Settling selection of Chlamydomonas reinhardtii for samarium uptake.

Samarium (Sm) is a rare-earth element recently included in the list of critical elements due to its vital role in emerging new technologies. With an increasing demand for Sm, microbial bioremediation may provide a cost-effective and a more ecologically responsible alternative to remove and recover Sm. We capitalized on a previously selected Chlamydomonas reinhardtii strain tolerant to Sm (1.33 × 10-4 M) and acidic pH and carried out settling selection to increase the Sm uptake performance. We observed a rapid response to selection in terms of cellular phenotype. Cellular size decreased and circularity increased in a stepwise manner with every cycle of selection. After four cycles of selection, the derived CSm4 strain was significantly smaller and was capable of sequestrating 41% more Sm per cell (1.7 × 10-05 ± 1.7 × 10-06 ng) and twice as much Sm in terms of wet biomass (4.0 ± 0.4 mg Sm · g-1) compared to the ancestral candidate strain. The majority (~70%) of the Sm was bioaccumulated intracellularly, near acidocalcisomes or autophagic vacuoles as per TEM-EDX microanalyses. However, Sm analyses suggest a stronger response toward bioabsorption resulting from settling selection. Despite working with Sm and pH-tolerant strains, we observed an effect on fitness and photosynthesis inhibition when the strains were grown with Sm. Our results clearly show that phenotypic selection, such as settling selection, can significantly enhance Sm uptake. Laboratory selection of microalgae for rare-earth metal bioaccumulation and sorption can be a promising biotechnological approach.

An exploratory study on the possibilities of microalgal biotechnology to obtain the essential 6Li isotope as fusion fuel.

Future energy supply needs to overcome two challenges: environmental impact and dependence on geopolitically unstable countries. A very promising alternative is based on lithium, an element for batteries, and whose isotope 6Li will be essential in nuclear fusion. The objective of this research has been to determine if it is possible to achieve isotopic fractionation of lithium through a process mediated by microalgae. For this purpose, Chlamydomonas reinhardtii was selected and grown in presence of 5 mg/L of lithium. Results revealed that this specie survives at the selected lithium concentration, discriminates isotopes and preferentially capture 6Li (6δ = 10.029 ± 3.307) through a process independent of the cellular growth. Concomitate recovered up 0.206 mg/L of lithium along a process of 21 days. The result of this study lets to affirm that Chlamydomonas reinhardtii might be used to obtain lithium enriched in the lighter isotope.

Microbial biominers: Sequential bioleaching and biouptake of metals from electronic scraps.

Electronic scraps (e-scraps) represent an attractive raw material to mine demanded metals, as well as rare earth elements (REEs). A sequential microbial-mediated process developed in two steps was examined to recover multiple elements. First, we made use of an acidophilic bacteria consortium, mainly composed of Acidiphilium multivorum and Leptospidillum ferriphilum, isolated from acid mine drainages. The consortium was inoculated in a dissolution of e-scraps powder and cultured for 15 days. Forty-five elements were analyzed in the liquid phase over time, including silver, gold, and 15 REEs. The bioleaching efficiencies of the consortium were >99% for Cu, Co, Al, and Zn, 53% for Cd, and around 10% for Cr and Li on Day 7. The second step consisted of a microalgae-mediated uptake from e-scraps leachate. The strains used were two acidophilic extremotolerant microalgae, Euglena sp. (EugVP) and Chlamydomonas sp. (ChlSG) strains, isolated from the same extreme environment. Up to 7.3, 4.1, 1.3, and 0.7 µg by wet biomass (WB) of Zn, Al, Cu, and Mn, respectively, were uptaken by ChlSG biomass in 12 days, presenting higher efficiency than EugVP. Concerning REEs, ChlSG biouptake 14.9, 20.3, 13.7, 8.3 ng of Gd, Pr, Ce, La per WB. Meanwhile, EugVP captured 1.1, 1.5, 1.4, and 7.5, respectively. This paper shows the potential of a microbial sequential process to revalorize e-scraps and recover metals and REEs, harnessing extremotolerant microorganisms.

