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1.
Environ Monit Assess ; 192(11): 697, 2020 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-33043403

RESUMO

Environmental change is one of the primary issues faced by the farming community. Low rainfall and high temperature in arid and semiarid regions lead to the development of secondary salinisation, thus making the problem more severe. Under saline conditions, sodium is the most crucial cation that competes with potassium (K) and adversely affects plant metabolism by inhibiting plant enzymatic activities. Potassium-solubilising bacteria (KSB) play a vital role in solubilising fixed potassium and making it accessible to plants. In the current study, 42 KSB strains were isolated from paddy rhizosphere soil grown under salt-affected conditions. The plant-growth-promoting (PGP) properties of these rhizobacteria were also evaluated. Thirteen KSB strains, positive for all tested PGP traits, were evaluated for potassium solubilisation under sodium stress, namely, 0%, 3%, 5% and 7% NaCl stress. The five best strains (Acinetobacter pittii strain L1/4, A. pittii strain L3/3, Rhizobium pusense strain L3/4, Cupriavidus oxalaticus strain L4/12 and Ochrobactrum ciceri strain L5/1) based on the K-solubilising potential were identified by amplification, sequencing and bioinformatic analysis of the 16S rDNA sequences. The maximum potassium solubilisation was measured at 30 °C and pH 7 with glucose as carbon source. The application of these KSB strains significantly improved the shoot length, fresh weight, dry weight and chlorophyll contents of paddy plants grown under saline conditions. Hence, these strains could be halotolerant KSB bioinoculants that can be used to protect plants against salt stress.


Assuntos
Potássio , Microbiologia do Solo , Acinetobacter , Cupriavidus , Monitoramento Ambiental , Ochrobactrum , Rhizobium
2.
J Environ Qual ; 49(3): 754-761, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-33016404

RESUMO

Land application of manure introduces gastrointestinal microbes into the environment, including bacteria carrying antibiotic resistance genes (ARGs). Measuring soil ARGs is important for active stewardship efforts to minimize gene flow from agricultural production systems; however, the variety of sampling protocols and target genes makes it difficult to compare ARG results between studies. We used polymerase chain reaction (PCR) methods to characterize and/or quantify 27 ARG targets in soils from 20 replicate, long-term no-till plots, before and after swine manure application and simulated rainfall and runoff. All samples were negative for the 10 b-lactamase genes assayed. For tetracycline resistance, only source manure and post-application soil samples were positive. The mean number of macrolide, sulfonamide, and integrase genes increased in post-application soils when compared with source manure, but at plot level only, 1/20, 5/20, and 11/20 plots post-application showed an increase in erm(B), sulI, and intI1, respectively. Results confirmed the potential for temporary blooms of ARGs after manure application, likely linked to soil moisture levels. Results highlight uneven distribution of ARG targets, even within the same soil type and at the farm plot level. This heterogeneity presents a challenge for separating effects of manure application from background ARG noise under field conditions and needs to be considered when designing studies to evaluate the impact of best management practices to reduce ARG or for surveillance. We propose expressing normalized quantitative PCR (qPCR) ARG values as the number of ARG targets per 100,000 16S ribosomal RNA genes for ease of interpretation and to align with incidence rate data.


Assuntos
Esterco , Solo , Animais , Antibacterianos/farmacologia , Produtos Agrícolas , Resistência Microbiana a Medicamentos/genética , Microbiologia do Solo , Suínos
3.
J Environ Qual ; 49(4): 858-868, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33016490

RESUMO

Golf courses require extensive use of inputs to meet the needs of playability and aesthetics. The impact of these inputs on soil biological health is largely unknown. Two field trials were conducted at a golf course in Georgia to evaluate short-term effects of wetting agents (Cascade Plus and Duplex [C+D], Revolution [Rev]), plant growth regulators (PrimoMaxx [PM] and Cutless [CL]), and a product called PlantHelper (PH) on soil biological health by measuring microbial abundance and function. Quantitative polymerase chain reaction was used to measure microbial abundance, which included total bacteria, total fungi, and ammonia-oxidizing prokaryotes. Soil respiration and enzyme assays were used as additional indicators of soil health. In bentgrass putting green, total bacteria and ammonia-oxidizing bacteria decreased in abundance in response to the wetting agents and PH, indicating their sensitivity to the products. Whereas C+D stimulated urease activity, Rev and PH caused a short-lived but immediate increase in respiration, indicating that they acted as labile carbon sources. In a bermudagrass fairway, PM was the only product that caused an increase in total bacteria abundance. PrimoMaxx and CL caused a delayed increase in respiration, suggesting that they may have affected the microorganisms indirectly through their impact on root growth and exudate production later. Although CL caused a decrease in urease activity, none of the products significantly affected phosphatase activity. Overall, the products did not seem to have a lasting impact on soil biological health, although long-term studies are needed to confirm these observations.


