Evaluation of behaviour of Lachancea thermotolerans biocontrol agents on grape fermentations.

Previous researches have showed that Lachancea thermotolerans strains RCKT4 and RCKT5 inhibited the growth of Aspergillus. However, currently, there are no data on their nutritional preferences, as a possible substrate competitor against Saccharomyces cerevisiae, and their effects on fermentation. In this work, we observed that the biocontrol yeasts and S. cerevisiae BSc203, based on the utilization of 16 carbonate sources, revealed significant differences in the nutritional profile (biocontrol yeasts NS:0·25, BSc203 NS:0·56). Lachancea thermotolerans strains did not occupy the same niche as that of BSc203 (NOI:0·44). The biocontrol agents and BSc203 presented similar competitive attitude in terms of the sugar, ethanol and sulphite tolerances. During fermentation, the biocontrol yeasts were found to tolerate up to 12% v/v ethanol, 250 mg ml-1 of total SO2 and 30° Brix sugar. In mixed cultures, L. thermotolerans strains did not negatively affect the growth of BSc203 and the wine quality, except when RCKT4 was initially inoculated at a high proportion in the mixed culture 1MSK4 (1%BSc203/99%RCKT4), resulting in a lower production of CO2 and ethanol, in comparison with pure BSc203. RCKT5, at a high proportion, in 1MSK5 (1%BSc203/99%RCKT5) presented promising oenological properties. This fermentation showed lower acetic acid contents and higher total acidity than pure BSc203. SIGNIFICANCE AND IMPACT OF THE STUDY: Generally it is not evaluated if the biofungicide yeasts sprayed on vegetables alter the quality of the fermented products. This work focused on the importance of assessing the possible effects of yeast-based fungicides used in vineyards on grape fermentation, especially on Saccharomyces cerevisiae growth. In this context, the competition between biofungicide yeasts and S. cerevisiae under winemaking conditions is investigated.

Use of yeasts from different environments for the control of Penicillium expansum on table grapes at storage temperature.

A wide range of fresh fruits and vegetables is attacked by Penicillium species causing diseases during their postharvest handling. Many of these species are psychrotrophic and they are able to cause food spoilage at refrigeration temperature as happens with table grapes. After the harvest, grape bunches are stored inside boxes with SO2 generator pads to reduce the contamination with fungal conidia. However, SO2 residues are dangerous to people allergic to sulfites and they negatively affect the quality of fresh fruit. Biological control of phytopathogens with microbial antagonists naturally present on fruit surfaces could be helpful against postharvest diseases. The present study aimed to select native yeasts isolated from fermentation microenvironments and the surface of refrigerated grapes for their use in the biological control of P. expansum on table grapes stored in cold rooms. Non-pathogenic and pathogenic Penicillium species were isolated, and the four most aggressive pathogen isolates were identified as Penicillium expansum. Twenty yeast isolates identified as Aureobasidium pullulans, Cryptococcus magnus, Metschnikowia pulcherrima and Rhodotorula glutinis presented positive antagonistic activity against Penicillium expansum; they controlled the development of at least one of the fungi, significantly reducing the disease incidence. The results showed that three antagonistic yeasts (M. pulcherrima 22, 36 and 43) reduced the disease incidence and severity of all 4 P. expansum isolates. It was also found that the fruit surface is not the only source for isolation of biological control agents. Microenvironments with different stress conditions could be a promising source to isolate antagonistic microorganisms.

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

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.

[Yeast diversity in Bulnesia retama and Larrea divaricata canopies and associated soils]. / Diversidad de levaduras en canopias y suelos asociados con Bulnesia retama y Larrea divaricata.

Bush like vegetation dominates arid environments, and there is nutrients accumulation under shrub canopies and relatively unfertile soils between vegetal patches areas. Plants are one of the most common habitats for yeasts. There are many reports about yeasts inhabiting different plant components. Nevertheless, there are no reports about yeasts associated with Zygophyllaceae, an important shrub family of the Argentinean Province of Monte. The objective of this work was to analyzed yeast biodiversity of Bulnesia retama and Larrea divaricata canopies and associated soils, at Medanos Grandes of Caucete, San Juan, Argentina. Eighty seven (87) isolated yeasts were identified. From B. retama canopy and associated soil was observed a larger taxonomical diversity respect to L. divaricata. Nine (9) and ten (10) species were isolated from canopy and associated soil of B. retama, respectively. From L. divaricata canopy were 4 species and 3 species from its associated soil isolated. Identified genera were: Candida, Debaryomyces, Dekkera, Saccharomyces, Torulaspora, Sporidiobolus and Pichia. Fourteen (14) species were found at all microenvironments.

