Biomineralization of lithium nanoparticles by Li-resistant Pseudomonas rodhesiae isolated from the Atacama salt flat.

BACKGROUND: The Atacama salt flat is located in northern Chile, at 2300 m above sea level, and has a high concentration of lithium, being one of the main extraction sites in the world. The effect of lithium on microorganism communities inhabiting environments with high concentrations of this metal has been scarcely studied. A few works have studied the microorganisms present in lithium-rich salt flats (Uyuni and Hombre Muerto in Bolivia and Argentina, respectively). Nanocrystals formation through biological mineralization has been described as an alternative for microorganisms living in metal-rich environments to cope with metal ions. However, bacterial lithium biomineralization of lithium nanostructures has not been published to date. In the present work, we studied lithium-rich soils of the Atacama salt flat and reported for the first time the biological synthesis of Li nanoparticles. RESULTS:  Bacterial communities were evaluated and a high abundance of Cellulomonas, Arcticibacter, Mucilaginibacter, and Pseudomonas were determined. Three lithium resistant strains corresponding to Pseudomonas rodhesiae, Planomicrobium koreense, and Pseudomonas sp. were isolated (MIC > 700 mM). High levels of S2- were detected in the headspace of P. rodhesiae and Pseudomonas sp. cultures exposed to cysteine. Accordingly, biomineralization of lithium sulfide-containing nanomaterials was determined in P. rodhesiae exposed to lithium salts and cysteine. Transmission electron microscopy (TEM) analysis of ultrathin sections of P. rodhesiae cells biomineralizing lithium revealed the presence of nanometric materials. Lithium sulfide-containing nanomaterials were purified, and their size and shape determined by dynamic light scattering and TEM. Spherical nanoparticles with an average size < 40 nm and a hydrodynamic size ~ 44.62 nm were determined. CONCLUSIONS: We characterized the bacterial communities inhabiting Li-rich extreme environments and reported for the first time the biomineralization of Li-containing nanomaterials by Li-resistant bacteria. The biosynthesis method described in this report could be used to recover lithium from waste batteries and thus provide a solution to the accumulation of batteries.

Biomineralization of lithium nanoparticles by Li-resistant Pseudomonas rodhesiae isolated from the Atacama salt flat

BACKGROUND: The Atacama salt flat is located in northern Chile, at 2300 m above sea level, and has a high concentration of lithium, being one of the main extraction sites in the world. The effect of lithium on microorganism communities inhabiting environments with high concentrations of this metal has been scarcely studied. A few works have studied the microorganisms present in lithium-rich salt flats (Uyuni and Hombre Muerto in Bolivia and Argentina, respectively). Nanocrystals formation through biological mineralization has been described as an alternative for microorganisms living in metal-rich environments to cope with metal ions. However, bacterial lithium biomineralization of lithium nanostructures has not been published to date. In the present work, we studied lithium-rich soils of the Atacama salt flat and reported for the first time the biological synthesis of Li nanoparticles. RESULTS: Bacterial communities were evaluated and a high abundance of Cellulomonas, Arcticibacter, Mucilaginibacter, and Pseudomonas were determined. Three lithium resistant strains corresponding to Pseudomonas rodhesiae, Planomicrobium koreense, and Pseudomonas sp. were isolated (MIC > 700 mM). High levels of S2− were detected in the headspace of P. rodhesiae and Pseudomonas sp. cultures exposed to cysteine. Accordingly, biomineralization of lithium sulfide-containing nanomaterials was determined in P. rodhesiae exposed to lithium salts and cysteine. Transmission electron microscopy (TEM) analysis of ultrathin sections of P. rodhesiae cells biomineralizing lithium revealed the presence of nanometric materials. Lithium sulfide-containing nanomaterials were purified, and their size and shape determined by dynamic light scattering and TEM. Spherical nanoparticles with an average size < 40 nm and a hydro-dynamic size ~ 44.62 nm were determined. CONCLUSIONS: We characterized the bacterial communities inhabiting Li-rich extreme environments and reported for the first time the biomineralization of Li-containing nanomaterials by Li-resistant bacteria. The biosynthesis method described in this report could be used to recover lithium from waste batteries and thus provide a solution to the accumulation of batteries.

Computer-aided design of T-cell epitope-based vaccines: addressing population coverage.

