Effects of Glomus mosseae on the toxicity of heavy metals to Vicia faba

A glasshouse pot experiment was conducted to investigate effects of the arbuscular mycorrhizal fungus Glomus mosseae on the growth of Vicia faba and toxicity induced by heavy metals （HMs） （Cu, Zn, Pb and Cd） in a field soil contaminated by a mixture of these metals. There was also uninoculation treatment （NM） simultaneously. Mycorrhizal （GM） plants have significantly increased growth and tolerance to toxicity induced by heavy metals compared with NM plants. P uptake was significantly increased in GM plants. Mycorrhizal symbiosis reduced the transportation of HMs fi＇om root to shoot by immobilizing HMs in the mycorrhizal, shown by increasing the ratios of HMs from root to shoot. Oxidative stress, which can induce DNA damage, is an important mechanism of heavy metal toxicity. GM treatment decreased oxidative stress by intricating antioxidative systems such as peroxidases and non-enzymic systems including soluble protein. The DNA damage induced by heavy metals was detected using comet assay, which showed DNA damage in the plants was decreased by the GM treatment.     

Submerged vegetation removal promotes shift of dominant phytoplankton functional groups in a eutrophic lake

Historical data indicate that the dominance of submerged plants in Dianchi Lake in the 1960 s was characterized by low algal density with dominance of non-toxic group J（Scenedesmus,Pediastrum,etc.）. The removal of submerged plants,which began in the 1970 s,resulted in the expansion of bloom-forming Microcystis（group M）. Laboratory experiments suggested that Microcystis aeruginosa was inclined to grow and develop at elevated temperatures. The growth of Scenedesmus obliquus was slower than that of co-cultivated M. aeruginosa in the absence of Ceratophyllum demersum,especially at higher temperatures. The existence of submerged plant C. demersum could inhibit the growth of the harmful algae M. aeruginosa and this inhibitory effect by C. demersum was enhanced with an increase in temperature. Instead,with C. demersum,the growth of S. obliquus was not inhibited,but the co-cultivated M. aeruginosa was eliminated in a short time. Combined with the historical data and laboratory experiments,it was indicated that the submerged plants might play important roles in the dominance of the non-toxic group J in the historical succession. Consequently,the introduction of the submerged plant such as C. demersum might alter the dominant phytoplankton functional groups from M to J and benefit the restoration of the eutrophic lake.     

Cobalt and manganese stress in the microalga Pavlova viridis （Prymnesiophyceae）： Effects on lipid peroxidation and antioxidant enzymes

Pollution of marine environment has become an issue of major concern in recent years.Serious environmental pollution by heavy metals results from their increasing utilization in industrial processes and because most heavy metals are transported into the marine environment and accumulated without decomposition.The aim of the present study is to investigate the effects on growth,pigments, lipid peroxidation,and some antioxidant enzyme activities of marine microalga Pavlova viridis,in response to elevated concentrations of cobalt(Co)and manganese(Mn),especially with regard to the involvement of antioxidative defences against heavy metal-induced oxidative stress.In response to Co~(2 ),lipid peroxidation was enhanced compared to the control,as an indication of the oxidative damage caused by metal concentration assayed in the microalgal cells but not Mn~(2 ).Exposure of Pavlova viridis to the two metals caused changes in enzyme activities in a different manner,depending on the metal assayed:after Co~(2 )treatments,total superoxide dismutase(SOD)activity was irregular,although it was not significantly affected by Mn~(2 )exposure.Co~(2 )and Mn~(2 )stimulated the activities of catalase(CAT)and glutathione(GSH),whereas,ghitathione peroxidase(GPX)showed a remarkable increase in activity in response to Co~(2 )treatments and decreased gradually with Mn~(2 )concentration,up to 50μmol/L,and then rose very rapidly,reaching to about 38.98% at 200μmol/L Mn~(2 ).These results suggest that an activation of some antioxidant enzymes was enhanced,to counteract the oxidative stress induced by the two metals at higher concentration.     

