在不同营养条件下铜绿微囊藻对模拟微重力胁迫的响应

通过测定在不同重力水平和营养条件下培养的铜绿微囊藻(Microcystis aeruginosa)的各项生理生化指标,研究了培养基的营养物质浓度对微囊藻细胞响应模拟微重力胁迫的影响。结果表明,在正常浓度的BG-11(富营养)和营养盐浓度减为1/10的BG-11(贫营养)培养基中培养的微囊藻对模拟微重力胁迫都很敏感,培养2d后多项生理生化指标显著改变;但是在富营养和贫营养条件下,模拟微重力的作用效果是截然不同的。对培养在BG-11中的微囊藻细胞来说,模拟微重力抑制其生长和光合活性,导致细胞内色素(叶绿素a和类胡萝卜素)、蛋白(藻蓝蛋白和可溶性蛋白)和毒素含量显著升高,向外分泌的毒素含量降低;而对培养在1/10BG-11中的藻细胞来说,模拟微重力促进其生长和光合活性,导致细胞内色素、蛋白和毒素含量降低,并使得毒素分泌增强。模拟微重力或营养限制单独作用所造成的影响相似,且后者的作用效果强于前者。当二者同时存在时,模拟微重力可以部分抵消营养限制对微囊藻生长和代谢的影响,这可能是由于模拟微重力下藻细胞的生长受到抑制而导致营养需求降低,也可能是由于模拟微重力提高了藻细胞利用营养物质的效率。总之,微囊藻对模拟微重力胁迫的响应与培养基的营养条件有关。     

一株枯草芽孢杆菌的生长特性及抑藻效果研究

溶藻微生物能引起水华蓝藻的快速消亡,从而达到控制水华之目的。为了探讨枯草芽孢杆菌(Bacillus subtilis)对铜绿微囊藻(Microcystis aeruginosa)及小球藻(Chlorell)的抑制效果,在实验室条件下研究了枯草芽孢杆菌对两种藻类生长的影响、抑制藻类生长的作用方式以及发酵液处理下铜绿微囊藻丙二醛(MDA)及谷胱甘肽(GSH)含量、超氧化物歧化酶(SOD)及过氧化氢酶(CAT)活性。试验结果表明,筛选出的菌株具有较好的环境适应性和抑制藻类生长的能力,其抑制效果是通过分泌胞外物质实现的。经过枯草芽孢杆菌处理后,铜绿微囊藻的叶绿素a及藻体蛋白含量均显著低于对照组,而胞内MDA及GSH含量显著升高,SOD及CAT活性也有增高的趋势。     

甘薯愈伤组织对干旱胁迫和盐胁迫的生理反应对比

研究干旱胁迫和盐胁迫对“芦选一号”。日‘薯愈伤组织可溶性蛋白、可溶性糖、脯氨酸含量、SOD活性等的影响,从而在细胞水平上探讨甘薯抵御渗透胁迫的生理机制。并分析甘薯细胞对干旱处理（PEG-6000）和盐处理（NaCl）的反应差异。结果表明,可溶性蛋白质含量在干旱胁迫下缓慢升高,在轻度和中度盐胁迫的生长前期和中期有较大幅度的上升。但后期下降,表明短时间盐胁迫下,Na^＋可能促进可溶性蛋白的合成;MDA在重度干旱胁迫下的含量显著低于重度盐胁迫,而SOD活性显著高于盐胁迫。表明在盐胁迫下细胞膜透性增加的主要原网是膜脂过氧化作用。干旱处理则是PEG-6000脱水的直接结果;重度干旱胁迫下,可溶性糖含量在短期内迅速升高,然后下降,而脯氨酸含量则在胁迫中后期迅速上升。脯氨酸可能有补偿可溶性糖含量降低的作用。     

微囊藻毒素对细长聚球藻生长及生理生化特性的影响

采用改良的微囊藻毒素提取、制备方法可获得一定纯度的MC。经HPLC分析 ,MC RR的含量在 95 %以上。用微囊藻毒素处理细长聚球藻 ,发现毒素能显著抑制聚球藻的生长 ,降低聚球藻的可溶性蛋白与可溶性、不可溶碳水化合物含量 ,改变PC/Chl比值 ,抑制光合系统PSⅡ活性 ,进而导致光合作用减弱 ,生化反应减慢 ,从而抑制该藻的细胞分裂 ,使生长受阻     

