RESUMO
In this study, we sought to compose consortia of plant growth-promoting (PGP) and trace element tolerant bacteria, to improve plant growth and inhibit uptake and translocation of trace elements, eventually allowing the cultivation of profitmaking crops on trace elements polluted soils, reducing the risks of entrance of these elements into the food chain. Sunflower (Helianthus annuus L.) was grown on two polluted military soils (MS1 and MS2) in greenhouse microcosms and inoculated with three different bacterial consortia (C1, C2, C3). Growth and physiological status of the plants were unaffected during the experiment with the inoculation. After 2 months, plants were harvested. Consortium C2 and C3 decreased Pb shoot bioaccumulation by respectively 80-85% when plants were grown in the MS1 and even to concentrations below detection limit in plants grown in MS2. Differences in uptake and (sub)cellular localization of Pb and Cd in selected bacterial isolates were investigated in vitro by TEM-EDX. Pb absorption was observed by Bacillus wiedmanni ST29 and Bacillus paramycoides ST9 cultures. While adsorption at the bacterial cell wall was observed by Bacillus paramycoides ST9 and retention in the extracellular matrix by Cellulosimicrobium cellulans ST54.
Assuntos
Helianthus , Poluentes do Solo , Oligoelementos , Actinobacteria , Bacillus , Biodegradação Ambiental , Humanos , Chumbo , Raízes de Plantas/química , Solo , Poluentes do Solo/análiseRESUMO
The area of soils polluted with heavy metals is increasing due to industrialization and globalization. Aromatic plant species can be a suitable alternative way for agricultural valorization and phytomanagement of such soils by the commercialization of essential oils avoiding risks for the food chain. The potential of growing Helianthus petiolaris in heavy metal polluted soils was assessed in pot experiments using spiked soils and soils from a shooting range. In terms of phytostabilization, H. petiolaris could grow in soils containing 1000 mg/kg Pb2+, 50 mg/kg Cd2+, accumulating more than three times the soil Cd content in the aerial parts and translocating significant amounts of Pb to the aerial parts when growing in soils polluted with up to 500 mg/kg Pb. When phytostabilization is considered, phytotoxicity of heavy metals strongly depends on the rhizospheric microbial communities, either by mitigating trace element phytotoxicity or promoting plant growth via phytohormone production. So, the effects of heavy metals on the diversity of the rhizospheric bacterial community were assessed using DNA-fingerprinting.
Assuntos
Helianthus , Metais Pesados , Poluentes do Solo , Biodegradação Ambiental , Cádmio , Chumbo , SoloRESUMO
Although the use of the pesticide 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT) was banned from the mid-1970s, its most abundant and recalcitrant degradation product, 2,2-bis(p-chlorophenyl)-1,1-dichloro-ethylene (DDE), is still present in terrestrial and aquatic ecosystems worldwide. Zucchini (Cucurbita pepo ssp. pepo) has been shown to accumulate high concentrations of DDE and was proposed for phytoremediation of contaminated soils. We performed a field trial covering a full plant life cycle. C. pepo plants inoculated with the plant growth-promoting endophytic strains Sphingomonas taxi UH1, Methylobacterium radiotolerans UH1, Enterobacter aerogenes UH1, or a consortium combining these 3 strains were grown on a DDE-contaminated field for 100 days. The effects of these inoculations were examined at both the plant level, by evaluating plant weight and plant DDE-content, and at the level of the cultivable and total endophytic communities. Inoculating plants with S. taxi UH1, M. radiotolerans UH1, and the consortium increased plant weight. No significant effects of the inoculations were observed on DDE-concentrations in plant tissues. However, the amount of DDE accumulated by C. pepo plants per growing season was significantly higher for plants that were inoculated with the consortium of the 3 strains. Therefore, inoculation of C. pepo with DDE-degrading endophytes might be promising for phytoremediation applications.
