纳米银抑制铜绿微囊藻的机理研究

[目的]纳米银可以抑制铜绿微囊藻的繁殖及减少其叶绿素a的合成,但具体机理还不清楚,该研究探讨纳米银抑制铜绿微囊藻的生化和分子机理。[方法]用琼脂糖凝胶电泳法检测了经纳米银作用后铜绿微囊藻基因组的降解情况,用硫代巴比妥酸(TBA)法检测了细胞膜氧化产物丙二醛(MDA)的含量及用实时荧光定量PCR检测了叶绿素a合成基因chl L的表达量的变化。[结果]经纳米银作用后的铜绿微囊藻的基因组电泳图显示相对严重的断裂现象,丙二醛含量明显增多,叶绿素合成基因chl L的表达量也显著下降。[结论]纳米银可以损坏铜绿微囊藻的细胞膜与基因组,进而影响基因表达,使叶绿素合成相关的chl L基因表达量显著下降,抑制铜绿微囊藻的繁殖,甚至致其死亡。     

三种柑橘类果皮提取物对铜绿微囊藻生长的影响

通过分析测定生物量、叶绿素a含量以及叶绿素荧光参数,研究了3种柑橘类果皮甲醇提取液对铜绿微囊藻生长的影响。结果表明,3种提取液都能有效抑制铜绿微囊藻的生长、叶绿素a合成与光合系统Ⅱ（PSⅡ）活性,并且抑制效果随着作用浓度增加而增强。3种提取液抑制作用强弱的顺序为：蜜橘〉西柚〉脐橙。当蜜橘皮提取液浓度大于1.10g/L时,抑藻效果显著（P〈0.05）,培养9d后对铜绿微囊藻生长的抑制率达到86.4%,且在实验期间抑制作用没有减弱。当脐橙皮与西柚皮提取液的浓度大于3.31g/L时,抑藻效果显著（P〈0.05）,但培养5d后抑制作用开始减弱。据此推测,3种柑橘类果皮提取液中存在一类或几类物质,能够抑制铜绿微囊藻的叶绿素a合成,降低PSⅡ活性,从而降低其光合作用效率,导致铜绿微囊藻的生长受到抑制。且这类物质能自然降解,随着作用时间的延长,其抑藻效果也逐渐消失。     

甲磺隆对微囊藻生长和光合系统的影响

研究选取了水体常见蓝藻优势种类——铜绿微囊藻(Microcystis aeruginosa PCC7806)作为研究对象, 了解磺酰脲类除草剂甲磺隆(Metsulfuron-methyl)对铜绿微囊藻生长和光合系统的影响。研究表明, 当甲磺隆浓度大于80 mg/L时, 对铜绿微囊藻的生长具有显著抑制。通过回归分析和Probit分析, 甲磺隆对铜绿微囊藻生长的EC₅₀为81.998 mg/L。细胞色素研究结果显示, 实验第6天, 各浓度处理下单位细胞内Chl.a和类胡萝卜素含量均低于对照组, 且当甲磺隆浓度为80 mg/L时, 单位细胞内类胡萝卜素含量显著低于对照组。快速叶绿素荧光诱导动力学变化结果分析显示, 实验第6天甲磺隆胁迫下单位反应中心捕获的用于电子传递的能量(ET₀/RC)及单位反应中心用于电子传递的量子产额(φE₀)受到显著抑制, 综合细胞色素变化结果显示, 甲磺隆能显著抑制光合系统反应中心电子受体侧电子性能。综上所述, 甲磺隆可能作用于光合系统反应中心电子受体侧, 从而对铜绿微囊藻光合系统造成影响。     

