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The ability to form biofilms is a functional trait shared by many bacterial species. Biofilms provide bacteria a sheltered environment where the nutrients and oxygen gradients create a heterogeneous matrix and promote cells to differentiate their metabolism and functions according to the position they occupy inside the matrix. Species of the Microcystis genus are among the most common bloom-forming cyanobacteria. They are unicellular microorganisms able to form colonies and to reach high biomass during blooms in lakes, reservoirs and estuaries worldwide. Colonial lifestyle provides several advantages under stressing conditions, including adaptation to different light intensities, protection from toxic substances and grazing, while allowing them to grow when the nutrient supply is low. Although the biology, ecology and colony formation have been extensively recognized in Microcystis spp., the analysis of the progression from unicellular to multicellular phases in this cyanobacterium have been always addressed as individual phenotypic plasticity and rarely as a multi-specific community of interrelated microorganisms. Here, we re-interpreted the evidence coming from different studies about the Microcystis lifestyle and propose a new way to analyze the available information about this cyanobacterial group. We specifically address the characteristics shared by bacterial biofilms and Microcystis colonies and suggest that the morphological changes from single cells to colonies are due to a cascade of events leading to the formation of a multi-specific biofilm. Studying the formation of colonies using this framework would help to better understand the life cycle of Microcystis, its functional relationship with the associated microbiome and the factors triggering microcystin production, helping to design strategies for prevention and control of the blooms caused by these organisms. Taking into account the biology and the ecological strategies of Microcystis, a conceptual model of emergence and decay of these floating multi-specific biofilms is proposed.

This edited book presents eleven chapters addressing the politics of water in Latin America. It brings together contributions from members of the WATERLAT-GOBACIT Network (www.waterlat.org) from Argentina, Brazil, Mexico, the United Kingdom and Uruguay. In addition to academics, the contributors also include members of public sector andcivil society organizationsengaged in debates and activities connected with the democratisation of water politics. The title of the book reflects a concern with the historical processes of appropriation, control, distribution, etc., of water and water-based services, which can be examined as processes of water territorialization, which includes the territorialization of the production of knowledge about water. The chapters cover a range of empirical examples, from the impacts of large-scale water infrastructures andextractivist activities (mining, agribusinesses), the (mis)management of water-related risks and disasters, the complex and conflictive characterof water management in metropolitan areas, the social and political struggles featuring social movements and other actors confrontingpowerful public and private interests in their quest to democratise water politics and management, among other issues.

Addressing ecological and evolutionary processes explaining biodiversity patterns is essential to identify the mechanisms driving community assembly. In the case of bacteria, the formation of new ecologically distinct populations or ecotypes is proposed as one of the main drivers of diversification. New ecotypes arise when mutation in key functional genes or acquisition of new metabolic pathways by horizontal gene transfer allow the population to exploit new resources, making possible their coexistence with parental population. Recently, we have reported the presence of toxic, microcystin-producing organisms from the Microcystis aeruginosa complex (MAC) through a wide environmental gradient (800 km) in South America, ranging from freshwater to estuarine-marine waters. In order to explain this finding, we hypothesize that the success of toxic organisms of MAC in such array of environmental conditions is due to the existence of ecotypes having different environmental preferences. So, we analysed the genetic diversity of microcystin-producing populations of Microcystis aeruginosa complex (MAC) by qPCR and high resolution melting analysis (HRMA) of a functional gene (mcyJ, involved in microcystin synthesis) and explored its relationship with the environmental conditions through the gradient by functional classification and regression trees (fCART). Six groups of mcyJ genotypes were distinguished and selected by different combinations of water temperature, conductivity and turbidity, determining the environmental preferences of each group. Since these groups were based on the basis of similar sequence and ecological characteristics they were defined as ecotypes of toxic MAC. Taking into account that the role of microcystins in MAC biology and ecology has not yet been elucidated, we propose that the toxin might have a role in MAC fitness that would be mainly controlled by the physical environment in a way such that the ecotypes that thrive in the riverine zone of the gradient would be more stable and less influenced by salinity fluctuations than those living at the marine limit of the estuary. These would periodically disappear or being eliminated by salinity increases, depending on the estuary dynamics. Thus, ecotypes generation would be an important mechanism allowing toxic MAC adapting to and succeed in a wide array of environmental conditions.