Assuntos
Cucurbita , Poluentes do Solo , Biodegradação Ambiental , Diclorodifenil Dicloroetileno/análise , Ecossistema , Endófitos , Raízes de PlantasRESUMO
Poplar clones were studied for their phytoextraction capacity in the second growth cycle (6-year growth) on a site in the Belgian Campine region, which is contaminated with Cd and Zn via historic atmospheric deposition of nearby zinc smelter activities. The field trial revealed regrowth problems for some clones that could not be predicted in the first growth cycle. Four allometric relations were assessed for their capacity to predict biomass yield in the second growth cycle. A power function based on the shoot diameter best estimates the biomass production of poplar with R2 values between 0.94 and 0.98. The woody biomass yield ranged from 2.1 to 4.8 ton woody Dry Mass (DM) ha-1 y-1. The primary goal was to reduce soil concentrations of metals caused by phytoextraction. Nevertheless, increased metal concentrations were determined in the topsoil. This increase can partially be explained by the input of metals from deeper soil layers in the top soil through litterfall. The phytoextraction option with poplar short rotation coppice in this setup did not lead to the intended soil remediation in a reasonable time span. Therefore, harvest of the leaf biomass is put forward as a crucial part of the strategy for soil remediation through Cd/Zn phytoextraction.
Assuntos
Biodegradação Ambiental , Metais Pesados , Populus , Poluentes do Solo , Bélgica , Folhas de Planta , MadeiraRESUMO
Hydrophobins are small secreted proteins that are present as several gene copies in most fungal genomes. Their properties are now well understood: they are amphiphilic and assemble at hydrophilic/hydrophobic interfaces. However, their physiological functions remain largely unexplored, especially within mycorrhizal fungi. In this study, we identified hydrophobin genes and analysed their distribution in eight mycorrhizal genomes. We then measured their expression levels in three different biological conditions (mycorrhizal tissue vs. free-living mycelium, organic vs. mineral growth medium and aerial vs. submerged growth). Results confirmed that the size of the hydrophobin repertoire increased in the terminal orders of the fungal evolutionary tree. Reconciliation analysis predicted that in 41% of the cases, hydrophobins evolved from duplication events. Whatever the treatment and the fungal species, the pattern of expression of hydrophobins followed a reciprocal function, with one gene much more expressed than others from the same repertoire. These most-expressed hydrophobin genes were also among the most expressed of the whole genome, which suggests that they play a role as structural proteins. The fine-tuning of the expression of hydrophobin genes in each condition appeared complex because it differed considerably between species, in a way that could not be explained by simple ecological traits. Hydrophobin gene regulation in mycorrhizal tissue as compared with free-living mycelium, however, was significantly associated with a calculated high exposure of hydrophilic residues.
Assuntos
Proteínas Fúngicas/genética , Duplicação Gênica , Genoma Fúngico , Micorrizas/genética , Genômica , MicélioRESUMO
In this study different bacterial inoculation methods were tested for tobacco plants growing in a mine-soil contaminated with Pb, Zn, and Cd. The inoculation methods evaluated were: seed inoculation, soil inoculation, dual soil inoculation event, and seed+soil inoculation. Each inoculum was added at two bacterial densities (10(6) CFUs mL(-1) and 10(8) CFUs mL(-1)). The objectives were to evaluate whether or not the mode of inoculation or the number of applied microorganisms influences plant response. The most pronounced bacterial-induced effect was found for biomass production, and the soil inoculation treatment (using 10(6) CFUs mL(-1)) led to the highest increase in shoot dry weight yield (up to 45%). Bacterial-induced effects on shoot metal concentrations were less pronounced; although a positive effect was found on shoot Pb concentration when using 10(8) CFUs mL(-1) in the soil inoculation (29% increase) and in the seed+soil inoculation (34% increase). Also shoot Zn concentration increased by 24% after seed inoculation with 10(6) CFUs mL(-1). The best effects on the total metal yield were not correlated with an increasing number of inoculated bacteria. In fact the best results were found after a single soil inoculation using the lower cellular density of 10(6) CFUs mL(-1).