Assuntos
Microbiologia do Solo , Solo , Amônia , Archaea , Bactérias
4.
Sci Total Environ ; 741: 140494, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32886976

RESUMO

Here, we examined the effects of low and high concentrations of perfluorooctanesulfonate (PFOS) on rhizosphere soil N cycling processes in the presence of Lythrum salicaria and Phragmites communis over 4 months. Compared with the control group, the nitrate nitrogen (NO3--N) content of the bulk soil in the low PFOS (0.1 mg kg-1) treatment significantly decreased (27.7%), the ammonium nitrogen (NH4+-N) content significantly increased (8.7%), and the pH value and total organic carbon (TOC) content slightly increased (0.3% and 1.1%, respectively). Compared with the low PFOS treatment, the content of NO3-N, NH4+-N and pH value in the bulk soil of the high PFOS treatment (50 mg kg-1) significantly increased (1.0%, 53.8% and 61.8%, respectively), and the TOC content significantly decreased (8.2%). Soil protease levels were high in the low PFOS treatment, but low in the high PFOS treatment. PFOS produced inverted U-shaped responses in the potential nitrification (1.5, 3.0, and 1.1 mg N d-1 kg-1 in no, low, and high PFOS, respectively), denitrification (0.19, 0.30, and 0.22 mg N d-1 kg-1 in no, low, and high PFOS, respectively), and N2O emission rates (0.01, 0.03, and 0.02 mg N d-1 kg-1 in no, low, and high PFOS, respectively) of bulk soil. The abundance of the archaea amoA gene decreased with increasing PFOS concentration, whereas that of bacterial amoA increased; inverted U-shaped responses were observed for narG, nirK, nirS, and nosZ. In the PFOS-contaminated rhizosphere soil, the observed changes differed from those in the bulk soil and differed between treatments. P. communis tended to upregulate each step of the nitrogen cycle under low PFOS conditions, whereas L. salicaria tended to inhibit them. Under high PFOS conditions, both test plants tended to act as inhibitors of the soil N-cycle; thus, the effects of PFOS on soil N transformation were plant-specific.


Assuntos
Rizosfera , Solo , Ácidos Alcanossulfônicos , Desnitrificação , Fluorcarbonetos , Nitrificação , Nitrogênio/análise , Ciclo do Nitrogênio , Microbiologia do Solo
5.
Sci Total Environ ; 741: 140463, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32886986

RESUMO

Microplastics (MPs) have become a global environmental concern while soil plastic pollution has been largely overlooked. In view of the severe antibiotic contamination in arable soils owing to land application of sewage sludge and animal manure, the invasion of MPs along with antibiotics may pose an unpredictable threat to soil microbial communities and ecological health. In this work, polyethylene MPs and ciprofloxacin (CIP) were applied to a soil microcosm to investigate the CIP degradation behavior and their combined effects on soil microbial communities. Compared with that of the individual amendment of CIP, the co-amendment of CIP and MPs reduced the CIP degradation efficiency during the 35 d cultivation period. In addition, the high-throughput sequencing results illustrated that the combined loading of MPs and CIP in soil significantly decreased the microbial diversity compared with that of individual contamination. As for the community structure, the microbial compositions at the phylum level were consistent among all treatments, and the most dominant phyla were Proteobacteria, Actinobacteria, and Chloroflexi. At the genus level, only one genus, namely Arthrobacter, was remarkably changed in the CIP-amended soil compared with that in the blank control, but four genera were significantly altered in the MPs-CIP co-amended soil. Serratia and Achromobacter were abundant in the combined polluted soil, which might have been involved in accelerated depletion of soil total nitrogen based on redundancy analysis. These findings may contribute to the understanding of bacterial responses to the combined pollution of MPs and antibiotics in soil ecosystems.


