Assessment of the ecological security of immobilized enzyme remediation process with biological indicators of soil health

This study used the enzymes extracted from an atrazine-degrading strain, Arthrobacter sp. DNS10, which had been immobilized by sodium alginate to rehabilitate atrazine-polluted soil. Meanwhile, a range of biological indices were selected to assess the ecological health of contaminated soils and the ecological security of this bioremediation method. The results showed that there was no atrazine detected in soil samples after 28 days in EN?+?AT (the soil containing atrazine and immobilized enzyme) treatment. However, the residual atrazine concentration of the sample in AT (the soil containing atrazine only) treatment was about 5.02?±?0.93 mg?kg^?1. These results suggest that the immobilized enzyme exhibits an excellent ability in atrazine degradation. Furthermore, the immobilized enzyme could relieve soil microbial biomass carbon and soil microbial respiration intensity to 772.33?±?34.93 mg?C?kg^?1 and 5.01?±?0.17 mg?CO₂?g^?1?soil?h^?1, respectively. The results of the polymerase chain reaction–degeneration gradient gel electrophoresis experiment indicated that the immobilized enzyme also could make the Shannon–Wiener index and evenness index of the soil sample increase from 1.02 and 0.74 to 1.51 and 0.84, respectively. These results indicated that the immobilized enzymes not only could relieve the impact from atrazine on the soil, but also revealed that the immobilized enzymes did no significant harm on the soil ecological health.     

Combined bioremediation of atrazine-contaminated soil by <Emphasis Type="Italic">Pennisetum</Emphasis> and <Emphasis Type="Italic">Arthrobacter</Emphasis> sp. strain DNS10

Strain DNS10 was isolated from the black soil collected from the northeast of China which had been cultivated with atrazine as the sole nitrogen source. Pennisetum is a common plant in Heilongjiang Province of China. The main objective of this paper was to evaluate the efficiency of plant–microbe joint interactions (Arthrobacter sp. DNS10 + Pennisetum) in atrazine degradation compared with single-strain and single-plant effects. Plant–microbe joint interactions degraded 98.10 % of the atrazine, while single strain and single plant only degraded 87.38 and 66.71 % after a 30-day experimental period, respectively. The results indicated that plant–microbe joint interactions had a better degradation effect. Meanwhile, we found that plant–microbe joint interactions showed a higher microbial diversity. The results of microbial diversity illustrated that the positive effects of cropping could improve soil microbial growth and activity. In addition, we planted atrazine-sensitive plants (soybean) in the soil after repair. The results showed that soybean growth in soil previously treated with the plant–microbe joint interactions treatment was better compared with other treatments after 20 days of growth. This was further proved that the soil is more conducive for crop cultivation. Hence, plant–microbe joint interactions are considered to be a potential tool in the remediation of atrazine-contaminated soil.     

Atrazine biodegradation by Arthrobacter strain DAT1: effect of glucose supplementation and change of the soil microbial community

The objective of this study was to investigate the impact of glucose supplementation on the soil microbiota inoculated with the atrazine-degrading Arthrobacter strain DAT1. Soil microcosms with different treatments were constructed for biodegradation tests. The impact of glucose supplementation on atrazine degradation capacity of the strain DAT1 and the strain’s survival and growth were assessed. The densities of the 16S rRNA gene and the atrazine-metabolic trzN gene were determined using quantitative PCR. The growth of the strain DAT1 and the bacterial community structure were characterized using terminal restriction fragment length polymorphism. Glucose supplementation could affect atrazine degradation by the strain DAT1 and the strain’s trzN gene density and growth. The density of the16S rRNA gene decreased during the incubation period. Glucose supplementation could alter the bacterial community structure during the bioaugmentation process. Glucose supplementation could promote the growth of the autochthonous soil degraders that harbored novel functional genes transforming atrazine. Further study will be necessary in order to elucidate the impact of exogenous carbon on autochthonous and inoculated degraders. This study could add some new insights on atrazine bioremediation.     