Epitope-based vaccines (EVs) make use of short antigen-derived peptides corresponding to immune epitopes, which are administered to trigger a protective humoral and/or cellular immune response. EVs potentially allow for precise control over the immune response activation by focusing on the most relevant - immunogenic and conserved - antigen regions. Experimental screening of large sets of peptides is time-consuming and costly; therefore, in silico methods that facilitate T-cell epitope mapping of protein antigens are paramount for EV development. The prediction of T-cell epitopes focuses on the peptide presentation process by proteins encoded by the major histocompatibility complex (MHC). Because different MHCs have different specificities and T-cell epitope repertoires, individuals are likely to respond to a different set of peptides from a given pathogen in genetically heterogeneous human populations. In addition, protective immune responses are only expected if T-cell epitopes are restricted by MHC proteins expressed at high frequencies in the target population. Therefore, without careful consideration of the specificity and prevalence of the MHC proteins, EVs could fail to adequately cover the target population. This article reviews state-of-the-art algorithms and computational tools to guide EV design through all the stages of the process: epitope prediction, epitope selection and vaccine assembly, while optimizing vaccine immunogenicity and coping with genetic variation in humans and pathogens.

Maestro de la psiquiatría chilena: entrevista con Fernando Oyarzún / Master of Chilean psychiatry: an interview with Fernando Oyarzún

El Dr. Fernando Oyarzún es Maestro de la Psiquiatría Chilena y ha dedicado su carrera académica al desarrollo de un enfoque clínico-antropológico en psiquiatría. Desde su perspectiva elaboró una "idea médica de la persona', la que promueve la personalización del acto médico en psiquiatría y medicina. Método: En una entrevista personal este trabajo describe los logros profesionales del Dr.Oyarzún y sus concepciones clínicas-antropológicas. Conclusión: El legado intelectual del Dr. Oyarzún va más allá del campo de la medicina, conformando una perspectiva original de las relaciones humanas.

Dr. Fernando Oyarzún is a Master of Chilean Psychiatry, who has devoted his academic career to the development of a clinical-anthropologic approach in psychiatry. From this perspective, he elaborated a "medical idea of the person", which promote the personalization of medical act in psychiatry and medicine. Method: In a personal interview, this paper describe Dr. Oyarzún s professional achievements and his clinical-anthropologic conceptions. Conclusion: Dr. Oyarzún’s intellectual legacy goes beyond the medicine field, conforming an original perspective of human relationships.

Impacto de la eclampsia en la morbimortalidad materna y perinatal / Impact of the eclampsia in maternal and perinatal morbimortality

Objetivo: Determinan la incidencia de la eclampsia y evaluar su impacto sobre la morbilídad y mortalidad materna y perinatal. Material y método: Se realizó un estudio retrospectivo desde 1988 a 1998 en el hospital Guillermo Grant Benavente Concepción, Chile. Se analizaron 117 pacientes con eclampsia y sus recién nacidos, incluidos 6 gemelares, fueron excluidas de este estudio todas las pacientes con convulsiones no eclámpticas, el análisis estadístico se efectuó mediante la obtención de promedios, medianas y tasas. Resultados: La incidencia fue de 0.17 por ciento La mayoría de las pacientes eran primigestas (76 por ciento) y el 45,3 por ciento adolescentes El 82 por ciento tuvieron control prenatal. Los signos más frecuentes de eclampsia fueron aumento de los reflejos osteotendinosos 50,4 por ciento, cefalea 37,6 por ciento y vómitos 11,1 por ciento. El promedio de la presión arterial fue de 206/110 mmHg. El 68,4 por ciento convulsionó durante la gestación, 5,1 por ciento intraparto y 9,4 por ciento postparto. Los pacientes tuvieron un promedio de 2,4 convulsiones. La mayoría (82,9 por ciento) recibió terapia medicamentosa con sulfato de magnesio, Las patologías asociadas más frecuentemente fueron parto prematuro (34,2 por ciento), retardo del crecimiento intrauterino (25,2 por ciento) y DPPNI (5,2 por ciento). La cesárea se presentó en el 87,2 por ciento de los casos. Las complicaciones multisistémicas ocurrieron principalmente en los territorios cardiorespiratorio 19,7 por ciento, neurológico 13.7 por ciento, hematológico 11.1 por ciento y renal 2,6 por ciento. El 34,2 por ciento de los recién nacidos presentó asfixia al nacer, el 43,9 por ciento eran prematuros y el 25,2 por ciento presentó RCIU. Hubo 8 muertes maternas (6,8 por ciento) por complicaciones multisistémicas. La tasa de mortalidad materna fue de 1,17x 10.000 Nacidos Vivos (N.V), la tasa de mortalidad fetal tardía de 1,32 x 10.000 N.V (9 casos) y la neonatal precoz de 0,44 x 10.000 N.V (3 casos). La mortalidad perinatal fue de 1,76 X 10.000 N.V. Conclusión: La eclampsia tiene un impacto negativo en la morbimortalidad materna y perinatal (AU)

A Novel Population of Phytophthora, Similar to P. infestans, Attacks Wild Solanum Species in Ecuador.