The Upcoming 6Li Isotope Requirements Might Be Supplied by a Microalgal Enrichment Process.

Lithium isotopes are essential for nuclear energy, but new enrichment methods are required. In this study, we considered biotechnology as a possibility. We assessed the Li fractionation capabilities of three Chlorophyte strains: Chlamydomonas reinhardtii, Tetraselmis mediterranea, and a freshwater Chlorophyte, Desmodesmus sp. These species were cultured in Li containing media and were analysed just after inoculation and after 3, 12, and 27 days. Li mass was determined using a Inductively Coupled Plasma Mass Spectrometer, and the isotope compositions were measured on a Thermo Element XR Inductively Coupled Plasma Mass Spectrometer. The maximum Li capture was observed at day 27 with C. reinhardtii (31.66 µg/g). Desmodesmus sp. reached the greatest Li fractionation, (δ6 = 85.4‰). All strains fractionated preferentially towards 6Li. More studies are required to find fitter species and to establish the optimal conditions for Li capture and fractionation. Nevertheless, this is the first step for a microalgal nuclear biotechnology.

Fluctuation analysis to select for Samarium bio-uptaking microalgae clones the repurposing of a classical evolution experiment.

Rare Earth Elements (REE) increasing demand prompts the research of biotechnological approaches to exploit secondary resources. We made use of the adapted Fluctuation analyses experiment to obtain Chlamydomonas reinhardtii ChlA strains resistant to Samarium (Sm) as the reference REE. The starting hypothesis was that adaptation to metal-containing media leads to an enhanced metal uptake. ChlA was able to adapt to 1.33·10-4 Sm M and pH~3 by pre-existing genetic variability, allowing the evolutionary rescue of 13 of the 99 populations studied. The rescuing resistant genotypes presented a mutation rate of 8.65·10-7 resistant cells per division. The resulting resistant population contradicted the expected fitness cost associated with the adaptation to Sm, selection resulted in larger and faster-growing resistant cells. Among the three isolated strains studied for Sm uptake, only one presented uplifted performance compared to the control population (46.64 µg Sm g-¹ of wet biomass and 3.26·10-7 ng Sm per cell, mainly bioaccumulated within the cells). The selection of microalgae strains with improved tolerance to REEs by this methodology could be a promising solution for REES sequestration. However, increased tolerance can be independent or have negative effects on uptake performance and cellular features studied are not directly correlated with the metal uptake. SUMMARY SENTENCE: Repurposing a classic laboratory evolution experiment to select for microalgae Samarium adapted strains for metals recovery and biotechnology approaches. DATA AVAILABILITY STATEMENT: All data generated or analyzed during this study are included in this published article (and its raw files).

Rapid Colonization of Uranium Mining-Impacted Waters, the Biodiversity of Successful Lineages of Phytoplankton Extremophiles.

Anthropogenic extreme environments are emphasized as interesting sites for the study of evolutionary pathways, biodiversity, and extremophile bioprospection. Organisms that grow under these conditions are usually regarded as extremophiles; however, the extreme novelty of these environments may have favor adaptive radiations of facultative extremophiles. At the Iberian Peninsula, uranium mining operations have rendered highly polluted extreme environments in multiple locations. In this study, we examined the phytoplankton diversity, community structure, and possible determining factors in separate uranium mining-impacted waters. Some of these human-induced extreme environments may be able to sustain indigenous facultative extremophile phytoplankton species, as well as alleged obligate extremophiles. Therefore, we investigated the adaptation capacity of three laboratory strains, two Chlamydomonas reinhardtii and a Dictyosphaerium chlorelloides, to uranium-polluted waters. The biodiversity among the sampled waters was very low, and despite presenting unique taxonomic records, ecological patterns can be identified. The microalgae adaptation experiments indicated a gradient of ecological novelty and different phenomena of adaptation, from acclimation in some waters to non-adaptation in the harshest anthropogenic environment. Certainly, phytoplankton extremophiles might have been often overlooked, and the ability to flourish in extreme environments might be a functional feature in some neutrophilic species. Evolutionary biology and microbial biodiversity can benefit the study of recently evolved systems such as uranium-polluted waters. Moreover, anthropogenic extremophiles can be harnessed for industrial applications.

