水体pH和铜绿微囊藻增殖的关系研究

以水华生物铜绿微囊藻（Microcystis aeruginosa）为研究对象,在实验室内研究了水体pH变化和微藻生长的关系,以期了解铜绿微囊藻对水体pH的适应和调节能力。试验分2组,一组每天测定水体实际pH后调整水体pH为设计值,另一组试验开始时调节pH至设计值后不人为改变,每天测定pH。结果表明,铜绿微囊藻偏好碱性...     

低功率密度超声波强化絮凝沉降除藻技术研究

超声波强化絮凝沉降除藻技术能够提高絮凝沉降除藻效率,但以往研究采用的较高超声波功率限制了这一组合技术的应用。通过探究低功率密度超声波(0.5～1.0 W/L)对絮凝沉降技术去除微囊藻的增效作用,比较了增重剂种类及用量、超声波预处理的时间和距离、超声波预处理与絮凝沉降的间隔时长、日光照射时长等因素对除藻率的影响,并通过水池试验验证了低功率密度超声波的增效作用。结果显示:(1)超声波的处理距离对除藻率无显著影响,但增加超声波预处理时长则明显有利于提高除藻率,处理30 s时的除藻率显著高于仅处理10 s时的除藻率;(2)除藻率的日均变幅较大,当日光光照时长为3～9 h时,试验组的除藻率平均比对照组高17%,日光照射时长为0 h和12 h时,试验组与对照组的除藻率则无显著差异;(3)随着超声波预处理与絮凝沉降间隔时长的增加,除藻率会明显下降,仅当间隔时长不超过30 min时,试验组的除藻率才显著高于对照组;(4)水池原位试验中,试验组的除藻率高达70.47%,显著高于对照组的58.12%。研究表明,低功率密度超声波预处理能明显增加絮凝沉降除藻率,且应在日光开始减弱的下午作业。     

金鱼藻和狐尾藻对铜绿微囊藻生长及藻毒素释放的影响

通过加入金鱼藻(Ceratophyllum)、狐尾藻(Myriophyllum)与铜绿微囊藻(Microcystis aeruginosa)共同培养的实验方式,测定其过程中藻密度、总氮和总磷、藻毒素含量的变化,研究金鱼藻、狐尾藻对微囊藻生长及藻毒素释放的影响.结果表明,金鱼藻、狐尾藻不仅能很好地抑制铜绿微囊藻的生长,吸收水中的氮磷元素,还能在一定程度上抑制微囊藻毒素的释放.其中狐尾藻对铜绿微囊藻密度的抑制率能高达91.19%,对氮和磷的吸附率分别为66.84%和53.75%,对藻毒素MC-LR的抑制率达到44.23%.     

田螺科四种螺的肌肉主要营养成分

为了研究田螺科中华圆田螺、中国圆田螺、铜锈环棱螺和梨形环棱螺这4种螺的肌肉营养成分差异,评价其营养价值,本研究采用国标法对其肌肉中常规营养成分和氨基酸组成进行测定分析。结果显示,4种螺的肌肉中除灰分外,水分、粗蛋白质和粗脂肪含量均存在显著差异。肌肉中水分以中国圆田螺最高,为81.28%,显著高于其他3种螺;肌肉蛋白质以中华圆田螺最高,为13.11%,显著高于中国圆田螺和梨形环棱螺;肌肉脂肪含量以梨形环棱螺最高,为1.05%,显著高于其他3种螺。肌肉氨基酸测定结果显示,4种螺的肌肉中均含有16种氨基酸,其中包括人体必需的7种氨基酸和2种半必需氨基酸,第一限制性氨基酸均为蛋氨酸。此外,4种螺的鲜味氨基酸含量较高,均超过40%,且谷氨酸含量均远高于其他15种氨基酸。4种螺肉的必需氨基酸占总氨基酸的比例均在33%以上,其中中国圆田螺和梨形环棱螺在35%以上,与WHO/FAO模式推荐的标准(35.38%)相近,但4种螺EAAI值较低,均不到80,其中梨形环棱螺的EAAI值最高,达到74.86。研究表明,4种螺类肌肉营养组成较丰富,氨基酸比例均衡,均属于优质蛋白源。尤其是鲜味氨基酸含量丰富,具有较...     