Assuntos
Microbiota , Poluentes do Solo/análise , Animais , Antibacterianos , Ciprofloxacino/análise , Microplásticos , Plásticos , Polietileno , Solo , Microbiologia do Solo
6.
Environ Monit Assess ; 192(10): 622, 2020 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-32894359

RESUMO

Soils are facing new environmental contaminants, such as nanomaterials. While these emerging contaminants are increasingly being released into soil, their potential impact on this medium and their effect on soil's major chemical components (e.g., sulfate, nitrate, ammonia, and phosphate) have yet to be examined, as well as their relation with microbial toxicity. Herein, column experiments were conducted to investigate the behavior of major ions under 10 and 200 mg/L multiple contaminations of graphene nanomaterials in agricultural and undisturbed soils, as well as the retention of the graphene nanomaterials in the soil and their effect on soil zeta potentials throughout the column. Moreover, to evaluate the impact of the risks of graphene nanomaterial contamination on soil major ions, the present study also examines the bacterial toxicity. The results showed that graphene retention was influenced the soil zeta potentials. Graphene also influenced the concentrations of the major ions in soil and the order of the influence degree was sulfate > phosphate > ammonia > nitrate. The changes of the major ions in soil by the exposure of graphene nanomaterials have also affected the response of selected bacteria.


Assuntos
Grafite , Nanoestruturas , Poluentes do Solo/análise , Monitoramento Ambiental , Íons , Solo , Microbiologia do Solo
7.
J Environ Sci (China) ; 97: 45-53, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32933739

RESUMO

Estuarine wetland is the transitional interface linking terrestrial with marine ecosystems, and wetland microbes are crucial to the biogeochemical cycles of nutrients. The soil samples were collected in four seasons (spring, S1; summer, S2; autumn, S3; and winter, S4) from Suaeda wetland of Shuangtaizi River estuary, Northeast China, and the variations of bacterial community were evaluated by high-throughput sequencing. Soil properties presented a significant seasonal change, including pH, carbon (C) and total nitrogen (TN), and the microbial diversity, richness and structure also differed with seasons. Canonical correspondence analysis (CCA) and Mantel tests implied that soil pH, C and TN were the key factors structuring the microbial community. Gillisia (belonging to Bacteroidetes) and Woeseia (affiliating with Gammaproteobacteria) were the two primary components in the rhizosphere soils, displaying opposite variations with seasons. Based on PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) prediction, the xenobiotics biodegradation related genes exhibited a seasonal decline, while the majority of biomarker genes involved in nitrogen cycle showed an ascending trend. These findings could advance the understanding of rhizosphere microbiota of Suaeda in estuarine wetland.


Assuntos
Chenopodiaceae , China , Estuários , Filogenia , Rios , Estações do Ano , Solo , Microbiologia do Solo , Áreas Alagadas
8.
Sci Total Environ ; 740: 140403, 2020 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-32927559

RESUMO

Waste amendments, such as steel slag and biochar, have been reported as a strategy for improving soil fertility, crop productivity, and carbon (C) sequestration in agricultural lands. However, information regarding the subsequent effects of steel slag and biochar on C cycling and the underlying microbial mechanisms in paddy soils remains limited. Hence, this study aimed to examine the effect of these waste amendments (applied in 2015-2017) on total soil CO2 emissions, total and active soil organic C (SOC) contents, and microbial communities in the early and late seasons in a subtropical paddy field. The results showed that despite the exogenous C input from these waste amendments (steel slag, biochar and slag + biochar), they significantly (P < 0.05) decreased total CO2 emissions (e.g., by 41.9-59.6% at the early season), compared to the control soil. These amendments also significantly (P < 0.001) increased soil salinity and pH. The increased soil pH had a negative effect (r = -0.37, P < 0.05) on microbial biomass C (MBC). The biochar and slag + biochar treatments (cf. control) significantly (P < 0.001) increased SOC contents in the both seasons. The amendments altered the soil microbial community structure that associated with soil C cycling: (1) all three amendments increased the relative abundance of Agromyces and Streptomyces, which was associated with higher soil pH (cf. control); and (2) biochar and slag + biochar treatments caused a higher relative abundance of Sphingomonas, which was supported by high SOC contents under those amendments. Overall, this study demonstrated that the steel slag and biochar amendments altered microbial community composition due to changes in key soil properties, such as salinity, pH and SOC contents, with implications for increasing soil C stocks while mitigating CO2 emissions in the paddy field.