Evidence of microalgal isotopic fractionation through enrichment of depleted uranium.

Resulting from the nuclear fuel cycle, large amounts of depleted uranium (DU) tails are piling up, waiting for possible use or final disposal. To date, the recovery of the residual 235U isotope contained in DU has been conducted only marginally by physical processes. Relative isotope abundances are often mediated by biological processes, and the biologically driven U isotopic fractionation has been previously identified in reducing bacteria. Our results indicate that the cells of two microalgal strains (freshwater Chlamydomonas sp. (ChlGS) and marine Tetraselmis mediterranea (TmmRU)) took up DU from the exposure solutions, inducing U isotopic fractionation with a preference for the fissile 235U isotope over 238U. The n(235U)/n(238U) isotopic fractionation magnitudes (δ235) were 23.6 ± 12.5‰ and 370.4 ± 103.9‰, respectively. These results open up new perspectives on the re-enrichment of DU tailings, offering a potential biological alternative to obtain reprocessed natural-equivalent uranium. Additionally, the findings present implications for identifying biological signatures in the geologic records.

Improvement of the Uranium Sequestration Ability of a Chlamydomonas sp. (ChlSP Strain) Isolated From Extreme Uranium Mine Tailings Through Selection for Potential Bioremediation Application.

The extraction and processing of uranium (U) have polluted large areas worldwide, rendering anthropogenic extreme environments inhospitable to most species. Noticeably, these sites are of great interest for taxonomical and applied bioprospection of extremotolerant species successfully adapted to U tailings contamination. As an example, in this work we have studied a microalgae species that inhabits extreme U tailings ponds at the Saelices mining site (Salamanca, Spain), characterized as acidic (pH between 3 and 4), radioactive (around 4 µSv h-1) and contaminated with metals, mainly U (from 25 to 48 mg L-1) and zinc (from 17 to 87 mg L-1). After isolation of the extremotolerant ChlSP strain, morphological characterization and internal transcribed spacer (ITS)-5.8S gene sequences placed it in the Chlamydomonadaceae, but BLAST analyses identity values, against the nucleotide datasets at the NCBI database, were very low (<92%). We subjected the ChlSP strain to an artificial selection protocol to increase the U uptake and investigated its response to selection. The ancestral strain ChlSP showed a U-uptake capacity of ≈4.30 mg U g-1 of dry biomass (DB). However, the artificially selected strain ChlSG was able to take up a total of ≈6.34 mg U g-1 DB, close to the theoretical maximum response (≈7.9 mg U g-1 DB). The selected ChlSG strain showed two possible U-uptake mechanisms: the greatest proportion by biosorption onto cell walls (ca. 90%), and only a very small quantity, ~0.46 mg g-1 DB, irreversibly bound by bioaccumulation. Additionally, the kinetics of the U-uptake process were characterized during a microalgae growth curve; ChlSG cells removed close to 4 mg L-1 of U in 24 days. These findings open up promising prospects for sustainable management of U tailings waters based on newly evolved extremotolerants and outline the potential of artificial selection in the improvement of desired features in microalgae by experimental adaptation and selection.

The limit of the genetic adaptation to copper in freshwater phytoplankton.

