotic (low) or ionophoric (high) PMKT concentrations are used.Additionally, low dosages of PMKT promoted Hog1p phosphorylation and glycerol accumulation. 2011 Elsevier Inc. All rights reserved.
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pmkt2 a new killer toxin from Pichia membranifaciens and its promising biotechnological properties for control of the spoilage yeast brettanomyces bruxellensis
Microbiology, 2009Co-Authors: Antonio Santos, San M Mauro, Enrique Bravo, Domingo MarquinaAbstract:Pichia membranifaciens CYC 1086 secretes a killer toxin (PMKT2) that is inhibitory to a variety of spoilage yeasts and fungi of agronomical interest. The killer toxin in the culture supernatant was concentrated by ultrafiltration and purified to homogeneity by two successive steps, including native electrophoresis and HPLC gel filtration. Biochemical characterization of the toxin showed it to be a protein with an apparent molecular mass of 30 kDa and an isoelectric point of 3.7. At pH 4.5, optimal killer activity was observed at temperatures up to 20 °C. Above approximately this pH, activity decreased sharply and was barely noticeable at pH 6. The toxin concentrations present in the supernatant during optimal production conditions exerted a fungicidal effect on a variety of fungal and yeast strains. The results obtained suggest that PMKT2 has different physico-chemical properties from PMKT as well as different potential uses in the biocontrol of spoilage yeasts. PMKT2 was able to inhibit Brettanomyces bruxellensis while Saccharomyces cerevisiae was fully resistant, indicating that PMKT2 could be used in wine fermentations to avoid the development of the spoilage yeast without deleterious effects on the fermentative strain. In small-scale fermentations, PMKT2, as well as P. membranifaciens CYC 1086, was able to inhibit B. bruxellensis, verifying the biocontrol activity of PMKT2 in simulated winemaking conditions.
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cwp2p the plasma membrane receptor for Pichia membranifaciens killer toxin
Molecular Microbiology, 2007Co-Authors: Antonio Santos, Manuel San Mauro, C Abrusci, Domingo MarquinaAbstract:Summary PMKT is a channel-forming killer toxin secreted by Pichia membranifaciens. To identify novel genes that mediate cellular resistance to PMKT we screened a collection of 288 deletion mutants. We found 29 open reading frames (ORFs) that, when deleted, confer resistance to PMKT. In addition, the deletion of 15 ORFs was observed to increase protoplast resistance, in agreement with the initial assumption that a plasma membrane receptor for PMKT exists. Whole cells and protoplasts of a cwp2D mutant were found to be completely resistant to PMKT and were unable to bind PMKT, indicating that Cwp2p interacts with it. A protein with a molecular mass of 11.7 kDa was purified from PMKT-affinity columns. This protein was sequenced and identified as Cwp2p. Glycosylphosphatidylinositol (GPI) anchoring-defective mutants were much less sensitive to PMKT, as were wild-type protoplasts pretreated with phosphatidylinositolspecific phospholipase C to remove GPI-anchored proteins, indicating that the GPI-anchored precursor of Cwp2p is also necessary for PMKT activity. Carboxyfluorescein-entrapped liposomes containing a purified GFP–Cwp2p fusion protein in their membranes were much more sensitive to PMKT than protein-free liposomes. Cwp2p and its GPI-anchored precursor are proposed for the first time to be involved as PMKT secondary receptors.
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the transcriptional response of saccharomyces cerevisiae to Pichia membranifaciens killer toxin
Journal of Biological Chemistry, 2005Co-Authors: Antonio Santos, Maria Del Mar Alvarez, Manuel San Mauro, C Abrusci, Domingo MarquinaAbstract:Abstract The transcriptional response of Saccharomyces cerevisiae to Pichia membranifaciens killer toxin (PMKT) was investigated. We explored the global gene expression responses of the yeast S. cerevisiae to PMKT using DNA microarrays, real time quantitative PCR, and Northern blot. We identified 146 genes whose expression was significantly altered in response to PMKT in a non-random functional distribution. The majority of induced genes, most of them related to the high osmolarity glycerol (HOG) pathway, were core environmental stress response genes, showing that the coordinated transcriptional response to PMKT is related to changes in ionic homeostasis. Hog1p was observed to be phosphorylated in response to PMKT implicating the HOG signaling pathway. Individually deleted mutants of both up- (99) and down-regulated genes (47) were studied for altered sensitivity; it was observed that the deletion of up-regulated genes generated hypersensitivity (82%) to PMKT. Deletion of down-regulated genes generated wild-type (36%), resistant (47%), and hypersensitive (17%) phenotypes. This is the first study that shows the existence of a transcriptional response to the poisoning effects of a killer toxin.
