[Show abstract][Hide abstract] ABSTRACT: Application of the conventional bioreactors based on biosorption for removal of heavy metals is limited because they can be broken through by heavy metals. The novel calcifying cyanobacteria reactors based co-precipitation of heavy metals with carbonate minerals induced by cyanobacteria may be a promising alternative technology to overcome the shortcomings of biosorption. In this study, removal of cadmium (Cd) from wastewater using three calcifying bacterium Nostoc calcicola reactors was investigated. N. calcicola can significantly increase aquatic phase pH in the reactor, associated with a decrease of dissolved inorganic carbon (DIC) content in the effluent. During the two-month operation of the bioreactors, over 98% of Cd removal was obtained with an initial Cd2+ concentration of 2.5 μM. Cd2+ was mainly sequestrated in organic-bound fraction, followed by a small amount of carbonate and exchangeable fractions in the N. calcicola cell. A crystalline compound of Ca, C, and O, as well as a small amount of Cd on the surface of N. calcicola cell, was observed. The two-month high Cd removal efficiency of the N. calcicola reactors shows the calcifying cyanobacteria reactors have advantages over the conventional biosorption system, which can be shortly broken through for removal of heavy metals. Although the results revealed that calcifying cyanobacterium reactor is a promising way to remove Cd from water, assessment of its longer-term performance of heavy metal removal is needed.
[Show abstract][Hide abstract] ABSTRACT: Acidic copper mine tailings with high levels of heavy metals and arsenic pose a great risk to ecosystems and human beings. Physiological responses and phytoaccumulation of heavy metals and arsenic in Medicago sativa L. growing in soils with various proportions of acidic copper mine tailings were assessed in this study. Seed germination of M. sativa was enhanced by 5-10% tailings but inhibited at higher proportions (30% and 50%) of tailings. Seedling growth, cell membrane and photosynthesis were adversely affected when the plants were grown in soils with high proportions of tailings. The activities of antioxidant enzymes (catalase, superoxide dismutase and guaiocol peroxidase) increased with increasing proportions of tailings, indicating that the antioxidant system was not impaired and can tolerate the toxicity of mine tailings. The plants grew well in soil containing up to 50% of acidic copper mine tailings. Heavy metals and arsenic except Hg were overwhelmingly immobilized in roots. Medicago sativa is a promising plant species for revegetation and phytostabilization of acidic copper mine tailings in arid lands. However, the high mobility of Hg from root to shoot may pose risk to animals.
Journal of Geochemical Exploration 05/2015; DOI:10.1016/j.gexplo.2015.05.011 · 2.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Oxidative dissolution of natural rhodochrosite by the Mn(II) oxidizing bacterium Pseudomonas putida strain MnB1 was investigated based on batch and electrochemical experiments using natural rhodochrosite as the working electrode. Tafel curves and batch experiments revealed that bacterial exopolymers (EPS) significantly increased dissolution of natural rhodochrosite. The corrosion current significantly increased with reaction time for EPS treatment. However, the corrosion process was blocked in the presence of cells plus extra EPS due to formation of the passivation layer. Moreover, the scanning electron microscopy and the energy dispersive spectroscopy (SEM-EDS) results showed that the surface of the natural rhodochrosite was notably changed in the presence of EPS alone or/and bacterial cells. This study is helpful for understanding the role of EPS in bacterially oxidation of Mn(II). It also indicates that the Mn(II) oxidizing bacteria may exert their effects on Mn(II) cycle and other biological and biogeochemical processes much beyond their local ambient environment because of the catalytically dissolution of solid Mn(II) by EPS and the possible long distance transport of the detached EPS.
[Show abstract][Hide abstract] ABSTRACT: Nitrate and arsenic are common pollutants in groundwater. However, we are still lacking technologies that can remove nitrate and arsenic simultaneously using a single species of microorganism. In the present study, the potential of synchronous removal of nitrate and arsenite from water by a single anaerobic nitrate-reducing Fe(II) oxidizing Citrobacter freundii strain PXL1 was assessed. The strain PXL1 could grow well in arsenite concentration of 2.85–13.65 μM and efficiently oxidize Fe(II), reduce nitrate and remove As(III) from water. Scanning electron microscopy, X-ray diffraction spectroscopy, and Fourier transform infrared spectroscopy analysis showed that the strain PXL1 produced poorly crystalline Fe(III) oxides. As(III) was removed mainly by adsorption and co-precipitation of the biogenic Fe(III) oxides. The anaerobic nitrate-dependent Fe(II) oxidizing bacteria including C. freundii PXL1 are promising microbes for in situ remediation of nitrate and arsenite contaminated groundwater.