不同氮、磷浓度对铜绿微囊藻生长、光合及产毒的影响

对一株从野外分离得到的铜绿微囊藻产毒株进行分批培养,在不同的氮磷条件下研究其生长、光合荧光及毒素含量的变化。结果表明:正磷酸盐浓度不变时,铵氮浓度的改变对铜绿微囊藻的生长有明显影响。叶绿素a(Chl.a)含量在铵氮浓度为1.83-18.3mg/L时明显较大;微囊藻毒素(包括MC-LR和MC-RR)的含量在铵氮浓度为1.83mg/L时达到最大;当铵氮浓度为0-1.83mg/L时,随着铵氮浓度升高,可变荧光FV和MC的产量均增大,同时MC异构体的种类增多;铵氮浓度过大对M.aeruginosa的生长、生理和产毒均有抑制作用。在另一组实验中,即铵氮浓度不变而正磷酸盐浓度增大时,Chl.a含量呈总体下降的趋势,并且与FV/Fm呈显著正相关关系(P<0.01,r=0.97),MC(MC-LR和MC-RR)的含量在正磷酸盐浓度小于0.56mg/L时明显升高,MC-LR与FV/Fm呈显著正相关关系(P<0.01,r=0.967)。       

磷浓度对铜绿微囊藻、大型溞和金鱼藻三者相互作用的影响

为了解磷浓度对生物操纵和水生植被恢复效果的影响,以铜绿微囊藻、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,在25℃、2000—3000lx光强和11mg/L氮浓度条件下,研究两者和三者共培养时4种磷浓度(0.2、0.5、1.0、1.5 mg/L)下各自的增长率和培养液中氮磷去除率的变化。结果表明:两者共培养时,磷浓度不大于0.2mg/L时,有利于大型溞的繁殖和金鱼藻的生长;磷浓度介于0.5—1.5mg/L时,铜绿微囊藻呈正增长趋势,而金鱼藻的生长则明显受抑制。三者共培养时,所有磷浓度下的大型溞数量及金鱼藻生物量均不同程度的升高,且铜绿微囊藻的生长得到了有效抑制,以磷浓度为0.2—0.5mg/L时效果最佳;N/P比值对藻、溞、草间的相互作用有重要影响,在藻-溞系统中,大型沉水植物的加入可以大大提高抑藻效果,减小N/P比值波动带来的不利影响。磷浓度为0.5mg/L时的水体氮磷去除效果好于其他磷浓度梯度。     

枯草芽孢杆菌fmb60菌株非核糖体肽类化合物对铜绿微囊藻生长的抑制作用

铜绿微囊藻是一种分布广泛的水华微藻,可对人类健康和生态环境造成严重危害,而枯草芽孢杆菌作为一种生防微生物可通过非核糖体肽合成酶合成多种生物活性物质。因此,枯草芽孢杆菌fmb60非核糖体肽(Non-ribosomal peptide,NRP)类产物对铜绿微囊藻生长抑制作用的研究在水华治理方面具有重要的意义。利用基因组挖掘技术从枯草芽孢杆菌fmb60中分离鉴定出bacillibactin、表面活性素(Surfactin)和芬芥素(Fengycin)3种NRP类产物,进而通过添加不同浓度的NRP类产物研究其对铜绿微囊藻生长的影响,结果显示其对铜绿微囊藻4 d的半效应浓度值EC50.4 d为26.5 mg/L,且随着样品浓度的增加,枯草芽孢杆菌fmb60的NRP类产物对铜绿微囊藻的抑制作用增强。当向其分别加入50 mg/L的样品时,培养4 d的铜绿微囊藻Fv/Fm、Fv/Fo、Yield参数分别比对照组降低了2.8%、1.7%、2.0%。表明枯草芽孢杆菌fmb60 NRP类产物能够显著抑制铜绿微囊藻的光合作用强度及代谢合成,从而为枯草芽孢杆菌抑藻剂的开发奠定理论基础。     

