Cell wall surface layer (S-layer) promotes colony formation in Microcystis: comparison of S-layer characteristics between colonial and unicellular forms of Microcystis and function conformation

Colony is a key to Microcystis becoming a dominant population and forming blooms. To find the mechanism of colony formation, we investigated cell wall structures of colonial and unicellular strains. Results showed that colonial strains had significant surface layer protein (S-layer) on the surface of cells than unicellular strains by transmission electron microscopy. Western blot showed colonial strains had more S-layer than the unicellular strains. When the S-layer gene (GenBank accession number CAO89090.1) of Microcystis aeruginosa PCC7806 was expressed in Synechocystis sp. PCC6803, PCC6803 aggregated into colonial morphology. The results indicated that the S-layer could promote colony formation in Microcystis. Based on the S-layer sequences of PCC6803 and PCC7806, nine S-layer genes in other Microcystis strains were screened from the GenBank. Sequence comparing showed that the S-layers conserved regions were all located in N-terminal. The S-layers contain repeats-in-toxin (RTX) sequences with Ca²⁺-binding site, and their amino acid composition, hydrophobicity, isoelectric point, etc. were consistent with the characteristics of RTX-type S-layer in bacteria.

     

Fast determination of phenoxy acid herbicides in carrots and apples using liquid chromatography coupled triple quadrupole mass spectrometry

A fast, simple and inexpensive method has been developed for the analysis of phenoxy acid herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA), 2-(4-chloro-o-tolyloxy)propionic acid (MCPP), 2-(4-aryloxyphenoxy)propionic acid (Fluazifop) and 2-(4-aryloxyphenoxy)propionic acid (Haloxyfop) in carrots and apples by liquid chromatography coupled to triple quadrupole mass spectrometry (LC/MS/MS). The compounds were analyzed by QuEChERS (quick, easy, cheap, effective, rugged, safe) methodology without cleanup.

The recoveries were performed at two spiked levels (0.05 and 0.5 mg/kg) for both matrices with six replicates for each level. The mean recoveries ranged from 70–92% for both apples and carrots. The precision of the method expressed as relative standard deviation (RSD%) was found to be in the range 3–15%. For all compounds, good linearity (r² > 0.99) was obtained over the range of concentration from 0.05 μ g/mL to 0.5 μ g/mL, corresponding to the pesticide concentrations of 0.05 mg/kg and 0.5 mg/kg, respectively. The determination limits (LOQs) ranged from 0.01 ng/mL to 1.3 ng/mL in solvent, whereas, the LOQs calculated in matrix ranged from 0.05 ng/g to 21.0 ng/g for apples and from 0.06 ng/g to 10.2 ng/g for carrots. The developed methodology combines the advantages of both QuEChERS and LC/MS/MS producing a very rapid, sensitive and cheap method useful for the routine analytical laboratories.     

The evaluation of an analytical method for polychlorinated terpenes (PCC) in biological samples using an internal standard

The quantitative analysis of PCC (Toxaphene) residues in biological samples using gas chromatography with electron capture detection has been evaluated. Dechlorane 603, a chloroalicyclic compound is used as internal standard and modifications of the injection system for proper evaporation of this high-boiling compound is described. In the cleanup procedure PCB (and 1 – 3 % of the PCC) are removed by adsorption chromatography. Chlordane components and DDT compounds remaining in the PCC fraction constitute 5 – 10 % and 13 – 16 %, respectively, of the peak area in the chromatograms of the samples investigated. The quantitative results are influenced by the number of PCC-peaks chosen for the calculations and have to be specified together with the PCC-levels reported. The recoveries of PCC from spiked samples (20 ug PCC per gram crude fat above “natural” level) are 61 – 98 %, the lower figures obtained with samples containing low levels of PCC-residues. The practical limit of detection is about 10 ng PCC per g extracted fat.     