[Show abstract][Hide abstract] ABSTRACT: The microbiology of mining environments has become a research topic of great importance. The present study reports on six bacterial and three fungal isolates which were characterized on a molecular basis. The phylogenetic analysis distributed the bacterial isolates into six groups in which groups A, B and C belonged to Bacillus beringensis, Bacillus sp. and Bacillus megaterium, respectively, while groups D, E and F constituted strains of Pseudomonas putida, Acidothiobacillus sp. and Kocuria sp., respectively. Fungi isolated belonged to the genera Aspergillus, Fusarium and Hypocrea. These isolates showed metal resistances to six heavy metals: Cu, Cr, Pb, Cd, Sb and Ni. For the bacteria, the minimum inhibitory concentrations (MICs) of these metals were in the range of 1-11 mM, whereas for fungi, the MIC was in the range of 5-20 mM. The multiple heavy metal-resistant bacterial species may be further screened for application to bioremediation.
[Show abstract][Hide abstract] ABSTRACT: The herbicidal effects of harmaline extracted from Peganum harmala seed on cell growth and photosynthesis of green algae Chlorella pyrenoidosa were investigated using chlorophyll a fluorescence and thermoluminescence techniques. Exposure to harmaline inhibited cell growth, pigments contents and oxygen evolution of C. pyrenoidosa. Oxygen evolution was more sensitive to harmaline toxicity than cell growth or the whole photosystem II (PSII) activity, maybe it was the first target site of harmaline. The JIP-test parameters showed that harmaline inhibited the donor side of PSII. Harmaline decreased photochemical efficiency and electron transport flow of PSII but increased the energy dissipation. The charge recombination was also affected by harmaline. Amplitude of the fast phase decreased and the slow phase increased at the highest level of harmaline. Electron transfer from QA(-) to QB was inhibited and backward electron transport flow from QA(-) to oxygen evolution complex was enhanced at 10μgmL(-1) harmaline. Exposure to 10μgmL(-1) harmaline caused appearance of C band in thermoluminescence. Exposure to 5μgmL(-1) harmaline inhibited the formation of proton gradient. The highest concentration of harmaline treatment inhibited S3QB(-) charge recombination but promoted formation of QA(-)YD(+) charge pairs. P. harmala harmaline may be a promising herbicide because of its inhibition of cell growth, pigments synthesis, oxygen evolution and PSII activities.
[Show abstract][Hide abstract] ABSTRACT: Urumqi City is the farthest metropolis from an ocean in the world. This communication measured the concentrations of eight potentially harmful metals Cr, Pb, Hg, Ni, Cd, Zn, Cu, and Sr and metalloids As and Sb in the street dusts collected from Urumqi City and compared them with those noted in Taipei City. Although the geological environments of Taipei and Urumqi differ markedly; however, the potential harmful metals and metalloids studied are surprisingly similar in their distributions in these two cities. Particularly, As is a common pollutant that poses severe health risks to residents in both cities. Hence, the anthropogenic rather than geogenic factors pre-dominate the formation and distributions of street dusts. This finding suggests common control strategy may be applicable to different metropolis on the confinement of adverse health effects by the street dusts.
Journal of the Taiwan Institute of Chemical Engineers 09/2014; 45(5). DOI:10.1016/j.jtice.2014.04.018 · 3.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Pollution with antibiotics poses a great risk to aquatic ecosystems. Although some toxic effects of antibiotics on photosystem II (PSII) have been documented, their toxicity to photosystem I (PSI) is still unclear. In this study, effects of ofloxacin on activities of both PSI and PSII of Microcystis aeruginosa (Kützing) Kützing were investigated. Exposure to 0.1 mg L−1 ofloxacin led to increases in contents of chlorophyll a and carotenoids and photosynthetic activity of M. aeruginosa. PSI activity and its electron transport were not affected by 0.1 mg L−1 ofloxacin. When M. aeruginosa was exposed to ≥10 mg L−1 ofloxacin, the electron transport rates of PSI and PSII, the yield of cyclic electron flow (CEF) and the contribution of linear electron flow (LEF) to PSI decreased whereas Y(NA) (limitation of donor side of PSI) and Y(NO) (the quantum yield of non-regulated energy dissipation in PSII) significantly increased. CEF had a significant contribution to alleviating the inhibitory effect of ofloxacin on PSI of M. aeruginosa treated with low concentrations of ofloxacin. The protective role CEF for tolerance of PSI to the toxicity of ofloxacin decreased with increasing ofloxacin concentration.