Las floraciones de cianobacterias tóxicas son un problema mundial. La eutrofización antrópica y la generación de embalses han promovido su desarrollo en la Cuenca del Plata, favoreciendo principalmente al complejo Microcystis aeruginosa (CMA). En este trabajo describimos las floraciones excepcionales de CMA ocurridas en el verano 2019 en la costa del Río de la Plata y Atlántica de Uruguay y discutimos sus mecanismos moduladores en base a datos biológicos, meteorológicos y oceanográficos de muestreos, imágenes satelitales y re-análisis. Las floraciones fueron extensas (Carmelo a Rocha; 500 km) y persistentes (ca.: 4 meses). En todos los casos fueron organismos del CMA con estructura genética similar y su presencia estuvo asociada a niveles cuantificables y elevados de microcistina. En base a las características oceanográficas y la similitud genética entre los organismos, se hipotetiza que las floraciones tienen un origen común, probablemente asociado a tributarios con alta carga de nutrientes y alto tiempo de residencia del agua en la Cuenca baja del Plata. Las precipitaciones extremas generaron caudales récord que transportaron las cianobacterias hasta el Río de la Plata, donde las condiciones de viento y temperatura particulares facilitaron su transporte y arribo a la costa de Rocha, llegando a ambientes de relevancia para la conservación (e.g. Laguna de Rocha).

En este trabajo se evaluó la dinámica y toxicidad de Microcystis spp. en el embalse de Salto Grande en invierno y verano de 2013, así como la diversidad genética de sus poblaciones tóxicas mediante análisis de melting de alta resolución de amplicones del gen mcyJ. La abundancia de células de Microcystis spp. varió entre los distintos sitios y entre estaciones, detectándose una abundancia signifcativamente mayor de células y genotipos tóxicos así como de microcistina-LR en verano. Además, se detectaron dos grupos de genotipos mcyJ (clusters 1 y 2) con diferentes preferencias ambientales. El 1 estuvo integrado por muestras de Microcystis spp. obtenidas en condiciones de bajas temperaturas (? 17,6 °C) y mayor conductividad (~52-58 µS cm-1), presentando bajo número de células y ausencia de microcistina-LR. Las muestras incluidas en el cluster 2 se caracterizaron por ser de verano (temperatura entre 17,6 y 25,9 ºC), presentar menor conductividad (~50-52 µS cm-1), alta abundancia de células y presencia de microcistina-LR. Nuestros resultados sugieren que las poblaciones tóxicas de Microcystis que ?orecen en verano serían diferentes a las que se mantienen durante el invierno y que la temperatura y conductividad del agua serían variables relevantes que controlarían su abundancia y toxicidad.

