Cultivo y crecimiento de dos especies de diatomeas bentónicas aisladas del Salar del Huasco (Norte de Chile, 20° S) a diferentes condiciones de temperatura, luz y nutrientes

Benthic diatoms are cultured usually under laboratory conditions to be used as a food source for other organisms, ofaquaculture interest or for biotechnological applications. Laboratory experiments demonstrate the incidence of the physicaland chemical variables on abundance and growth rates of diatoms. While macronutrients are usually selected and dosed intocommon culture mediums to meet the general requirements of a wide range of diatoms, the availability and optimizationof micronutrients are more susceptible to each organism’s particular physiological conditions. The aim of this study was tocharacterize the growth of two species of benthic diatoms isolated from the Salar de Huasco in batch cultures at differentconditions of temperature (10, 15 and 20 °C), light intensity (40, 80 and 120 ?mol m-2 s-1) and concentrations of silica (1.06x 10-4 M Na2SiO3 x 9H2O and 2.12 x 10-4 M Na2SiO3 x 9H2O) and selenium (10-8 M H2SeO3) in f/2 medium, on a lightdarkcycle of 18:6 h. Both Nitzschia epithemioides Grunow in Cleve & Grunow (1880) as Nitzschia sp. showed highermaximum cell densities (692800 ± 107704 and 649600 ± 68942 cells ml-1, respectively) and exponential growth rates(1.80±0.56 and 0.97±0.32 div. d-1, respectively) at the highest temperature (20°C). The light intensity to which the cultureswere exposed had no effect on cell density and exponential growth rate in both taxa. Regarding to nutrients, an increasein silicates concentrations on the culture medium could promote the growth of N. epithemioides and Nitzschia sp. since atendency was observed to higher cell densities (1.08 x 106 ± 84,639 and 1.32 x 106 ± 109,038 cells ml-1, respectively) andexponential growth rates (1.98 ± 0.44 and 0.95 ± 0.18 div. d-1, respectively) with respect at the normal f/2 medium and f/2medium plus selenium. Simultaneous addition of silicate and selenium to the culture medium increased the maximum celldensity of the two strains under study, but this increase was significant (p = 0.05) only for N. epithemioides and amongthe normal f/2 medium (719200 ± 116895 cells ml-1) and the f/2 medium with double the amount of silicate and selenium(1498800 ± 209599 cells ml-1). However, the exponential growth rates were not significantly different when comparedto those of the control (without the addition of silicate and selenium). In conclusion both N. epithemioides and Nitzschiasp shown an increased cell density and exponential growth rate at 20 °C. The different light intensities not significantlyinfluenced the growth of both taxa. An increase in the concentration of silicates or simultaneous increase in silicatesand selenium in the culture medium can be considered as possible strategy to increase cell density of benthic diatom N.epithemioides in batch cultures.de alimento de otros organismos de interés acuícola o para aplicaciones biotecnológicas. Experimentos de laboratoriodemuestran la incidencia de las variables físicas y químicas sobre la abundancia y tasas de crecimiento de las diatomeas.Mientras los macronutrientes están generalmente seleccionados y dosificados en los medios de cultivo más comunespara satisfacer los requerimientos generales de un amplio rango de diatomeas, la disponibilidad y optimización demicronutrientes son más susceptibles a las condiciones fisiológicas particulares de cada organismo. El objetivo de esteestudio fue caracterizar el crecimiento de dos especies de diatomeas bentónicas aisladas del Salar de Huasco en cultivostipo batch, a diferentes condiciones de temperatura (10, 15 y 20 °C), intensidad de la luz (40, 80 y 120 ?mol m-2 s-1), y concentraciones de sílice (1.06 x 10-4 M Na2SiO3 x 9H2O y 2.12 x 10-4 M Na2SiO3 x 9H2O) y selenio (10-8 M H2SeO3)en medio f/2, a un ciclo 18:6 h luz-oscuridad. Tanto Nitzschia epithemioides Grunow in Cleve & Grunow (1880) comoNitzschia sp, exhibieron las mayores densidades celulares máximas (692800 ± 107704 y 649600 ± 68942 células mL-1,respectivamente) y tasas de crecimiento exponencial (1,80 ± 0,56 y 0,97 ± 0,32 div. d-1, respectivamente) a la temperaturamás elevada (20 °C). La intensidad de luz a la cual los cultivos fueron expuestos no afectó la densidad celular y tasa decrecimiento exponencial en ambos taxa. En cuanto a los nutrientes, un incremento en la concentración de silicatos en elmedio de cultivo, podría favorecer el crecimiento de N. epithemioides y Nitzschia sp. ya que se observó una tendenciaal aumento en la densidad celular (1,08 x 106 ± 84.639 y 1,32 x 106 ± 109.038 células mL-1, respectivamente) y tasa decrecimiento exponencial (1,98 ± 0,44 y 0,95 ± 0,18 div. d-1, respectivamente) con respecto a los medios f/2 normal y f/2más selenio. La adición simultanea de silicato y selenio al medio de cultivo aumentó las densidades celulares máximas delas dos cepas bajo estudio, pero este aumento fue significativo (p = 0,05) sólo para N. epithemioides y entre los medios decultivo f/2 normal (719200 ± 116895 células mL?1) y medio f/2 con el doble de silicato y selenio (1498800 ± 209599 célulasmL-1). Sin embargo, las tasas de crecimiento exponencial no tuvieron diferencias significativas con el control (sin adiciónde silicato y selenio). En conclusión tanto N. epithemioides y Nitzschia sp. muestran un aumento en la densidad celular yla tasa de crecimiento exponencial a 20 °C. Las diferentes intensidades de luz evaluadas no influyeron significativamenteen el crecimiento de ambos taxa. Un aumento en la concentración de silicatos o aumento simultáneo de silicatos y selenioen el medio de cultivo puede ser considerado como posible estrategia para incrementar la densidad celular de la diatomeabentónica N. epithemioides en cultivos discontinuos