Journal of Bioscience and Bioengineering 09/2014; 119(2). DOI:10.1016/j.jbiosc.2014.07.014 · 1.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The
knowledge of the effects of Sb(V) on the physiological characteristics of cyanobacteria was still limited. In the present study, responses of photosystem I and II (PSI and PSII), cyclic electron flow (CEF), and interphotosystem electron transport of Microcystis aeruginosa to 5–100 mg/l Sb(V) were synchronously measured using the Dual-PAM-100. 5 mg/l Sb (V) significantly inhibited PSII activity, but had no significant effects on PSI activity. At higher concentrations of Sb(V), the quantum yield and electron transport of PSI were less affected compared to PSII. The ratio of Y(II)/Y(I) significantly decreased with increasing Sb(V) concentration. It decreased from 0.7 for control to 0.4 for 100 mg/l Sb(V)-treated cells, indicating that the change of the distribution of quantum yields between two photosystems and more serious inhibition of PSII under stress of Sb(V) compared to PSI. CEF was activated associated with the inhibition of linear electron flow after exposure to Sb(V). The contribution of Y(CEF) to the quantum yield and activity of PSI increased with increasing Sb(V) concentrations. The cyclic electron transport rate made a significant contribution to electron transport rate of PSI, especially at high Sb(V) concentration (100 mg/l) and high illumination (above 555 μmol photons/m2/s). The stimulation of CEF was essential for the higher tolerance of PSI than PSII to Sb(V).
Current Microbiology 08/2014; 70(1). DOI:10.1007/s00284-014-0678-5 · 1.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In total, 34 urban street dust samples were collected in Taipei City. Concentrations of potential harmful metals Cr, Pb, Hg, Ni, Cd, Zn, Cu, and Sr and metalloids As and Sb in street dust samples were measured and their sources and potential health risks to humans were evaluated. Traffic emissions were the main source of the potential harmful metals and metalloids in street dust samples from Taipei. Exposure routes for all studied potential harmful metals and metalloids, except for that of Hg, follow ingestion > dermal contact > inhalation. Children are at higher health risk than adults. The As, Sb, Cr, and Pb concentrations in Taipei have adverse non-cancer health effects on residential children. Carcinogenic risk of As exposure for children and adults in Taipei were higher than the threshold value (10−6–10−4). The study highlights the determinant role of anthropogenic factors in the formation of street dust.
Journal of the Taiwan Institute of Chemical Engineers 07/2014; 45(4). DOI:10.1016/j.jtice.2014.01.003 · 3.00 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Responses of photosystem I and II activities of Microcystis aeruginosa to various concentrations of Cu(2+) were simultaneously examined using a Dual-PAM-100 fluorometer. Cell growth and contents of chlorophyll a were significantly inhibited by Cu(2+). Photosystem II activity [Y(II)] and electron transport [rETRmax(II)] were significantly altered by Cu(2+). The quantum yield of photosystem II [Y(II)] decreased by 29 % at 100 μg L(-1) Cu(2+) compared to control. On the contrary, photosystem I was stable under Cu(2+) stress and showed an obvious increase of quantum yield [Y(I)] and electron transport [rETRmax(I)] due to activation of cyclic electron flow (CEF). Yield of cyclic electron flow [Y(CEF)] was enhanced by 17 % at 100 μg L(-1) Cu(2+) compared to control. The contribution of linear electron flow to photosystem I [Y(II)/Y(I)] decreased with increasing Cu(2+) concentration. Yield of cyclic electron flow [Y(CEF)] was negatively correlated with the maximal photosystem II photochemical efficiency (F v/F m). In summary, photosystem II was the major target sites of toxicity of Cu(2+), while photosystem I activity was enhanced under Cu(2+) stress.
