Many phototrophic flagellates ingest prokaryotes. This mixotrophic trait becomes a critical aspect of the microbial loop in planktonic food webs because of the typical high abundance of these flagellates. Our knowledge of their selective feeding upon different groups of prokaryotes, particularly under field conditions, is still quite limited. In this study, we investigated the feeding behavior of three species (Rhodomonas sp., Cryptomonas ovata, and Dinobryon cylindricum) via their food vacuole content in field populations of a high mountain lake. We used the catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) protocol with probes specific for the domain Archaea and three groups of Eubacteria: Betaproteobacteria, Actinobacteria, and Cytophaga-Flavobacteria of Bacteroidetes. Our results provide field evidence that contrasting selective feeding exists between coexisting mixotrophic flagellates under the same environmental conditions and that some prokaryotic groups may be preferentially impacted by phagotrophic pressure in aquatic microbial food webs. In our study, Archaea were the preferred prey, chiefly in the case of Rhodomonas sp., which rarely fed on any other prokaryotic group. In general, prey selection did not relate to prey size among the grazed groups. However, Actinobacteria, which were clearly avoided, mostly showed a size of Ͻ0.5 m, markedly smaller than cells from the other groups.IMPORTANCE That mixotrophic flagellates are not randomly feeding in the main prokaryotic groups under field conditions is a pioneer finding in species-specific behavior that paves the way for future studies according to this new paradigm. The particular case that Archaea were preferentially affected in the situation studied shows that phagotrophic pressure cannot be disregarded when considering the distribution of this group in freshwater oligotrophic systems.KEYWORDS Archaea, mixotrophic protist, selective feeding M ixotrophic behavior, the combination of phototrophic and phagotrophic nutritional modes within a single cell, has been increasingly documented in aquatic systems (1, 2). Phagotrophy occurs in a variety of phytoplankton flagellate groups, including Chrysophyceae, dinoflagellates, prymnesiophytes, and cryptophytes, which comprise some picoeukaryotes (3-5). Currently, there is no doubt of the ubiquity of mixotrophy and its significance in the functioning of planktonic systems. Under oligotrophic conditions, phototrophic flagellates can account for up to 80% of total bacterial grazing (4,6,7).Predation by protists is among the primary mortality factors of prokaryotes in planktonic communities and thus is an important selective pressure. It becomes a structuring factor of the abundance, morphology, composition, and activity of bacterial assemblages (8, 9). The impact of protist predation appears to be modulated by the characteristics of the system (e.g., productivity) and predator and prey traits (10). Over

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Wastewater from the leather tannery industry contains high concentrations of heavy metals, especially chromium, as well as high values of inorganic nutrients and organic matter which, if not treated prior to discharge, may alter the quality of surface water bodies. As an alternative treatment to these industrial effluents, we propose the use of microalgae, due to their ability to remove contaminants. This study evaluates the growth of the microalga Scenedesmus sp. in three different dilutions of wastewater (20%, 50%, and 100%) at a tannery in Bogotá, Colombia, for a period of 15 days. We assess the removal of hexavalent chromium, nutrients (nitrites, nitrates, phosphates and sulfates), and Biochemical Oxygen Dilution (BOD). Results indicate a growth of Scenedesmus proportional to the dilution of the effluent, with greater biomass in undiluted wastewater. This biomass achieved the removal of Cr+6 (>98%), nitrates (>90%) and phosphates (>99%), and BOD (>88%) which can be attributed to a shared microalgae-bacteria effect. Thus, we conclude that the microalgae Scenedesmus sp. Used the waste effluent as a growth substrate, improving its effect during a phycoremediation process.Keywords: Phycoremediation, Scenedesmus, Tanneries, Chromium. ResumenLas aguas residuales de la industria del curtido de pieles (curtiembres) presentan elevadas concentraciones de metales pesados, especialmente de cromo, así como altos valores de nutrientes inorgánicos y materia orgánica, que de no ser tratados previa a su descarga puede alterar la calidad de los cuerpos de agua superficiales. Como un tratamiento alternativo a estos efluentes industriales, se propone el uso de microalgas, debido a su capacidad de remoción de contaminantes. En el presente trabajo se evaluó el crecimiento de la microalga Scenedesmus sp. en tres diluciones diferentes de una agua residual (20%, 50% y 100%) de una Curtiembres del Barrio San Benito de la ciudad de Bogotá, por un periodo de 15 días, valorando la remoción de cromo hexavalente (Cr+6), nutrientes (nitritos, nitratos, fosfatos y sulfatos) y reducción de la demanda bioquímica de oxigeno (DBO). Como resultado se obtuvo un crecimiento de Scenedesmus que proporcional a la dilución del efluente, con mayor obtención de biomasa en el agua residual sin diluir. Esta biomasa redujo la concentración de Cr+6 (>98%) así como los nitratos (>90%) y fosfatos (>99%) los cuales pudieron ser tomados por la microalga para su crecimiento, pero adicionalmente se observó una reducción de nitritos (>98%), sulfatos (>92%) y DBO (>88%) que puede ser atribuible a un efecto compartido microalga-bacteria. De esta forma se puede concluir que la microalga utilizo el efluente residual como un sustrato de crecimiento, mejorando la calidad del mismo en un proceso de ficorremediación.