Caracterización ultraestructural y molecular de cepas de Tetraselmis (Chlorodendrophyceae, Chlorophyta) aisladas de Chile

Species of the genus Tetraselmis (Chlorodendrophyceae, Chlorophyta) have traditionally been used in aquaculture facilities as food forlarval varieties of marine organisms. Recently, some strains with high lipid content have been considered as having potential for biofuelproduction. Although many Tetraselmis species are relatively well-characterized using light and electron microscopical methods,there are still taxonomic ambiguities among the species. DNA sequence analysis, which provides a reliable and more convenient toolfor species delimitation, has been poorly used in Tetraselmis. In this study, three strains of Tetraselmis, isolated from coastal Chileanwaters, have been characterized using an integrative approach (light and electron microscopy, molecular phylogeny of ITS, includingsecondary structure analysis). According to the pyrenoid ultrastructure of the strains investigated two of them (from Dichato andColiumo) belong to the subgenus Parviselmis, while the Caldera strain corresponds to the subgenus Tetrathele. Even though it was notpossible to identify the strains at species level, it was clearly demonstrated by phylogenetic analyses of ITS-1 and ITS-2 sequencesand by ITS-2 secondary structure that the Dichato and Coliumo strains are the same species, and could belong either to T. suecica or T.chui. However, the Caldera strain might correspond to an undescribed species. As our study has shown, the genus Tetraselmis needs tobe taxonomically revised using an integrative approach, which includes the investigations of authentic strains of this genus.Especies del género Tetraselmis (Chlorodendrophyceae, Chlorophyta) han sido tradicionalmente usadas en centros acuícolas comoalimento para larvas de una variedad de organismos marinos. Adicionalmente, algunas cepas con alto contenido de lípidos hansido recientemente consideradas como fuente potencial para la producción de biodiesel. Aunque muchas especies de Tetraselmis seencuentran morfológica y ultraestructuralmente bien caracterizadas, todavía hay ambigüedades taxonómicas al interior del género. Elanálisis de secuencias de ADN, una herramienta complementaria y conveniente para delimitar especies, ha sido pobremente utilizadoen Tetraselmis. En este estudio, se caracterizaron tres cepas de Tetraselmis, aisladas de aguas costeras chilenas, utilizando un enfoqueintegrativo (morfología, ultraestructura y filogenia molecular). Basado en la ultraestructura del pirenoide de las cepas estudiadas,dos de ellas (Dichato y Coliumo) pertenecen al subgénero Parviselmis, mientras que la cepa de Caldera corresponde al subgéneroTetrathele. Aunque no fue posible identificar las cepas a nivel específico, el análisis filogenético de las secuencias ITS-1 e ITS-2y la estructura secundaria del ITS-2 demostraron claramente que las cepas de Dichato y Coliumo son la misma especie, y podríanpertenecer a T. suecica o a T. chui, mientras que la cepa de Caldera podría corresponder a una especie no descrita aún para la ciencia.Los resultados obtenidos demuestran la necesidad de llevar a cabo una revisión taxonómica del género Tetraselmis, utilizando unenfoque integrativo, el cual incluya las cepas auténticas de las especies