Antonio Santos - One of the best experts on this subject based on the ideXlab platform.
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the biology of Pichia membranifaciens killer toxins
Toxins, 2017Co-Authors: Ignacio Belda, Domingo Marquina, Javier Ruiz, Alejandro Alonso, Antonio SantosAbstract:The killer phenomenon is defined as the ability of some yeast to secrete toxins that are lethal to other sensitive yeasts and filamentous fungi. Since the discovery of strains of Saccharomyces cerevisiae capable of secreting killer toxins, much information has been gained regarding killer toxins and this fact has substantially contributed knowledge on fundamental aspects of cell biology and yeast genetics. The killer phenomenon has been studied in Pichia membranifaciens for several years, during which two toxins have been described. PMKT and PMKT2 are proteins of low molecular mass that bind to primary receptors located in the cell wall structure of sensitive yeast cells, linear (1→6)-β-d-glucans and mannoproteins for PMKT and PMKT2, respectively. Cwp2p also acts as a secondary receptor for PMKT. Killing of sensitive cells by PMKT is characterized by ionic movements across plasma membrane and an acidification of the intracellular pH triggering an activation of the High Osmolarity Glycerol (HOG) pathway. On the contrary, our investigations showed a mechanism of killing in which cells are arrested at an early S-phase by high concentrations of PMKT2. However, we concluded that induced mortality at low PMKT2 doses and also PMKT is indeed of an apoptotic nature. Killer yeasts and their toxins have found potential applications in several fields: in food and beverage production, as biocontrol agents, in yeast bio-typing, and as novel antimycotic agents. Accordingly, several applications have been found for P. membranifaciens killer toxins, ranging from pre- and post-harvest biocontrol of plant pathogens to applications during wine fermentation and ageing (inhibition of Botrytis cinerea, Brettanomyces bruxellensis, etc.).
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the transcriptional response of saccharomyces cerevisiae to proapoptotic concentrations of Pichia membranifaciens killer toxin
Fungal Genetics and Biology, 2011Co-Authors: Antonio Santos, Domingo MarquinaAbstract:abstract PMKT (Pichia membranifaciens killer toxin) reportedly has antimicrobial activity against yeasts and fila-mentous fungi. In previous research we posited that high PMKT concentrations pose a serious challengefor cell survival by disrupting plasma membrane electrochemical gradients, inducing a transcriptionalresponse similar to that of certain stimuli such as hyperosmotic shock. This response was related tothe HOG-pathway with Hog1p phosphorylation and a transitional increase in intracellular glycerol accu-mulation. Such a response was consistent with the notion that the effect induced by high PMKT concen-trations lies in an alteration to the ionic homeostasis of the sensitive cell.By contrast, the evidence presented here shows that low PMKT doses lead to a cell death process in Sac-charomyces cerevisiae accompanied by cytological and biochemical indicators of apoptotic programmedcell death, namely, the production of reactive oxygen species, DNA strand breaks, metacaspase activationand cytochrome c release. Furthermore, dying cells progressed from an apoptotic state to a secondarynecrotic state, and the rate at which this change occurred was proportional to the intensity of the stim-ulus. We have explored the global gene expression response of S. cerevisiae during that stimulus. Theresults obtained from DNA microarrays indicate that genes related with an oxidative stress responsewere induced in response to proapoptotic concentrations of PMKT, showing that the coordinated tran-scriptional response is not coincident with that obtained when ionophoric concentrations of PMKT areused. By contrast, cwp2D mutants showed no signs of apoptosis, indicating that the initial steps of thekiller mechanism coincide when proapoptotic (low) or ionophoric (high) PMKT concentrations are used.Additionally, low dosages of PMKT promoted Hog1p phosphorylation and glycerol accumulation. 2011 Elsevier Inc. All rights reserved.