Oxidative stress and DNA damages induced by cadmium accumulation

Experimental evidence shows that cadmium （Cd） could induce oxidative stress and then causes DNA damage in animal cells, however, whether such effect exists in plants is still unclear. In the present study, Vicia faba plants was exposed to 5 and 10 mg/L Cd for 4 d to investigate the distribution of Cd in plant, the metal effects on the cell lipids, antioxidative enzymes and DNA damages in leaves. Cd induced an increase in Cd concentrations in plants. An enhanced level of lipid peroxidation in leaves and an enhanced concentration of H2O2 in root tissues suggested that Cd caused oxidative stress in Vicia faba. Compared with control, Cd-induced enhancement in superoxide dismutase activity was significant at 5 mg/L than at 10 mg/kg in leaves, by contrast, catalase and peroxidaseactivities were significantly suppressed by Cd addition. DNA damage was detected by neutral/neutral, alkaline/neutral and alkaline/alkaline Comet assay. Increased levels of DNA damages induced by Cd occurred with reference to oxidative stress in leaves, therefore, oxidative stress induced by Cd accumulation in plants contributed to DNA damages and was possibly an important mechanism of Cd-phytotoxicity in Vicia faba plants.     

Antibacterial potency of housefly larvae extract from sewage sludge through bioconversion

Use of the fly to convert sewage sludge into nutrient-rich soil conditioner and amendment is an attractive approach for sludge bioconversion. During this process, fecal coliforms, an indicating pathogen, in sludge were reduced to 5.3 × 102 most probable number /g dry solid from initial 3.32 × 106 MPN/g dry solid. It was also found that the extract of larvae grown in sludge during bioconversion have an observable inhibitory effect against bacteria compared to larvae grown in wheat bran as measured by minimum bacterial concentration tests. In vitro antimicrobial assay tests over time also showed that the extract had strong inhibitory efficiencies of ca. 99% against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Serratia marcescens, while the efficiency was 69% and 57% against Bacillus subtilis and Klebsiella pneumoniae, respectively. The observed pathogenic bacterial cell membrane damage was found to be responsible for the phenomenon mentioned above, with nuclear acids leaching out quickly and alkaline phosphatase increasing in the outer membrane, followed by an increase of β-galactosidase in the inner membrane. Clearly, housefly larvae extract from sewage sludge through bioconversion possesses antibacterial potency against pathogenic bacteria.     

Growth and phosphate uptake kinetics of Microcystis aeruginosa under various environmental conditions

Growth and uptake of exogenous phosphate by Microcystis aeruginosa in batch culture under different temperature, photoperiod, and turbulence were studied by the method of phosphate isotope tracer. Relatively high temperature, long photoperiod and strong turbulence increased the cell density of M. aeruginosa in these batch cultures. The initial rapid uptake of phosphate by M. aeruginosa was independent of the temperature, photoperiod, and turbulence. Similarly, maximum exogenous phosphate uptake was not related to these environmental factors. However, elevated temperature and turbulence shortened the time, required to obtain maximum P accumulation. The growth of M. aeruginosa could alleviate the phosphorous leakage. Total amounts of exogenous phosphate uptake to M. aeruginosa and the phosphorus leakage of M. aeruginosa were significantly influenced by the growth state of M. aeruginosa closely correlated with the environmental factors. The maximum volume of exogenous phosphate uptake to M. aeruginosa was 46% of added exogenous phosphate in water with 16 hours of photoperiod. Thus, total amounts of exogenous phosphate uptake to M. aeruginosa were more strongly affected by the photoperiod length than temperature and turbulence.     

Combined remediation of DDT congeners and cadmium in soil by Sphingobacterium sp. D-6 and Sedum alfredii Hance

Combined pollution of 1,1,1-trichloro-2,2-bis (4-chlorophenyl) ethane (DDT) and cadmium (Cd) in agricultural soils is of great concern because they present serious risk to food security and human health.In order to develop a cost-effective and safe method for the removal of DDTs and Cd in soil,combined remediation of DDTs and Cd in soil by Sphingobacterium sp.D-6 and the hyperaccumulator,Sedum alfredii Hance was investigated.After treatment for 210 days,the degradation half-lives of DDTs in soils treated by strain D-6 decreased by 8.1% to 68.0% compared with those in the controls.The inoculation of strain D-6 into soil decreased the uptake of DDTs by pak choi and S.alfredii.The shoots/roots ratios of S.alfredii for the Cd accumulation ranged from 12.32 to 21.75.The Cd concentration in soil decreased to 65.8%-71.8% for S.alfredii treatment and 14.1%-58.2% for S.alfredii and strain D-6 combined treatment,respectively,compared with that in the control.The population size of the DDTs-degrading strain,Simpson index (1/D) and soil respiratory rate decreased in the early stage of treatment and then gradually increased,ultimately recovering to or exceeding the initial level.The results indicated that synchronous incorporation of strain D-6 and S.alfredii into soil was found to significantly (p 0.05) enhance the degradation of DDTs in soil and the hyperaccumulation of Cd in S.alfredii.It was concluded that strain D-6 and S.alfredii could be used successfully to control DDTs and Cd in contaminated soil.     