Callus induction and plant regeneration of Ulex europaeus

Abstract A callus induction and plant regeneration protocol was developed from leaf and thorn explants for the plant Ulex europaeus . Explants were incubated on 2% sucrose half-strength Murashige and Skoog Medium (MS) with various combinations of plant growth regulators and antioxidants. The best frequency of callus and shoot formation was obtained with 2,4-dichlorophenoxyacetic acid (2,4-D) 1 mg/l x kinetin (Kin) 0.2 mg/l (DK Medium; callus induction) and zeatin (Z) 1 mg/l (DK medium; shoot induction). Both media were supplemented with ascorbic acid 200 mg/l to prevent browning and death of the explants. The regenerated shoots transferred to rooting medium (half-strength MS Medium, 2% sucrose) showed rapid growth and development of roots (100%). Rooted plantlets were successfully transferred to soil in pots containing a 3:1 mixture of soil and vermiculite

Formulation of an equation to predict fat mass using bioelectrical impedance in adults in a wide range of ages and body mass index Formulación de una ecuación para predecir la masa grasa corporal a partir de bioimpedanciometría en adultos en un amplio ran

Background: Bioelectrical impedance (BIA) has a good correlation and agreement with reference techniques, such as dual energy X-ray absorptiometry (DEXA), to assess body composition. Aim: To develop and assess the concordance of an equation to predict body fat mass derived from anthropometric data, gender, age and resistance obtained from bioelectrical impedance in adults, using DEXA as the reference method. Patients and Methods: Cross-sectional study of 62 women and 59 men aged 18 to 64 years with a body mass index ranging from 18.5 to 34.8 kg/ m 2. The equation was constructed using a predictive statistical model, considering sex, age, weight, resistance index (height 2(cm)/ resistance (ohms)), as independent variables, and fat mass as the dependent variable. Results: The R 2 of the regression model was 0.96, and the standard error of estimation was 2.58 kg (p < 0.001). When comparing with DEXA, no significant differences were observed for the estimation of FM, between the equation

Extubocellulus spinifer (Hargraves & Guillard) Hasle, Stosch & Syvertsen (Cymatosiraceae, Bacillariophyceae): First report of the species from the Southeastern Pacific with comments on the variability of some of its morphological features Extubocellulus spinifer (Hargraves & Guillard) Hasle, Stosch & Syvertsen, (Cymatosiraceae, Bacillariophyceae): Primera cita para el Pacífico Suroriental, con comentarios acerca de la variabilidad de algunas de sus características morfológicas

During the taxonomic analysis of strains from marine phytoplankton samples, it was found that a sample contained isolated or short chains of 2-4 small cells. Observations under the electron microscopes revealed the presence of Extubocellulus spinifer (Hargraves & Guillard) Hasle, Stosch & Syvertsen, a minute species until now not reported for the Southeastern Pacific Ocean. In this paper we describe the characteristics of the Chilean cells, comment on the variability of some of its morphological features, and discuss about the differences between the two known species of the genus.Durante el análisis de cepas provenientes de muestras de fitoplancton marino se observó que una de ellas contenía células muy pequeñas, aisladas o formando cortas cadenas de 2-4 individuos. Observaciones realizadas con microscopía electrónica revelaron la presencia de Extubocellulus spinifer (Hargraves & Guillard) Hasle, Stosch & Syvertsen, una diminuta especie no señalada hasta ahora para el Pacífico Suroriental. En el presente trabajo se describen las características de las células chilenas, se comenta acerca de la variabilidad de algunas de sus características morfológicas, y se discute sobre las diferencias entre las dos especies conocidas del género

Diversidad taxonómica de microalgas en cuerpos dulceacuícolas someros y acidófilos del sur de Chile