Assuntos
Oryza , Solo , Dióxido de Carbono/análise , Carvão Vegetal , Microbiologia do Solo , Aço
9.
Proc Biol Sci ; 287(1934): 20201268, 2020 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-32873207

RESUMO

Microplastics are recognized as an emerging contaminant worldwide. Although microplastics have been shown to strongly affect organisms in aquatic environments, less is known about whether and how microplastics can affect different taxa within a soil community, and it is unclear whether these effects can cascade through soil food webs. By conducting a microplastic manipulation experiment, i.e. adding low-density polyethylene fragments in the field, we found that microplastic addition significantly affected the composition and abundance of microarthropod and nematode communities. Contrary to soil fauna, we found only small effects of microplastics on the biomass and structure of soil microbial communities. Nevertheless, structural equation modelling revealed that the effects of microplastics strongly cascade through the soil food webs, leading to the modification of microbial functioning with further potential consequences on soil carbon and nutrient cycling. Our results highlight that taking into account the effects of microplastics at different trophic levels is important to elucidate the mechanisms underlying the ecological impacts of microplastic pollution on soil functioning.


Assuntos
Microbiota , Microplásticos , Microbiologia do Solo , Poluentes do Solo , Cadeia Alimentar , Solo
10.
PLoS One ; 15(8): e0237748, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32866195

RESUMO

Soil microbiota are considered a source of undiscovered bioactive compounds, yet cultivation of most bacteria within a sample remains generally unsuccessful. Two main reasons behind the unculturability of bacteria are the presence of cells in a viable but not culturable state (such as dormant cells) and the failure to provide the necessary growth requirements in vitro (leading to the classification of some bacterial taxa as yet-to-be-cultured). The present work focuses on the development of a single procedure that helps distinguish between both phenomena of unculturability based on viability staining coupled with flow cytometry and fluorescence-activated cell sorting. In the selected soil sample, the success rate of cultured bacteria was doubled by selecting viable and metabolically active bacteria. It was determined that most of the uncultured fraction was not dormant or dead but likely required different growth conditions. It was also determined that the staining process introduced changes in the taxonomic composition of the outgrown bacterial biomass, which should be considered for further developments. This research shows the potential of flow cytometry and fluorescence-activated cell sorting applied to soil samples to improve the success rate of bacterial cultivation by estimating the proportion of dormant and yet-to-be-cultured bacteria and by directly excluding dormant cells from being inoculated into growth media.


Assuntos
Bactérias/crescimento & desenvolvimento , Técnicas Microbiológicas/métodos , Microbiota/fisiologia , Microbiologia do Solo , Bactérias/química , Bactérias/genética , Biomassa , Separação Celular/métodos , Meios de Cultura , DNA Bacteriano/isolamento & purificação , Estudos de Viabilidade , Citometria de Fluxo/métodos , Corantes Fluorescentes/química , Filogenia , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Coloração e Rotulagem/métodos
11.
Ecotoxicol Environ Saf ; 203: 111047, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32888598

RESUMO

Understanding azo dye degrading enzymes and the encoding of their functional genes is crucial for the elucidation of their molecular mechanisms. In this study, a thermophilic strain capable of degrading azo dye was isolated from the soil near a textile dye manufacturing factory. Based on its morphological, physiological and biochemical properties, as well as 16S rRNA gene sequence analysis, the strain was identified as Anoxybacillus sp. PDR2. The decolorization ratios of 100-600 mg/L Direct Black G (DBG) by strain PDR2 reached 82.12-98.39% within 48 h of dyes. Genome analysis revealed that strain PDR2 contains a circular chromosome of 3791144 bp with a G + C content of 42.48%. The genetic basis of azo dye degradation by strain PDR2 and its capacity to adapt to harsh environments, were further elucidated through bioinformatics analysis. RNA-Seq and qRT-PCR technology confirmed that NAD(P)H-flavin reductase, 2Fe-2S ferredoxin and NAD(P)-dependent ethanol dehydrogenase genes expressed by strain PDR2, were the key genes involved in DBG degradation. The combination of genome and transcriptome analysis was utilized to explore the key genes of strain PDR2 involved in azo dye biodegradation, with these findings providing a valuable theoretical basis for the practical treatment of azo dye wastewater.