高效阿特拉津降解菌株DNSIO降解条件优化

从长期施用阿特拉津的寒地黑土耕层（0～10cm）土壤中筛选到一株能以除草剂阿特拉津为氮源生长的降解菌株,结合16SrRNA序列分析结果,将该菌株命名为Arthrobacter sp．DNSl0。在接种量为10。CFU／mL的条件下,菌株DNSl0在24h内对100mg／L阿特拉津的降解率为99．41％。单因子实验结果表明,菌株DNSl0适宜生长和降解的条件范围是：温度25～35＇12,pH值5．0～8．0,培养液盐度0．1％～2％,对阿特拉津最大耐受浓度可达1200mg／L。正交实验法进一步表明,该菌株保持较好生长及降解能力的最优方案是温度30℃,pH值7．5,培养液盐度0．5％。影响其降解能力的环境因素的主次顺序依次是：温度〉盐度〉pH值。     

Synthesis, properties and application research of atrazine Fe3O4@SiO2 magnetic molecularly imprinted polymer

Introduction

Magnetic Fe₃O₄ nanoparticles were prepared by coprecipitation and then were coated with SiO₂ on the surface.

Materials and methods

Fe₃O₄@SiO₂ composite microspheres were modified by KH570. Using molecular imprinting technology, atrazine magnetic molecularly imprinted polymer was prepared by using atrazine as template molecule, methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linkers. The morphology, composition and magnetic properties of magnetic nanoparticles were characterized. The recognition selectivity of polymer was studied for template molecule and simulation by UV spectrophotometry. The adsorption properties and selectivity ability were analyzed by Scatchard analysis.

Results

Scatchard linear regression analysis indicated that there are two binding sites of the target molecules. The magnetic molecularly imprinted polymer has been applied to the analysis of atrazine in real samples.

Conclusion

The results show that: the recovery rates and the relative standard deviation were 94.0??98.7% and 2.1??4.0% in corn, the recovery rates and the relative standard deviation were 88.7??93.5% and 2.8??7.2% in water.     

Isolation and characterization of a Rhodococcus strain with phenol-degrading ability and its potential use for tannery effluent biotreatment

Introduction

Wastewater derived from leather production may contain phenols, which are highly toxic, and their degradation could be possible through bioremediation technologies.

Materials, methods and results

In the present work, microbial degradation of phenol was studied using a tolerant bacterial strain, named CS1, isolated from tannery sediments. This strain was able to survive in the presence of phenol at concentrations of up to 1,000?mg/L. On the basis of morphological and biochemical properties, 16S rRNA gene sequencing, and phylogenetic analysis, the isolated strain was identified as Rhodococcus sp. Phenol removal was evaluated at a lab-scale in Erlenmeyer flasks and at a bioreactor scale in a stirred tank reactor. Rhodococcus sp. CS1 was able to completely remove phenol in a range of 200 to 1,000?mg/L in mineral medium at 30 ± 2?°C and pH 7 as optimal conditions. In the stirred tank bioreactor, we studied the effect of some parameters, such as agitation (200?C600 rpm) and aeration (1?C3?vvm), on growth and phenol removal efficiency. Faster phenol biodegradation was obtained in the bioreactor than in Erlenmeyer flasks, and maximum phenol removal was achieved at 400?rpm and 1 vvm in only 12?h. Furthermore, Rhodococcus sp. CS1 strain was able to grow and completely degrade phenols from tannery effluents after 9?h of incubation.

Conclusion

Based on these results, Rhodococcus sp. CS1 could be an appropriate microorganism for bioremediation of tannery effluents or other phenol-containing wastewaters.     

Bioremediation of acidic oily sludge-contaminated soil by the novel yeast strain Candida digboiensis TERI ASN6

Background, aim, and scope

Primitive wax refining techniques had resulted in almost 50,000 tonnes of acidic oily sludge (pH 1–3) being accumulated inside the Digboi refinery premises in Assam state, northeast India. A novel yeast species Candida digboiensis TERI ASN6 was obtained that could degrade the acidic petroleum hydrocarbons at pH 3 under laboratory conditions. The aim of this study was to evaluate the degradation potential of this strain under laboratory and field conditions.