Reduction of Cr(VI) by malic acid in aqueous Fe-rich soil suspensions

Detoxification of Cr(VI) through reduction by organic reductants has been regarded as an effective way for remediation of Cr(VI)-polluted soils. However, such remediation strategy would be limited in practical applications due to the low Cr(VI) reduction rate. In this study, the catalytic effect of two Fe-rich soils (Ultisol and Oxisol) on Cr(VI) reduction by malic acid was evaluated. As the results shown, the two soils could obviously accelerate the reduction of Cr(VI) by malic acid at low pH conditions, while such catalytic effect was gradually suppressed as the increase in pH. After reaction for 48 h at pH 3.2, Oxalic acid was found in the supernatant of Ultisol, suggesting the oxidization of hydroxyl in malic acid to carboxyl and breakage of the bond between C₂ and C₃. It was also found that the catalytic reactivity of Ultisol was more significant than that of Oxisol, which could be partly attributed to the fact that the amount of Fe(II) released from the reductive dissolution of Ultisol by malic acid was larger than that of Oxisol. With addition of Al(III), the catalytic effect from Ultisol was inhibited across the pH range examined. On the contrary, the presence of Cu(II) would increase the catalytic effect of Ultisol, which was more pronounced with the increase in pH. This study proposed a potential way for elimination of the environmental risks posed by the Cr(VI) contamination by use of the natural soil surfaces to catalyze Cr(VI) reduction by the organic reductant such as malic acid, a kind of organic reductant originating from soil organic decomposition process or plant excretion.     

Extractability of trace elements in precipitated calcium carbonate (PCC) waste from an integrated pulp and paper mill complex

From the utilization point of view, it is notable that the total element concentrations in the precipitated calcium carbonate (PCC) waste were significantly lower than the maximal allowable heavy metal concentrations for fertilizers used in agriculture and in forestry, set on the basis of the EU and Finnish legislation. The easily soluble Ca concentration of 168.5g kg(-1) (d.w.) in PCC waste was 105 times higher than the typical value of 1.6g kg(-1) (d.w.) in the coarse mineral soil in Finland indicates that the PCC waste is a potential agent for soil remediation and for improving soil fertility if it is used as fertilizer. According to a five-stage sequential extraction procedure, the highest concentrations of most of the elements occurred either in HF+HNO3+HCl or H2O2+CH3COONH4 fraction. This means that the major part of the elements retained in the PCC waste are not easy to extract (leach) under conditions normally found in nature. This is beneficial since, if inorganic materials and by-products are utilized in earth construction, the content of harmful compounds must be low and the harmful components must be tightly bound to the matrix.     

Zero-valent iron and iron oxide-coated sand as a combination for removal of co-present chromate and arsenate from groundwater with humic acid

The combination of zero-valent iron (Fe⁰) and iron oxide-coated sand (IOCS) was used to remove Cr(VI) and As(V) from groundwater in this study. The efficiency and the removal mechanism of Cr(VI) and As(V) by using this combination, with the influence of humic acid (HA), were investigated using batch experiments. Results showed that, compared to using Fe⁰ or IOCS alone, the Fe⁰-IOCS can perform better on the removal of both Cr(VI) and As(V). Metal extraction studies showed that As(V) was mainly removed by IOCS and iron corrosion products while Cr(VI) was mainly removed by Fe⁰ and its corrosion products. Competition was found between Cr(VI) and As(V) for the adsorption sites on the iron corrosion products. HA had shown insignificant effects on Cr(VI) removal but some effects on As(V) removal kinetics. As(V) was adsorbed on IOCS at the earlier stage, but adsorbed/coprecipitated with the iron corrosion products at the later stage.     

Effective removal of coordinated copper from wastewater using a new dithiocarbamate-type supramolecular heavy metal precipitant

A new dithiocarbamate-type heavy metal precipitant, sodium 1,3,5-hexahydrotriazinedithiocarbamate (HTDC), was prepared and used to remove coordinated copper from wastewater. In the reported dithiocarbamate-type precipitants, HTDC possesses the highest percentage of the effective functional groups. It could effectively precipitate copper to less than 0.5 mg l⁻¹ from both synthetic and actual industrial wastewater containing CuEDTA in the range of pH 3–9. UV–vis spectral investigation and elemental analysis suggested that the precipitate was a kind of coordination supramolecular compound, [Cu₃(HTDC)₂]_n. The toxicity characteristic leaching procedure (TCLP) and semi-dynamic leaching test (SDLT) indicated that the supramolecular precipitate was non-hazardous and stable in weak acid and alkaline conditions. Tests of an anion exchange resin D231 provided a clue to simultaneously remove excess HTDC and residual CuEDTA in practical process of wastewater treatment.     