Las floraciones de cianobacterias potencialmente tóxicas es uno de los problemas más difundidos en los sistemas acuáticos a nivel global. Sin embargo, no existen programas de monitoreo sensibles y directamente aplicables a la predicción de las floraciones y su gestión. Con este objetivo se combinaron conceptos ecológicos y genéticos para generar herramientas para el monitoreo de cianobacterias. Se utilizaron dos aproximaciones: agrupación de organismos en grupos funcionales basados en morfología y análisis moleculares (PCR cuantitativo en tiempo real) que indican presencia de genes que codifican para la expresión de cianotoxinas (mcy). Para evaluar las herramientas se realizaron seis campañas de muestreo bimensuales (2013-2014) en seis estaciones con dos sitios en cada una, a lo largo del Río Uruguay y del Estuario Río de la Plata, desde Salto Grande hasta Punta del Este. Se observó un gradiente marcado en las variables meteorológicas, físico-químicas, y mayores abundancias de organismos planctónicos en Salto Grande y Punta del Este. Se encontró la presencia en todo el gradiente de poblaciones tóxicas, con mayor abundancia en Salto, particularmente del complejo Microcystis aeruginosa (CMA). Las variables ambientales más importantes en determinar el gradiente ambiental y las variaciones en las variables biológicas fueron la salinidad, la temperatura, el viento y la turbidez. Los resultados de los nuevos indicadores (presencia en red del CMA y genes mcy) coincidieron con los tradicionales (ej. clorofila-a) en los casos de floraciones más severas, y ambos fueron sustantivamente más sensibles en situaciones de bajas abundancias. La conjunción de los resultados se aplicó a la construcción de un protocolo de monitoreo y un sistema de alerta.

Las floraciones de cianobacterias en cuerpos de agua dulce constituyen un problema mundial, asociado a la eutrofización (enriquecimiento de nutrientes) y cambios hidrológicos de los ecosistemas. En este estudio se generó una base de datos históricos (n= 3061 para 64 ecosistemas, de 1980 a 2014), elaborada por un grupo de trabajo interinstitucional (OSE, DINAMA, IM, Universidad de la República e IIBCE), y se analizó la distribución de cianobacterias planctónicas y de cianotoxinas (microcistina, saxitoxina y cilindrospermopsina) en Uruguay. Los valores de clorofila ay nutrientes totales indicaron procesos de eutrofización en diversos ecosistemas. En dos mapas georreferenciados se visualiza la distribución de cianobacterias en el país, según indicadores cuantitativos globales, y de la microcistina (cianotoxina más frecuente). En dichos mapas se destacan los embalses (Río Uruguay y Río Negro) y las playas del Río de la Plata como las zonas de mayor riesgo de exposición a cianobacterias según las categorías de la Organización Mundial de la Salud para aguas recreacionales. Además, se analizaron muestras de floraciones (espuma) y se cuantificó 20 mg L-1de microcistinas totales y la presencia de genes que sugieren diferentes variedades de microcistinas. Se generó información básica que podrá ser útil para programas de monitoreo nacionales e investigación.

We present a resource for instructors that contains results and data sets from the Ames test. Our aim is to share the results we have collected in previous semesters with other instructors, so they will be able to “conduct” the Ames test without the need to set foot in a laboratory classroom. Instructors will be able to use our online resource to perform the test remotely, as a supplement to their laboratory classroom, or even under hybrid circumstances. The coronavirus disease 2019 (COVID-19) pandemic brought many changes, including the way we, as instructors, were able to carry out our educational curricula, since access to laboratory classrooms was not always possible. While COVID-19 restrictions are still in place, and thus access to laboratory classrooms is limited or null, instructors can use our online resource, without the need to set foot in a laboratory classroom. When COVID-19 restrictions are lifted and access to laboratory classrooms is permitted, instructors can follow the procedures we describe and compare their results with ours, which appear in Results and Discussion, or use our data sets as take-home assignments for their students. In addition to its use in detecting the potential mutagenicity of different samples, we have found the Ames test to be extremely useful for developing problem-solving skills by means of exercises like the ones included in this resource. Furthermore, the potential of this test as a starting point for problem-based learning is remarkable. Some suggestions for its use in active learning settings are provided.

We describe a simple and effective method for the extraction of potential mutagens from sediment samples. This method is straightforward and does not require expensive laboratory equipment, thus enabling instructors to analyze the presence of mutagenic substances in a conventional classroom setting. Additionally, we found that students felt encouraged to add the Ames test to the list of analyses they traditionally employ with sediment samples. This link between the environment and the Ames test provided an authentic learning context for students, bridging the gap between the "real-world" and the classroom laboratory, and thus making the educational experience more engaging and meaningful.