Assuntos
Inoculantes Agrícolas/fisiologia , Nicotiana/metabolismo , Nicotiana/microbiologia , Rhodococcus/fisiologia , Poluentes do Solo/metabolismo , Inoculantes Agrícolas/crescimento & desenvolvimento , Biodegradação Ambiental , Cádmio/análise , Cádmio/metabolismo , Brotos de Planta/química , Brotos de Planta/metabolismo , Rhodococcus/crescimento & desenvolvimento , Microbiologia do Solo , Poluentes do Solo/análise , Nicotiana/química , Nicotiana/crescimento & desenvolvimentoRESUMO
Gentle remediation options (GROs) are risk management strategies or technologies involving plant (phyto-), fungi (myco-), and/or bacteria-based methods that result in a net gain (or at least no gross reduction) in soil function as well as effective risk management. GRO strategies can be customised along contaminant linkages, and can generate a range of wider economic, environmental and societal benefits in contaminated land management (and in brownfields management more widely). The application of GROs as practical on-site remedial solutions is still limited however, particularly in Europe and at trace element (typically metal and metalloid) contaminated sites. This paper discusses challenges to the practical adoption of GROs in contaminated land management, and outlines the decision support tools and best practice guidance developed in the European Commission FP7-funded GREENLAND project aimed at overcoming these challenges. The GREENLAND guidance promotes a refocus from phytoremediation to wider GROs- or phyto-management based approaches which place realisation of wider benefits at the core of site design, and where gentle remediation technologies can be applied as part of integrated, mixed, site risk management solutions or as part of "holding strategies" for vacant sites. The combination of GROs with renewables, both in terms of biomass generation but also with green technologies such as wind and solar power, can provide a range of economic and other benefits and can potentially support the return of low-level contaminated sites to productive usage, while combining GROs with urban design and landscape architecture, and integrating GRO strategies with sustainable urban drainage systems and community gardens/parkland (particularly for health and leisure benefits), has large potential for triggering GRO application and in realising wider benefits in urban and suburban systems. Quantifying these wider benefits and value (above standard economic returns) will be important in leveraging funding for GRO application and soft site end-use more widely at vacant or underutilized sites.
Assuntos
Biodegradação Ambiental , Poluição Ambiental , Técnicas de Apoio para a Decisão , Europa (Continente) , Metais Pesados/análise , Plantas , Gestão de Riscos/métodos , Microbiologia do Solo , Poluentes do Solo/análise , Oligoelementos/análiseRESUMO
In the central part of the Iberian Peninsula there are old sealed landfills containing soils co-contaminated by several heavy metals (Cu, Zn, Pb, Cd, Ni, As, Cr, Fe, Al, Mn) and organic pollutants of different families (hydrocarbons, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, pesticides and other organochlorinated compounds, phenols and volatile compounds), which this work will address. We have focused on phytoremedial plants that are able to deal with this type of complex pollution, not only species that tolerate the joint effect of heavy metals in the soil, but also those that can take advantage of associated bacteria to efficiently break down organic compounds. This study was carried out with Lupinus luteus and its endophytes in two greenhouse experiments: A) growing in a substrate artificially contaminated with benzo(a)pyrene (BaP), and B) using real co-contaminated landfill soils. Endophytes of roots and shoots were isolated in both bioassays. Plant growth-promotion tests and organic pollutant tolerance and degradation tests were conducted on all strains isolated in bioassay A), and on those proving to be pure cultures from bioassay B). The selected landfill is described as are isolation and test procedures. Results indicate that plants did not show toxicity symptoms when exposed to BaP but did when grown in landfill soil. Some endophytes demonstrated plant growth-promotion capacity and tolerance to BaP and other organic compounds (diesel and PCB commercial mixtures). A few strains may even have the capacity to metabolize those organic pollutants. The overall decline in plant growth-promotion capacity in those strains isolated from the landfill soil experiment, compared with those from the bioassay with BaP, may indicate that lupin endophytes are not adapted to metal concentration in roots and shoots and fail to grow. As a result, most isolated root endophytes must have colonized root tissues from the soil. While preliminary degradation tests showed promising results (some strains exhibiting the potential to use organic pollutants as their sole source of carbon), these are not conclusive and further in-depth degradation assays need to be performed.