This research is the first taxonomic approach about the microalgae inhabiting shallow acidophilus freshwater bodies (Chapito pool, “small dam” and Tepual stream) within the Katalapi Park, X Region, Chile. A total of 80 taxa were identified based on morphocytological attributes, being the Streptophyta-Zygnematophyceae the most abundant group with a dominance of Desmidiaceae (47 species), follow by Cyanobacteria (14), Euglenophyceae (12), Chlorophyta-Chlorophyceae (5), and Dinophyceae and Ochrophyta-Raphidophyceae with one taxon each group. The genera with the higher number of species were Cosmarium (12), Closterium (11) and Staurastrum (8). The pH ranged from 5.0 to 6.1 during the recollection period. Most of the desmids species identified (70.2 %) are from acidophilus environments, 48.6 % are indicators of mesotrophy and 21.6% of meso-oligotrophic habitats. Twenty-four species are cited for the first time for Chile. Although the study was restricted to a relatively small area, the results suggest that a great diversity of microalgae might be also found in similar ecological areas within the country.Esta investigación es el primer aporte taxonómico sobre las microalgas que habitan en cuerpos de agua acidófilos, someros (Laguna Chapito, “pequeño tranque” y estero Tepual) al interior del Parque Katalapi, X Región, Chile. Se identificó un total de 80 taxa basado en atributos morfocitológicos, siendo el grupo Streptophyta-Zygnematophyceae el más abundante con dominancia de Desmidiaceae (47 especies), seguido por Cyanobacteria (14), Euglenophyceae (12), Chlorophyta-Chlorophyceae (5), y Dinophyceae y Ochrophyta- Raphidophyceae con un taxón cada grupo. Los géneros con el mayor número de especies fueron Cosmarium (12), Closterium (11) y Staurastrum (8). El rango de pH durante el periodo de recolección fluctuó entre 5,0 a 6,1. La mayoría de las especies de desmidiaceas identificadas (70,2 %) son de ambientes acidófilos, el 48,6 % son indicadoras de mesotrofía y el 21,6% de hábitats meso-oligotróficos. Veinticuatro especies se citan por primera vez para Chile. Aunque el estudio estuvo restringido a un área relativamente pequeña, los resultados sugieren la potencialidad de encontrar una gran diversidad de microalgas en áreas ecológicas similares en el país

The growth, toxicity and genetic characterization of seven strains of Alexandrium catenella (Whedon and Kofoid) Balech 1985 (Dinophyceae) isolated during the 2009 summer outbreak in southern Chile

The dinoflagellate Alexandrium catenella causes recurrent harmful algal blooms in southern Chile. This species belongs to the “Alexandrium tamarense/catenella/fundyense species complex” (the “tamarensis complex”), defined by morphological attributes. Ribosomal sequences serve to differentiate five evolutionary lineages (clades) in this species complex. These distinctions reflect the geographic distribution and toxicity of the populations rather than their morphological designations. Despite the social and economic impact that harmful blooms produce in Chile, few strains of A. catenella have been isolated. Moreover, physiological and/or genetic studies of the group are scarce. The aim of this work was to examine possible physiological and genetic variability among populations of A. catenella having different geographical origins but isolated from the same toxic event. Seven strains of A. catenella were isolated and established from phytoplankton samples collected in the Aysén and Los Lagos regions of southern Chile during a recent outbreak (February–March 2009). Growth, toxicity, and ITS sequences were compared among these strains. All the strains included in this study were grouped with strains belonging to the previously described “North America” clade. The genetic diversity detected among Chilean strains was 3%, a much higher value than those reported for comparisons among strains from other parts of the world. In addition, a remarkable variability of growth parameters and toxicity was detected among strains. Strain PFB45 showed the highest PSP toxin content, whereas strain PFB41 had the lowest value of this parameter but had the highest maximum cell density. In strains PFB38, PFB42, and PFB37, more than 98% of the total PSP toxin content occurred in the form of gonyautoxins (primarily GTX-4,1 and GTX-3,2). In strains PFB39, PFB36, and PFB45, neoSTX, and STX toxins were detected. These results demonstrated remarkable variability at the genetic and physiological level among strains of A. catenella isolated from the same outbreak. No correlations were found between the phenotypic traits (growth and toxicity) and the genetic affiliation of the strains studied.Versión del editor3,083