Periodic Reporting for period 1 - BIOTAC (Soil bioremediation through flagellated bacteria: unravelling the mechanisms for enhancing bacterial tactic response)
Période du rapport: 2021-01-01 au 2022-12-31
Soils are extremely complex, heterogeneous and evolving ecosystems with essential functions for the development of life and human activities. They are non-renewable resources at the human time scale, and its preservation is then a synonym of biosphere protection. Chemical pollution is one of the main causes of deterioration of soil ecosystem services and a severe environmental problem at a global scale with significant ecological risks. Pollution of soils with hydrophobic organic chemicals (HOCs) is of special concern due to their high toxicity and persistence.
Microbial communities are the main drivers of soil ecological functioning, and the exploitation of their specific capabilities in bioremediation is a low-impact and cost-effective strategy to restore ecosystem services and soil functionality in polluted environments. Bacterial dispersal has a significant impact on pollutant turnover in contaminated soils. Flagellated bacteria able to degrade organic pollutants, hold tactic responses to a variety of stimuli and reach pollutant hotspots, enhancing the access to poorly bioavailable carbon sources by steepening pollutant concentration gradients at interfaces. However, bacterial motility in porous media is often restricted due to high cell deposition rates and adhesion to soil particles, and in this sense, the modulating role of biological and chemical effectors is decisive.
The main objective of BIOTAC was the study of the microbiological mechanisms involved in the bioavailability enhancement and turnover of HOCs in soils through microbial dispersal, and their application for the development of innovative soil bioremediation strategies based on the enhancement of pollutant biodegradation through the improvement of the transport of bacteria towards pollutant hotspots. BIOTAC results could be used as a powerful tool to unravel the mechanisms that promote pollutant turnover and to select the best actions to improve these “hidden” microscale processes, and apply them for the restoration and risk reduction in degraded soils.
Microbial communities are the main drivers of soil ecological functioning, and the exploitation of their specific capabilities in bioremediation is a low-impact and cost-effective strategy to restore ecosystem services and soil functionality in polluted environments. Bacterial dispersal has a significant impact on pollutant turnover in contaminated soils. Flagellated bacteria able to degrade organic pollutants, hold tactic responses to a variety of stimuli and reach pollutant hotspots, enhancing the access to poorly bioavailable carbon sources by steepening pollutant concentration gradients at interfaces. However, bacterial motility in porous media is often restricted due to high cell deposition rates and adhesion to soil particles, and in this sense, the modulating role of biological and chemical effectors is decisive.
The main objective of BIOTAC was the study of the microbiological mechanisms involved in the bioavailability enhancement and turnover of HOCs in soils through microbial dispersal, and their application for the development of innovative soil bioremediation strategies based on the enhancement of pollutant biodegradation through the improvement of the transport of bacteria towards pollutant hotspots. BIOTAC results could be used as a powerful tool to unravel the mechanisms that promote pollutant turnover and to select the best actions to improve these “hidden” microscale processes, and apply them for the restoration and risk reduction in degraded soils.
BIOTAC aimed at study the mechanisms operating with flagellated bacteria for bioavailability enhancements and, therefore, a faster turnover of HOCs in soils. We studied, at the microorganism scale, the role of bacterial taxis in chemical gradients (chemotaxis) in pollutant bioavailability, modelling and integrating them with other microbial adaptations (i. e. the production of biosurfactants). We have developed strategies to improve bacterial transport to pollutant sources, using carefully selected biological and chemical effectors (respectively including, mycelial networks and organic compounds), that favour flagella-mediated taxis, and the comobilization of immotile degrading strains. All this knowledge, was applied in controlled soil bioremediation experiments, in order to study the enhancement of HOCs’ degradation.
The tasks performed during this fellowship were ascribed to eight specific work packages (WP), five of which were related to purely scientific tasks, and the last three to dissemination, training and project management activities. The main results achieved are summarized in the next bullet points:
-WP1. Bacterial taxis as the driver for enhancing pollutant bioavailability and biodegradability: Characterization and quantification of chemotactic motility parameters of Pseudomonas putida G7 in bulk and porous media (including microfluidic devices) and development of a mathematical model of bacterial dispersion in micropores (in collaboration with AgroParisTech, France).
-WP2. Role of “fungal highways” in the motility and degradation efficiency of flagellated bacterial strains: Study of the effect of fungal highways on the dispersion of chemotactic bacteria and immotile bacteria in engineered porous systems (including microfluidic devices). Activities developed during the secondment in UFZ (Germany).
