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10 páginas.- 4 figuras.- 4 tablas.- 45 referencias.- The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.2c03149, Recent research has demonstrated that chemotactic bacteria can disperse inside microsized pores while traveling toward favorable conditions. Microbe–microbe cotransport might enable nonmotile bacteria to be carried with motile partners to enhance their dispersion and reduce their deposition in porous systems. The aim of this study was to demonstrate the enhancement in the dispersion of nonmotile bacteria (Mycobacterium gilvum VM552, a polycyclic aromatic hydrocarbon-degrader, and Sphingobium sp. D4, a hexachlorocyclohexane-degrader, through micrometer-sized pores near the exclusion-cell-size limit, in the presence of motile Pseudomonas putida G7 cells. For this purpose, we used bioreactors equipped with two chambers that were separated with membrane filters with 3, 5, and 12 μm pore sizes and capillary polydimethylsiloxane (PDMS) microarrays (20 μm × 35 μm × 2.2 mm). The cotransport of nonmotile bacteria occurred exclusively in the presence of a chemoattractant concentration gradient, and therefore, a directed flow of motile cells. This cotransport was more intense in the presence of larger pores (12 μm) and strong chemoeffectors (γ-aminobutyric acid). The mechanism that governed cotransport at the cell scale involved mechanical pushing and hydrodynamic interactions. Chemotaxis-mediated cotransport of bacterial degraders and its implications in pore accessibility opens new avenues for the enhancement of bacterial dispersion in porous media and the biodegradation of heterogeneously contaminated scenarios., This research was funded by European Union's Horizon 2020 research and innovation program under the Marie Sklodowska- Curie grant agreement no. 895340 (BIOTAC project) and by the Spanish Ministry of Science and Innovation (PID2019- 109700RB-C21) .

Soil contamination with fuel derived organic compounds is a problem principally caused by emissions and residues from the petrochemical industry, traffic accidents, and accidental leaks in pipelines or in underground fuel storage tanks. Soils contaminated with fuels have a high environmental risk, since they can contaminate other environmental compartments, with the inherent risks for human health and for the environment. Sorption to soil particles, volatilization, leaching, degradation (chemical, photochemical and biological oxidation), plant translocation, etc., are the principal processes that will influence on the final fate of soil contaminants in the environment. In order to interpret, evaluate the risks and make decisions about the effects of fuel compounds and assure and adequate protection of the environment, it is very important to understand the toxicology, analytics and the behaviour and fate in the environment. Within this context, the present doctoral thesis has the following objectives: Development of analytical methods for volatile compounds (MTBE, ETBE and BTEX) and diesel range organics (DRO) in soil and water. Application of those methods to the characterization of a site contaminated with hydrocarbons. Study of the dynamics of petroleum contaminants in the soil-plant-water-air system through sorption and leaching experiments and a experiment with root exudates, to study the effect of plants on contaminant mobility through soils. Characterization of gasoline and diesel phytotoxicity, with crop plants bioassays. At last, application of a phytoremediation procedure with Lupinus luteus growing on the A and B horizons of a Cambisol contaminated with diesel (1%, w/w), with the inoculation of best plant growth promoting and degrader bacteria, with the best results from previous experiment. The experiments carried out in this thesis, allowed to obtain a wide knowledge of the behaviour of those contaminants in the soil system, and to predict their final fate in the environment, in addition to their toxic effect once released in soil. The proposed remediation techniques, through bacteria assisted phytoremediation, resulted in a clean, cheap, reliable and highly efficient technique, what predicts satisfactory results in its application to real soils.

Traballo Fin de Máster en Enxeñaría Ambiental. Curso 2019-2020 La baja biodisponibilidad del hexaclorociclohexano (HCH) afecta a la efectividad de procesos de biorremediación de suelos contaminados por HCH. Para aumentar la solubilidad aparente del HCH y potenciar su biodisponibilidad, se estudió el efecto de la acción micelar de una gran variedad de líquidos iónicos con actividad surfactante (i.e. Surface-Active Ionic Liquids o SAILs) y surfactantes convencionales sobre la solubilidad de HCH. Se prepararon disoluciones de SAILs/surfactantes y HCH (a una concentración ca. 10 veces su límite de solubilidad) utilizando dos concentraciones distintas de SAILs/surfactantes (siempre >CMC). Los resultados varían según el isómero de HCH, el SAIL/surfactante y la concentración utilizada. De forma adicional, se estudió la ecotoxicidad de los SAILs/surfactantes en dos especies vegetales. Este estudio demuestra la potencialidad de los SAILs y surfactantes para su aplicación en biorremediación de suelos contaminados por HCH y propone varios SAILs para futuras investigaciones. The low bioavailability of hexachlorocyclohexane (HCH) affects the effectiveness of bioremediation processes of HCH-contaminated soils. The effect of the micellar action of a variety of surfactant-active ionic liquids (i.e. SAILs) and conventional surfactants on the apparent solubility of HCH and its bioavailability was studied. Solutions of SAILs/surfactants and HCH (at a concentration ca. 10 times its solubility limit) were prepared using two different concentrations of SAILs/surfactants (always >CMC). The results varied according to the HCH isomer, the SAIL/surfactant and the concentration used. Additionally, the ecotoxicity of SAILs/surfactants was studied in two plant species. This study demonstrates the potential of SAILs and surfactants for their application in bioremediation of HCH-contaminated soils and proposes several SAILs for future research.