Copper is one of the most frequently used algaecides to control blooms of toxic cyanobacteria in water supply reservoirs. Among the negative impacts derived from the use of this substance is the increasing resistance of cyanobacteria to copper toxicity, as well as changes in the community structure of native phytoplankton. Here, we used the ratchet protocol to investigate the differential evolution and maximum adaptation capacity of selected freshwater phytoplankton species to the exposure of increasing doses of copper. Initially, a dose of 2.5 µM CuSO4·5H2O was able to completely inhibit growth in three strains of the toxic cyanobacterium Microcystis aeruginosa, whereas growth of the chlorophyceans Dictyosphaerium chlorelloides and Desmodesmus intermedius (represented by two different strains) was completely abolished at 12 µM. A significant increase in resistance was achieved in all derived populations during the ratchet experiment. All the chlorophyceans were able to adapt to up to 270 µM of copper sulfate, but 10 µM was the highest concentration that M. aeruginosa strains were able to cope with, although one of the replicates adapted to 30 µM. The recurrent use and increasing doses of copper in water reservoirs could lead to the selection of copper-resistant mutants of both chlorophyceans and cyanobacteria. However, under high concentrations of copper, the composition of phytoplankton community could undergo a drastic change with cyanobacteria being replaced by copper-resistant chlorophyceans. This result stems from a distinct evolutionary potential of these species to adapt to this substance.

Microalgas: ¿los primeros ingenieros nucleares? / Microalgae: the first nuclear engineers?

Self-sustaining nuclear chain reactions ran spontaneously 1.7 billion years ago at Oklo (Gabon, Africa) are a mystery. It was hypothesized that the microalgae concentrated enough rich-uranium in Oklo as for a natural reactor to start operating. The key to understanding as microalgae could do this is in an extremely U-contaminated pond of Saelices uranium-mine (Spain). Some microalgae colonized this extreme pond due to spontaneous mutations of single-genes. These U-resistant microalgae concentrate 115 mg U/g dried-biomass by bio-adsorption and bioaccumulation and are able to enrich uranium producing isotopic fractionation 235U/238U. Consequently, microalgae could be able to build a nuclear reactor in appropriate circumstances (AU)

Las reacciones nucleares en cadena auto-sostenibles que ocurrieron espontáneamente hace 1.700 millones años en Oklo (Gabón, África) son un misterio. Hipotéticamente las microalgas concentraron suficiente uranio enriquecido para que un reactor nuclear natural comenzara a operar. La clave está en un estanque contaminado por uranio en la mina de Saelices (España). Algunas microalgas colonizaron este estanque extremo debido a mutaciones espontáneas de genes individuales. Estas microalgas Uranio-resistentes concentran 115 mg U / g de biomasa seca mediante bio-absorción y bioacumulación, siendo capaces de enriquecer uranio produciendo fraccionamiento isotópico 235U/238U. Estas microalgas podrían construir un reactor nuclear en circunstancias apropiadas (AU)

Disentangling mechanisms involved in the adaptation of photosynthetic microorganisms to the extreme sulphureous water from Los Baños de Vilo (S Spain).

Los Baños de Vilo (S Spain) is a natural spa characterized by extreme sulphureous waters; however, populations of chlorophyceans inhabit in the spa. The adaptation mechanisms allowing resistance by photosynthetic microorganisms to the extreme sulphureous waters were studied by using a modified Luria-Delbrück fluctuation analysis. For this purpose, the adaptation of the chlorophycean Dictyosphaerium chlorelloides and the cyanobacterium Microcystis aeruginosa (both isolated from non-sulphureous water) were analysed in order to distinguish between physiological adaptation (acclimation) and genetic adaptation by the selection of rare spontaneous mutations. Acclimation to the extreme water was achieved by D. chlorelloides; however, M. aeruginosa cells proliferated as a consequence of selection of favoured mutants (i.e. genetic adaptation). The resistant cells of M. aeruginosa appeared with a frequency of 7.1 × 10(-7) per cell per generation, and the frequency of the resistant allele, under non-selective conditions, was estimated to be 1.1 × 10(-6) per cells as a consequence of the balance mutation-selection. It could be hypothesized that the populations of eukaryotic algae living in the Los Baños de Vilo could be the descendants of chlorophyceans that arrived fortuitously at the spa in the past. On the other hand, cyanobacteria could quickly adapt by the selection of favoured mutants. The single mutation that allows resistance to sulphureous water from Baños de Vilo in M. aeruginosa represents a phenotypic burden impairing growth rate and photosynthetic performance. The resistant-variant cells of M. aeruginosa showed a lower acclimated growth rate and a decreased maximum quantum yield and photosynthetic efficiency, in comparison to the wild-type cells.