Assuntos
Biodegradação Ambiental , Endófitos , Lupinus/metabolismo , Metais Pesados/metabolismo , Raízes de Plantas/microbiologia , Poluentes do Solo/análise , Bactérias/metabolismo , Benzo(a)pireno/farmacocinética , Benzo(a)pireno/toxicidade , Bioensaio , Carbono/metabolismo , Hidrocarbonetos/análise , Hidrocarbonetos/farmacocinética , Lupinus/efeitos dos fármacos , Lupinus/crescimento & desenvolvimento , Metais Pesados/análise , Raízes de Plantas/metabolismo , Bifenilos Policlorados/análise , Bifenilos Policlorados/farmacocinética , Hidrocarbonetos Policíclicos Aromáticos/análise , Hidrocarbonetos Policíclicos Aromáticos/farmacocinética , Solo , Microbiologia do Solo , Poluentes do Solo/farmacocinética , Espanha , Instalações de Eliminação de ResíduosRESUMO
Gentle Remediation Options (GRO) are risk management strategies or techniques for contaminated sites that result in no gross reduction in soil functionality (or a net gain) as well as risk management. Intelligently applied GROs can provide: (a) rapid risk management via pathway control, through containment and stabilisation, coupled with a longer term removal or immobilisation/isolation of the contaminant source term; and (b) a range of additional economic (e.g. biomass generation), social (e.g. leisure and recreation) and environmental (e.g. CO2 sequestration) benefits. In order for these benefits to be optimised or indeed realised, effective stakeholder engagement is required. This paper reviews current sector practice in stakeholder engagement and its importance when implementing GRO and other remediation options. From this, knowledge gaps are identified, and strategies to promote more effective stakeholder engagement during GRO application are outlined. Further work is required on integrating stakeholder engagement strategies into decision support systems and tools for GRO (to raise the profile of the benefits of effective stakeholder engagement and participation, particularly with sector professionals), and developing criteria for the identification of different stakeholder profiles/categories. Demonstrator sites can make a significant contribution to stakeholder engagement via providing evidence on the effectiveness of GRO under varying site contexts and conditions. Effective and sustained engagement strategies however will be required to ensure that site risk is effectively managed over the longer-term, and that full potential benefits of GRO (e.g. CO2 sequestration, economic returns from biomass generation and "leverage" of marginal land, amenity and educational value, ecosystem services) are realised and communicated to stakeholders.
Assuntos
Conservação dos Recursos Naturais/métodos , Tomada de Decisões , Recuperação e Remediação Ambiental/métodos , Biodegradação Ambiental , União Europeia , Medição de Risco , SoloRESUMO
Phytoextraction has a promising potential as an environmentally friendly clean-up method for soils contaminated with toxic metals. To improve the development of efficient phytoextraction strategies, better knowledge regarding metal uptake, translocation and detoxification in planta is a prerequisite. This review highlights our current understanding on these mechanisms, and their impact on plant growth and health. Special attention is paid to the central role of glutathione (GSH) in this process. Because of the high affinity of metals to thiols and as a precursor for phytochelatins (PCs), GSH is an essential metal chelator. Being an important antioxidant, a direct link between metal detoxification and the oxidative challenge in plants growing on contaminated soils is observed, where GSH could be a key player. In addition, as redox couple, oxidized and reduced GSH transmits specific information, in this way tuning cellular signalling pathways under environmental stress conditions. Possible improvements of phytoextraction could be achieved by using transgenic plants or plant-associated microorganisms. Joined efforts should be made to cope with the challenges faced with phytoextraction in order to successfully implement this technique in the field.