Antifungal modes of action of Saccharomyces and other biocontrol yeasts against fungi isolated from sour and grey rots.

The aim of this study was to determine the putative modes of action of 59 viticultural yeasts (31 Saccharomyces and 28 non-Saccharomyces) that inhibited fungi isolated from sour and grey rot in grapes. Inhibition of fungal mycelial growth by metabolites, enzyme activities (laminarinases, chitinases), antifungal volatiles, competition for nutrients (siderophores, Niche Overlap Index (NOI)), inhibition of fungal spore germination and decreased germinal tube length and induction of resistance were assayed. Biofungicide yeasts were classified into "antifungal patterns", according to their mechanisms of action. Thirty isolates presented at least two of the mechanisms assayed. We propose that inhibition of fungal mycelial growth by metabolites, laminarinases, competition for nutrients, inhibition of fungal spore germination and decreased germinal tube length, and antifungal volatiles by Saccharomyces and non-Saccharomyces viticultural yeasts is used as putative biocontrol mechanisms against phytopathogenic fungi. Twenty-four different antifungal patterns were identified. Siderophore production (N)and a combination of siderophore production and NOI>0.92 (M)were the most frequent antifungal patterns observed in the biofungicide yeasts assayed. Elucidation of these mechanisms could be useful for optimization of an inoculum formulation, resulting in a more consistent control of grey and sour rot with Saccharomyces and non-Saccharomyces biocontrol yeasts.

Primary angiitis of the central nervous system: report of five biopsy-confirmed cases from Colombia.

INTRODUCTION: Primary (isolated) angiitis of the central nervous system (PACNS) is a rare cause of cerebrovascular disease (CVD), and few leptomeningeal and brain biopsy (LBB)-confirmed cases have been reported from South America. METHODS: We retrospectively reviewed charts of patients with diagnosis of cerebral angiitis admitted between March 1991 and July 2001 to a single university hospital in Medellin, Colombia. Patients with definitive diagnosis of PACNS by Alrawi et al.'s LBB criteria were selected. We excluded other causes of cerebral angiitis as well as cases without LBB confirmation. RESULTS: We report five patients, four men and one woman, with a mean age at onset of 24.4 years, and an average disease progression of 12.4 days. Four presented with headache and motor weakness, three had seizures, and two had alterations of consciousness. Cerebral MRI was abnormal in all five cases; brain CT in four, and cerebral angiography in two. The cerebrospinal fluid (CSF) was abnormal in two patients. Leptomeningeal and brain biopsies revealed mononuclear infiltration in the wall of small blood vessels in all. Three had concurrent meningeal and cerebral involvement, two had necrotizing angiitis, and one had vascular and encephalitic lesions. All received only steroid treatment; the 1-year follow-up revealed good prognosis without relapses. CONCLUSION: We report five biopsy-proven cases of PACNS from Colombia associated with neurological and neuroimaging abnormalities; these patients presented a mild inflammatory disease that was correlated with few CSF abnormalities and good response to single steroid treatment without relapses. Leptomeningeal and brain biopsy is mandatory for a definitive diagnosis.

[Subacute combined degeneration. A description of the case of a strictly vegetarian child]. / Degeneración combinada subaguda. Descripción de un caso en un niño vegetariano estricto.

INTRODUCTION: Cyanocobalamin (vitamin B12) is an essential cofactor of various metabolic pathways. Lack of it leads to symptoms which may be constitutional, of skin or mucous membranes, hematological or neuropsychiatric disorders. Neurological involvement in adults has been well described and analyzed in the literature, however there are fewer cases of children. In the cases described in children the deficiency was related to maternal malnutrition, and socioeconomic and cultural problems. Since vegetarianism is a custom followed by different social groups we wish to draw attention to this as a cause of vitamin B12 deficiency and the neurological disorder this may cause. CLINICAL CASE: We describe the case of a 10 year old boy, a member of a religious community who were strict vegetarians. Over three months he developed: a cognitive disorder, pyramidal syndrome of his legs, involvement of the posterior spinal cord, peripheral motor and sensory alterations which, together with the complementary investigations, was found to be compatible with subacute combined degeneration due to vitamin B12 deficiency. CONCLUSION: We draw attention to the clinical and laboratory aspects of this disorder and the importance of taking the possibility of this diagnosis into account in children with nutritional risk factors.