Materials and methods

The ability of TERI ASN6 to degrade the hydrocarbons found in the acidic oily sludge was established by gravimetry and gas chromatography–mass spectroscopy. Following this, a feasibility study was done, on site, to study various treatments for the remediation of the acidic sludge. Among the treatments, the application of C. digboiensis TERI ASN6 with nutrients showed the highest degradation of the acidic oily sludge. This treatment was then selected for the full-scale bioremediation study conducted on site, inside the refinery premises.

Results

The novel yeast strain TERI ASN6 could degrade 40 mg of eicosane in 50 ml of minimal salts medium in 10 days and 72% of heneicosane in 192 h at pH 3. The degradation of alkanes yielded monocarboxylic acid intermediates while the polycyclic aromatic hydrocarbon pyrene found in the acidic oily sludge yielded the oxygenated intermediate pyrenol. In the feasibility study, the application of TERI ASN6 with nutrients showed a reduction of solvent extractable total petroleum hydrocarbon (TPH) from 160 to 28.81 g kg^?1 soil as compared to a TPH reduction from 183.85 to 151.10 g kg^?1 soil in the untreated control in 135 days. The full-scale bioremediation study in a 3,280-m² area in the refinery showed a reduction of TPH from 184.06 to 7.96 g kg^?1 soil in 175 days.

Discussion

Degradation of petroleum hydrocarbons by microbes is a well-known phenomenon, but most microbes are unable to withstand the low pH conditions found in Digboi refinery. The strain C. digboiensis could efficiently degrade the acidic oily sludge on site because of its robust nature, probably acquired by prolonged exposure to the contaminants.

Conclusions

This study establishes the potential of novel yeast strain to bioremediate hydrocarbons at low pH under field conditions.

Recommendations and perspectives

Acidic oily sludge is a potential environmental hazard. The components of the oily sludge are toxic and carcinogenic, and the acidity of the sludge further increases this problem. These results establish that the novel yeast strain C. digboiensis was able to degrade hydrocarbons at low pH and can therefore be used for bioremediating soils that have been contaminated by acidic hydrocarbon wastes generated by other methods as well.     

Identification of cadmium-excluding welsh onion (Allium fistulosum L.) cultivars and their mechanisms of low cadmium accumulation

Purpose

Screening out cadmium (Cd) excluding cultivars of a crop in agricultural production is an effective way to prohibit Cd entering into food chain.

Methods

A judging criterion for Cd-excluding cultivars based on food safety was suggested and used in the identification of Cd-excluding welsh onion (Allium fistulosum L.) cultivars. A pot culture experiment was carried out to screen out Cd-excluding cultivars, of which the results were confirmed by plot experiments. The relevant factors of Cd accumulation in the pseudostem were analyzed and used in the correlation analysis aiming to study the low Cd accumulation mechanisms.

Results

The concentration of Cd in the pseudostem of welsh onions was 0.08?C0.20, 0.18?C0.41, and 0.26?C0.61?mg/kg fresh weight (FW) under three treatments (1.0, 2.5, and 5.0?mg/kg), respectively. The significant (p? ₃ ^? ?CN, and eight other elements in the tested welsh onion cultivars. Two cultivars were identified as Cd-excluding cultivars, mainly because the accumulation of Cd in their pseudostem was only 0.041?±?0.003 and 0.046?±?0.002?mg/kg FW, and 0.054?±?0.001 and 0.066?±?0.011?mg/kg FW, when growing in plots with Cd concentration of 0.49 and 0.99?mg/kg, respectively.

Conclusions

Ribentiegancongwang and Wuyeqi could be identified as Cd-excluding cultivars. Low bioaccumulation factor of the roots was the main mechanism of Cd-excluding welsh onion cultivars.     