乙烯利处理下罂粟有机渗透调节物质的变化

本研究采用随机区组设计探明不同浓度乙烯利处理与罂粟渗透调节物质的关系.在罂粟苗期对植株喷施不同浓度的乙烯利,并测定其叶片中渗透调节物质可溶性糖、可溶性蛋白和脯氨酸相对含量的变化.测定分析结果表明:随着处理浓度的升高和时间的延长,可溶性糖含量和脯氨酸含量呈增长趋势.≥8 000 mg/L浓度处理的可溶性糖含量极显著地高于CK;≥4 000 mg/L浓度处理的脯氨酸含量极显著地高于CK;浓度为16 000 mg/L的处理对可溶性蛋白含量影响极显著地高于其余各处理,≤2 000 mg/L浓度处理与CK相比差异不显著.因此研究显示,低浓度乙烯利处理能使罂粟相对适应胁迫,但高浓度乙烯利处理会影响罂粟的生长发育.一定程度上为利用乙烯利防除毒品原植物罂粟提供了理论依据.     

微囊藻毒素缓解过氧化氢胁迫下铜绿微囊藻损伤的初步研究

过氧化氢可抑制藻类生长, 同时会导致微囊藻毒素(Microcystins, MCs)的释放, 实验设置4个处理组探讨了外源微囊藻毒素MC-LR对H2O2胁迫下铜绿微囊藻生理生化变化的影响。结果表明: 在H2O2胁迫下, 微囊藻的生长和光合活性受到显著抑制, 藻细胞存活率降低, ROS含量明显增加, SOD活性上升。与单独H2O2胁迫相比, 加入MC-LR能增加微囊藻细胞的存活率。250 mol/L H2O2处理24h和48h后, 在培养基中加入200 ng/mL MC-LR可以缓解H2O2对铜绿微囊藻光合系统PSII活性的抑制作用。当微囊藻暴露于250 mol/L H2O2环境中时, 添加了MC-LR处理组藻细胞中的ROS含量明显减少(P0.05)。在相同浓度H2O2且加入了外源MC-LR后藻细胞SOD活性下降(P0.05)。因此, 微囊藻毒素MC-LR可缓解250 mol/L H2O2引起的氧化损伤并增强微囊藻自身的生存能力。研究结果有利于阐明H2O2胁迫影响产毒蓝藻生长代谢的途径及MCs生物学意义。       

细胞型朊蛋白抑菌活性的初步探索

目的:研究细胞型朊蛋白(PrP~c)有无抑菌活性。方法:把Pr Pc分别与金黄色葡萄球菌、枯草芽孢杆菌、巨大芽孢杆菌、苏云金芽孢杆菌、大肠杆菌等5种菌孵育一定时间,然后用碘化丙锭对上述5种样品染色后采用流式细胞仪检测各样品的荧光信号。结果:通过对流式细胞仪的荧光信号进行分析,发现PrP~c对金黄色葡萄球菌和枯草芽孢杆菌具有明显的抑制活性,而另外3种菌的样品没有检测到荧光信号的增强,亦即PrP~c对这3种菌无抑菌活性。结论:细胞型朊蛋白有一定的抑菌活性,有望成为一种新型的抗菌肽。     

念珠藻葛仙米生理生化特性对不同低温胁迫的响应

研究了不同培养温度下对念珠藻葛仙米的生长和相关生理生化特性的变化.结果表明,低温抑制葛仙米的生长,在2℃～5℃低温下其生长甚至完全停止;在10℃低温胁迫下,其生长延滞期变长,其后仍能保持正常生长.低温胁迫下,葛仙米光合系统II(PSII)的光合效率(Fv/Fm)的变化趋势与生长曲线相似;细胞电解质渗透率在低温胁迫初期尚能保持比较低的水平,但随着时间延长而升高;可溶性糖和还原性糖含量的变化则随胁迫加剧有不同程度升高.可溶性蛋白含量则在低温下保持比较低的水平.这些结果表明,低温对葛仙米的生长和光合作用具有抑制作用,但葛仙米也表现出了一定的抵抗低温胁迫的能力,并通过调节细胞膜的渗透性、重新合成低温适应调节物质(如总糖和可溶性糖等)来减少低温伤害,从而适应低温胁迫.     