ABSTRACT Twenty-six isolates of a Phytophthora population from two wild solanaceous species, Solanum tetrapetalum (n 11) and S. brevifolium (n = 15), were characterized morphologically, with genetic and phenotypic markers, and for pathogenicity on potato and tomato. Based on morphology, ribosomal internal transcribed spacer region 2 (ITS2) sequence, and pathogenicity, all isolates closely resembled P. infestans and were tentatively placed in that species. Nonetheless, this population of Phytophthora is novel. Its primary host is neither potato nor tomato, and all isolates had three restriction fragment length polymorphism (RFLP) bands (probe RG57) and a mitochondrial DNA haplotype that have not been reported for P. infestans. All the isolates were the A2 mating type when tested with a P. infestans A1 isolate. The A2 mating type has not been found among isolates of P. infestans from potato or tomato in Ecuador. Geographical substructing of the Ecuadorian A2 population was detected. The three isolates from the village of Nono, identical to the others in all other aspects, differed by three RFLP bands; those from Nono lacked bands 10 and 16, but possessed band 19. Most of the Ecuadorian A2 isolates were nonpathogenic on potato and tomato, but a few caused very small lesions with sparse sporulation on necrotic tissue. Cluster analysis of multilocus genotypes (RFLP, mating type, and two allozymes) dissociated this A2 population from genotypes representing clonally propagated populations of P. infestans worldwide. The current hypotheses for the historical global movements of P. infestans do not satisfactorily explain the origin or possible time of introduction into Ecuador of this A2 population. Assuming the population is P. infestans, its presence in Ecuador suggests either a hitherto unreported migration of the pathogen or an indigenous population that had not previously been detected.

Salmonellosis y fístula bilio-cutánea / Bilio-cutaneous fistula and salmonellosis

Se describe el caso de una paciente de 52 años que en 1987 tuvo una fiebre tifoidea demostrada bacteriológicamente (hemocultivos positivos a salmonella parathyphy B) y tratada con cloramfenicol por 10 días. En 1989 es atendida por una colección purulenta localizada en la pared abdominal cercana a la vesícula biliar, la que se drena quirúrgicamente, pero queda con una fístula cutánea que exuda un líquido purulento verdoso. En 1994 se efectúa una ecotomografía y una fistulografía que demuestran una vesícula litiástica, escleroatrófica y una fístula bilio-cutánea que se resecan. El cultivo de la secreción purulenta demostró la existencia de una salmonella parathyphy C similar a la detectada en el cuadro original tratado 7 años antes. Desde 1994 a la fecha la paciente esta sana y sin fístula

Host Specificity of Phytophthora infestans on Tomato and Potato in Ecuador.

ABSTRACT Sixty Ecuadorian isolates of Phytophthora infestans from potato and 60 isolates from tomato were compared for dilocus allozyme genotype, mitochondrial DNA haplotype, mating type, and specific virulence on 11 potato R-gene differential plants and four tomato cultivars, two of which contained different Ph genes. Restriction fragment length polymorphism (RFLP) fingerprints of subsamples of isolates from each host were compared by using RG57 as the probe. All potato isolates had the allozyme genotype, haplotype, and mating type of the clonal lineage EC-1, which had been previously described in Ecuador. With the same markers, only one isolate from tomato was classified as EC-1; all others belonged to the globally distributed US-1 clonal lineage. RFLP fingerprints of isolate subsets corroborated this clonal lineage classification. Specific virulence on potato differentials was broadest among potato isolates, while specific virulence on tomato cultivars was broadest among tomato isolates. Some tomato isolates infected all tomato differentials but no potato differentials, indicating that specific virulence for the two hosts is probably controlled by different avirulence genes in P. infestans. In two separate experiments, the diameters of lesions caused by nine isolates from potato and 10 from tomato were compared on three tomato and three potato cultivars. All isolates produced larger lesions on the host from which they were isolated. No isolates were found that were highly aggressive on both tomato and potato. We conclude that there are two different populations of P. infestans in Ecuador and that they are separated by host.

Comparison of Soil Receptivity to Thielaviopsis basicola, Aphanomyces euteiches, and Fusarium solani f. sp. pisi Causing Root Rot in Pea.

