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      Comportamiento de una cepa salvaje de Saccharomyces cerevisiae killer y su isogénica sensible respecto de diferentes fuentes de nitrógeno en cultivos mixtos Translated title: Behaviour of a wild Saccharomyces cerevisiae killer yeast and its isogenic sensitive one with respect to different nitrogen sources in mixed cultures

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          Abstract

          La composición química del vino constituye el fundamento de la posterior respuesta sensorial del producto y está determinada por varios factores, como las relaciones levadura-levadura. Se denomina fenómeno killer a la secreción por parte de ciertas cepas de levadura de una proteína tóxica que mata a células denominadas sensibles. El conocimiento del comportamiento en condición aeróbica de cultivos mixtos killer-sensible es útil para relacionarlo con la primera fase de la fermentación enológica, ya que en ella puede definirse la prevalencia o no de la cepa killer. Además, el empleo de mutantes con el plásmido curado permite comparaciones más precisas. El objetivo fue analizar el mecanismo de competencia por sustrato en levaduras killer de Saccharomyces cerevisiae y su mutante sensible con el plásmido curado, empleando distintas fuentes de nitrógeno. Si las muestras se incuban a temperatura de inactivación de la toxina, se evita la infraestimación de células sensibles. Los resultados del co-cultivo de las cepas en proporciones iguales muestran el rol desempeñado por la fuente de nitrógeno en la actividad killer. Cuando el inóculo es 10%K-90%S, el modelo de exclusión competitiva planteado para levaduras killer deja paso a otras variables de competencia.

          Translated abstract

          Wine chemical composition is the outcome of complex chemosensory interactions that are difficult to predict because of the influences of many variables, like as yeast-yeast interactions. Killer phenomenon implicates the secretion of a toxic protein by some yeasts, that kill other yeasts called sensitive. The knowledge of the behaviour of killer-sensitive mixed cultures in aerobic conditions is useful to be related with the first stages of oenological fermentation. In these stages it can be defined the killer prevalence in the medium. Also, the use of cured plasmid mutants allows better comparisons. The objective was to analyse the mechanism of substrate competition in Saccharomyces cerevisiae killer strains and its sensitive cured plasmid mutant, using different nitrogen sources. When samples were incubated at the toxin inactivation temperature, the infraestimation of sensitive cells is avoided. Results obtained in co-cultures (50%K-50%S) show the role of the nitrogen source in killer activity. Results obtained with 10%K-90%S inoculum, show that there are another competence variables than the competitive exclusion model for killer yeasts.

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          Most cited references 29

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          Yeast interactions and wine flavour.

           Daniel Fleet (2003)
          Wine is the product of complex interactions between fungi, yeasts and bacteria that commence in the vineyard and continue throughout the fermentation process until packaging. Although grape cultivar and cultivation provide the foundations of wine flavour, microorganisms, especially yeasts, impact on the subtlety and individuality of the flavour response. Consequently, it is important to identify and understand the ecological interactions that occur between the different microbial groups, species and strains. These interactions encompass yeast-yeast, yeast-filamentous fungi and yeast-bacteria responses. The surface of healthy grapes has a predominance of Aureobasidium pullulans, Metschnikowia, Hanseniaspora (Kloeckera), Cryptococcus and Rhodotorula species depending on stage of maturity. This microflora moderates the growth of spoilage and mycotoxigenic fungi on grapes, the species and strains of yeasts that contribute to alcoholic fermentation, and the bacteria that contribute to malolactic fermentation. Damaged grapes have increased populations of lactic and acetic acid bacteria that impact on yeasts during alcoholic fermentation. Alcoholic fermentation is characterised by the successional growth of various yeast species and strains, where yeast-yeast interactions determine the ecology. Through yeast-bacterial interactions, this ecology can determine progression of the malolactic fermentation, and potential growth of spoilage bacteria in the final product. The mechanisms by which one species/strain impacts on another in grape-wine ecosystems include: production of lytic enzymes, ethanol, sulphur dioxide and killer toxin/bacteriocin like peptides; nutrient depletion including removal of oxygen, and production of carbon dioxide; and release of cell autolytic components. Cell-cell communication through quorum sensing molecules needs investigation.
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            Escherichia coli O157:H7: clinical, diagnostic, and epidemiological aspects of human infection.

             P Tarr (1994)
            E. coli O157:H7 is one of many E. coli organisms that contain genes encoding one or more toxins similar in structure and function to Shiga toxin. E. coli O157:H7 is the most frequently isolated diarrheagenic type of E. coli isolated in North America today; this pathogen can cause serious, even fatal disease. Syndromes caused by E. coli O157:H7 include diarrhea, hemorrhagic colitis, and HUS. Poorly cooked ground beef has been the most frequently implicated vehicle of transmission, but additional vehicles are being identified. Treatment consists of rehydration during hemorrhagic colitis and support of the patient during the multiple systemic complications of HUS. A policy of routine screening for E. coli O157:H7 in clinical microbiology laboratories, without reliance on the physician to request that this organism be sought or the technician to notice blood in the stool, is the most effective way to find cases. Timely and accurate diagnosis can prevent secondary transmission, avert unnecessary and possibly dangerous procedures and/or therapies, and detect continuing outbreaks. SLTEC strains other than E. coli O157:H7 may cause diseases similar to or less severe than those caused by E. coli O157:H7. At present, however, screening for such pathogens in clinical laboratories is too labor-intensive to be practical. Education and legislation should promote safe food-preparation and food-handling practices. Research should be directed at reducing the carriage of E. coli O157:H7 at its bovine source, minimizing the microbial content of food and water, and averting systemic microangiopathic hemolytic anemia after infection with this pathogen.
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              Double-stranded RNA viruses of Saccharomyces cerevisiae.

               Reed Wickner (1996)
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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Journal
                ram
                Revista argentina de microbiología
                Rev. argent. microbiol.
                Asociación Argentina de Microbiología (Ciudad Autónoma de Buenos Aires, , Argentina )
                0325-7541
                1851-7617
                June 2005
                : 37
                : 2
                : 73-77
                Affiliations
                San Juan orgnameUniversidad Nacional de San Juan. orgdiv1Facultad de Ingeniería orgdiv2Instituto de Biotecnología
                San Juan orgnameUniversidad Nacional de San Juan. orgdiv1Facultad de Ciencias Exactas, Físicas y Naturales orgdiv2Departamento de Geofísica, Astronomía y Biología cristinanally@ 123456yahoo.com.ar
                Article
                S0325-75412005000200002

                This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 21, Pages: 5
                Product
                Product Information: SciELO Argentina

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