Assuntos
Glutationa/metabolismo , Metais/metabolismo , Plantas/metabolismo , Poluentes do Solo/metabolismo , Antioxidantes/metabolismo , Bactérias , Biodegradação Ambiental , Transporte Biológico , Quelantes/metabolismo , Fungos , Oxirredução , Fitoquelatinas/metabolismo , Desenvolvimento Vegetal , Plantas/microbiologia , Plantas Geneticamente Modificadas , Compostos de Sulfidrila/metabolismoRESUMO
Gentle remediation options (GRO) are based on the combined use of plants, associated microorganisms and soil amendments, which can potentially restore soil functions and quality. We studied the effects of three GRO (aided-phytostabilisation, in situ stabilisation and phytoexclusion, and aided-phytoextraction) on the soil microbial biomass and respiration, the activities of hydrolase enzymes involved in the biogeochemical cycles of C, N, P, and S, and bacterial community structure of trace element contaminated soils (TECS) from six field trials across Europe. Community structure was studied using denaturing gradient gel electrophoresis (DGGE) fingerprinting of Bacteria, α- and ß-Proteobacteria, Actinobacteria and Streptomycetaceae, and sequencing of DGGE bands characteristic of specific treatments. The number of copies of genes involved in ammonia oxidation and denitrification were determined by qPCR. Phytomanagement increased soil microbial biomass at three sites and respiration at the Biogeco site (France). Enzyme activities were consistently higher in treated soils compared to untreated soils at the Biogeco site. At this site, microbial biomass increased from 696 to 2352 mg ATP kg-1 soil, respiration increased from 7.4 to 40.1 mg C-CO2 kg-1 soil d-1, and enzyme activities were 2-11-fold higher in treated soils compared to untreated soil. Phytomanagement induced shifts in the bacterial community structure at both, the total community and functional group levels, and generally increased the number of copies of genes involved in the N cycle (nirK, nirS, nosZ, and amoA). The influence of the main soil physico-chemical properties and trace element availability were assessed and eventual site-specific effects elucidated. Overall, our results demonstrate that phytomanagement of TECS influences soil biological activity in the long term.
Assuntos
Biodegradação Ambiental , Microbiologia do Solo , Poluentes do Solo/análise , Oligoelementos/análise , Bactérias/efeitos dos fármacos , Betaproteobacteria , Biomassa , Eletroforese em Gel de Gradiente Desnaturante , Europa (Continente) , França , Plantas , Solo/química , Poluentes do Solo/toxicidade , Oligoelementos/toxicidadeRESUMO
In a lysimeter set-up, compost addition to an industrial contaminated soil slightly reduced phytotoxicity to bean seedlings. The "Phytotoxicity Index" (on a scale from 1 to 4) decreased from 3.5 to 2.8. The same treatment also reduced metal accumulation in grasses: mean Zn, Cd and Pb concentrations decreased respectively from 623 to 135, from 6.2 to 1.3 and from 10.7 to <6 mg kg-1 dry weight. When combined with inorganic metal immobilizing amendments, compost had a beneficial effect on plant responses additional to the inorganic amendments alone. Best results were obtained when using compost (C)+cyclonic ashes (CA)+steel shots (SS). The "Phytotoxicity Index" decreased to 1.7, highest diversity of spontaneously colonizing plants occurred, and metal accumulation in grasses reduced to values for uncontaminated soils. Based on the first year evaluation, C+CA+SS showed to be an efficient treatment for amendment assisted phytostabilization of the contaminated Overpelt soil.
Assuntos
Biodegradação Ambiental , Metais/toxicidade , Phaseolus/crescimento & desenvolvimento , Poluentes do Solo/toxicidade , Sedimentos Geológicos , Substâncias Húmicas , Concentração de Íons de Hidrogênio , Metais/análise , Metais/metabolismo , Phaseolus/química , Phaseolus/metabolismo , Poluentes do Solo/metabolismoRESUMO
A lysimeter approach (under natural climatologic conditions) was used to evaluate the effect of four metal immobilizing soil treatments [compost (C), compost+cyclonic ashes (C+CA), compost+cyclonic ashes+steel shots (C+CA+SS)) and cyclonic ashes+steel shots (CA+SS)] on metal leaching through an industrially contaminated soil. All treatments decreased Zn and Cd leaching. Strongest reductions occurred after CA+SS and C+CA+SS treatments (Zn: -99.0% and -99.2% respectively; Cd: -97.2% and -98.3% respectively). Copper and Pb leaching increased after C (17 and >30 times for Cu and Pb respectively) and C+CA treatment (4.4 and >3.7 times for Cu and Pb respectively). C+CA+SS or CA+SS addition did not increase Cu leaching; the effect on Pb leaching was not completely clear. Our results demonstrate that attention should be paid to Cu and Pb leaching when organic matter additions are considered for phytostabilization of metal contaminated soils.