In vitro immunotoxicity of untreated and treated urban wastewaters using various treatment processes to rainbow trout leucocytes

Municipal effluents are known to impede the immune system of aquatic organisms. The purpose of this study was to examine the immunotoxicity of urban wastewaters before and after 6 treatment processes from 12 cities toward trout leucocytes. Freshly prepared trout leucocytes were exposed to increasing concentrations of solid phase (C18) extracts of wastewaters for 24 hr at 15℃. Immunocompetence was determined by following changes in leucocyte viability and the proportion of cells able to ingest at least one (immunoactivity) and at least three (immunoefficiency) fluorescent beads. The influents were treated by six different treatment strategies consisting of facultative aerated lagoons, activated sludge, biological aerated filter, biological nutrient removal, chemically-assisted physical treatment and trickling filter/solid contact. Water quality parameters of the wastewaters revealed that the plants effectively removed total suspended solids and reduced the chemical oxygen demand. The results revealed that the effluents' immunotoxic properties were generally more influenced by the properties of the untreated wastewaters than by the treatment processes. About half of the incoming influents decreased leucocyte viability while 4 treatment plants were able to reduce toxicity. The influents readily increased phagocytosis activity for 8/12 influents while it was decreased in 4/12 influents. This increase was abolished for 4/12 of the effluents using treatments involving biological and oxidative processes. In conclusion, municipal effluents have the potential to alter the immune system in fish and more research will be needed to improve the treatments of wastewaters to better protect the quality of the aquatic environment.     

A method to extract algae toxin of microcystin-LR

A simple and low-cost method to obtain cyanobacterial toxin microcystin-LR(MC-LR) was developed. A new strain of Microcystis aeruginosa,named DC-1, producing microcystin-LR but not microcystin-RR, was separated from the field blooming algae samples of Dianchi Lake.in southwest of China. Following three times‘freeze and thaw treatment, the cultivated DC-cells were extracted with 40% methanol in water.The extract was centrifuged and the supernatant applied to a Hydrophilic-Lipophilic Balance(HLB) SPE cartridge.Eluted impuries with a certain gradient from 30% to 50% methanol in water, MC-LR was finally eluted from the HLB cartridge with 60%.may be used in adsorption and biodegradation experiments instead of using expensive standard reagents.     

Uptake of radioiodide by Paenibacillus sp., Pseudomonas sp., Burkholderia sp. and Rhodococcus sp. isolated from a boreal nutrient-poor bog

Radionuclides, like radioiodine(~(129)I), may escape deep geological nuclear waste repositories and migrate to the surface ecosystems. In surface ecosystems, microorganisms can affect their movement. Iodide uptake of six bacterial strains belonging to the genera Paenibacillus,Pseudomonas, Burkholderia and Rhodococcus isolated from an acidic boreal nutrient-poor bog was tested. The tests were run in four different growth media at three temperatures. All bacterial strains removed iodide from the solution with the highest efficiency shown by one of the Paenibacillus strains with 99% of iodide removed from the solution in one of the used growth media. Pseudomonas, Rhodococcus and one of the two Paenibacillus strains showed highest iodide uptake in 1% yeast extract with maximum values for the distribution coefficient(K_d) ranging from 90 to 270 L/kg DW. The Burkholderia strain showed highest uptake in 1% Tryptone(maximum K_d170 L/kg DW). The Paenibacillus strain V0-1-LW showed exceptionally high uptake in 0.5% peptone + 0.25% yeast extract broth(maximum K_d 1,000,000 L/kg DW). Addition of 0.1% glucose to the 0.5% peptone + 0.25% yeast extract broth reduced iodide uptake at 4℃ and 20℃ and enhanced iodide uptake at 37℃ compared to the uptake without glucose. This indicates that the uptake of glucose and iodide may be competing processes in these bacteria. We estimated that in in situ conditions of the bog,the bacterial uptake of iodide accounts for approximately 0.1%–0.3% of the total sorption of iodide in the surface, subsurface peat, gyttja and clay layers.     