CdCl2对豌豆种子萌发和幼苗生长的影响

以豌豆为实验材料,采用水培方法研究了Cd2 单盐胁迫对豌豆种子萌发与生长的影响。结果显示:(1)Cd2 质量浓度≤1 mg/L时,促进种子萌发,Cd2 质量浓度达到5 mg/L时抑制种子的萌发。(2)随Cd2 质量浓度的增加Cd2 对幼苗根生长的抑制作用逐渐增强;Cd2 质量浓度≤5 mg/L时,促进茎的生长,≥10 mg/L时,抑制茎的生长;且Cd2 对幼苗根生长的抑制作用大于茎。(3)低浓度Cd2 能促进幼苗叶绿素合成,当Cd2 质量浓度高于1 mg/L时,则对幼苗叶绿素合成有抑制作用,且随Cd2 质量浓度增加叶绿素含量逐渐下降。(4)Cd2 诱发的胚根细胞核、染色体畸变率随着Cd2 质量浓度增加而增大。(5)过氧化物酶(POD)同工酶的活性随着Cd2 质量浓度升高而明显增强,Cd2 质量浓度为1 mg/L时POD活性最强,但当Cd2 质量浓度达10 mg/L时,POD的灰度值明显下降。     

生长素吲哚乙酸对铜绿微囊藻生理生化及产毒特性的影响

为了探究生长素吲哚乙酸(IAA)对产毒铜绿微囊藻(Microcystis aeruginosa)的影响, 从生长、光合色素含量、叶绿素光诱导荧光特征、脂质氧化和微囊藻毒素合成特性等方面, 研究了IAA对M. aeruginosa CHAB6301生理生化及产毒的影响。结果表明, 在低浓度IAA(0.04和0.2 mg/L)条件下, 铜绿微囊藻生长、叶绿素含量、光合系统(PSⅡ)电子传递效率及藻毒素含量均无明显变化, 藻蓝蛋白、别藻蓝蛋白和丙二醛(MDA)含量均低于对照。高浓度IAA(1和5 mg/L)能够促进细胞生长, 提高叶绿素含量, 但是抑制藻蓝蛋白和别藻蓝蛋白含量, 降低膜脂过氧化程度和细胞内藻毒素合成。综合各指标测定结果, 低浓度IAA对M. aeruginosa CHAB6301生长和光合作用影响不明显, 而高浓度IAA可促进藻细胞生长和光合作用, 增加微囊藻水华形成几率。     

白屈菜红碱对铜绿微囊藻生长和光合系统的影响

为了阐明白屈菜红碱(Chelerythrine)对铜绿微囊藻(Microcystis aeruginosa)生长及光合系统的影响, 研究了白屈菜红碱胁迫下铜绿微囊藻M. aeruginosa NIES-843生长、细胞色素含量及叶绿素光诱导荧光动力学变化. 结果显示, 当白屈菜红碱浓度10 g/L时, M. aeruginosa NIES-843的生长受到显著抑制. 通过线性回归分析, 白屈菜红碱对M. aeruginosa NIES-843生长50%抑制浓度(EC50)为(30.621.32) g/L. 当白屈菜红碱浓度为160 g/L时, M. aeruginosa NIES-843单位细胞内叶绿素a (Chl. a)和类胡萝卜素含量均显著低于对照. Chl. a光诱导荧光动力学分析结果显示, 白屈菜红碱胁迫下单位反应中心吸收的光能(ABS/RC)、单位反应中心捕获的用于还原QA的能量(TR0/RC)及单位反应中心捕获的用于电子传递的能量(ET0/RC)均受到显著抑制. 光合系统Ⅱ(PSⅡ)能量分配比率参数分析结果显示, 白屈菜红碱能显著抑制光合系统反应中心电子供体侧电子传递.       

锌对2种淡水浮游藻类增殖的影响

选用铜绿微囊藻(Microcystis aeruginosa)和脆杆藻(Fragilariasp.)为试验材料,在不同锌离子浓度下对2类微藻的增殖影响进行研究分析.藻类增长潜力(AGP)实验结果显示,在Zn2 浓度为0.02~1.00μg/L的液体培养基中,铜绿微囊藻的生长增殖快,Zn2 浓度达到100.00μg/L时,受到明显抑制.Zn2 浓度在0.02μg/L时,脆杆藻的生长繁殖快,Zn2 浓度>0.10μg/L后,则受到不同程度的抑制.     