高温和干旱胁迫对鳞叶藓游离脯氨酸和可溶性糖含量的影响

研究了高温和干旱胁迫对鳞叶藓 (Taxiphyllumtaxirameum)游离脯氨酸和可溶性糖含量的影响。结果显示 ,高温和干旱均能诱导植物体内可溶性糖的积累。在 60℃高温胁迫下处理 ,可溶性糖含量随处理时间的延长而增加 ,最高值比对照增加了 2倍。PEG 60 0 0胁迫下处理可使可溶性糖含量分别增加 2 .4倍。经统计学检验 ,逆境条件与游离脯氨酸含量变化无关     

Zn对荇菜叶片保护酶活性、渗透调节物质含量和Ca2+定位分布的影响

本文以不同浓度Zn（0、5、10、15、20mg/L）处理9d的荇菜(Nymphoides peltatum (Gmel.)O. Kuntze)为实验材料,分析了Zn对叶片超氧化物歧化酶（SOD）和过氧化物酶（POD）活性、渗透调节物质（脯氨酸和可溶性糖）含量的影响,并用焦锑酸钙沉淀的细胞化学方法观察了Zn胁迫条件下叶肉细胞内Ca2+水平和分布的动态变化,以揭示水生植物对Zn胁迫的应答机制。研究结果表明,Zn明显抑制了SOD活性和刺激POD活性上升;脯氨酸和可溶性糖积累显著。电镜观察发现,正常条件下叶细胞中的Ca2+主要定位在胞间隙和液泡中,细胞基质和细胞核中较少。添加Zn后,胞间隙和液泡中的Ca2+逐渐进入细胞质,使细胞质中Ca2+浓度明显升高,特别是在质膜内侧和细胞核中出现大量较大的呈圆环状的钙沉淀颗粒。作者认为与保护酶活性紊乱相比,脯氨酸和可溶性糖在荇菜对Zn胁迫的适应中发挥更大的作用。同时细胞内Ca2+水平的增加,可能与许多生理生化过程的改变有关,其在质膜和细胞核等局部区域的大量分布,将会引发对植物的伤害,直至最终死亡。由此可见,荇菜体内多种防御系统同时对Zn胁迫做出反应,包括诱导胁迫相关酶（POD）活性,增加渗透调节物质（脯氨酸和可溶性糖）合成或含量以及改变疏松结合钙的亚细胞分布和含量等。     

微囊藻毒素对沉水植物苦草生长发育的影响

MC RR抑制大型沉水植物苦草 (Vallisnerianatans (Lour.)Hara .)的生长和发育。在 0 0 0 0 1— 10mg/L的浓度下 ,苦草种子的发芽、子叶生长、真叶的形成和生长、不定根的形成和生长以及根毛的生长都受到了一定的抑制作用。当MC RR浓度≥ 0 .1mg/L时 ,处理第 30d ,MC RR对苦草鲜重和第一片真叶的生长有极显著的抑制作用 ,当MC RR浓度为 10mg/L时 ,根的生长和叶片的发生也受到了极显著的抑制作用     

Growth and antioxidant system of the cyanobacterium Synechococcus elongatus in response to microcystin-RR

Microcystins, one type of the cyanobacterial toxins, show a broad range of hazardous effects on other organisms. Most of the researches on the toxic effects of microcystins have involved in animals and higher plants. Little work, however, has been done on evaluating the mechanisms of microcystin toxicity on algae. In this study, the toxicological effects of microcystin-RR (MC-RR) on the cyanobacterium Synechococcus elongatus were investigated. For this purpose, six physio-biochemical parameters (cell optical density, reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GSH-Px) and glutathione S-transferase (GST)) were tested in algal cells when exposed to 100 g^–1 microcystin-RR. The results showed that the growth of Synechococcus elongatus (expressed as optical density) was significantly inhibited compared with the control. At the same time, the treated algae exhibited a pronounced increase in production of ROS and MDA after 6 days exposure to microcystin-RR. Significant changes in GSH levels and GSH-Px, GSH activities were also detected in algal cells, with higher values being observed in the toxin treated algae after 6 days exposure. GST activities in the treated algae exhibited a decline after exposure and rapid augmentation on day 3, thereafter, they kept at a high level when compared to the control group. GSH contents and GSH-Px activities were also significantly raised in the toxin-treated algae cells from day 3, but they showed a sharp decrease on day 4, which was the onward of cell proliferation. These results suggested that oxidative stress manifested by elevated ROS levels and MDA contents might be responsible for the toxicity of microcystin to Synechococcus elongatus and the algal cells could improve their antioxidant ability through the enhancement of enzymatic and non-enzymatic preventive substances.     