Thermal and spectroscopic studies on sorption of nickel(II) ion on protonated baker's yeast

Protonated form (Hy) of yeast was subjected to thermal analysis (TGA and DTG) in the temperature range 60–800 °C. Chemically bound water volatilizes around 200 °C and the matrix undergoes extensive oxidative decomposition at 450 °C, the weight loss reaching 75% at 800 °C. The sorption capacity of the matrix for nickel(II) ion increases on heat treatment from 60 to 200 °C (from 16.9 to 25.0 mg/g), but was reduced on heating to higher temperatures at an initial nickel(II) ion concentration of 1200 mg/g. The FTIR spectra of Hy and nickel(II) ion saturated yeast, indicated that biosorption occurs on the sugar and nucleic acid regions, possibly involving –COOH and –NH groups.     

无机陶瓷纳滤膜分离高钠盐废水中的锶

本实验研究表明,仅用截留分子量为1000的无机陶瓷纳滤膜分离高钠盐模拟溶液中的锶,分离效果并不理想.为提高陶瓷纳滤膜对锶的选择分离效果,选择了分子量为3000的聚丙烯酸作为陶瓷纳滤膜分离的强化剂,重点探讨了溶液pH值、聚丙烯酸浓度、温度及离子强度对模拟溶液盐分离效果和膜通量的影响,并得到了适宜的锶钠分离条件.实验结果表明,在适宜条件下,通过聚丙烯酸强化和两级分离,陶瓷纳滤膜可大大提高模拟溶液中锶离子的选择分离效果,锶/钠的分离因子高达205.     

自然水体中主要有毒有机物的研究进展

介绍了主要有毒有机物多环芳烃(PAHs)、多氯联苯(PCBs)、有机氯农药(OCPs)在环境中的危害及其来源,着重评述了近年来中国自然水体中和沉积物中该类污染物的研究进展,指出新的检测技术的开发、有毒有机物的生殖毒性和生态环境风险影响方法学的研究及污染区域污染控制、消减及修复是今后该领域的工作重点.     

Relationship between chromium(VI) resistance and extracellular polymeric substances (EPS) concentration by some cyanobacterial isolates

BACKGROUND, AIM, AND SCOPE: Chromium(VI) resistance and its association with extracellular polymeric substance (EPS) concentration in cyanobacteria was investigated. Increased EPS concentration was associated with Cr(VI) resistance. The most resistant isolate, Chroococcus sp. H(4), secreted the most EPS (427 mg/L). MATERIALS AND METHODS: EPS concentration of the two most resistant isolates (Chroococcus sp. H(4) and Synechocystis sp. S(63)) was investigated following exposure to 15 and 35 ppm Cr(VI). The composition of EPS produced by Chroococcus sp. H(4) following exposure to 10 ppm Cr(VI) was analyzed using high-performance liquid chromatography. Control EPS was composed of glucose (99%) and galactronic acid (1%); in the presence of 10 ppm Cr(VI), EPS composition changed to glucose (9%), xylose (75%), rhamnose (14%), and galacturonic acid (2%). RESULTS AND DISCUSSION: Results indicated that (1) exposure to elevated concentrations of Cr(VI) affected the composition of EPS produced by Chroococcus sp. H(4), and (2) there was a correlation between Cr(VI) resistance and EPS concentration in some cyanobacteria.     