Photoacclimation of cultured strains of the cyanobacterium Microcystis aeruginosa to high-light and low-light conditions.

The cyanobacterium Microcystis aeruginosa forms blooms that can consist of colonies. We have investigated how M. aeruginosa acclimatizes to changing light conditions such as can occur during blooms. Three different strains were exposed to two irradiance levels: lower (LL) and higher (HL) than the irradiance-onset saturation parameter. We measured the photosynthetic pigment concentrations, PSII photochemical efficiency, electron transport rate (ETR), irradiance-saturated ETR and ETR efficiency. The relationship between ETR and photosynthetic oxygen production and the excess in PSII capacity were also studied for one strain. Higher values of chlorophyll a and phycocyanin and lower values of total carotenoids were found under LL conditions in the three strains. The strains showed clear differences in the irradiance-saturated ETR and in ETR efficiency under both LL and HL treatments. No differences were found in the linear relationship between ETR and photosynthetic oxygen production under both irradiance treatments. LL-acclimated cells showed higher PSII excess capacity than HL ones, possibly because their higher pigment content could result in a higher light stress than HL cells when forming surface blooms. The fact that the genetically different strains show different photosynthetic physiologies suggests that the very dynamic light climate observed in lakes may allow their coexistence.

Estimating the capability of microalgae to physiological acclimatization and genetic adaptation to petroleum and diesel oil contamination.

There is increasing scientific interest in how phytoplankton reacts to petroleum contamination, since crude oil and its derivatives are generating extensive contamination of aquatic environments. However, toxic effects of short-term petroleum exposure are more widely known than the adaptation of phytoplankton to long-term petroleum exposure. An analysis of short-term and long-term effects of petroleum exposure was done using experimental populations of freshwater (Scenedesmus intermedius and Microcystis aeruginosa) and marine (Dunaliella tertiolecta) microalgae isolated from pristine sites without crude oil product contamination. These strains were exposed to increased levels of petroleum and diesel oil. Short-term exposure to petroleum or diesel oil revealed a rapid inhibition of photosynthetic performance and cell proliferation in freshwater and marine phytoplankton species. A broad degree of inter-specific variation in lethal contamination level was observed. When different strains were exposed to petroleum or diesel oil over the long-term, the cultures showed massive destruction of the sensitive cells. Nonetheless, after further incubation, some cultures were able to grow again due to cells that were resistant to the toxins. By means of a fluctuation analysis, discrimination between cells that had become resistant due to physiological acclimatization and resistant cells arising from rare spontaneous mutations was accomplished. In addition, an analysis was done as to the maximum capacity of adaptation to a gradual contamination process. An experimental ratchet protocol was used, which maintains a strong selection pressure in a temporal scale up to several months over very large experimental populations of microalgae. Microalgae are able to survive to petroleum contamination as a result of physiological acclimatization without genetic changes. However, when petroleum concentration exceeds the physiological limits, survival depends exclusively on the occurrence on mutations that confer resistance and subsequent selection of these mutants. Finally, it is certain that further mutations and selection will ultimately determine adaptation of microalgae to the environmental forcing.

Effects of adaptation, chance, and history on the evolution of the toxic dinoflagellate Alexandrium minutum under selection of increased temperature and acidification.