Proteomic analysis of cellular response to microcystin in human amnion FL cells

Microcystins (MC), the potent inhibitor of protein phosphatase 1 and 2A, are hepatotoxins of increasing importance due to its high acute toxicity and potent tumor promoting activity. So far, the exact mechanisms of MC-induced hepatotoxicity and tumor promoting activity have not been fully elucidated. To better understand the mechanisms underlying microcystin-RR (MC-RR) induced toxicity as well as provide the possibility for the establishment of biomarkers for MC-RR exposure, differential proteome analysis on human amnion FL cells treated by MC-RR was carried out using two-dimensional gel electrophoresis (2-DE) followed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. Image analysis of silver-stained 2-dimensional gels revealed that 89 proteins showed significant differential expression in MC-RR treated cells compared with control, and 8 proteins were unique to MC-RR treated cells and 8 proteins were only detected in control cells. Sixty-six proteins were further identified with high confidence by peptide mass fingerprinting. Some of the identified differentially expressed proteins have clearly relationship with the process of apoptosis, signal transduction, and cytoskeleton alteration which are consistent with the literature. The functional implications of alterations in the levels of these proteins were discussed. However, most of which have not been reported previously to be involved in cellular processes responded to MC-RR. Therefore, this work will provide new insight into the mechanism of MC-RR toxicity.     

Cell size and the initiation of DNA replication in bacteria

In eukaryotes, DNA replication is coupled to the cell cycle through the actions of cyclin-dependent kinases and associated factors. In bacteria, the prevailing view, based primarily from work in Escherichia coli, is that growth-dependent accumulation of the highly conserved initiator, DnaA, triggers initiation. However, the timing of initiation is unchanged in Bacillus subtilis mutants that are ~30% smaller than wild-type cells, indicating that achievement of a particular cell size is not obligatory for initiation. Prompted by this finding, we re-examined the link between cell size and initiation in both E. coli and B. subtilis. Although changes in DNA replication have been shown to alter both E. coli and B. subtilis cell size, the converse (the effect of cell size on DNA replication) has not been explored. Here, we report that the mechanisms responsible for coordinating DNA replication with cell size vary between these two model organisms. In contrast to B. subtilis, small E. coli mutants delayed replication initiation until they achieved the size at which wild-type cells initiate. Modest increases in DnaA alleviated the delay, supporting the view that growth-dependent accumulation of DnaA is the trigger for replication initiation in E. coli. Significantly, although small E. coli and B. subtilis cells both maintained wild-type concentration of DnaA, only the E. coli mutants failed to initiate on time. Thus, rather than the concentration, the total amount of DnaA appears to be more important for initiation timing in E. coli. The difference in behavior of the two bacteria appears to lie in the mechanisms that control the activity of DnaA.     

The role of microcystins in maintaining colonies of bloom-forming Microcystis spp

Microcystis is a cosmopolitan genus of cyanobacteria and occurs in many different forms. Large surface blooms of the cyanobacterium are well known in eutrophic lakes throughout the globe. We evaluated the role of microcystins (MCs) in promoting and maintaining bloom-forming cell aggregates at environmentally relevant MC concentrations (0.25-10 μg l(-1)). MCs significantly enhanced Microcystis colony sizes. Colonial diameters in microcystin-RR (MC-RR)-treated cultures (at 1 μg l(-1)) were significantly larger than control colonies, by factors of 1.5, 2.6 and 2.7 in Microcystis wesenbergii DC-M1, M. ichthyoblabe TH-M1 and Microcystis sp. FACHB1027 respectively. Depletion of extracellular MC concentrations caused Microcystis colony size to decrease, suggesting that released MCs are intimately involved in the maintenance of Microcystis colonial size. MC-RR exposure did not influence Microcystis growth rate, but did significantly increase the production of extracellular polysaccharides (EPS). In addition, MC-RR exposure appeared to trigger upregulation of certain parts of four polysaccharide biosynthesis-related genes: capD, csaB, tagH and epsL. These results strongly indicate that induction of polysaccharides by MC-RR was the major mechanism through which MCs enhanced colony formation in Microcystis spp. Cellular release of MCs, therefore, may play a key role in the persistence of algal colonies and the dominance of Microcystis.     

Inhibition of Escherichia coli growth and respiration by polymyxin B covalently attached to agarose beads.