[Factorial and discriminant analyses of neuropsychological variables in familial and sporadic late onset Alzheimer disease]. / Anàlisis factorial y discriminante de variables neuropsicológicas en la demencia tipo Alzheimer de inicio tardío, familiar y esporádica.

INTRODUCTION: Prevalence of late onset Alzheimer's disease (LOAD) both familial and sporadic is increasing with the raising proportion of third-age population. There are evidences either supporting or rejecting the existence of differences in the behavior of neuropsychological variables between familial and sporadic cases of LOAD. OBJECTIVE: To identify neuropsychological variables discriminating between familial and sporadic cases of LOAD, in order to detect clinical manifestations that may provide information on the pathological process of the neurodegenerative process. PATIENTS AND METHODS: Using sequential sampling, we selected individuals affected by LOAD according to the criteria of the DSM-IV and NINCS-ADRDA. The following neuropsychological protocol was used: CERAD, Wisconsin, Phonological Fluency, Rey's Figure, Raven, A Cancellation Test, WAIS (Arithmetic); also used were: Global Deterioration Scale, Functional Assessment Staging of Reisberg (FAST), Barthel and Yesavage. Parametrical and non-parametrical univariate, factorial (principal components) and discriminant analyses were performed. In total, 52 patients were analyzed (average age: 74.8 years; mean age at onset of the disease: 69 years; time of disease's evolution: 5.7 years; average of educational level: 6.4 years). RESULTS: No significant statistical differences were found in clinical or neuropsychological variables between familial and sporadic cases of LOAD. Additionally, neither variables nor models were detected discriminating significantly between them. CONCLUSION: Familial and sporadic cases of LOAD present the same clinical and neuropsychological phenotype which makes very probable that sporadic cases are low penetrance familial ones.

Occurrence of killer yeasts in Argentine wineries.

Fifty-six wine must samples, from wineries in various regions of Argentina, were examined at different fermentation stages for the presence of killer yeast strains. The distribution of isolated killer strains was markedly different from one region to another.

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

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.

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.

Diversidad de levaduras en canopias y suelos asociados con Bulnesia retama y Larrea divaricata / Yeast diversity in Bulnesia retama and Larrea divaricata canopies and associated soils.

Los ambientes áridos están dominados por vegetación arbustiva, con acumulación de nutrientes bajo la canopia de los arbustos y con suelos relativamente infértiles en los interparches. Los distintos componentes de los vegetales constituyen uno de los hábitat más comunes para las levaduras. Existen numerosos antecedentes acerca de investigaciones sobre levaduras cuyo hábitat lo constituyen árboles y arbustos, sin embargo no existen referencias sobre levaduras asociadas a las Zigofiláceas, una familia de matorrales preponderantes en la Provincia de Monte argentino. El objetivo de este trabajo fue conocer la biodiversidad de levaduras en suelos y canopias asociados con Bulnesia retama y Larrea divaricata, en los Médanos Grandes de Caucete, San Juan, Argentina. Sobre un total de 87 aislamientos de levaduras identificados, se observó una mayor diversidad taxonómica en las asociadas tanto al suelo como a la parte aérea de B. retama, respecto de L. divaricata. A partir de la canopia de B. retama y su suelo asociado se aislaron 9 y 10 especies de levaduras respectivamente, mientras que de la parte aérea y suelo de L. divaricata 4 y 3. Los géneros identificados fueron: Candida, Debaryomyces, Dekkera, Saccharomyces, Torulaspora, Sporidiobolus y Pichia. En total se encontraron 14 especies en todos los microambientes.

Bush like vegetation dominates arid environments, and there is nutrients accumulation under shrub canopies and relatively unfertile soils between vegetal patches areas. Plants are one of the most common habitats for yeasts. There are many reports about yeasts inhabiting different plant components. Nevertheless, there are no reports about yeasts associated with Zigophyllaceae, an important shrub family of the Argentinean Province of Monte. The objective of this work was to analyzed yeast biodiversity of Bulnesia retama and Larrea divaricata canopies and associated soils, at Médanos Grandes of Caucete, San Juan, Argentina. Eighty seven (87) isolated yeasts were identified. From B. retama canopy and associated soil was observed a larger taxonomical diversity respect to L. divaricata. Nine (9) and ten (10) species were isolated from canopy and associated soil of B. retama, respectively. From L. divaricata canopy were 4 species and 3 species from its associated soil isolated. Identified genera were: Candida, Debaryomyces, Dekkera, Saccharomyces, Torulaspora, Sporidiobolus and Pichia. Fourteen (14) species were found at all microenvironments.