Plant species influences the composition of root system microbiome and its antibiotic resistance profile in a constructed wetland receiving primary treated wastewater.

Introduction: Constructed wetlands (CWs) are nature-based solutions for wastewater treatment where the root system microbiome plays a key role in terms of nutrient and pollutant removal. Nonetheless, little is known on plant-microbe interactions and bacterial population selection in CWs, which are mostly characterized in terms of engineering aspects.

Methods: Here, cultivation-independent and cultivation-based analyses were applied to study the bacterial communities associated to the root systems of and co-occurring in the same cell of a CW receiving primary treated wastewaters.

Flavonoids influence key rhizocompetence traits for early root colonization and PCB degradation potential of LB400.

Introduction: Flavonoids are among the main plant root exudation components, and, in addition to their role in symbiosis, they can broadly affect the functionality of plant-associated microbes: in polluted environments, for instance, flavonoids can induce the expression of the enzymatic degradative machinery to clean-up soils from xenobiotics like polychlorinated biphenyls (PCBs). However, their involvement in root community recruitment and assembly involving non-symbiotic beneficial interactions remains understudied and may be crucial to sustain the holobiont fitness under PCB stress.

Methods: By using a set of model pure flavonoid molecules and a natural blend of root exudates (REs) with altered flavonoid composition produced by mutant lines affected in flavonoid biosynthesis and abundance (null mutant , flavonoid aglycones hyperproducer , and flavonoid conjugates hyperaccumulator ), we investigated flavonoid contribution in stimulating rhizocompetence traits and the catabolic potential of the model bacterial strain for PCB degradation LB400.

Deciphering the interaction of bacteria inoculants with the recipient endophytic community in grapevine micropropagated plants.

Engineering the plant microbiome with beneficial endophytic bacteria can improve the growth, health, and productivity of the holobiont. Here, we administered two beneficial bacterial strains, VR04 sp. and GR12 sp.

DNA stable isotope probing on soil treated by plant biostimulation and flooding revealed the bacterial communities involved in PCB degradation.

Polychlorinated biphenyl (PCB)-contaminated soils represent a major treat for ecosystems health. Plant biostimulation of autochthonous microbial PCB degraders is a way to restore polluted sites where traditional remediation techniques are not sustainable, though its success requires the understanding of site-specific plant-microbe interactions. In an historical PCB contaminated soil, we applied DNA stable isotope probing (SIP) using C-labeled 4-chlorobiphenyl (4-CB) and 16S rRNA MiSeq amplicon sequencing to determine how the structure of total and PCB-degrading bacterial populations were affected by different treatments: biostimulation with Phalaris arundinacea subjected (PhalRed) or not (Phal) to a redox cycle and the non-planted controls (Bulk and BulkRed).

Strain BD413 Can Acquire an Antibiotic Resistance Gene by Natural Transformation on Lettuce Phylloplane and Enter the Endosphere.

Antibiotic resistance spread must be considered in a holistic framework which comprises the agri-food ecosystems, where plants can be considered a bridge connecting water and soil habitats with the human microbiome. However, the study of horizontal gene transfer events within the plant microbiome is still overlooked. Here, the environmental strain BD413 was used to study the acquisition of extracellular DNA (exDNA) carrying an antibiotic resistance gene (ARG) on lettuce phylloplane, performing experiments at conditions (i.

Pollution and edaphic factors shape bacterial community structure and functionality in historically contaminated soils.

Studies about biodegradation potential in soils often refer to artificially contaminated and simplified systems, overlooking the complexity associated with contaminated sites in a real context. This work aims to provide a holistic view on microbiome assembly and functional diversity in the model site SIN Brescia-Caffaro (Italy), characterized by historical and uneven contamination by organic and inorganic compounds. Here, physical and chemical analyses and microbiota characterization were applied on one-hundred-twenty-seven soil samples to unravel the environmental factors driving bacterial community assembly and biodegradation potential in three former agricultural fields.

Rhizosheath-root system changes exopolysaccharide content but stabilizes bacterial community across contrasting seasons in a desert environment.

Background: In hot deserts daily/seasonal fluctuations pose great challenges to the resident organisms. However, these extreme ecosystems host unique microenvironments, such as the rhizosheath-root system of desert speargrasses in which biological activities and interactions are facilitated by milder conditions and reduced fluctuations. Here, we examined the bacterial microbiota associated with this structure and its surrounding sand in the desert speargrass Stipagrostis pungens under the contrasting environmental conditions of summer and winter in the Sahara Desert.

Bacterial Inoculants Mitigating Water Scarcity in Tomato: The Importance of Long-Term Experiments.

Global population growth and climate change raise a challenge to agriculture, which, combined with the issues concerning the use of chemical fertilizers, have generated increasing attention in the use of plant-associated bacteria as a sustainable strategy in agri-food systems. The objective of this study is to evaluate the ability of five bacterial strains, previously isolated from the rhizosphere or endosphere of plants adapted to harsh environmental conditions, to act as potential plant biofertilizers in different conditions of water availability. The strain biosafety for a deliberate environmental release was investigated through a literature survey and antibiotic resistance testing.

'Cry-for-help' in contaminated soil: a dialogue among plants and soil microbiome to survive in hostile conditions.