Assuntos
Anoxybacillus/isolamento & purificação , Compostos Azo/análise , Corantes/análise , Genes Bacterianos , Microbiologia do Solo , Anoxybacillus/genética , Anoxybacillus/metabolismo , Compostos Azo/metabolismo , Biodegradação Ambiental , China , Corantes/metabolismo , Perfilação da Expressão Gênica , Genômica , RNA Ribossômico 16S/genética , Solo/química , Indústria Têxtil
12.
Ecotoxicol Environ Saf ; 205: 111267, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32992213

RESUMO

Arsenic is a common contaminant in gold mine soil and tailings. Microbes present an opportunity for bio-treatment of arsenic, since it is a sustainable and cost-effective approach to remove arsenic from water. However, the development of existing bio-treatment approaches depends on isolation of arsenic-resistant microbes from arsenic contaminated samples. Microbial cultures are commonly used in bio-treatment; however, it is not established whether the structure of the cultured isolates resembles the native microbial community from arsenic-contaminated soil. In this milieu, a culture-independent approach using Illumina sequencing technology was used to profile the microbial community in situ. This was coupled with a culture-dependent technique, that is, isolation using two different growth media, to analyse the microbial population in arsenic laden tailing dam sludge based on the culture-independent sequencing approach, 4 phyla and 8 genera were identified in a sample from the arsenic-rich gold mine. Firmicutes (92.23%) was the dominant phylum, followed by Proteobacteria (3.21%), Actinobacteria (2.41%), and Bacteroidetes (1.49%). The identified genera included Staphylococcus (89.8%), Pseudomonas (1.25), Corynebacterium (0.82), Prevotella (0.54%), Megamonas (0.38%) and Sphingomonas (0.36%). The Shannon index value (3.05) and Simpson index value (0.1661) indicated low diversity in arsenic laden tailing. The culture dependent method exposed significant similarities with culture independent methods at the phylum level with Firmicutes, Proteobacteria and Actinobacteria, being common, and Firmicutes was the dominant phylum whereas, at the genus level, only Pseudomonas was presented by both methods. It showed high similarities between culture independent and dependent methods at the phylum level and large differences at the genus level, highlighting the complementarity between the two methods for identification of the native population bacteria in arsenic-rich mine. As a result, the present study can be a resource on microbes for bio-treatment of arsenic in mining waste.


Assuntos
Actinobacteria/efeitos dos fármacos , Arsênico/toxicidade , Firmicutes/efeitos dos fármacos , Metagenômica/métodos , Proteobactérias/efeitos dos fármacos , Poluentes do Solo/toxicidade , Actinobacteria/citologia , Actinobacteria/genética , Arsênico/análise , Biodegradação Ambiental , Meios de Cultura/química , Farmacorresistência Bacteriana/efeitos dos fármacos , Firmicutes/citologia , Firmicutes/genética , Ouro , Testes de Sensibilidade Microbiana , Microbiota/efeitos dos fármacos , Microbiota/genética , Mineração , Proteobactérias/citologia , Proteobactérias/genética , RNA Ribossômico 16S/genética , Solo/química , Microbiologia do Solo , Poluentes do Solo/análise
13.
Nat Commun ; 11(1): 4897, 2020 09 29.
Artigo em Inglês | MEDLINE | ID: mdl-32994415

RESUMO

Soil microbial respiration is an important source of uncertainty in projecting future climate and carbon (C) cycle feedbacks. However, its feedbacks to climate warming and underlying microbial mechanisms are still poorly understood. Here we show that the temperature sensitivity of soil microbial respiration (Q10) in a temperate grassland ecosystem persistently decreases by 12.0 ± 3.7% across 7 years of warming. Also, the shifts of microbial communities play critical roles in regulating thermal adaptation of soil respiration. Incorporating microbial functional gene abundance data into a microbially-enabled ecosystem model significantly improves the modeling performance of soil microbial respiration by 5-19%, and reduces model parametric uncertainty by 55-71%. In addition, modeling analyses show that the microbial thermal adaptation can lead to considerably less heterotrophic respiration (11.6 ± 7.5%), and hence less soil C loss. If such microbially mediated dampening effects occur generally across different spatial and temporal scales, the potential positive feedback of soil microbial respiration in response to climate warming may be less than previously predicted.