Assuntos
Biodegradação Ambiental , Metais/metabolismo , Phaseolus/metabolismo , Poluentes do Solo/metabolismo , Adsorção , Cádmio/análise , Cádmio/metabolismo , Cobre/análise , Cobre/metabolismo , Resíduos Industriais , Chumbo/análise , Chumbo/metabolismo , Metais/análise , Phaseolus/química , Poluentes do Solo/análise , Aço , Poluentes da Água/análise , Poluentes da Água/metabolismo , Zinco/análise , Zinco/metabolismoRESUMO
2,2-bis(p-chlorophenyl)-1,1-dichloro-ethylene (DDE) is the most abundant and persistent degradation product of the pesticide 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT) and is encountered in contaminated soils worldwide. Both DDE and DDT are classified as Persistent Organic Pollutants (POPs) due to their high hydrophobicity and potential for bioaccumulation and biomagnification in the food chain. Zucchini (Cucurbita pepo ssp. pepo) has been shown to accumulate high concentrations of DDE and other POPs and has been proposed as a phytoremediation tool for contaminated soils. The endophytic bacteria associated with this plant may play an important role in the remedial process. Therefore, this research focuses on changes in endophytic bacterial communities caused by the exposure of C. pepo to DDE. The total bacterial community was investigated using cultivation-independent 454 pyrosequencing, while the cultivable community was identified using cultivation-dependent isolation procedures. For both procedures, increasing numbers of endophytic bacteria, as well as higher diversities of genera were observed when plants were exposed to DDE. Several bacterial genera such as Stenotrophomonas sp. and Sphingomonas sp. showed higher abundance when DDE was present, while, for example Pseudomonas sp. showed a significantly lower abundance in the presence of DDE. These findings suggest tolerance of different bacterial strains to DDE, which might be incorporated in further investigations to optimize phytoremediation with the possible use of DDE-degrading endophytes.
Assuntos
Bactérias/efeitos dos fármacos , Cucurbita/microbiologia , Diclorodifenil Dicloroetileno/toxicidade , Endófitos/efeitos dos fármacos , Poluentes do Solo/toxicidade , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Biodegradação Ambiental , Biodiversidade , Cucurbita/química , Cucurbita/efeitos dos fármacos , Cucurbita/metabolismo , Diclorodifenil Dicloroetileno/análise , Diclorodifenil Dicloroetileno/metabolismo , Endófitos/classificação , Endófitos/genética , Endófitos/isolamento & purificação , Praguicidas/análise , Praguicidas/metabolismo , Praguicidas/toxicidade , Poluentes do Solo/análise , Poluentes do Solo/metabolismoRESUMO
Trans-generational adaptation is important to respond rapidly to environmental challenges and increase overall plant fitness. Besides well-known mechanisms such as epigenetic modifications, vertically transmitted endophytic bacteria might contribute to this process. The cultivable and total endophytic communities of several generations of Arabidopsis thaliana seeds harvested from plants exposed to cadmium (Cd) or not exposed were investigated. The diversity and richness of the seed endophytic community decreased with an increasing number of generations. Aeromicrobium and Pseudonocardia were identified as indicator species in seeds from Cd-exposed plants, while Rhizobium was abundantly present in both seed types. Remarkably, Rhizobium was the only genus that was consistently detected in seeds of all generations, which suggests that the phenotypic characteristics were more important as selection criteria for which bacteria are transferred to the next plant generation than the actual genera. Production of IAA was an important trait for endophytes from both seed types, while ACC deaminase activity and Cd tolerance were mainly associated with seed endophytes from Cd-exposed plants. Understanding how different factors influence the seed endophytic community can help us to improve seed quality and plant growth through different biotechnological applications.