An open question in environmental ecology regards the mechanisms triggered by root chemistry to drive the assembly and functionality of a beneficial microbiome to rapidly adapt to stress conditions. This phenomenon, originally described in plant defence against pathogens and predators, is encompassed in the 'cry-for-help' hypothesis. Evidence suggests that this mechanism may be part of the adaptation strategy to ensure the holobiont fitness in polluted environments.

PCB vertical and horizontal movement in agricultural soils of a highly contaminated site: Role of soil properties, cultivation history and PCB physico-chemical parameters.

The agricultural areas of a historically contaminated National Relevance Site (SIN Brescia Caffaro) in Italy are an ideal case for studying the long term vertical and horizontal movement of polychlorinated biphenyls (PCBs) in soil. Here, a former large producer of PCBs (Caffaro S.p.

New Data Set of Polychlorinated Dibenzo--dioxin and Dibenzofuran Half-Lives: Natural Attenuation and Rhizoremediation Using Several Common Plant Species in a Weathered Contaminated Soil.

In this paper, a new data set of polychlorinated dibenzo--dioxin and dibenzofuran (PCDD/Fs) half-lives (HLs) in soil is presented. Data are derived from a greenhouse experiment performed with an aged contaminated soil under semi-field conditions, obtained from a National Relevance Site (SIN) located in Northern Italy (SIN Brescia-Caffaro). Ten different treatments (combination of seven plant species with different soil conditions) were considered together with the respective controls (soil without plants).

Unveiling the Microbiota Diversity of the Xerophyte Argania spinosa L. Skeels Root System and Residuesphere.

The microbiota associated to xerophyte is a "black box" that might include microbes involved in plant adaptation to the extreme conditions that characterize their habitat, like water shortage. In this work, we studied the bacterial communities inhabiting the root system of Argania spinosa L. Skeels, a tree of high economic value and ecological relevance in Northern Africa.

Microbial assisted phytodepuration for water reclamation: Environmental benefits and threats.

Climate changes push for water reuse as a priority to counteract water scarcity and minimize water footprint especially in agriculture, one of the highest water consuming human activities. Phytodepuration is indicated as a promising technology for water reclamation, also in the light of its economic and ecological sustainability, and the use of specific bacterial inocula for microbial assisted phytodepuration has been proposed as a further advance for its implementation. Here we provided an overview on the selection and use of plant growth promoting bacteria in Constructed Wetland (CW) systems, showing their advantages in terms of plant growth support and pollutant degradation abilities.

Novel PCB-degrading Rhodococcus strains able to promote plant growth for assisted rhizoremediation of historically polluted soils.

Extended soil contamination by polychlorinated biphenyls (PCBs) represents a global environmental issue that can hardly be addressed with the conventional remediation treatments. Rhizoremediation is a sustainable alternative, exploiting plants to stimulate in situ the degradative bacterial communities naturally occurring in historically polluted areas. This approach can be enhanced by the use of bacterial strains that combine PCB degradation potential with the ability to promote plant and root development.

Rhizoremediation of weathered PCBs in a heavily contaminated agricultural soil: Results of a biostimulation trial in semi field conditions.

This paper describes the results of a rhizoremediation greenhouse experiment planned to select the best plant species and soil management for the bioremediation of weathered polychlorinated biphenyls (PCBs). We evaluated the ability of different plant species to stimulate activity and diversity of the soil microbial community leading to the reduction of PCB concentrations in a heavily contaminated soil (at mg kg-1 dw level), of the national priority site for remediation (SIN) "Brescia-Caffaro" in Italy. Biostimulation was determined in large size (6kg) pots, to reflect semi-field conditions with a soil/root volume ratio larger than in most rhizoremediation experiments present in the literature.

Rhizoremediation half-lives of PCBs: Role of congener composition, organic carbon forms, bioavailability, microbial activity, plant species and soil conditions, on the prediction of fate and persistence in soil.

Polychlorinated biphenyls (PCBs) are persistent organic pollutants widely produced and used in many countries until the increasing concern about their environmental risk lead to their ban in the 1980s. Although their emissions decreased, PCBs are nowadays still present in the environment and can be reemitted from reservoir compartments such as contaminated soils. In the last two decades, there has been a growing interest in bioremediation technologies that use plants and microorganisms (i.

Bacteria Associated to Plants Naturally Selected in a Historical PCB Polluted Soil Show Potential to Sustain Natural Attenuation.

The exploitation of the association between plants and microorganisms is a promising approach able to boost natural attenuation processes for soil clean-up in vast polluted areas characterized by mixed chemical contamination. We aimed to explore the selection of root-associated bacterial communities driven by different plant species spontaneously established in abandoned agricultural soils within a historical polluted site in north Italy. The site is highly contaminated by chlorinated persistent organic pollutants, mainly constituted by polychlorobiphenyls (PCBs), together with heavy metals and metalloids, in variable concentrations and uneven distribution.

Phyto-rhizoremediation of polychlorinated biphenyl contaminated soils: An outlook on plant-microbe beneficial interactions.

Polychlorinated biphenyls (PCBs) are toxic chemicals, recalcitrant to degradation, bioaccumulative and persistent in the environment, causing adverse effects on ecosystems and human health. For this reason, the remediation of PCB-contaminated soils is a primary issue to be addressed. Phytoremediation represents a promising tool for in situ soil remediation, since the available physico-chemical technologies have strong environmental and economic impacts.