The roles of adaptation, chance, and history on evolution of the toxic dinoflagellate Alexandrium minutum Halim, under selective conditions simulating global change, have been addressed. Two toxic strains (AL1V and AL2V), previously acclimated for two years at pH 8.0 and 20°C, were transferred to selective conditions: pH 7.5 to simulate acidification and 25°C. Cultures under selective conditions were propagated until growth rate and toxin cell quota achieved an invariant mean value at 720 days (ca. 250 and ca. 180 generations for strains AL1V and AL2V, respectively). Historical contingencies strongly constrained the evolution of growth rate and toxin cell quota, but the forces involved in the evolution were not the same for both traits. Growth rate was 1.5-1.6 times higher than the one measured in ancestral conditions. Genetic adaptation explained two-thirds of total adaptation while one-third was a consequence of physiological adaptation. On the other hand, the evolution of toxin cell quota showed a pattern attributable to neutral mutations because the final variances were significantly higher than those measured at the start of the experiment. It has been hypothesized that harmful algal blooms will increase under the future scenario of global change. Although this study might be considered an oversimplification of the reality, it can be hypothesized that toxic blooms will increase but no predictions can be advanced about toxicity.

Use of a real-time remote monitoring network (RTRM) to characterize the Guadalquivir estuary (Spain).

The temporal variability of hydrological variables in the Guadalquivir estuary was examined during three years through a real-time remote monitoring network (RTRM). The network was developed with the aim of studying the influence of hydrodynamical and hydrological features within the estuary on the functioning of the pelagic ecosystem. Completing this data-gathering network, monthly cruises were performed in order to measure biogeochemical variables that are indicative of the trophic status of the aquatic environment. The results showed that several sources of physical forcing, such as wind, tide-associated currents and river discharge were responsible for the spatio-temporal patterns of dissolved oxygen, salinity and turbidity in the estuary. The analysis was conducted under tidal and flood regime, which allowed us to identify river discharge as the main forcing agent of the hydrology inside the estuary. In particular, episodes of elevated turbidity detected by the network, together with episodes of low salinity and dissolved oxygen were closely related to the increase in water supply from a dam located upstream. The network installed provided accurate data that can be rapidly used for research or educational applications and by policy-makers or agencies in charge of the management of the coastal area.

Diferenciación entre clones productores de tóxina y no tóxicos de Microcystis aeruginosa mediante el uso de lectinas / Separation between toxin-producing and non-toxic clones of Microcystis aeruginosa using lectins

Microcystis aeruginosa (the most widespread toxic cyanobacteria worldwide) occurs in dense blooms composed of toxin-producing and non-toxic strains. Current microscopy techniques monitoring of toxic cyanobacteria are unable to distinguish toxic and non-toxic strains. In contrast, a new assay using lectins is able to differentiate among the different M. aeruginosa strains based on microcystin production. We analyze thirty-five cultured strains of M. aeruginosa isolated from 4 different blooms in three water supply reservoirs and a lagoon as well as a lot of M. aeruginosa colonies directly collected from field samples. All non-toxic M. aeruginosa strains were positively bound with UEA-1 lectin and by several other lectins. In contrast, the most toxic strains remain unbound. This procedure also was successful in field samples. Although other techniques allow for the differentiation between toxic and non-toxic strains, none of them is as fast, simple and easy as lectin-binding pattern(AU)

Microcystis aeuruginosa (la cianobacteria tóxica más extendida mundialmente) es la responsable de "blooms" o floraciones que están compuestos por cepas tóxicas y no tóxicas. Las técnicas de microscopia utilizadas actualmente no permiten distinguir entre las cepas tóxicas y las no tóxicas. Por el contrario, un nuevo procedimiento empleando lectinas es capaz de diferenciar entre las cepas de M. aeruginosa basándose en la producción de microcistina. Se analizaron treinta y cinco cepas aisladas de M. aeruginosa aisladas de cuatro blooms diferentes en tres depósitos de abastecimiento de agua y en una laguna, así como una gran cantidad de colonias de M. aeruginosa directamente recogidos de muestras de campo. Todas las cepas no tóxicas de M. aeruginosa fueron marcadas positivamente con la lectina UEA-1 y por varias otras lectinas. Sin embargo, las cepas más tóxicas permanecieron sin marcar. Este procedimiento también tuvo éxito en muestras de campo. Aunque existen otras técnicas que permiten la diferenciación entre cepas tóxicas y no tóxicas, ninguna es tan rápida y simple como el marcaje por lectinas(AU)

Adaptation of microalgae to lindane: a new approach for bioremediation.