Assuntos
Carbono/análise , Metagenoma/genética , Microbiota/fisiologia , Microbiologia do Solo , Solo/química , Aclimatação/genética , Archaea/genética , Archaea/isolamento & purificação , Archaea/metabolismo , Bactérias/genética , Bactérias/isolamento & purificação , Bactérias/metabolismo , Carbono/metabolismo , Ciclo do Carbono , Celulose/metabolismo , DNA Ambiental/genética , DNA Ambiental/isolamento & purificação , Fungos/genética , Fungos/isolamento & purificação , Fungos/metabolismo , Aquecimento Global , Pradaria , Temperatura Alta/efeitos adversos , Metagenômica , Modelos Genéticos , Raízes de Plantas/química , Poaceae/química
14.
Ecotoxicol Environ Saf ; 205: 111328, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32950805

RESUMO

Understanding the degradation of pentachlorophenol (PCP) by indigenous microorganisms stimulated by an electron donor and shuttle in paddy soil, and the influences of PCP/electron donor/shuttle on the native microbial community are important for biodegradation and ecological and environmental safety. Previous studies focused on the kinetics and the microbial actions of PCP degradation, however, the effects of toxic and antimicrobial PCP and electron donor/shuttle on the microbial community diversity and composition in paddy soil are poorly understood. In this study, the effects of PCP, an electron donor (lactate), and the electron shuttle (anthraquinone-2, 6-disulfonate, AQDS) on the microbial community in paddy soil were investigated. The results showed that the presence of PCP reduced the microbial diversity compared to the control during PCP degradation, while increased the microbial diversity was observed in response to lactate and AQDS. The addition of PCP stimulated the microorganisms involved in PCP dechlorination, including Clostridium, Desulfitobacterium, Pandoraea, and unclassified Veillonellaceae, which were dormant in raw soil without PCP stress. In all of the treatments with PCP, the addition of lactate or AQDS enhanced PCP dechlorination by stimulating the growth of functional groups involved in PCP dechlorination and by changing the microbial community during dechlorination process. The microbial community tended to be uniform after complete PCP degradation (28 days). However, when lactate and AQDS were present simultaneously in PCP-contaminated soil, lactate acted as a carbon source or electron donor to promote the activities of microbial community, and AQDS changed the redox potential because of the production of reduced AQDS. These findings enhance our understanding of the effect of PCP and a biostimulation method for PCP biodegradation in soil ecosystems at the microbial community level, and suggest the appropriate selection of an electron donor/shuttle for accelerating the bioremediation of PCP-contaminated soils.


Assuntos
Microbiota/efeitos dos fármacos , Pentaclorofenol/toxicidade , Microbiologia do Solo , Poluentes do Solo/toxicidade , Solo/química , Antraquinonas/farmacologia , Biodegradação Ambiental , Transporte de Elétrons , Ácido Láctico/farmacologia
15.
Ecotoxicol Environ Saf ; 205: 111333, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32979802

RESUMO

Plant growth-promoting rhizobacteria (PGPR) are a specific category of microbes that improve plant growth and promote greater tolerance to metal stress through their interactions with plant roots. We evaluated the effects of phytoremediation combining the cadmium accumulator Solanum nigrum L. and two Cd- and Pb-resistant bacteria isolates. To understand the interaction between PGPR and their host plant, we conducted greenhouse experiments with inoculation treatments at Nanjing Agricultural University (Jiangsu Province, China), in June 2018. Two Cd- and Pb-resistant PGPR with various growth-promoting properties were isolated from heavy metal-contaminated soil. 16S rRNA analyses indicated that the two isolates were Bacillus genus, and they were named QX8 and QX13. Pot experiments demonstrated that inoculation may improve the rhizosphere soil environment and promote absorption of Fe and P by plants. Inoculation with QX8 and QX13 also enhanced the dry weight of shoots (1.36- and 1.7-fold, respectively) and roots (1.42- and 1.96-fold) of plants growing in Cd- and Pb-contaminated soil, and significantly increased total Cd (1.28-1.81 fold) and Pb (1.08-1.55 fold) content in aerial organs, compared to non-inoculated controls. We also detected increases of 23% and 22% in the acid phosphatase activity of rhizosphere soils inoculated with QX8 and QX13, respectively. However, we did not detect significant differences between inoculated and non-inoculated treatments in Cd and Pb concentrations in plants and available Cd and Pb content in rhizosphere soils. We demonstrated that PGPR-assisted phytoremediation is a promising technique for remediating heavy metal-contaminated soils, with the potential to enhance phytoremediation efficiency and improve soil quality.