模拟自然水体中藻-溞-草间的相互作用研究

为了解氮磷浓度对生物操纵效果及同时恢复水生植被的影响,以小球藻、大型溞和金鱼藻分别作为浮游植物、浮游动物和大型沉水植物的代表,模拟自然条件研究了不同氮磷浓度对三者生长和相互作用的影响.结果表明:金鱼藻和小球藻共培养时,在氮浓度介于2.92～12.60mg·L-1、磷浓度介于0.06 ～0.85 mg·L-1,金鱼藻增长不明显,甚至出现负增长;而小球藻的增长率则远高于金鱼藻.小球藻和大型溞共培养时,氮、磷浓度分别为1.26～ 10.53 mg·L-1和0.04～1.16 mg·L-1时均占据优势,对小球藻的抑制效果显著,抑藻及氮磷去除效果明显好于金鱼藻和小球藻共培养,而且磷的去除效果优于氮.三者共培养时,在氮浓度介于3.15 ～23.92 mg·L-1、磷浓度介于0.07 ～0.64 mg·L-1时,大型溞与金鱼藻的增长率都较高,而小球藻则维持在较低的增长水平,水质改善效果较好;当氮、磷浓度分别升至25.95 mg·L-1和1.18 mg·L-1时,大型潘和金鱼藻的增长率均下降,水质变差.大型溞和金鱼藻的联合控藻效果好于其单一的控制效果,该效果明显受到氮磷浓度的影响.     

农业废物好氧堆肥中环境因子对nirK、nirS和nosZ数量的影响

应用定量聚合酶链式反应(real-time PCR)技术对农业废物好氧堆肥过程中参与反硝化过程的功能基因(nirK、nirS和nosZ)丰度在堆体不同位置处随时间的变化情况进行了研究.结果表明,随着堆肥进程,3种基因数量整体呈现出先升后降的变化规律,且不同位置处的反硝化基因数量之间存在着显著的差异性.使用Canoco 4.5软件对获得的反硝化功能基因丰度数据与不同时期不同层次堆体温度、pH、含水率、NH4+-N、NO3--N和水溶性有机碳(WSC)等环境因子的相关性进行冗余分析(redundancy analysis,RDA).基于手动选择的RDA分析结果表明,WSC、NH4+-N和堆体温度对反硝化基因丰度有着显著的影响(P<0.05),且前2个因子达到了极显著水平(P<0.01).应用t-value回归分析方法单独分析每种环境因子与3种基因的相关性,其中nirK与温度和pH显著正相关(P<0.05),nirS与温度显著正相关(P<0.05),nosZ与NH4+-N显著正相关(P<0.05)、与WSC显著负相关(P<0.05).     

凤眼莲化感物质对铜绿微囊藻、斜生栅藻生长及细胞数相对比例的影响

为探索化感物质在蓝藻水华治理方面的应用潜力,选取在凤眼莲根系分泌物中发现的5种化感物质（亚油酸、亚油酸甘油酯、丙酰胺、N-苯基—2-萘胺和壬酸）,研究了3种剂量下（0.1、1.0、10.0mg.L-1）其对单一、混合培养铜绿微囊藻和斜生栅藻生长的影响.结果发现,化感物质成分、剂量和藻类培养方式对铜绿微囊藻和斜生栅藻生长...     

底泥对洋河水库微囊藻和鱼腥藻生长影响的研究

采用批量培养的方法研究洋河水库底泥浸出液对洋河水库微囊藻和鱼腥藻生长的影响.结果表明,厌氧条件底泥浸出液对鱼腥藻生长速率有促进作用,添加2%、20%、50%的厌氧底泥浸出液的鱼腥藻生长速率比M11培养基中分别高出36.6%、47.2%、36.0%;而添加厌氧底泥浸出液对微囊藻生长有抑制作用,微囊藻最大生物量随底泥浸出液的添加量增加而减小.与添加厌氧底泥浸出液相比,添加好氧条件的底泥浸出液对鱼腥藻生长速率也有一定的促进作用,添加20%的好氧底泥浸出液的鱼腥藻生长速率比M11培养基中高出37.2%;而添加好氧底泥浸出液对微囊藻生长影响不明显.在添加厌氧底泥浸出液的培养基中增加铁,则微囊藻的最大生物量显著增加,表明底泥浸出液对微囊藻生长的影响可能是较高浓度的有机质与铁的结合影响了微囊藻对铁的利用.     