-WP3. Enhancement of bacterial dispersal using chemoeffectors: Characterization of chemotactic motility inside pores (including microfluidic devices).
-WP4. Synergies with other bioavailability-enhancing and catabolic mechanisms: Characterization and optimization of biosurfactant production of Bacillus subtilis DSM10, applied in WP5, together with P. putida G7.
-WP5. Assessing the risks and benefits from flagellated bacteria and pollutant bioavailability enhancements in mesocosms with field-contaminated soils: Greenhouse bioremediation experiments of kerosene-contaminated soils, using B. subtilis DSM10 as a biosurfactant producer and P. putida G7 as a co-mobilizer agent to enhance kerosene bioavailability.
Scientific papers, and communications to conferences and workshops, as well as knowledge transfer activities, assured the exploitation and dissemination of the results, and their accessibility for further research activities related to BIOTAC. Results have also been disseminated through BIOTAC twitter account (@BIOTAC_MSC), Dr. Balseiro-Romero twitter (@m_balseiro) and ResearchGate (https://www.researchgate.net/profile/Maria-Balseiro-Romero(s’ouvre dans une nouvelle fenêtre)) accounts, and outreach activities of IRNAS-CSIC (https://www.irnas.csic.es/en/(s’ouvre dans une nouvelle fenêtre)).
The tasks performed during this fellowship were ascribed to eight specific work packages (WP), five of which were related to purely scientific tasks, and the last three to dissemination, training and project management activities. The main results achieved are summarized in the next bullet points:
-WP1. Bacterial taxis as the driver for enhancing pollutant bioavailability and biodegradability: Characterization and quantification of chemotactic motility parameters of Pseudomonas putida G7 in bulk and porous media (including microfluidic devices) and development of a mathematical model of bacterial dispersion in micropores (in collaboration with AgroParisTech, France).
-WP2. Role of “fungal highways” in the motility and degradation efficiency of flagellated bacterial strains: Study of the effect of fungal highways on the dispersion of chemotactic bacteria and immotile bacteria in engineered porous systems (including microfluidic devices). Activities developed during the secondment in UFZ (Germany).
-WP3. Enhancement of bacterial dispersal using chemoeffectors: Characterization of chemotactic motility inside pores (including microfluidic devices).
-WP4. Synergies with other bioavailability-enhancing and catabolic mechanisms: Characterization and optimization of biosurfactant production of Bacillus subtilis DSM10, applied in WP5, together with P. putida G7.
-WP5. Assessing the risks and benefits from flagellated bacteria and pollutant bioavailability enhancements in mesocosms with field-contaminated soils: Greenhouse bioremediation experiments of kerosene-contaminated soils, using B. subtilis DSM10 as a biosurfactant producer and P. putida G7 as a co-mobilizer agent to enhance kerosene bioavailability.
Scientific papers, and communications to conferences and workshops, as well as knowledge transfer activities, assured the exploitation and dissemination of the results, and their accessibility for further research activities related to BIOTAC. Results have also been disseminated through BIOTAC twitter account (@BIOTAC_MSC), Dr. Balseiro-Romero twitter (@m_balseiro) and ResearchGate (https://www.researchgate.net/profile/Maria-Balseiro-Romero(s’ouvre dans une nouvelle fenêtre)) accounts, and outreach activities of IRNAS-CSIC (https://www.irnas.csic.es/en/(s’ouvre dans une nouvelle fenêtre)).
The results of BIOTAC are of a high value for European research on soil bioremediation and on soil microscale processes involved in the bioavailability of hydrophobic pollutants. BIOTAC project has unravelled the mechanisms governing bacterial dispersal in porous media, specifically, those mechanisms mediated by chemotactic motility. The results have involved a very innovative progress on soil remediation. The soil scientific community agree on the key role of microbial dispersal for enhancing pollutant bioavailability, but it is still not widely investigated and demonstrated in porous and soil media. BIOTAC has demonstrated how bacterial dispersal can be enhanced through the use of optimal bio- and chemoeffectors, not only for flagellated but also for non-motile microbes. The mechanisms have been studied both macro- and microscopically. This knowledge is very significant for understanding the hidden and still widely unknown microscale soil processes, so necessary for the study of soil microbiology and the accurate upscaling of those mechanisms in soil process modelling.