盐酸和硝酸介质中己二胺接枝壳聚糖微球吸附Hg(Ⅱ)的行为

制备并表征了氯化和氨化壳聚糖微球,考察了己二胺接枝壳聚糖微球(HDA-CS)在盐酸和硝酸介质中吸附Hg(Ⅱ)的行为及影响因素。结果表明,盐酸介质中,pH 3.0时,HDA-CS对Hg(Ⅱ)有较高的初始吸附速率,最大吸附容量为128.6 mg/g;硝酸介质中,pH 3.5时,它对Hg(Ⅱ)的最大吸附容量为37.7 mg/g。前者是后者的3.4倍。以1.0 mol/L的H2SO4为解吸剂,HDA-CS复用3次无溶解和流失现象。HDA-CS对Hg(Ⅱ)的吸附主要是质子化氨基与汞配阴离子以静电引力实现的。     

Mobility and recalcitrance of organo-chromium(III) complexes

Hexavalent chromium [Cr(VI)] is a major industrial pollutant. Bioremediation of Cr(VI) to Cr(III) is a viable clean-up approach. However, Cr(VI) bioreduction also produces soluble organo–Cr(III) complexes, and little is known about their behavior in the environment. When tested with soil columns, citrate–Cr(III) showed little sorption to soil; malate–Cr(III) had limited partitioning with soil; and histidine–Cr(III) exhibited significant interaction with soil. It appears that the mobility varies depending on the organic ligand. Further, Ralstonia eutropha JMP 134 and Pseudomonas aeruginosa pAO1 readily degraded malate, citrate, and histidine, but not the corresponding organo–Cr(III) complexes. The recalcitrance is not due to toxicity, but the complexes are likely to cause hindrance to enzymes, as malate dehydrogenase and amino acid oxidase could not use malate–Cr(III) and histidine–Cr(III), respectively. The data are in agreement with the reports of soluble organo–Cr(III) complexes in the environment.     

Arsenic(III) and iron(II) co-oxidation by oxygen and hydrogen peroxide: Divergent reactions in the presence of organic ligands

Iron-catalyzed oxidation of As(III) to As(V) can be highly effective for toxic arsenic removal via Fenton reaction and Fe(II) oxygenation. However, the contribution of ubiquitous organic ligands is poorly understood, despite its significant role in redox chemistry of arsenic in natural and engineered systems. In this work, selected naturally occurring organic ligands and synthetic ligands in co-oxidation of Fe(II) and As(III) were examined as a function of pH, Fe(II), H₂O₂, and radical scavengers (methanol and 2-propanol) concentration. As(III) was not measurably oxidised in the presence of excess ethylenediaminetetraacetic acid (EDTA) (i.e. Fe(II):EDTA < 1:1), contrasting with the rapid oxidation of Fe(II) by O₂ and H₂O₂ at neutral pH under the same conditions. However, partial oxidation of As(III) was observed at a 2:1 ratio of Fe(II):EDTA. Rapid Fe(II) oxidation in the presence of organic ligands did not necessarily result in the coupled As(III) oxidation. Organic ligands act as both iron speciation regulators and radicals scavengers. Further quenching experiments suggested both hydroxyl radicals and high-valent Fe species contributed to As(III) oxidation. The present findings are significant for the better understanding of aquatic redox chemistry of iron and arsenic in the environment and for optimization of iron-catalyzed arsenic remediation technology.     

Chlorinated anisoles and veratroles in fish. Model compounds. Instrumental and sensory determinations

Model compounds of polychlorinated anisoles (PCA) and veratroles (PCV) have been used in development of their analysis in fish. Individual PCAs and PCVs in fish were identified from GC peaks by retention time, selected ion monitoring and flavour in sniff detector. Trout exposed to spent bleach liquor and fish in recipient of pulp chlorobleaching had significantly higher PCA and PCV contents than fish at less polluted reference areas. Taste impairment points of fish fillets given by a blind panel correlated significantly with PCA/PCV contents but also with contents of polychlorophenols (PCP), quaiacols (PCG) and catechols (PCC).     

2,3,7,8-TCDD-mediated toxicity in peripheral blood mononuclear cells is alleviated by the antioxidants present in <Emphasis Type="Italic">Gelidiella acerosa</Emphasis>: an in vitro study