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pmkt2 a new killer toxin from Pichia membranifaciens and its promising biotechnological properties for control of the spoilage yeast brettanomyces bruxellensis
Microbiology, 2009Co-Authors: Antonio Santos, San M Mauro, Enrique Bravo, Domingo MarquinaAbstract:Pichia membranifaciens CYC 1086 secretes a killer toxin (PMKT2) that is inhibitory to a variety of spoilage yeasts and fungi of agronomical interest. The killer toxin in the culture supernatant was concentrated by ultrafiltration and purified to homogeneity by two successive steps, including native electrophoresis and HPLC gel filtration. Biochemical characterization of the toxin showed it to be a protein with an apparent molecular mass of 30 kDa and an isoelectric point of 3.7. At pH 4.5, optimal killer activity was observed at temperatures up to 20 °C. Above approximately this pH, activity decreased sharply and was barely noticeable at pH 6. The toxin concentrations present in the supernatant during optimal production conditions exerted a fungicidal effect on a variety of fungal and yeast strains. The results obtained suggest that PMKT2 has different physico-chemical properties from PMKT as well as different potential uses in the biocontrol of spoilage yeasts. PMKT2 was able to inhibit Brettanomyces bruxellensis while Saccharomyces cerevisiae was fully resistant, indicating that PMKT2 could be used in wine fermentations to avoid the development of the spoilage yeast without deleterious effects on the fermentative strain. In small-scale fermentations, PMKT2, as well as P. membranifaciens CYC 1086, was able to inhibit B. bruxellensis, verifying the biocontrol activity of PMKT2 in simulated winemaking conditions.
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cwp2p the plasma membrane receptor for Pichia membranifaciens killer toxin
Molecular Microbiology, 2007Co-Authors: Antonio Santos, Manuel San Mauro, C Abrusci, Domingo MarquinaAbstract:Summary PMKT is a channel-forming killer toxin secreted by Pichia membranifaciens. To identify novel genes that mediate cellular resistance to PMKT we screened a collection of 288 deletion mutants. We found 29 open reading frames (ORFs) that, when deleted, confer resistance to PMKT. In addition, the deletion of 15 ORFs was observed to increase protoplast resistance, in agreement with the initial assumption that a plasma membrane receptor for PMKT exists. Whole cells and protoplasts of a cwp2D mutant were found to be completely resistant to PMKT and were unable to bind PMKT, indicating that Cwp2p interacts with it. A protein with a molecular mass of 11.7 kDa was purified from PMKT-affinity columns. This protein was sequenced and identified as Cwp2p. Glycosylphosphatidylinositol (GPI) anchoring-defective mutants were much less sensitive to PMKT, as were wild-type protoplasts pretreated with phosphatidylinositolspecific phospholipase C to remove GPI-anchored proteins, indicating that the GPI-anchored precursor of Cwp2p is also necessary for PMKT activity. Carboxyfluorescein-entrapped liposomes containing a purified GFP–Cwp2p fusion protein in their membranes were much more sensitive to PMKT than protein-free liposomes. Cwp2p and its GPI-anchored precursor are proposed for the first time to be involved as PMKT secondary receptors.
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the transcriptional response of saccharomyces cerevisiae to Pichia membranifaciens killer toxin
Journal of Biological Chemistry, 2005Co-Authors: Antonio Santos, Maria Del Mar Alvarez, Manuel San Mauro, C Abrusci, Domingo MarquinaAbstract:Abstract The transcriptional response of Saccharomyces cerevisiae to Pichia membranifaciens killer toxin (PMKT) was investigated. We explored the global gene expression responses of the yeast S. cerevisiae to PMKT using DNA microarrays, real time quantitative PCR, and Northern blot. We identified 146 genes whose expression was significantly altered in response to PMKT in a non-random functional distribution. The majority of induced genes, most of them related to the high osmolarity glycerol (HOG) pathway, were core environmental stress response genes, showing that the coordinated transcriptional response to PMKT is related to changes in ionic homeostasis. Hog1p was observed to be phosphorylated in response to PMKT implicating the HOG signaling pathway. Individually deleted mutants of both up- (99) and down-regulated genes (47) were studied for altered sensitivity; it was observed that the deletion of up-regulated genes generated hypersensitivity (82%) to PMKT. Deletion of down-regulated genes generated wild-type (36%), resistant (47%), and hypersensitive (17%) phenotypes. This is the first study that shows the existence of a transcriptional response to the poisoning effects of a killer toxin.
Marcela P Sangorrin - One of the best experts on this subject based on the ideXlab platform.