Assuntos
Cádmio/análise , Chumbo/análise , Rhizobiaceae/metabolismo , Microbiologia do Solo , Poluentes do Solo/análise , Solanum nigrum/efeitos dos fármacos , Biodegradação Ambiental , Cádmio/metabolismo , China , Chumbo/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , RNA Ribossômico 16S , Rizosfera , Solo/química , Poluentes do Solo/metabolismo , Solanum nigrum/crescimento & desenvolvimento , Solanum nigrum/metabolismo
16.
Bull Environ Contam Toxicol ; 105(3): 481-489, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32914331

RESUMO

The purpose of this study is to enhance the biodegradability of atrazine with FH-1 and NJ-1 alone by selecting the mixing ratio, optimizing the culture medium and conditions. The results showed that FH-1 and NJ-1 have the best biodegradation effect on atrazine being mixed in a volume ratio of 3:2. In a single factor experiment, sucrose and NH4Cl provided carbon and nitrogen sources for the mixed bacteria. Subsequently, composition of fermentation medium was further optimized using Box-Behnken design of response surface methodology. Based on the results, growth of mixed bacteria and biodegradation of atrazine performed best effects with a biodegradation rate of 85.6% when sucrose and NH4Cl amounts were 35.30 g/L and 10.28 g/L. The optimal medium condition was 10% inoculum of mixed bacteria, with initial atrazine concentration of 50 mg/L, neutral or weakly alkaline pH value, 30°C. The biodegradation rate reached 97.4%, 11.8% higher than the unoptimized condition.


Assuntos
Atrazina/metabolismo , Biodegradação Ambiental , Herbicidas/metabolismo , Klebsiella/metabolismo , Arthrobacter/metabolismo , Atrazina/análise , Carbono/metabolismo , Herbicidas/análise , Nitrogênio/metabolismo , Microbiologia do Solo
17.
Chemosphere ; 254: 126894, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957292

RESUMO

The anthropogenic release of trifluoroacetic acid (TFA) into the environmental media is not limited to photochemical oxidation of CFC alternatives and industrial emissions. Biological degradation of some fluorochemicals is expected to be a potential TFA source. For the first time, we assess if the potential precursors [6:2 fluorotelomer alcohol (6:2 FTOH), 4:2 fluorotelomer alcohol (4:2 FTOH), acrinathrin, trifluralin, and 2-(trifluoromethyl)acrylic acid (TFMAA)] can be biologically degraded to TFA. Results show that 6:2 FTOH was terminally transformed to 5:3 polyfluorinated acid (5:3 FTCA; 12.5 mol%), perfluorohexanoic acid (PFHxA; 2.0 mol%), perfluoropentanoic acid (PFPeA; 1.6 mol%), perfluorobutyric acid (PFBA; 1.7 mol%), and TFA (2.3 mol%) by day 32 in the landfill soil microbial culture system. 4:2 FTOH could remove multiple -CF2 groups by microorganisms and produce PFPeA (2.6 mol%), PFBA (17.4 mol%), TFA (7.8 mol%). We also quantified the degradation products of TFMAA as PFBA (1.3 mol%) and TFA (6.3 mol%). Furthermore, we basically analyzed the biodegradation contribution of short-chain FTOH as raw material residuals in commercial products to the TFA burden in the environmental media. We estimate global emission of 3.9-47.3 tonnes of TFA in the period from 1961 to 2019, and project 3.8-46.4 tonnes to be emitted from 2020 to 2040 via the pathway of 4:2 and 6:2 FTOH biodegradation (0.6-7.1 and 0.6-7.0 tonnes in China, respectively). Direct evidence of the experiments indicates that biodegradation of fluorochemicals is an overlooked source of TFA and there are still some unspecified mechanisms of TFA production pathways.


Assuntos
Fluorcarbonetos/química , Microbiologia do Solo , Poluentes do Solo/análise , Ácido Trifluoracético/análise , Biodegradação Ambiental , China , Modelos Teóricos , Solo/química
18.
Chemosphere ; 254: 126909, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957299

RESUMO

Soil contamination by heavy metals (HMs) is an environmental problem, and nanoremediation by using zero-valent iron nanoparticles (nZVI) has attracted increasing interest. We used ecotoxicological test and global transcriptome analysis with DNA microarrays to assess the suitability of C. elegans as a useful bioindicator to evaluate such strategy of nanoremediation in a highly polluted soil with Pb, Cd and Zn. The HMs produced devastating effect on C. elegans. nZVI treatment reversed this deleterious effect up to day 30 after application, but the reduction in the relative toxicity of HMs was lower at day 120. We stablished gene expression profile in C. elegans exposed to the polluted soil, treated and untreated with nZVI. The percentage of differentially expressed genes after treatment decreases with exposure time. After application of nZVI we found decreased toxicity, but increased biosynthesis of defensive enzymes responsive to oxidative stress. At day 14, when a decrease in toxicity has occurred, genes related to specific heavy metal detoxification mechanisms or to response to metal stress, were down regulated: gst-genes, encoding for glutathione-S-transferase, htm-1 (heavy metal tolerance factor), and pgp-5 and pgp-7, related to stress response to metals. At day 120, we found increased HMs toxicity compared to day 14, whereas the transcriptional oxidative and metal-induced responses were attenuated. These findings indicate that the profiled gene expression in C. elegans may be considered as an indicator of stress response that allows a reliable evaluation of the nanoremediation strategy.