Nitrogen impacts on atrazine-degrading Arthrobacter strain and bacterial community structure in soil microcosms

The objective of this study was to investigate the impacts of exogenous nitrogen on a microbial community inoculated with the atrazine-degrading Arthrobacter sp. in soil amended with a high concentration of atrazine. Inoculated and uninoculated microcosms for biodegradation tests were constructed. Atrazine degradation capacity of the strain DAT1 and the strain's atrazine-metabolic potential and survival were assessed. The relative abundance of the strain DAT1 and the bacterial community structure in soils were characterized using quantitative PCR in combination with terminal restriction fragment length polymorphism. Atrazine degradation by the strain DAT1 and the strain's atrazine-metabolic potential and survival were not affected by addition of a medium level of nitrate, but these processes were inhibited by addition of a high level of nitrate. Microbial community structure changed in both inoculated and uninoculated microcosms, dependent on the level of added nitrate. Bioaugmentation with the strain DAT1 could be a very efficient biotechnology for bioremediation of soils with high concentrations of atrazine.     

Thermophilic desulfurization of dibenzothiophene and different petroleum oils by Klebsiella sp. 13T

Purpose

Biodesulfurization (BDS) has the potential to desulfurize dibenzothiophene (DBT) and its alkylated derivatives, the compounds that are otherwise refractory to hydrodesulfurization (HDS). Thermophilic microorganisms are more appropriate to be used for BDS applications following HDS. The aim of the present study was to isolate a thermophilic microorganism and to explore its commercial relevance for BDS process.

Methods

The desulfurizing thermophilic strain was isolated and enriched from various soil and water samples using sulfur free medium (SFM) supplemented with DBT. Microbiological and genomic approach was used to characterize the strain. Desulfurization reactions were carried out using DBT and petroleum oils at 45°C followed by different analytical procedures.

Results

We report the isolation of a thermophilic bacterium Klebsiella sp. 13T from contaminated soils collected from petroleum refinery. HPLC analysis revealed that Klebsiella sp. 13T could desulfurize DBT to 2-hydroxybiphenyl (2-HBP) at 45°C through 4S pathway. In addition, adapted cells of Klebsiella sp. 13T were found to remove 22?C53% of sulfur from different petroleum oils with highest sulfur removal from light crude oil.

Conclusion

Klebsiella sp. 13T is a potential candidate for BDS because of its thermophilic nature and capability to desulfurize petroleum oils.     

Harvesting of Chlorella sp. using hollow fiber ultrafiltration

Introduction

The suitability of the application of ultrafiltration (UF) to harvest Chlorella sp. from the culture medium was examined. We investigated the effects of two improved UF system, forward air?Cwater flushing and backwash with permeate, on the concentration process.

Materials and methods

Backwash with permeate was selected as an optimization of the improved UF system, which was more effective for permeate flux recovery. Moreover, the hollow fiber UF system by adding periodical backwash with permeate was examined for Chlorella sp. harvesting.

Results and discussion

It was found that Chlorella sp. could be concentrated with high recovery in a lab-scale experiment. An overall algal biomass recovery of above 90% was achieved when the volume concentration factor was 10. For an original biomass of 1.3?±?0.05?g/L, 1?min backwash followed by 20?min forward concentrating was more effective, which resulted in a recovery of 94% and a high average flux of 30.3?L/m²/h. In addition, the algal recovery was highly correlated to the volume concentration factor and the initial biomass. A high concentration factor or a high initial biomass resulted in a low biomass recovery.     

Efficient biosorption of chromium(VI) ion by dry Araucaria leaves

Background

In this paper, batch removal of hexavalent chromium from aqueous solutions by Araucaria heterophylla leaves was investigated. The batch experiments were conducted to study the adsorption of metal species and effect of different pH, contact time, metal concentration, biosorbent concentration, and adsorption capacity.

Method

Freundlich and Langmuir??s isotherm model were used to describe the adsorption behavior, and the experimental results fitted Freundlich model well.

Results

The adsorption efficiency observed for all chromium concentrations, i.e., 1, 3, 5, and 10?mg/L was 100% and the equilibrium was achieved in 30?min for 1 and 3?mg/L, whereas for 5 and 10?mg/L, it was less than 60?min. FTIR spectra was taken to identify functional groups involved in the biosorption.

Conclusion

Thus, Araucaria leaves can be considered as one of the cheap and efficient biosorbent for toxic hexavalent chromium removal from natural or wastewaters.     