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Enhancing the efficacy of yeast biocontrol agents against postharvest pathogens through nutrient profiling and the use of other additives
Biological Control, 2018Co-Authors: Betina R. Gramisci, M. Cecilia Lutz, Christian Ariel Lopes, Marcela P SangorrinAbstract:Abstract Vishniacozyma victoriae and Pichia membranifaciens were selected in a previous work for their biocontrol effectiveness against Penicillium expansum and Botrytis cinerea, the causal agents of blue and grey mold of pear fruits. The objective of this study was to determine the effects of different nutrient or additives on the growth of the two antagonist yeasts and of the two fungal pathogens in order to develop a rational selection based on nutritional profiles to be used in biocontrol enhancement of decay in pear fruits. Twenty-six different nutrient sources including 18 amino acids, five sugars, three inorganic nitrogen and one iron source were tested in vitro for their effect on the growth of the two yeasts and the two pathogens. Nutrients that promoted the growth of the yeasts and inhibited the growth of pathogens were applied with the antagonist to wounded fruits to evaluate their effect on enhancing biocontrol in cold storage. In general, the effect of each additive was specific to the yeasts and pathogens used in the in situ assays. The combination of the yeast and some additives resulted in a significantly higher activity with respect to the single treatments applied separately, producing synergistic effects. The effect of the exogenous application of CaCl2 and chitosan together with the antagonist yeasts was also evaluated against the two pathogens. The most effective mixtures were the CaCl2 with the two antagonist yeasts. Our research demonstrates that manipulating the chemical environment by adding several amino acid and/or Cl2Ca results in improved antagonistic activity of Vishniacozyma victoriae and Pichia membranifaciens against two postharvest diseases of pear fruits.
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TdKT, a new killer toxin produced by Torulaspora delbrueckii effective against wine spoilage yeasts.
International Journal of Food Microbiology, 2015Co-Authors: Maria Leticia Villalba, Julieta Susana Saez, Christian Ariel Lopes, Silvana Maria Del Monaco, Marcela P SangorrinAbstract:Abstract Microbiological spoilage is a major concern throughout the wine industry, and control tools are limited. This paper addresses the identification and partial characterization of a new killer toxin from Torulaspora delbrueckii with potential biocontrol activity of Brettanomyces bruxellensis, Pichia guilliermondii, Pichia manshurica and Pichia membranifaciens wine spoilage. A panel of 18 different wine strains of T. delbrueckii killer yeasts was analysed, and the strain T. delbrueckii NPCC 1033 (TdKT producer) showed a significant inhibitory effect on the growth of all different spoilage yeasts evaluated. The TdKT toxin was then subjected to a partial biochemical characterization. Its estimated molecular weight was > 30 kDa and it showed glucanase and chitinase enzymatic activities. The killer activity was stable between pH 4.2 and 4.8 and inactivated at temperature above 40 °C. Pustulan and chitin — but not other cell wall polysaccharides — prevented sensitive yeast cells from being killed by TdKT, suggesting that those may be the first toxin targets in the cell wall. TdKT provoked an increase in necrosis cell death after 3 h treatment and apoptotic cell death after 24 h showing time dependence in its mechanisms of action. Killer toxin extracts were active at oenological conditions, confirming their potential use as a biocontrol tool in winemaking.
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Efficacy and putative mode of action of native and commercial antagonistic yeasts against postharvest pathogens of pear.
International journal of food microbiology, 2013Co-Authors: M. Cecilia Lutz, Christian A Lopes, M Eugenia Rodriguez, M Cristina Sosa, Marcela P SangorrinAbstract:Putative mechanisms of action associated with the biocontrol capacity of four yeast strains (Cryptoccocus albidus NPCC 1248, Pichia membranifaciens NPCC 1250, Cryptoccocus victoriae NPCC 1263 and NPCC 1259) against Penicillium expansum and Botrytis cinerea were studied by means of in vitro and in situ assays. C. albidus(YP), a commercial yeast was also evaluated for comparative purposes. The yeast strains exhibited a variety of different mechanisms including: wound colonization, germination inhibition, biofilm formation, secretion of killer toxins, competition for nutrient and secretion of hydrolytic enzymes (protease, chitinase and glucanase). The relationship between strains (and their associated antagonist mechanisms) and in situ antagonist activity was also evaluated. Results indicate that mechanisms such as production of hydrolytic enzymes, the ability for colonization of wounds, production of killer toxin and inhibition of germination are the most important for biocontrol activity. Our study indicate that multiple modes of action may explain why P. membranifaciens NPCC 1250 and C. victoriae NPCC 1263 provided excellent control of postharvest pears disease.