荔枝落叶对铜绿微囊藻生长和光合作用的影响

利用浮游植物荧光分类仪对暴露于不同浓度荔枝落叶浸出液下铜绿微囊藻的生长、最大光合作用效率(Fv/Fm)、实际光合作用效率(YⅡ)、光能利用效率(α)、最大相对电子传递速率(r ETRmax)和光饱和系数(Ik)进行了为期15 d的检测,研究浸出液对铜绿微囊藻生长和光合作用的影响.结果发现,浸泡5 d的荔枝落叶浸出液可以抑制藻的生长,呈明显的浓度抑制型变化,随着时间的延长,抑制作用下滑.荧光参数Fv/Fm、YⅡ和α与浸出液浓度由负相关转为正相关或保持正相关关系,浸出液可能早期对藻光合作用发生胁迫,或通过提高光能利用效率来度过胁迫环境,r ETRmax、Ik和叶绿素a浓度与浸出液浓度由负相关转为显著负相关关系.三维荧光图谱结果表明,第15 d时,在投量为2.0 g·L-1时,色氨酸及酪氨酸荧光峰强度约为1.2g·L-1投量情况下的1/3,同时腐殖酸的荧光峰强度减弱.进一步研究藻细胞生长的半抑制浓度EC50值表明,与传统的农作物秸秆控藻比较,其EC50值较低,可能荔枝落叶化感控藻效果较强,只需较低的浸出液浓度而能达到较好的控藻效果.     

胶质芽孢杆菌对印度芥菜富集土壤Cd及土壤pH的影响

采用根袋法盆栽试验,研究接种活菌量浓度分别为1×1010 cfu·kg-1 (T1)和2×1010 cfu·kg-1(T2)的胶质芽孢杆菌,对印度芥菜富集土壤Cd、土壤有效态Cd含量及土壤pH的影响.结果表明,以不接种菌液作为对照,处理T1、T2地上部分生物富集系数分别为13.58、16.83,与对照相比分别提高42.95％、77.16％;地下部分生物富集系数分别为4.35、4.83,分别比对照提高24.64％、38.40％;土壤的净化率分别是对照的1.73、2.20倍.对照组土壤有效态Cd含量随着时间的延长而降低,根际和非根际土壤分别降低32.93％和45.54％;但T1和T2处理中,根际、非根际土壤有效态Cd含量分别提高15.15％、31.73％和36.54％、45.28％.收获时,处理T1、T2根际土壤pH降低率分别是对照的1.08、1.10倍.不同浓度胶质芽孢杆菌处理下土壤pH与有效态Cd含量均呈显著负线性关系.综上,胶质芽孢杆菌主要是通过改变土壤pH来影响土壤Cd生物有效性,从而促进超富集植物的修复效果.本研究可为微生物辅助植物修复重金属污染土壤提供一定理论依据和实践指导.     

铜绿假单胞菌对白腐菌产木质纤维素降解酶的影响

采用固态发酵的方法,考察了两株不同型号的铜绿假单胞菌（AB93066和ATCC9027）对白腐菌（黄孢原毛平革菌）产木质纤维素降解酶（木素过氧化物酶LiP、锰过氧化物酶MnP和羧甲基纤维素酶CMCase）的影响,并对酶提取液的pH值、表面张力及稻草降解残渣中挥发性有机质含量的变化进行了分析.结果表明,添加5.72%的A...     

黄连根茎浸提物对隆线溞的急性毒性作用

黄连根茎和制剂具有抗菌等作用,广泛用于水产养殖.试验以隆线溞单克隆生物株为供试生物,研究了不同浓度的黄连根茎浸提物(Coptis chinensis root extracts,CRE)对隆线溞泳动能力、存活率及趋光性的影响.结果表明,黄连根茎浸提物对水溞具有急性毒性,半致死浓度半抑制浓度趋光指数显著改变的浓度,后者仅4.27 mg·L-1(以CRE浓度计),远远低于防治鱼病黄连进入水体的浓度.因此,水产养殖使用黄连药物对水溞存在生物毒性.此外,导致隆线溞趋光指数显著改变的CRE浓度比半致死浓度低30.62~36.51倍,测试时间从48 h或24 h缩短到3 h,且容易观察,利用隆线溞趋光性的改变可快速监测CRE对其的毒害作用.在水产养殖中,如果滥用黄连制剂,会影响水生食物链,导致水生态系统失衡.     

白洋淀荷茎叶提取液对铜绿微囊藻及四尾栅藻化感效应

本研究探讨了活体荷不同部位(茎和叶)提取出液对铜绿微囊藻、四尾栅藻生长化感效应,为推广荷遏制水华暴发及制作抑藻制剂提供理论基础.实验设计了5个浓度梯度,结果表明,荷叶浸出液对藻类的抑制效果优于荷茎浸出液,当荷叶浸出质量浓度为25 g.L-1时,对铜绿微囊藻及四尾栅藻的抑制率分别为71.33%、78.14%.浸出液成分的GC-MS分析表明,荷叶和茎浸出液都含有丙酰胺,质量浓度分别为1.1 mg.L-1、0.2 mg.L-1.并根据概率计算法,分别计算了两种藻类的半浓度效应.