Assuntos
Arabidopsis/microbiologia , Bactérias/isolamento & purificação , Cádmio/farmacologia , Endófitos/isolamento & purificação , Actinobacteria/classificação , Actinobacteria/isolamento & purificação , Actinobacteria/metabolismo , Arabidopsis/efeitos dos fármacos , Bactérias/classificação , Bactérias/metabolismo , Proteínas de Bactérias/metabolismo , Biodiversidade , Carbono-Carbono Liases/metabolismo , Endófitos/classificação , Endófitos/metabolismo , Fenótipo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/microbiologia , Rhizobium/classificação , Rhizobium/isolamento & purificação , Rhizobium/metabolismo , Sementes/efeitos dos fármacos , Sementes/microbiologia , Análise de Sequência de DNARESUMO
Metazachlor is a chloroacetamide herbicide, frequently used in Brassica napus cultivations around the world. Its primary target is the inhibition of very long chain fatty acid biosynthesis. This study included a morphological and physiological screening of hydroponically grown B. napus, exposed to a concentration range of 0, 0.25, 0.50, 0.75 and 1.0kg metazachlor per hectare. The results indicate that within a month after application, growth and development of B. napus are severely affected by low metazachlor doses. At intermediate metazachlor concentrations, loss of phosphorous and potassium from the plant tissues suggests destabilisation of cellular membranes, which may be a direct consequence of metazachlor application. This membrane instability could be indirectly linked with alterations of electron transport and a reduction of carbon assimilation. At increased metazachlor doses of 0.75kga.i.ha(-1), pigment concentrations are strongly reduced. However, chlorophyll fluorescence parameters seem to remain unaffected at metazachlor doses up to 0.75kga.i.ha(-1). At a metazachlor concentration of 1.0kga.i.ha(-1), negative effects are observed on all tested parameters, resulting in limited survival. The results indicate photosynthesis is assured at intermediate metazachlor concentrations for the cost of growth and development. It is clear that photosynthesis plays a key role in the survival strategy of young plants to overcome initially induced chemical stress.
Assuntos
Acetamidas/toxicidade , Brassica napus/efeitos dos fármacos , Herbicidas/toxicidade , Fotossíntese/efeitos dos fármacos , Brassica napus/metabolismo , Relação Dose-Resposta a DrogaRESUMO
Endophytic bacteria often have beneficial effects on their host plants that can be exploited for bioremediation applications but, according to the literature, only 0.001-1% of all endophytic microbes should be cultivable. This study compared the cultivated endophytic communities of the roots and shoots of Cucurbita pepo with the total endophytic communities as determined by cultivation-dependent techniques and 454 pyrosequencing. The ten most abundant taxa of the total communities aligned well with the cultivated taxa; however, the abundance of these taxa in the two communities differed greatly. Enterobacter showed very low presence in the total communities, whereas they were dominantly present in the cultivated communities. Although Rhizobium dominated in total root and shoot communities, it was poorly cultivable and even then only in growth media containing plant extract. Since endophytes likely contribute to plant-growth promotion, cultivated bacterial strains were tested for their plant-growth promoting capabilities, and the results were correlated with their abundance in the total community. Bacillus and Pseudomonas showed promising results when considering cultivability, abundance in the total community and plant-growth promoting capability. This study demonstrated that, although a limited number of bacterial genera were cultivable, current cultivation-dependent techniques may be sufficient for further isolation and inoculation experiments that aim to improve phytoremediation efficiency.