Lindane is especially worrisome because its persistence in aquatic ecosystems, tendency to bioaccumulation and toxicity. We studied the adaptation of freshwater cyanobacteria and microalgae to resist lindane using an experimental model to distinguish if lindane-resistant cells had their origin in random spontaneous pre-selective mutations (which occur prior to the lindane exposure), or if lindane-resistant cells arose by a mechanism of physiological acclimation during the exposure to the selective agent. Although further research is needed to determine the different mechanisms contributing to the bio-elimination of lindane, this study, however, provides an approach to the bioremediation abilities of the lindane-resistant cells. Wild type strains of the experimental organisms were exposed to increasing lindane levels to estimate lethal concentrations. Growth of wild-type cells was completely inhibited at 5mg/L concentration of lindane. However, after further incubation in lindane for several weeks, occasionally the growth of rare lindane-resistant cells was found. A fluctuation analysis demonstrated that lindane-resistant cells arise only by rare spontaneous mutations that occur randomly prior to exposure to lindane (lindane-resistance did not occur as a result of physiological mechanisms). The rate of mutation from lindane sensitivity to resistance was between 1.48 × 10(-5) and 2.35 × 10(-7) mutations per cell per generation. Lindane-resistant mutants exhibited a diminished fitness in the absence of lindane, but only these variants were able to grow at lindane concentrations higher than 5mg/L (until concentrations as high as 40 mg/L). Lindane-resistant mutants may be maintained in uncontaminated waters as the result of a balance between new resistant mutants arising from spontaneous mutation and resistant cells eliminated by natural selection waters via clone selection. The lindane-resistant cells were also used to test the potential of microalgae to remove lindane. Three concentrations (4, 15 and 40 mg/L) were chosen as a model. In these exposures the lindane-resistant cells showed a great capacity to remove lindane (until 99% lindane was eliminated). Apparently, bioremediation based on lindane-resistant cells could be a great opportunity for cleaning up of lindane- and other chlorinated organics-polluted habitats.

Warming will affect phytoplankton differently: evidence through a mechanistic approach.

Although the consequences of global warming in aquatic ecosystems are only beginning to be revealed, a key to forecasting the impact on aquatic communities is an understanding of individual species' vulnerability to increased temperature. Despite their microscopic size, phytoplankton support about half of the global primary production, drive essential biogeochemical cycles and represent the basis of the aquatic food web. At present, it is known that phytoplankton are important targets and, consequently, harbingers of climate change in aquatic systems. Therefore, investigating the capacity of phytoplankton to adapt to the predicted warming has become a relevant issue. However, considering the polyphyletic complexity of the phytoplankton community, different responses to increased temperature are expected. We experimentally tested the effects of warming on 12 species of phytoplankton isolated from a variety of environments by using a mechanistic approach able to assess evolutionary adaptation (the so-called ratchet technique). We found different degrees of tolerance to temperature rises and an interspecific capacity for genetic adaptation. The thermal resistance level reached by each species is discussed in relation to their respective original habitats. Our study additionally provides evidence on the most resistant phytoplankton groups in a future warming scenario.

El papel del fitoplancton en el cambio climático: ¿cuánto depende nuestro destino de unas pequeñas microalgas? / The role of phytoplankton in climate change: depends our future of some small microalgae?