Seaweeds have been used as a source of traditional medicine worldwide for the treatment of various ailments, mainly due to their ability to quench the free radicals. The present study aims at evaluating the protective effect of methanolic extract of Gelidiella acerosa, an edible red seaweed against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced toxicity in peripheral blood mononuclear cells (PBMC). For evaluating the protective effect of G. acerosa, PBMC were divided into four groups: vehicle control, TCDD (10 nM), TCDD?+?G. acerosa (300 μg/ml), and G. acerosa alone treated. Scavenging of intracellular reactive oxygen species (ROS) induced by TCDD was assessed by the dichloro-dihydro-fluorescein diacetate (DCFH-DA) method. Alterations at macromolecular level were quantified through lipid peroxidation (LPO) level, protein carbonyl content (PCC) level, and comet assay. The cellular morphology upon TCDD toxicity and G. acerosa treatment was obtained by light microscopy and histopathological studies. The chemical composition present in the methanolic extract of G. acerosa was determined by gas chromatography-mass spectrometry (GC-MS) analysis. The results reveal that 10 nM TCDD caused significant (P?<?0.05) reduction in cell viability (94.10?±?0.99), and treatment with 300 μg/ml extract increased the cell viability (99.24?±?0.69). TCDD treatment resulted in a significant increase in the production of ROS, LPO (114?±?0.09), and PCC (15.13?±?1.53) compared to the control, whereas co-treatment with G. acerosa significantly (P?<?0.05) mitigated the effects. Further, G. acerosa significantly (P?<?0.05) prevented TCDD-induced genotoxicity and cell damage. GC-MS analysis showed the presence of n-hexadecanoic acid (retention time (RT) 13.15), cholesterol (RT 28.80), α-d-glucopyranose, 4-O-α-d-galactopyranosyl (RT 20.01), and azulene (RT 4.20). The findings suggest that G. acerosa has a strong protective ability against TCDD-induced cytotoxicity, oxidative stress, and DNA damage.     

The influence of organic acids in relation to acid deposition in controlling the acidity of soil and stream waters on a seasonal basis

Much uncertainty still exists regarding the relative importance of organic acids in relation to acid deposition in controlling the acidity of soil and surface waters. This paper contributes to this debate by presenting analysis of seasonal variations in atmospheric deposition, soil solution and stream water chemistry for two UK headwater catchments with contrasting soils. Acid neutralising capacity (ANC), dissolved organic carbon (DOC) concentrations and the Na:Cl ratio of soil and stream waters displayed strong seasonal patterns with little seasonal variation observed in soil water pH. These patterns, plus the strong relationships between ANC, Cl and DOC, suggest that cation exchange and seasonal changes in the production of DOC and seasalt deposition are driving a shift in the proportion of acidity attributable to strong acid anions, from atmospheric deposition, during winter to predominantly organic acids in summer.     

Hydroxytyrosol, the phenolic compound of olive oil protects human PBMC against oxidative stress and DNA damage mediated by 2,3,7,8-TCDD

The protective effect of hydroxytyrosol (HT), a strong antioxidant compound from extra virgin olive oil, against TCDD induced toxicity was investigated in human peripheral blood mononuclear cells (PBMC). PBMC (1 × 10⁶ cells mL⁻¹) were divided into four groups and were incubated in a CO₂ incubator (5% CO₂) for 12 h with vehicle, TCDD (10 nM), TCDD + HT (10 nM + 100 μM) and HT alone (100 μM) respectively. To clarify the role of HT against TCDD induced cytotoxicity, oxidative stress and the levels of antioxidant enzymes were assessed. Incubation of PBMC with TCDD significantly decreased cell viability, catalase (CAT) and glutathione peroxidase (GPx) and increased the levels of superoxide dismutase (SOD), glutathione reductase (GR) and oxidative stress markers such as lipid peroxidation products (LPO), protein carbonyl content (PCC) and reactive oxygen species (ROS). Whereas, HT had an effective antioxidant property as observed by the increased cell viability, normalization of antioxidant enzymes and decreased levels of LPO, PCC and ROS in PBMC co-treated with HT and TCDD. Apoptosis detection and comet assay results shows that HT, by acting as an antioxidant, prevents the damage to DNA induced by TCDD. In addition light microscopic and histopathological observations revealed that the cells are apoptotic and degenerated during TCDD treatment, whereas cells showed intact morphology during co-treatment with HT. On the whole, the results reveal that HT exerts a promising antioxidant potential in protecting the PBMC against TCDD induced oxidative stress, which might be due to the presence of catechol moiety in its structure.