Effects of perinatal exposure to bisphenol A and di(2-ethylhexyl)-phthalate on gonadal development of male mice

Purpose

In this study, we investigated the effects of maternal transfer of bisphenol A (BPA) and di(2-ethylhexyl) phthalate (DEHP) during gestational and weaning periods on gonadal development of male offspring.

Methods

Pregnant CD-1 mice were administered by gavages in corn oil with 0.1, 1, or 10 mg/kg/day of BPA and DEHP from gestational days (GD1?C21) to the weaning period (postnatal days (PND) 1?C21).

Results

Our data indicated that the exposure significantly reduced the male-to-female sex ratio and the sizes of the gonads of male pups as recorded at PND15. The testes of the perinatally exposed male pups were developed less and the expression levels of testicular anti-mullerian hormone, androgen receptor, cyclin A, and StAR were significantly lesser than the control male pups. The less developed testes were accompanied with significant reductions in the expression levels of Gnrh and Fsh at the hypothalamic?Cpituitary levels. The negative effects were found to be persistent in the sexually mature pups at PND42.

Conclusion

Our data reveal that the maternal transfer of BPA and DEHP may impose negative influence on the development and functions of the reproductive system of male pups.     

Characteristics of an aerobic denitrifier that utilizes ammonium and nitrate simultaneously under the oligotrophic niche

Introduction

An aerobic denitrifier was isolated from the Hua-Jia-Chi pond in China and identified as Pseudomonas mendocina 3-7 (Genbank No. HQ285879). This isolated strain could express periplasmic nitrate reductase which is essential for aerobic denitrification occurred when the dissolved oxygen (DO) level maintains at 3?C10?mg?L^?1.

Methods

To determine whether the ability of isolated strain is exhibited in the bioremediation of polluted drinking source water, the heterotrophic nitrification and aerobic denitrification characteristics of P. mendocina 3-7 under different cultural conditions such as oxygen level, nitrate and organic concentrations were studied from the nitrogenous balance in the paper.

Results and conclusions

By measuring the nitrogen balance in all experiments under different culture conditions, the removal of total organic carbon and ammonium was positively correlated with total nitrogen removal, especially under high substrate level. With substrate concentration decreasing, ammonium and nitrate removal occurred separately, and ammonium was completely utilized first under low substrate concentration. Compared to that under high substrate level, the specific growth rate of P. mendocina 3-7 was not low under the low substrate level and the pollutant removal efficiencies remained high, which implies the stronger nitrogen removal and acclimatization capacities of the strain in oligotrophic niches.     

Biodegradation of benzene, toluene, and xylene (BTX) in liquid culture and in soil by Bacillus subtilis and Pseudomonas aeruginosa strains and a formulated bacterial consortium

Purpose

The major aromatic constituents of petroleum products viz. benzene, toluene, and mixture of xylenes (BTX) are responsible for environmental pollution and inflict serious public concern. Therefore, BTX biodegradation potential of individual as well as formulated bacterial consortium was evaluated. This study highlighted the role of hydrogen peroxide (H₂O₂), nitrate, and phosphate in stimulating the biodegradation of BTX compounds under hypoxic condition.

Materials and methods

The individual bacterium viz. Bacillus subtilis DM-04 and Pseudomonas aeruginosa M and NM strains and a consortium comprising of the above bacteria were inoculated to BTX-containing liquid medium and in soil. The bioremediation experiment was carried out for 120?h in BTX-containing liquid culture and for 90?days in BTX-contaminated soil. The kinetics of BTX degradation either in presence or absence of H₂O₂, nitrate, and phosphate was analyzed using biochemical and gas chromatographic (GC) technique.

Results

Bacterial consortium was found to be superior in degrading BTX either in soil or in liquid medium as compared to degradation of same compounds by individual strains of the consortium. The rate of BTX biodegradation was further enhanced when the liquid medium/soil was exogenously supplemented with 0.01?% (v/v) H₂O₂, phosphate, and nitrate_. The GC analysis of BTX biodegradation (90?days post-inoculation) in soil by bacterial consortium confirmed the preferential degradation of benzene compared to m-xylene and toluene.

