The TCE-degrading poplar endophyte Pseudomonas putida W619-TCE was inoculated in poplar cuttings, exposed to 0, 200 and 400 mg l(-1) TCE, that were grown in two different experimental setups. During a short-term experiment, plants were grown hydroponically in half strength Hoagland nutrient solution and exposed to TCE for 3 days. Inoculation with P. putida W619-TCE promoted plant growth, reduced TCE phytotoxicity and reduced the amount of TCE present in the leaves. During a mid-term experiment, plants were grown in potting soil and exposed to TCE for 3 weeks. Here, inoculation with P. putida W619-TCE had a less pronounced positive effect on plant growth and TCE phytotoxicity, but resulted in strongly reduced amounts of TCE in leaves and roots of plants exposed to 400 mg l(-1) TCE, accompanied by a lowered evapotranspiration of TCE. Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), which are known intermediates of TCE degradation, were not detected.
"Genes involved in the catabolism of a wide variety of organic compounds, including many naturally-occurring products (eg, metabolites from the partial degradation of lignin), are chromosomally encoded in the P. putida genome. As stated above, some strains of this species colonize the rhizosphere of plants (Molina et al., 2000; Weyens et al., 2010; Li et al., 2013; Roca et al., 2013). This characteristic, "
[Show abstract][Hide abstract] ABSTRACT: Pseudomonas putida are strict aerobes that proliferate in a range of temperate niches and are of interest for environmental applications due to their capacity to degrade pollutants and ability to promote plant growth. Furthermore solvent tolerant strains are useful for biosynthesis of added-value chemicals. We present a comprehensive comparative analysis of nine strains and the first characterization of the Pseudomonas putida pangenome. The core genome of P. putida comprises approximately 3386 genes. The most abundant genes within the core genome are those that encode nutrient transporters. Other conserved genes include those for central carbon metabolism through the Entner-Doudoroff pathway, the pentose phosphate cycle, arginine and proline metabolism, and pathways for degradation of aromatic chemicals. Genes that encode transporters, enzymes and regulators for amino acid metabolism (synthesis and degradation) are all part of the core genome, as well as various electron transporters, which enable aerobic metabolism under different oxygen regimes. Within the core genome are thirty genes for flagella biosynthesis and twelve key genes for biofilm formation. Pseudomonas putida strains share 85% of the coding regions with Pseudomonas aeruginosa; however, in P. putida, virulence factors such as exotoxins and type III secretion systems are absent.
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"Recently, it was proposed that the addition of plant growthpromoting bacteria (preferably endophytes) is a simple and effective strategy to enhance plant growth and remediation of contaminants from the soil  . Endophytic bacteria can assist their host plant to overcome pollutant-induced stress responses and consequently improve plant growth and phytoremediation activity  . Several endophytic bacteria can also survive and colonize in the soil surrounding the roots, where they can penetrate into their associated plant via the roots , however, it was also observed that some phyllosphere bacteria may be a source of endophytic bacteria  . "
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to determine whether the inoculation of plant growth-promoting bacteria to plants, vegetated in soil irrigated with textile effluent, influences plant biomass production, and soil remediation. Three different plant species (Acacia ampliceps, Eucalyptus camaldulensis, and Leucaena leucocephala) with and without bacterial inoculation were grown in soil irrigated with secondary treated textile wastewater for one year. An endophytic bacterium, Burkholderia sp. strain PsJN, possessing plant growth-promoting 1-aminocyclopropane-1-carboxylate deaminase activity was inoculated to plants. There was more plant biomass production (up to 12%) and contaminants removal (up to 29%) from soil with bacterial inoculation as compared to soil having non-inoculated plants. Enhanced plant growth and soil remediation activity are associated with the survival and colonization of the inoculated bacterium in the rhizosphere and endosphere of plants. The highest plant biomass production and contaminants removal from soil were observed in the treatment, in which A. ampliceps was inoculated with Burkholderia sp. strain PsJN. These results suggest that plant-bacteria partnerships can be applied to improve plant growth and soil remediation during the application of industrial effluent for plant biomass production in the arid regions.
CLEAN - Soil Air Water 09/2014; 42(9). DOI:10.1002/clen.201300006 · 1.95 Impact Factor
"Rhizosphere bacteria, phyllosphere bacteria as well as endophytes can contribute to an improved phytoremediation efficiency (Valls and de Lorenzo, 2002; Lebeau et al., 2008; Kidd et al., 2009; Mastretta et al., 2009; Rajkumar et al., 2009; Taghavi et al., 2009; van der Lelie et al., 2009; Weyens et al., 2009b,c,d; 2010c; 2011; Becerra-Castro et al., 2011; 2012). "
[Show abstract][Hide abstract] ABSTRACT: Phytoextraction has been reported as an economically and ecologically sound alternative for the remediation of metal-contaminated soils. Willow is a metal phytoextractor of interest because it allows to combine a gradual contaminant removal with production of biomass that can be valorized in different ways. In this work two willow clones growing on a metal-contaminated site were selected: 'Belgisch Rood' (BR) with a moderate metal extraction capacity and 'Tora' (TO) with a twice as high metal accumulation. All cultivable bacteria associated with both willow clones were isolated and identified using 16SrDNA ARDRA analysis followed by 16SrDNA sequencing. Further all isolated bacteria were investigated for characteristics that might promote plant growth (production of siderophores, organic acids and indol acetic acid) and for their metal resistance. The genotypic and phenotypic characterization of the isolated bacteria showed that the TO endophytic bacterial population is more diverse and contains a higher percentage of metal-resistant plant growth promoting bacteria than the endophytic population associated with BR. We hypothesize that the difference in the metal accumulation capacity between BR and TO clones might be at least partly related to differences in characteristics of their associated bacterial population.
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