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production of volatile phenols by Pichia manshurica and Pichia membranifaciens isolated from spoiled wines and cellar environment in patagonia
Food Microbiology, 2011Co-Authors: Julieta Susana Saez, Christian A Lopes, Veronica E Kirs, Marcela P SangorrinAbstract:Abstract In order to detect spoilage yeast species in wines showing off-odors, different yeast isolation protocols were evaluated. Independently of the isolation method, only Saccharomyces cerevisiae and Pichia manshurica were detected. The spoilage capacity of P. manshurica regional isolates was evaluated in red wine and the production of volatile phenols was evidenced. To evaluate the possible source of contamination, yeasts from both grapes and cellar surfaces were obtained. Hanseniaspora uvarum and Zygoascus hellenicus were detected in both sound and damaged grapes from sunny areas. The most frequent species in cellar surfaces was Candida boidinii, Pichia membranifaciens and P. manshurica were detected in filters. The intra-specific genetic characterization of the P. manshurica isolates by mtDNA-RFLP demonstrated that the same strain was detected in both wine and filter. Most P. membranifaciens isolates produced 4-EP (maximum level of 1.895 mg/L) and particularly high levels of 4-EG (maximum level of 10.260 mg/L) were produced by P. manshurica isolates in synthetic wine-like medium. In this work the capacity of P. manshurica and P. membranifaciens species to produce volatile phenols was shown for the first time.
Alexandra Veiga - One of the best experts on this subject based on the ideXlab platform.
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Stress situations induce cyanide-resistant respiration in spoilage yeasts.
Journal of Applied Microbiology, 2003Co-Authors: Alexandra Veiga, Joao D Arrabaca, Maria C. Loureiro-diasAbstract:Aims: To investigate the conditions that promote the expression of cyanide-resistant respiration (CRR) in the spoilage yeasts Pichia membranifaciens and Debaryomyces hansenii. Methods and Results: CRR was detected by sensitivity of oxygen consumption to salicylhydroxamic acid. It was absent in both yeasts in the early exponential phase, but was triggered by several stress situations. Starvation under aerobic conditions, decreasing pH or incubation of the culture in a narrow temperature range below the maximum temperature for growth promoted the emergence of CRR in both yeasts. In D. hansenii, CRR was also induced by 1·5–2 mol l−1 NaCl. Although the presence of H2O2 and menadione induced CRR, radical scavengers had no effect on the emergence of CRR. Also, the level of reactive oxygen species did not vary with the CRR activity. Conclusions: Under aerobic conditions, a respiratory pathway alternative to the cytochrome chain is triggered by stress conditions in P. membranifaciens and D. hansenii. Significance and Impact of the Study: The relationship between stress situations and CRR must be taken into account in studies on the performance of spoilage yeasts in the food processing environments where several forms of stress are common.
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energy conversion coupled to cyanide resistant respiration in the yeasts Pichia membranifaciens and debaryomyces hansenii
Fems Yeast Research, 2003Co-Authors: Alexandra Veiga, Joao D Arrabaca, Filipe Sansonetty, Paula Ludovico, Manuela Cortereal, Maria C LoureirodiasAbstract:Cyanide-resistant respiration (CRR) is a widespread metabolic pathway among yeasts, that involves a mitochondrial alternative oxidase sensitive to salicylhydroxamic acid (SHAM). The physiological role of this pathway has been obscure. We used the yeasts Debaryomyces hansenii and Pichia membranifaciens to elucidate the involvement of CRR in energy conversion. In both yeasts the adenosine triphosphate (ATP) content was still high in the presence of antimycin A or SHAM, but decreased to low levels when both inhibitors were present simultaneously, indicating that CRR was involved in ATP formation. Also the mitochondrial membrane potential (ΔΨm), monitored by fluorescent dyes, was relatively high in the presence of antimycin A and decreased upon addition of SHAM. In both yeasts the presence of complex I was confirmed by the inhibition of oxygen consumption in isolated mitochondria by rotenone. Comparing in the literature the occurrence of CRR and of complex I among yeasts, we found that CRR and complex I were simultaneously present in 12 out of 13 yeasts, whereas in six out of eight yeasts in which CRR was absent, complex I was also absent. Since three phosphorylating sites are active in the main respiratory chain and only one in CRR, we propose a role for this pathway in the fine adjustment of energy provision to the cell.