Conclusions

It may be concluded that the bacterial consortium in the present study can degrade BTX compounds at a significantly higher rate as compared to the degradation of the same compounds by individual members of the consortium. Further, addition of H₂O₂ in the culture medium as an additional source of oxygen, and nitrate and phosphate as an alternative electron acceptor and macronutrient, respectively, significantly enhanced the rate of BTX biodegradation under oxygen-limited condition.     

Bacterial assisted phytoremediation for enhanced degradation of highly sulfonated diazo reactive dye

Purpose

Phytoremediation is the exploitation of plants and their rhizospheric microorganisms for pollutants treatment like textile dyes, which are toxic, carcinogenic and mutagenic from the effluent. The purpose of this work was to explore a naturally found plant and bacterial synergism to achieve an enhanced degradation of Remazol Black B dye (RBB).

Methods

In vitro cultures of Zinnia angustifolia were obtained by seed culture method. Enzymatic analysis of the plant roots and Exiguobacterium aestuarii strain ZaK cells was performed before and after decolorization of RBB. Metabolites of RBB formed after its degradation were analyzed using UV?CVis spectroscopy, high-performance liquid chromatography (HPLC), Fourier transform infrared (FTIR) and gas chromatography?Cmass spectrometry (GC-MS). Phytotoxicity studies were performed.

Results

The consortium ZE was found to be more efficient than individual plant and bacteria. Z. angustifolia roots showed significant induction in the activities of lignin peroxidase, laccase, DCIP reductase and tyrosinase during dye decolorization. E. aestuarii showed significant induction in the activities of veratryl alcohol oxidase, azo reductase and DCIP reductase. Analysis of metabolites revealed differential metabolism of RBB by plant, bacteria and consortium ZE. E. aestuarii and Z. angustifolia led to the formation of 3,6-diamino-4-hydroxynaphthalene-2-sulfonic acid, (ethylsulfonyl)benzene, and 3,4,6-trihydroxynaphthalene-2-sulfonic acid and propane-1-sulfonic acid, respectively, whereas consortium ZE produced 4-hydroxynaphthalene-2-sulfonic acid, naphthalene-2-sulfonic acid and 4-(methylsulfonyl)phenol. The phytotoxicity study revealed the nontoxic nature of the metabolites formed after dye degradation.

Conclusion

Consortium ZE was found to be more efficient and faster in the degradation of RBB when compared to degradation by Z. angustifoila and E. aestuarii individually.     

Bioremediation of chromium by novel strains Enterobacter aerogenes T2 and Acinetobacter sp. PD 12 S2

Purpose

This study had an objective to identify the most potent chromium-resistant bacteria isolated from tannery effluent and apply them for bioremediation of chromium in tannery effluents.

Methods

Two such strains (previously characterized and identified by us)??Enterobacter aerogenes (NCBI GenBank USA Accession no. GU265554) and Acinetobacter sp. PD 12 (NCBI GenBank USA Accession no. GU084179)??showed powerful chromium resistivity and bioremediation capabilities among many stains isolated from tannery waste. Parameters such as pH, concentration of hexavalent chromium or Cr (VI), and inoculum volume were varied to observe optimum bioconversion and bioaccumulation of Cr (VI) when the said strains were grown in M9 minimal salt media. E. aerogenes was used to remediate chromium from tannery effluents in a laboratory level experiment.

Results

Observation by Scanning Electron Microscope and chromium peak in Energy Dispersive X-ray Spectroscopic microanalysis revealed that E. aerogenes helped remediate a moderate amount of Cr (VI) (8?C16?mg?L^?1) over a wide range of pH values at 35?C37°C (within 26.05?h). High inoculum percentage of Acinetobacter sp. PD 12 also enabled bioremediation of 8?C16?mg?L^?1 of Cr (VI) over a wide range of temperature (25?C37°C), mainly at pH?7 (within 63.28?h). The experiment with real tannery effluent gave very encouraging results.