Biological Trace Element Research 06/2014; 160(2). DOI:10.1007/s12011-014-0039-z · 1.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Extracellular polymeric substances (EPS) are important components of activated sludge and play an important role in removing heavy metals. The interaction of soluble EPS (SEPS)/bound EPS (BEPS) with Pb(II) was investigated using excitation—emission matrix (EEM) fluorescence spectroscopy and infra-red spectrometry. One protein-like fluorescence peak (peak A) was identified from the EEM spectra of SEPS and BEPS, and one aromatic protein peak (peak B) was observed in the EEM spectra of SEPS. the interaction of Pb(II) with SEPS was governed by collision sorption, while the binding of Pb(II) to BEPS was due to complexation. Functional groups of proteins, polysaccharides, lipids, and uronic acid were involved in Pb(II) adsorption to SEPS/BEPS. The organic acids in SEPS are also responsible for binding Pb(II) to SEPS. Other groups such as the phosphate group in the fingerprint zone also participated in binding of Pb(II) to EPS. There were no significant differences in the values of binding constants and conditional stability constants between SEPS and BEPS.
[Show abstract][Hide abstract] ABSTRACT: Bosten Lake, the largest inland lake in China, has been contaminated with arsenic (As) due to anthropogenic activities. Salinity of the lake water has been increasing due to the extremely dry climate and salt drainage from the farmland. Effects of the increasing salinity on the geochemical behavior of arsenic in sediment are still unclear. In this study, vertical variation of geochemical fractions of As in sediment and arsenic concentration in porewater along the salinity gradient of Bosten Lake was studied. Effects of salinity and ions and anions in porewater on arsenic concentration were also examined. Arsenic content in the five Tessier fractions followed the decreasing order of residual ≫ exchangeable > Fe and Mn oxides > organic > carbonate. The ecological risk of arsenic in the sediment was at low or medium levels, indicated by the low percentage of exchangeable and carbonate bound fractions. Contrary to the decreasing electrical conductivity of porewater with depth, arsenic concentration in porewater showed an increasing trend with depth. Arsenic concentration in porewater increased from around zero at the surface layer of sediment to over 600 μg L−1 in deeper layers of some sites. Arsenic concentration inversely correlated with electrical conductivity in porewater. Arsenic concentration generally decreased with increasing concentrations of SO4 2−, Ca2+, Mg2+ and Na+ but showed no clear relation with concentrations of K+ and Cl−. This study implies that increase of salinity may decrease the release of arsenic from sediment and its ecological risk.
[Show abstract][Hide abstract] ABSTRACT: Anaerobic Fe(II) Oxidizing Denitrifiers (AFODN), a type of newly found Fe(II)-oxidizing bacteria, play an important role in iron and nitrogen cycling. In the present study, a novel AFODN strain PXL1 was isolated from anaerobic activated sludge. Phylogenetic analysis of 16S rRNA gene sequence revealed similarity between this strain and Citrobactor freundii. The strain reduced 30% of nitrate and oxidized 85% of Fe(II) over 72 h with an initial Fe(II) concentration of 3.4 mM and nitrate concentration of 9.5 mM. Oxidation of iron was dependent on the reduction of nitrate to nitrite in the absence of other electron donors or acceptors. Nitrate reduction and Fe(II) oxidation followed first-order reaction kinetics. Iron oxides accumulated in the culture were analyzed by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The strain recovered deposited oxidized Fe in the form of amorphous Fe oxides.
[Show abstract][Hide abstract] ABSTRACT: This study characterized the interactions of goethite, EPS from cyanobacterium Chroococcus sp. and Hg(II) using excitation emission matrix (EEM) spectra and adsorption isotherms. Three protein-like fluorescence peaks were noted to quench in the presence of Hg(II). The estimated conditional stability constant (logKa) and the binding constant (logKb) of the studied EPS-Hg(II) systems ranged 3.84-4.24 and 6.99-7.69, respectively. The proteins in EPS formed stable complex with Hg(II). The presence of proteins of Chroococcus sp. enhanced the adsorption capacity of Hg(II) on goethite; therefore, the goethite-EPS soil is a larger Hg(II) sink than goethite alone soil. Biosorption significantly affects the mobility of Hg(II) in goethite soils.
[Show abstract][Hide abstract] ABSTRACT: In presenting the calculation of the quantum yield of photosystem I, Y(I), the authors erroneously presented the wrong equation: Equation (4), page 232.
The right equation of Y(I) is (Pm'-P)/Pm, where ‘-P’ was missed in the previous version.