ABSTRACT Soil receptivity as a quantifiable characteristic ranging from conduciveness to suppressiveness to soilborne pea pathogens Thielaviopsis basicola and Aphanomyces euteiches was determined by analysis of differences in disease response curves obtained by artificial introduction of inoculum into natural field soil samples. Several parameters, including maximum root rot severity, the area under the health index curve, scores on the first axis of a principal component analysis (PCA) on dose responses, and Weibull model fitting were used to describe the disease responses. In all cases, the Weibull model gave satisfactory fits. PCA yielded a first axis that comprised 86% of the variance found when using Weibull predicted responses for T. basicola and 74% of the variance found for A. euteiches. This PCA axis essentially represented the average increase in disease severity due to the addition of increasing doses of inoculum to the soil. The Weibull scale parameter B, which represents the amount of inoculum necessary to increase root rot severity by 63% with respect to the level caused by pathogens naturally present in the soil, is another means of quantifying the receptivity of soils to these plant pathogens. Weibull parameter B, maximum root rot severity, the areaunder the health index curve, and the scores on the first PCA axis were strongly correlated for each of the pathogens tested individually. To compare the extent and behavior of soil receptivity responses to different pathogens, Weibull parameters B and C (slope at dose B) were chosen because of their universal definition, in contrast to PCA scores. Comparison of the average levels of Weibull parameters B and C indicated significant differences between the pathogens. Yet, no significant similarity in the ranking of the soils was found for the three pathogens, demonstrating that individual soils may interact with different pathogens in totally different ways. In general, soils were suppressive to T. basicola but conducive to A. euteiches, whereas their response to Fusarium solani f. sp. pisi ranged from conducive to suppressive. Therefore, risk assessment of soils prior to planting may require different strategies for each pathogen. Bioassays with soil samples taken before the last pea crop in 1987 and 1991 revealed a significant increase in the natural inoculum potential of soils that mainly was accounted for by A. euteiches and Pythium spp. These results strongly indicate that A. euteiches must be considered one of the most threatening pathogens to pea crops in the Netherlands.

First Report of Phytophthora infestans A2 Mating Type in Ecuador.

The tropical highlands of Ecuador are a genetic center for several Solanaceous species, including potato. In 1995 and 1996, severe late blight epidemics occurred in wild Solanum species, e.g., Solanum brevifolium, growing in the transitional area between the highlands and the coastal tropical lowlands near the city of Quito. Sixteen isolates of Phytophthora infestans were collected in 1995 and 36 isolates in 1996. Of these, three from 1995 and four from 1996 were A2 mating type. Extensive and systematic sampling of commercial potato and tomato in Ecuador have failed to reveal the presence of the A2 mating type (G. A. Forbes, X. M. Escobar, C. C. Ayala, J. Revelo, M. E. Ordoñez, B. A. Fry, K. Doucet, and W. E. Fry, Phytopathology, in press.). Apparently the A2 mating type reported for the first time in Ecuador is only associated with wild Solanaceous spp. Further research is required to determine the consequences of this event for management of late blight in both potato and tomato, two important field crops in the Andean highlands.

Síndrome de dolor lumbar y depresión / Low-back pain syndrome and depression

El síndrome de dolor lumbar (SDL) corresponde a un grupo heterogéneo de cuadros clínicos de diversa etiología que representa un problema creciente tanto a nivel médico como laboral. Se ha establecido alguna asociación entre dolor prolongado y manifestaciones depresivas. En este trabajo retrospectivo se estudió la prevalencia y factores pronósticos de la depresión mayor en un grupo de 335 pacientes con SDL derivados al Servicio de Salud Mental entre los años 1987-1989. La prevalencia de depresión mayor fue 14,3%. Las mujeres constituyeron el 35,4%de la muestra, cifra mayor a la de la población total de pacientes (p < 0,01). Los pacientes con depresión mayor fueron atendidos durante 5,2 meses, recibiendo un promedio de 8 consultas. A todos se les administró psicofármacos. El 31,3 fue derivado después de 6 meses de evolución del SDL. Evolucionó satisfactoriamente el 55,8. La única variable que influyó significativamente en la evolución fue la edad en los varones

Photosynthesis and stomatal conductance of potato leaves-effects of leaf age, irradiance, and leaf water potential.

Potatoes (Solanum tuberosum L., cv. Bintje) were grown in a naturally lit glasshouse. Laboratory measurements on leaves at three insertion levels showed a decline with leaf age in photosynthetic capacity and in stomatal conductance at near saturating irradiance. Conductance declined somewhat more with age than photosynthesis, resulting in a smaller internal CO2 concentration in older relative to younger leaves. Leaves with different insertion number behaved similarly. The changes in photosynthesis rate and in nitrogen content with leaf age were closely correlated. When PAR exceeded circa 100 W m(-2) the rate of photosynthesis and stomatal conductance changed proportionally as indicated by a constant internal CO2 concentration. The photosynthesis-irradiance data were fitted to an asymptotic exponential model. The parameters of the model are AMAX, the rate of photosynthesis at infinite irradiance, and EFF, the slope at low light levels. AMAX declined strongly with leaf age, as did EFF, but to a smaller extent. During drought stress photosynthetic capacity declined directly with decreasing water potential (range -0.6 to -1.1 MPa). Initially, stomatal conductance declined faster than photosynthetic capacity.