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Cyanide-resistant respiration is frequent, but confined to yeasts incapable of aerobic fermentation
Fems Microbiology Letters, 2000Co-Authors: Alexandra Veiga, Joao D Arrabaca, Maria C. Loureiro-diasAbstract:In Pichia membranifaciens, cyanide-resistant respiration (CRR) sensitive to salicylhydroxamic acid emerged after forced aeration of starved cells for 4 h. Surveying a large number of species by this simple methodology, we found that CRR is very frequent among yeasts. Remarkably, considering our results together with previous data in the literature, CRR was present in 24 out of 28 non-fermentative or Crabtree-negative yeasts and absent in 10 out of 12 Crabtree-positive yeasts. We submit that, as alternatives to cytochromic respiration, yeasts developed two strategies: either aerobic fermentation in Crabtree-positive yeasts or CRR in non-fermentative or Crabtree-negative yeasts.
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effects of weak acid preservatives on the growth and thermal death of the yeast Pichia membranifaciens in a commercial apple juice
International Journal of Food Microbiology, 2000Co-Authors: Alexandra Veiga, A MadeiralopesAbstract:Abstract Pichia membranifaciens exhibited a dissociative temperature profile (the temperature range of thermal death was distinct from the temperature range of growth) when incubation took place either in a commercial apple juice (AJ) or in a synthetic mineral medium with glucose and vitamins (MGV). In AJ the maximum temperature for growth (Tmax) was 38.6°C, which decreased to 36°C in the presence of either 1 mM sorbic or 1 mM benzoic acid. The minimum temperatures of thermal death (Tmind) were, respectively, 40 and 38°C with either of the acids. The yeast could grow with up to 2 mM sorbic or 3 mM benzoic acid, at 25°C, which is close to the optimum temperature for growth (Top). At temperatures slightly above Tmind, sorbic acid was an actual enhancer of death rather than benzoic, the latter conferring some protection. However, these effects were reversed at higher temperatures (above 43°C), at which benzoic acid was the most operative, in contrast to sorbic which was highly protective of the yeast against thermal death. The addition of acetaldehyde to sulphur-dioxide-containing juice reduced the lag phase and increased the overall specific growth rates. Sporulated or stationary vegetative cultures were more heat-resistant than exponential cultures, particularly at temperatures above 45°C.
Jose M Peinado - One of the best experts on this subject based on the ideXlab platform.
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1 6 β d glucan as cell wall receptor for Pichia membranifaciens killer toxin
Applied and Environmental Microbiology, 2000Co-Authors: Antonio Santos, Domingo Marquina, J A Leal, Jose M PeinadoAbstract:dation, infrared spectroscopy, and 1 H nuclear magnetic resonance) analyses of the fractions obtained showed that (136)-b-D-glucan was a receptor. Adsorption of most of the killer toxin to the (136)-b-D-glucan was complete within 2 min. Killer toxin adsorption to the linear (136)-b-D-glucan, pustulan, and a glucan from Penicillium allahabadense was observed. Other polysaccharides with different linkages failed to bind the killer toxin. The specificity of the killer toxin for its primary receptor provides an effective means to purify the killer toxin, which may have industrial applications for fermentations in which salt is present as an adjunct, such as olive brines. This toxin shows its maximum killer activity in the presence of NaCl. This report is the first to identify the (136)-b-D-glucan as a receptor for this novel toxin.
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(1→6)-β-d-Glucan as Cell Wall Receptor for Pichia membranifaciens Killer Toxin
Applied and Environmental Microbiology, 2000Co-Authors: Antonio Santos, Domingo Marquina, J A Leal, Jose M PeinadoAbstract:dation, infrared spectroscopy, and 1 H nuclear magnetic resonance) analyses of the fractions obtained showed that (136)-b-D-glucan was a receptor. Adsorption of most of the killer toxin to the (136)-b-D-glucan was complete within 2 min. Killer toxin adsorption to the linear (136)-b-D-glucan, pustulan, and a glucan from Penicillium allahabadense was observed. Other polysaccharides with different linkages failed to bind the killer toxin. The specificity of the killer toxin for its primary receptor provides an effective means to purify the killer toxin, which may have industrial applications for fermentations in which salt is present as an adjunct, such as olive brines. This toxin shows its maximum killer activity in the presence of NaCl. This report is the first to identify the (136)-b-D-glucan as a receptor for this novel toxin.