Camino García-Balboa

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.

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.

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.

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.

La presencia de biotoxinas en los moluscos es largamente conocida y ampliamente vigilada. En España, las dos que más se han detectado en los últimos años han sido las saxitoxinas y el ácido okadaico (toxinas PSP y DSP, respectivamente). A efecto de evitar intoxicaciones agudas en la población, existen unos límites máximos de toxinas que pueden estar presentes en el alimento de venta al consumidor. Sin embargo, la presencia de toxina a concentraciones inferiores a la legalmente establecida puede producir intoxicaciones crónicas o efectos a largo plazo. El objetivo del estudio es detectar la presencia de toxinas que están llegando a consumo humano, estén o no dentro del límite de concentración permitido. Se realizó un muestreo en diferentes pescaderías de la Comunidad de Madrid, sin incluir la propia ciudad de Madrid, y se analizó la concentración de toxinas PSP y DSP presentes en 50 muestras de mejillones, almejas, berberechos, vieiras y zamburiñas. Los resultados indican que un 4% de las muestras de los moluscos adquiridos contenían saxitoxinas y en un 6% se detectó ácido okadaico, ya sea en forma de trazas o con una positividad confirmada en base al método analítico, si bien los datos obtenidos cumplen los límites máximos establecidos a nivel comunitario.

El cambio ambiental global incrementa la proliferación de cianobacterias y la liberación de cianotoxinas muy peligrosas en aguas de abastecimiento y recreo. Estas citotoxinas pueden ocasionar graves problemas de salud, por lo que se hace necesario incrementar el control, especialmente en las aguas de baño, para evitar eventos indeseables en la población. Se analizaron cianobacterias productoras de toxinas y cianotoxinas (microcistinas) en muestras de columnas agua y de la superficie de las zonas de baño autorizadas por la Comunidad de Madrid, así como en embalses para abastecimiento de agua de consumo. Los muestreos se realizaron en los meses desde mayo a octubre de 2018. De cada lugar se realizaron, al menos, dos determinaciones en diferentes tiempos. Con excepción de la Playa de Presillas (Rascafría), en las zonas muestreadas se han detectado cianobacterias productoras de cianotoxinas, así como niveles de microcistina mayores de 1μg/L, considerado perjudicial para la salud. Los máximos tanto de microcistinas como de cianobacterias se encuentran en los meses de julio y agosto. El estudio confirma que hay presencia de microcistinas en concentraciones tóxicas en época de baño. Se hace necesario establecer controles de las cianotoxinas estableciendo un sistema de aviso de aparición de los blooms tóxicos en aguas de recreo.

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.