Photochemical degradation is an important process involved in the decay of macrophytes, but little is known on the response of heterotrophic bacteria to the chromophoric dissolved organic matter (CDOM) derived from different plant species. Here, we assessed the effect of photoaltered CDOM derived from Schoenoplectus californicus and Ruppia maritima on the composition and production of a bacterial community from a productive subtropical coastal lagoon. Chromophoric dissolved organic matter from plants extracts was characterised by optical methods before and after exposure to natural full solar radiation. Afterwards, bacteria from the lagoon were added and incubated in these extracts for 5 h. We found that CDOM from the plant extracts underwent photoalteration after exposure to natural solar radiation, inducing shifts in the original bacterial community composition. In both macrophyte extracts, the bacterial community significantly changed and became dominated by two populations with distinctive morphology. The main enriched bacteria in both plant extracts were large filaments that made up to 99% of the community biovolume. In the R. maritima extract, another type of enriched bacteria was detected, consisting of large rods. 16S rDNA sequencing showed that the enriched bacterial populations belonged to Exiguobacterium sp. (filaments) and Acinetobacter sp. (rods). Morphotype identities were confirmed by fluorescence in situ hybridisation using specific probes targeting those taxa. Our results suggest that solar-induced photoalteration of plant material in this coastal lagoon results in the growth of opportunistic bacterial taxa.

Las floraciones de cianobacterias tóxicas son un problema mundial. La eutrofización antrópica y la generación de embalses han promovido su desarrollo en la Cuenca del Plata, favoreciendo principalmente al complejo Microcystis aeruginosa (CMA). En este trabajo describimos las floraciones excepcionales de CMA ocurridas en el verano 2019 en la costa del Río de la Plata y Atlántica de Uruguay y discutimos sus mecanismos moduladores en base a datos biológicos, meteorológicos y oceanográficos de muestreos, imágenes satelitales y re-análisis. Las floraciones fueron extensas (Carmelo a Rocha; 500 km) y persistentes (ca.: 4 meses). En todos los casos fueron organismos del CMA con estructura genética similar y su presencia estuvo asociada a niveles cuantificables y elevados de microcistina. En base a las características oceanográficas y la similitud genética entre los organismos, se hipotetiza que las floraciones tienen un origen común, probablemente asociado a tributarios con alta carga de nutrientes y alto tiempo de residencia del agua en la Cuenca baja del Plata. Las precipitaciones extremas generaron caudales récord que transportaron las cianobacterias hasta el Río de la Plata, donde las condiciones de viento y temperatura particulares facilitaron su transporte y arribo a la costa de Rocha, llegando a ambientes de relevancia para la conservación (e.g. Laguna de Rocha). Cyanobacterial toxic blooms are a worldwide problem. In Río de la Plata basin, anthropic eutrophication and dam construction have promoted an increase in cyanobacteria blooms, especially those of the Microcystis aeruginosa complex (CMA). Here, we describe the exceptional blooms observed in the summer of 2019 on the coast of Río de la Plata and Atlantic coast of Uruguay. We discuss the main driving mechanisms using biological, meteorological and oceanographic sampling data, satellite images and reanalysis. The blooms covered a wide surface (Carmelo to Rocha; 500 km) and were persistent in time (ca. 4 months). Blooms were generated by CMA organisms having similar genetic structure and were associated to quantifiable and high microcystin concentrations. Given the observed oceanographic conditions and the similarity in organisms traits, we hypothesized that blooms had a common origin, probably associated with zones with high nutrient concentrations and high water residence time in the lower Río de la Plata basin. Extreme precipitations induced high water flows that transported cyanobacteria blooms downstream. In addition, anomalous wind and temperature conditions facilitated their arrival to the Atlantic coast along Rocha, to environments with particular relevance for biodiversity and conservation (e.g. Rocha coastal lagoon).