Polymyxin B was attached to agarose beads by stable covalent bonds and the antimicrobial activity of the immobilized peptide was examined. Polymyxin-agarose inhibited the growth of Escherichia coli and Pseudomonas aeruginosa, but not Bacillus subtilis. In addition, the respiration of E. coli, E. coli spheroplasts, and B. subtilis protoplasts was inhibited by immobilized polymyxin, whereas the respiration of B. subtilis was unaffected by polymyxin-agarose. The activity of polymyxin-agarose was not due to the release of free peptide from the derivative. These data indicate that polymyxin can inhibit the growth and respiration of gram-negative bacteria by interacting with the outer surface of these cells. It is proposed that perturbation of outer membrane structure by polymyxin-agarose indirectly affected the selective permeability of the inner membrane and inhibited respiration. The results of this study emphasize the importance of outer membrane structural integrity for the normal functions of gram-negative bacteria.     

The rpsD gene, encoding ribosomal protein S4, is autogenously regulated in Bacillus subtilis.

Although the mechanisms for regulation of ribosomal protein gene expression have been established for gram-negative bacteria such as Escherichia coli, the regulation of these genes in gram-positive bacteria such as Bacillus subtilis has not yet been characterized. In this study, the B. subtilis rpsD gene, encoding ribosomal protein S4, was found to be subject to autogenous control. In E. coli, rpsD is located in the alpha operon, and S4 acts as the translational regulator for alpha operon expression, binding to a target site in the alpha operon mRNA. The target site for repression of B. subtilis rpsD by protein S4 was localized by deletion and oligonucleotide-directed mutagenesis to the leader region of the monocistronic rpsD gene. The B. subtilis rpsD leader exhibits little sequence homology to the E. coli alpha operon leader but may be able to form a pseudoknotlike structure similar to that found in E. coli.     

Growth inhibition of Escherichia coli during heterologous expression of Bacillus subtilis glutamyl-tRNA synthetase that catalyzes the formation of mischarged glutamyl-tRNA1 Gln

It is known that Bacillus subtilis glutamyl-tRNA synthetase (GluRS) mischarges E. coli tRNA1 Gln with glutamate in vitro. It has also been established that the expression of B. subtilis GluRS in Escherichia coli results in the death of the host cell. To ascertain whether E. coli growth inhibition caused by B. subtilis GluRS synthesis is a consequence of Glu-tRNA1 Ghn formation, we constructed an in vivo test system, in which B. subtilis GluRS gene expression is controlled by IPTG. Such a system permits the investigation of factors affecting E. coli growth. Expression of E. coli glutaminyl-tRNA synthetase (GlnRS) also ameliorated growth inhibition, presumably by competitively preventing tRNA1 Gln misacylation. However, when amounts of up to 10 mM L-glutamine, the cognate amino acid for acylation of tRNA1 Gln, were added to the growth medium, cell growth was unaffected. Overexpression of the B. subtilis gatCAB gene encoding Glu-tRNAGln amidotransferase (Glu-AdT) rescued cells from toxic effects caused by the formation of the mischarging GluRS. This result indicates that B. subtilis Glu-AdT recognizes the mischarged E. coli GlutRNA1 Gln, and converts it to the cognate Gln-tRNA1 Gln species. B. subtilis GluRS-dependent Glu-tRNA1 Gln formation may cause growth inhibition in the transformed E. coli strain, possibly due to abnormal protein synthesis.     

Effect of berberine on Escherichia coli, Bacillus subtilis, and their mixtures as determined by isothermal microcalorimetry

The strong toxicity of pathogenic bacteria has resulted in high levels of morbidity and mortality in the general population. Developing effective antibacterial agents with high efficacy and long activity is in great demand. In this study, the microcalorimetric technique based on heat output of bacterial metabolism was applied to evaluate the effect of berberine on Escherichia coli, Bacillus subtilis, individually and in a mixture of both using a multi-channel microcalorimeter. The differences in shape of the power-time fingerprints and thermokinetic parameters of microorganism growth were compared. The results revealed that low concentration (20?μg/mL) of berberine began to inhibit the growth of E. coli and mixed microorganisms, while promoting the growth of B. subtilis; high concentration of berberine (over 100?μg/mL) inhibited B. subtilis. The endurance of E. coli to berberine was obviously lower than B. subtilis, and E. coli could decrease the endurance of B. subtilis to berberine. The sequence of half-inhibitory concentration (IC(50)) of berberine was: B. subtilis (952.37?μg/mL)?>?mixed microorganisms (682.47?μg/mL)?>?E. coli (581.69?μg/mL). Berberine might be a good selection of antibacterial agent used in the future. The microcalorimetric method should be strongly suggested in screening novel antibacterial agents for fighting against pathogenic bacteria.