Conclusion

The strain E. aerogenes can be used in bioremediation of Cr (VI) since it could work in actual environmental conditions with extraordinarily high capacity.     

Isolation of a novel Pseudomonas sp from soil that can efficiently degrade polyethylene succinate

Purpose

Polyethylene succinate (PES) is a biodegradable synthetic polymer and therefore widely used as a base material in plastic industry to circumvent the environmental problems related with the non-biodegradability of other polymers like polyethylene. Till date only few organisms have been reported to have the ability to degrade PES. Therefore for better management of PES-related environmental waste, the present study is targeted towards isolating mesophilic organism(s) capable of more efficient degradation of PES.

Results

Strain AKS2 was isolated from soil based on survival on a selection plate wherein PES was used as sole carbon source. Ribotyping and biochemical tests revealed that AKS2 is a new strain of Pseudomonas. Scanning electron and atomic force microscopic analysis of the PES films obtained after incubation with AKS2 confirmed PES-degradation ability of AKS2, wherein an alteration in surface topology was observed. The kinetics of PES weight loss showed that AKS2 degrades PES maximally during its logarithmic growth phase at a rate of 1.65?mg/day. This degradation is mediated by esterase activity and may also involve cell-surface hydrophobicity. It has also been observed that AKS2 is able to degrade PES considerably even in the presence of glucose, which is likely to increase the bioremediation potential of this isolate.

Conclusion

A new strain of Pseudomonas has been isolated from soil that is able to adhere to PES and degrade this polymer efficiently. This organism has the potential to be implemented as a useful tool for bioremediation of PES-derived materials.     

Reference gene selection for qPCR in mussel, Mytilus edulis, during gametogenesis and exogenous estrogen exposure

Purpose

The aim of this study is to develop a normalization method for real-time PCR data by analyzing the most stably expressed control genes in mussel (Mytilus edulis) reproductive tissue.

Methods

To facilitate this, six candidate genes, including several commonly used in the literature, were investigated in mussels at different stages of gametogenesis and following experimental exposure to a model estrogen (17b-estradiol). GeNorm and NormFinder softwares were employed to assess the stability of the reference genes.

Results

Our results demonstrate that the most stable reference genes are not the same in mussels at different stages of gametogenesis and in experimentally E2-exposed mussels. Interestingly, HEL (helicase) and ACT (actin) mRNA expression levels were most affected by the stage of gametogenesis and yet, in molluscan studies, ACT is possibly the most frequently used reference gene.

Conclusions

We demonstrate that the experimental results are highly dependent on the reference gene chosen and that statistically significant contrasting differences between sample groups are present or absent depending on the reference gene employed.     

Arsenic accumulation and speciation in the submerged macrophyte Ceratophyllum demersum L.

Introduction

Ceratophyllum demersum L. is a widespread submerged macrophyte in aquatic environments.

Methods

Simulation experiments were conducted in the laboratory to investigate arsenic (As) accumulation, speciation, and efflux of C. demersum exposed to arsenate and arsenite solutions.

Results

Plant shoots showed a significant accumulation of As with a maximum of 862 and 963???g?As?g^?1 dry weight after 4?days of exposure to 10???M arsenate and arsenite, respectively. Regardless of whether arsenate or arsenite was supplied to the plants, arsenite was the predominant species in plant shoots. Furthermore, a dramatically higher influx rate of arsenate compared with arsenite was observed in C. demersum exposed to As solutions without the addition of phosphate (P). Arsenate uptake was considerably inhibited by P in this study, suggesting that arsenate is taken up by C. demersum via the phosphate transporters. However, arsenite uptake was unaffected by P and markedly reduced in the presence of glycerol and antimonite (Sb), indicating arsenite shares the aquaporin transport pathway. In addition, C. demersum rapidly reduces arsenate to arsenite in the shoot of the plant and extrudes most of them (>60?%) to the external solutions. The efflux of arsenite was much higher than that of arsenate; the former is supposed to be both active and passive processes, and the latter through passive leakage.

Conclusion

C. demersum is a strong As accumulator and an interesting model plant to study As uptake and metabolism due to the lack of a root-to-shoot translocation barrier.