Reliable results for the determination of trace elements in urban and industrial wastewaters are of paramount importance for both checking the performance of sewage treatment and for detecting possible urban or industrial contamination sources. The quality control of measurements should in principle rely on external tools such as certified reference materials (CRM), which should represent, as closely as possible, the matrix of samples currently analysed, e.g., in the frame of environmental monitoring. To date, however, no CRM representatives of wastewater composition are available, which limits the possibility for control laboratories to check their QC externally. To fill this gap, the European Commission's Standards, Measurements and Testing Programme (formerly BCR) has started a European collaborative project of which the aim is to test the feasibility of preparation of wastewater reference materials and the analytical state-of-the-art to enable the certification of trace elements in such matrices. This paper presents the results of the first phase of this project, namely the feasibility study and the results of an interlaboratory trial.

Las aguas residuales de curtiembres conllevan un problema ambiental y de salud, debido a las altas concentraciones de contaminantes como el cromo, sulfuros, entre otros. Una forma de realizar el tratamiento de estas aguas es por medio del uso de microorganismos tales como las microalgas, debido a su capacidad de utilizar los compuestos inorgánicos y acumular metales y otras sustancias contaminantes. Esta capacidad podría verse magnificada con la inmovilización celular en diferentes matrices. En este artículo se presenta una evaluación de la capacidad de crecimiento y de remoción de nitrógeno, fósforo y cromo por parte de la microalga Scenedesmus sp., comparando la eficiencia entre las células libres e inmovilizadas en una matriz de esponja de Luffa. De esta manera, se obtuvo un mayor crecimiento en las células libres en comparación a las inmovilizadas, aunque sin diferencias significativas entre ambos experimentos. En ambos casos se observaron remociones superiores al 90% para NO–3 , NH+4, PO34 y cromo total, así como una reducción importante de la DBO y DQO (> 97 %) que puede deberse a efecto sinérgico con las bacterias presentes en los cultivos de la microalga. Finalmente, los porcentajes de lípidos en ambos casos fueron superiores al 20% indicando que esta biomasa podría presentar un alto potencial como materia prima para la generación de biodiesel.

This paper presents a mathematical model validated with experimental data for the analysis of biodiesel production from microalgae biomass, using as an alternative substrate industrial wastewater. System dynamics methodology was used for its development, by which the mathematical model representing the production of biomass and lipids was obtained, as well as the generation of biodiesel from microalgae oil. Biomass generation was represented by a basic growth model which assumes that there is no restriction for nutrients. This biomass generates a quantity of lipids according to the nitrogen-phosphorus ratio present in the industrial effluent, with higher production under low nitrogen concentration. Finally, these lipids are transformed into an amount of fatty acid methyl-ester that varies at a rate of transesterification. Validation and calibration of model behavior, was performed with experimental data obtained in tests of the Scenedesmus sp. microalgae growth in wastewater from the textile and tanning industry. The simulation of the model represented with significant approximation the growth and the generation of lipids for Scenedesmus sp. Furthermore, it was shown that wastewater from tanneries would allow increased production of biodiesel by favoring the generation of biomass rich in amount of lipids. Thus, the proposed model can be a useful tool for assessing the production of biodiesel using industrial wastewater as alternative growth substrates.

Although polystyrene (PS) is considered a non-biodegradable material, recent work has shown the degradation capacity of this material by microorganisms, especially those that are part of the natural microbiota of the digestive tract of some invertebrates. The present work sought to evaluate the growth of the larva of the mealworm (Tenebrio molitor) and its bacteria, using PS as the sole source of carbon. In this way it was possible to demonstrate the consumption of PS plates by the larva, found in holes and tunnels in the material, however, nutritionally it is not enough for the larva to gain biomass, notably reducing its size and time survival. Similarly, bacteria isolated from the digestive tract of T. molitor presented the ability to generate biofilms o n PS s heets, g enerating c hanges ( cracks, holes, etc.) in them, which were observed under scanning electron microscopy (SEM), indicating the possible use of this material as a carbon source for its growth.

"Uso de Scenedesmus para la remoción de metales pesados y nutrientes de aguas residuales de la industria textil", Ingeniería Solidaria, vol. 12, no. 20, pp. 95-105, oct. 2016Solidaria, vol. 12, no. 20, pp. 95-105, oct. . doi: http://dx.doi.org/10.16925/in.v19i20.1418 Resumen. Introducción: este artículo es producto de investigación derivado del proyecto "Uso de aguas residuales como sustratos alternativos para la generación de biomasa microalgal", desarrollado por el Semillero de Investigación en Ingeniería Ambiental y Bioprocesos (siiab), de la Universidad Sergio Arboleda, y ejecutado durante el 2015. El objetivo de la investigación fue evaluar el uso de la microalga Scenedesmus sp. como herramienta de tratamiento de las aguas residuales industriales producidas en una empresa de textiles ubicada en Bogotá (Colombia), las cuales presentan altas concentraciones de metales pesados, aluminio y nutrientes inorgánicos, lo que puede alterar la calidad de los cuerpos de agua superficiales o subterráneos. Metodología: durante la investigación se evaluaron tres diluciones diferentes del agua residual (100, 50 y 20 %), para valorar el efecto que podría presentar el efluente industrial sobre el crecimiento de la microalga en un periodo de 15 días. Resultados: se obtuvo un mayor crecimiento de Scenedesmus en el agua sin diluir (concentración 100 %) y se alcanzaron así reducciones de aluminio (88,8 %), cromo (85,21 %), nitratos (99,81 %) y nitritos (99,9 %) y en menor medida, de la carga orgánica (25,2 %). Conclusiones: la microalga Scenedesmus sp. exhibió un papel de ficorremediación sobre las aguas residuales de la industria textil, las cuales pueden ser utilizadas como sustratos alternativos para la generación de biomasa microalgal.Palabras clave: agua residual, remoción de metales, Scenedesmus, textiles.