音乐治疗效应的动物实验研究

近年来国内外关于音乐治疗效应的动物实验研究认为：音乐能影响动物的情绪;音乐还对动物的免疫功能、学习及记忆能力、以及动物的神经系统结构和功能等均有一定影响。该领域的研究有利于深入探索音乐疗法的作用机理。     

Time on task effects on safety

Reviewing the literature on time on task effects on safety shows contradictory evidence, especially with regard to 12 h shifts. It is argued that this might depend on methodological problems associated with the analysis of accident data, e.g. selectivity of samples, validity of data bases and study designs, especially for analyses at the company level. Analyses of aggregated data seem to indicate an exponential increase of accident risk with time on task beyond the normal working day. This is supported by some recent studies based on data from the Federal Republic of Germany.     

Perspectives on hair evolution based on some comparative studies on vertebrate cornification

Hair evolution contributed to the biological success of mammals. Hair origin from synapsid scales is speculative and requires extensive modifications of the morphogenetic process transforming lens-shaped dermis of scales into small dermal papillae in hair. Hair evolution from glands is hypothetical but is supported from studies on the signaling control of hair vs. glandular morphogenesis. Based on immunocytochemical and comparative studies, it is hypothesized that the onion-like organization of hair derived from glandular pegs which central part produced lipids and some keratin. In a following stage, involucrin, trichohyalin, and keratins were produced in the central cells of the gland and formed a solid medulla surrounded by keratinocytes of the inner root sheath. The origin of this protohair was possibly related to increased concentration of beta-catenin and other signaling molecules in epithelial cells following the evolution of a dermal papilla. The latter activated the keratogenic genes, already utilized in cells of the claws, in concentric layers of cells of the glandular peg. Lipidogenic genes were depressed. As new genes evolved in the genome of synapsids, new circular layers of keratinocytes containing specialized hard keratins and keratin-associated proteins were formed around medullary cells. The new keratinocytes probably originated the cortex separating medulla from the external cells that became the inner root sheath. The hypothesis indicates that in a following stage, the medulla was obliterated or replaced by cortical cells while the external part of the cortex formed a cuticular surface due to the different growth rate with inner root sheath cells.     

Studies on Biosynthesis on Biotin by Microorganisms

The accumulation of biotin-vitamers in the culture media of a large number of microorganisms (about 700 strains) was studied. The contents of the biotin-vitamers were quantitatively determined by microbiological assays with Lactobacillus arabinosus and Saccharomyces cerevisiae.

It was found that large amounts of biotin-vitamers were accumulated by various microorganisms such as Streptomyces, molds and bacteria, and that the yield of biotin-vitamers was enhanced by the addition of pimelic acid or azelaic acid to the media. It was also found that the main portion of the vitamers accumulated by many microorganisms did not support the growth of Lactobacillus arabinosus, while it did support that of Saccharomyces cerevisiae. The small amounts of true biotin were observed in the culture media of various Streptomyces and molds, but hardly in the culture media of bacteria.

The identification of biotin-vitamers accumulated by various microorganisms is described, and the distribution of the vitamers in microorganisms is also described.

The results presented in this paper show that the main component of the vitamers accumulated by many microorganisms is identified as desthiobiotin by anion exchange column chromatography, paper chromatography and chemical analysis. Small amounts of fraction B (unidentified vitamers) and Fraction D (biotin) were also detected in the culture media of various molds and Streptomyces. However, these fractions were not observed in the culture media of any bacteria tested.

It was also found that large amounts of an unknown biotin-vitamer was accumulated by various bacteria. The vitamer was avidin-uncombinable, and, from the paper electrophoretic studies, it was assumed that the vitamer might be an analogue of pelargonic acid.