Assuntos
Bacillus/crescimento & desenvolvimento , Cucurbita/microbiologia , Endófitos/crescimento & desenvolvimento , Enterobacter/crescimento & desenvolvimento , Raízes de Plantas/microbiologia , Brotos de Planta/microbiologia , Pseudomonas/crescimento & desenvolvimento , Rhizobium/crescimento & desenvolvimento , Bacillus/genética , Bacillus/isolamento & purificação , Biodiversidade , DNA Bacteriano/genética , Endófitos/genética , Endófitos/isolamento & purificação , Enterobacter/genética , Enterobacter/isolamento & purificação , Tipagem Molecular , Pseudomonas/genética , Pseudomonas/isolamento & purificação , RNA Ribossômico 16S , Rhizobium/genética , Rhizobium/isolamento & purificaçãoRESUMO
Many endophytes have beneficial effects on plants and can be exploited in biotechnological applications. Studies hypothesize that only 0.001-1% of all plant-associated bacteria are cultivable. Moreover, even after successful isolations, many endophytic bacteria often show reduced regrowth capacity. This research aimed to optimize isolation processes and culturing these bacteria afterwards. We compared several minimal and complex media in a screening. Beside the media themselves, two gelling agents and adding plant extract to media were investigated to enhance the number and diversity of endophytes as well as the growth capacity when regrown after isolation. In this work, 869 medium delivered the highest numbers of cultivable bacteria, as well as the highest diversity. When comparing gelling agents, no differences were observed in the numbers of bacteria. Adding plant extract to the media lead to a slight increase in diversity. However, when adding plant extract to improve the regrowth capacity, sharp increases of viable bacteria occurred in both rich and minimal media.
Assuntos
Bactérias/isolamento & purificação , Técnicas Bacteriológicas/métodos , Meios de Cultura/química , Endófitos/isolamento & purificação , Extratos Vegetais/metabolismo , Plantas/microbiologia , Bactérias/crescimento & desenvolvimento , Bactérias/metabolismo , Endófitos/crescimento & desenvolvimento , HumanosRESUMO
We studied the microbial functional diversity, biochemical activity, heavy metals (HM) availability and soil toxicity of Cd, Pb and Zn contaminated soils, kept under grassland or short rotation coppice (SRC) to attenuate the risks associated with HM contamination and restore the soil ecological functions. Soil microbial functional diversity was analyzed by the GeoChip, a functional gene microarray containing probes for genes involved in nutrient cycling, metal resistance and stress response. Soil under SRC showed a higher abundance of microbial genes involved in C, N, P and S cycles and resistance to various HM, higher microbial biomass, respiration and enzyme activity rates, and lower HM availability than the grassland soil. The linkages between functional genes of soil microbial communities and soil chemical properties, HM availability and biochemical activity were also investigated. Soil toxicity and N, P and Pb availability were important factors in shaping the microbial functional diversity, as determined by CCA. We concluded that in HM contaminated soils the microbial functional diversity was positively influenced by SRC management through the reduction of HM availability and soil toxicity increase of nutrient cycling. The presented results can be important in predicting the long term environmental sustainability of plant-based soil remediation.
Assuntos
Variação Genética , Metais Pesados/metabolismo , Rotação , Salix/metabolismo , Microbiologia do Solo , Poluentes do Solo/metabolismo , Solo/química , Biodegradação Ambiental , Biomassa , Metais Pesados/isolamento & purificação , Poluentes do Solo/isolamento & purificaçãoRESUMO
⢠The effects of environmental heavy metal pollution on the genetic structure of pioneer populations of the ectomycorrhizal basidiomycete Suillus luteus were assessed. ⢠Sporocarps were collected from nine different locations and characterized by amplified fragment length polymorphism (AFLP) markers. Six of the sampling sites were contaminated with heavy metals and were dominated by tolerant individuals. Considerable genetic diversity was found within geographic subpopulations, but no reduction of the genetic diversity of populations inhabiting contaminated soils was observed. Neither did significant clustering of subpopulations inhabiting contaminated soils occur. Overall, the genetic differentiation between subpopulations was low, but Bayesian inference indicated the presence of two genetically differentiated clusters of individuals, which may correspond to different intercompatibility groups in S. luteus. ⢠Heavy metal contamination seems to have a limited influence on the genetic structure of populations of S. luteus. Loss of diversity may have been prevented by sexual reproduction and rapid evolution of the tolerance trait or initial genetic bottlenecks may have been reduced by admixture and recurrent migration from surrounding populations colonizing noncontaminated soils.