Hoy en día estamos viviendo un período de cambio global rápidoen el cual alrededor de 30.000 especies llegan a extinguirse anualmentedebido a las actividades humanas que están alterando los procesosbiogeoquímicos a nivel de la biosfera. Los ciclos de la biosfera tal vezlleguen a ser menos predictibles si los microorganismos esencialessucumben al cambio climático y a las actividades antropogénicas. Enparticular, las microalgas y cianobacterias juegan un importante rol en elcontrol del cambio global pues son los principales productores primariosde los ecosistemas acuáticos, produciendo alrededor del 50% de lafotosíntesis total. El equilibrio entre respiración-oxidación (C6H12O6 + 6O2 ⇒ 6 CO2 + 6 H2O) y fotosíntesis (6 CO2 + 6 H2O ⇒ C6H12O6 + 6 O2)marca la pauta del CO2 y consecuentemente del cambio climático.Investigar la capacidad diferencial de respuesta del fitoplancton alforzamiento ambiental inducido por los humanos ha llegado a ser clavepara entender las futuras repercusiones sobre el funcionamiento de losecosistemas a nivel planetario. Nuestros estudios muestran que losdiferentes grupos funcionales del fitoplancton (p.e. fitoplancton oceánico,costero, simbionte de corales, continental…) tienen muy diferentecapacidad de adaptarse al cambio global. La capacidad de las diferentesmicroalgas puede explicarse en relación a la estructura genética de lapoblación, tasa de crecimiento, tasa de mutación, ploidía, preferencia dehábitat y grupo taxonómico. Las poblaciones de microalgas oceánicas sonlas que muestran la mínima capacidad de adaptación al cambio. Como elocéano es el mayor ecosistema de la Tierra, las perspectivas futuras noson buenas(AU)

The role of phytoplankton in climate change: depends our future ofsome small microalgae?Nowadays, we are living in a rapid global change period in whicharound 30,000 species go extinct annually due to those human activitiesthat are altering biosphere-level biogeochemistry processes. Biospherelevel cycles may become less predictable as essential microbes succumbto climatic change and anthropogenic activities. In particular, sincemicroalgae and cyanobacteria play an important role in control of globalchange because they are the principal primary producers of aquaticecosystems producing around 50% total photosynthesis. Balance betweenrespiration -oxidation (C6H12O6 + 6 O2 ⇒ 6 CO2 + 6 H2O) andphotosynthesis (6 CO2 + 6 H2O ⇒ C6H12O6 + 6 O2) is the pacemaker ofCO2 and consequently of climatic change. Investigating the differentialcapacity of the response of phytoplankton to human-inducedenvironmental forcing has become a key issue to understanding furtherthe future repercussions on the functioning of ecosystems at planetarylevel. Our studies show that different functional phytoplanktonic groups(ie. oceanic, coastal, coral-simbionts, continental phytoplankton…) havevery different capability for adaptation to global change. The capacity ofdifferent microalgal species to adapt to global change can be explained inrelation to population genetics structure, growth rate, mutation rate,ploidy, habitat preference and taxonomic group. Populations of oceanicmicroalgae showed the minimal capacity to adapt to change. Since openocean is the biggest ecosystem on the Earth, future perspectives are notgood(AU)

Evolutionary changes in growth rate and toxin production in the cyanobacterium Microcystis aeruginosa under a scenario of eutrophication and temperature increase.

Toxic blooms of the cyanobacterium Microcystis aeruginosa affect humans and animals in inland water systems worldwide, and it has been hypothesized that the development of these blooms will increase under the future scenario of global change, considering eutrophication and temperature increase as two important consequences. The importance of genetic adaptation, chance and history on evolution of growth rate, and toxin production of M. aeruginosa was studied under these new conditions. The experiment followed the idea of "replaying life's tape" by means of the simultaneous propagation of 15 independent isolates of three M. aeruginosa strains, which were grown under doubled nutrient concentration and temperature during c. 87 generations. Adaptation by new mutations that resulted in the enhancement of growth rate arose during propagation of derived cultures under the new environmental conditions was the main component of evolution; however, chance also contributed in a lesser extension to evolution of growth rate. Mutations were selected, displacing the wild-type ancestral genotypes. In contrast, the effect of selection on mutations affecting microcystin production was neutral. Chance and history were the pacemakers in evolution of toxin production. Although this study might be considered an oversimplification of the reality, it suggest that a future scenario of global change might lead to an increase in M. aeruginosa bloom frequency, but no predictions about the frequency of toxicity can be made.