Assuntos
Caenorhabditis elegans/efeitos dos fármacos , Ferro/química , Metais Pesados/toxicidade , Nanopartículas/química , Estresse Oxidativo/efeitos dos fármacos , Poluentes do Solo/toxicidade , Transcrição Genética/efeitos dos fármacos , Animais , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/genética , Ecotoxicologia , Nanopartículas Metálicas , Metais Pesados/análise , Estresse Oxidativo/genética , Solo/química , Microbiologia do Solo , Poluentes do Solo/análise , Toxicogenética
19.
Chemosphere ; 254: 126880, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957287

RESUMO

Electro-bioremediation is a promising technology for remediation of soil contaminated with persistent organic compounds such as polycyclic aromatic hydrocarbons (PAHs). During electro-bioremediation, electrical fields have been shown to increase pollutant degradation. However, it remains unclear whether there is an optimal strength for the electrical field applied that is conductive to the maximum role played by microbes. This study aimed to determine the optimal strength of electric field through the analysis of the effects of different voltages on the microbial community and activity. Four bench-scale experiments with voltages of 0, 1, 2 and 3 V cm-1 were conducted for 90 days in an aged PAH-contaminated soil. The spatiotemporal changes of the soil pH, moisture content and temperature, microbial biomass and community structure, and the degradation extent of PAHs were researched over 90 days. The results indicated that the total microbial biomass and degradation activity were highest at voltages of 2 V cm-1. The concentration of total phospholipid fatty acids, used to quantify soil microbial biomass, reached 65.7 nmol g-1 soil, and the mean degradation extent of PAHs was 44.0%. Similarly, the maximum biomass of actinomycetes, bacteria and fungus also occurred at the voltage of 2 V cm-1. The Gram-positive/Gram-negative and (cy17:0+cy 19:0)/(16:1ω7+18:1ω7) ratios also showed that the intensity of electric field and electrode reactions strongly influenced the microbial community structure. Therefore, to optimize the electro-bioremediation of PAH-contaminated soil, the strength of electric field needs to be selected carefully. This work provides reference for the development of novel electrokinetically enhanced bioremediation processes.


Assuntos
Biodegradação Ambiental , Microbiota , Hidrocarbonetos Policíclicos Aromáticos/metabolismo , Bactérias/metabolismo , Biomassa , Fungos/metabolismo , Hidrocarbonetos Policíclicos Aromáticos/análise , Solo/química , Microbiologia do Solo , Poluentes do Solo/análise
20.
J Environ Manage ; 271: 110941, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32778265

RESUMO

A real crude oil-contaminated soil was treated using a two-step method: biosurfactant-assisted soil washing and the biostimulated biotreating of the effluent. The mixture of surfactin and rhamnolipid could enhance the TPH removal from an oil-contaminated soil (32 g/kg) in the soil washing operation. 86% of TPH was removed from the oil-contaminated soil in the soil washing operation under the mixed biosurfactant (surfactin + rhamnolipid) of 0.6 g/L, the soil/water ratio of 20 w/v%, the temperature of 30 °C, and the washing time of 24 h, leaving an effluent containing 5028 mg/L TPH. The effluent was efficiently biotreated in the bioprocess with 5 g/L acclimate biomass daily stimulated with 0.1 mM H2O2, and the concentrtion of TPH decreased to 26 mg/L within 17 d corresponding a TPH biodegradation over 99%. The biostimulation with H2O2 caused the production of a high amount of peroxidase that could accelerate the biodegradation of TPH. Accordingly, the findings suggest that the biosurfactant-assisted washing operation combined with the H2O2-stimulated biodegradation process could be an enhanced green method for efficient treatment of the heavy oil-contaminated soils.


Assuntos
Petróleo , Poluentes do Solo/análise , Biodegradação Ambiental , Peróxido de Hidrogênio , Solo , Microbiologia do Solo , Tensoativos
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