Anti-Quorum-Sensing Activity of Tryptophan-Containing Cyclic Dipeptides

Quorum sensing (QS) can regulate the pathogenicity of bacteria and the production of some virulence factors. It is a promising target for screening to find anti-virulence agents in the coming post-antibiotics era. Cyclo (L-Trp-L-Ser), one variety of cyclic dipeptides (CDPs), isolated from a marine bacterium Rheinheimera aquimaris, exhibited anti-QS activity against Chromobacterium violaceum CV026 and Pseudomonas aeruginosa PAO1. Unlike the CDPs composed of phenylalanine or tyrosine, the anti-QS activity has been widely studied; however, cyclo (L-Trp-L-Ser) and derivatives, containing one tryptophan unit and one non-aromatic amino acid, have not been systematically explored. Herein, the cyclo (L-Trp-L-Ser) and seven derivatives were synthesized and evaluated. All tryptophane-contained CDPs were able to decrease the production of violacein in C. violaceum CV026 and predicted as binding within the same pocket of receptor protein CviR, but in lower binding energy compared with the natural ligand C₆HSL. As for P. aeruginosa PAO1, owning more complicated QS systems, these CDPs also exhibited inhibitory effects on pyocyanin production, swimming motility, biofilm formation, and adhesion. These investigations suggested a promising way to keep the tryptophan untouched and make modifications on the non-aromatic unit to increase the anti-QS activity and decrease the cytotoxicity, thus developing a novel CDP-based anti-virulence agent.     

Discovery of Marine Natural Products as Promising Antibiotics against Pseudomonas aeruginosa

Pseudomonas aeruginosa, one of the most intractable Gram-negative bacteria, has become a public health threat due to its outer polysaccharide layer, efflux transporter system, and high level of biofilm formation, all of which contribute to multi-drug resistance. Even though it is a pathogen of the highest concern, the status of the antibiotic development pipeline is unsatisfactory. In this review, we summarize marine natural products (MNPs) isolated from marine plants, animals, and microorganisms which possess unique structures and promising antibiotic activities against P. aeruginosa. In the last decade, nearly 80 such MNPs, ranging from polyketides to alkaloids, peptides, and terpenoids, have been discovered. Representative compounds exhibited impressive in vitro anti-P. aeruginosa activities with MIC values in the single-digit nanomolar range and in vivo efficacy in infectious mouse models. For some of the compounds, the preliminary structure-activity-relationship (SAR) and anti-bacterial mechanisms of selected compounds were introduced. Compounds that can disrupt biofilm formation or membrane integrity displayed potent inhibition of multi-resistant clinical P. aeruginosa isolates and could be considered as lead compounds for future development. Challenges on how to translate hits into useful candidates for clinical development are also proposed and discussed.     

微囊藻水华对淡水浮游动物轮虫和枝角类影响的研究进展

微囊藻是最为常见也是研究最多的水华蓝藻之一。有关微囊藻对浮游动物尤其是对枝角类溢属动物的影响,目前国内外已广泛报道。总体而言,产毒微囊藻对浮游动物具有明显的负面影响,但不同浮游动物对这种影响表现出不同的响应。关于微囊藻对浮游动物的毒性效应及影响,存在着一些相互冲突的观点并有很多种解释。本文就微囊藻水华对枝角类和轮虫的摄食、生长、繁殖和种间竞争的影响进行了综述,同时对由此引发的适应性特征进行了概述,旨在总结前人的研究成果,为今后的研究提供参考依据。[中国水产科学,2008,15（2）：367-375]     

甲基对硫磷降解菌P-29的筛选及降解特性研究

采用富集培养法,从长期受农药污染的土壤中分离得到1株能高效降解甲基对硫磷的菌株P-29,经鉴定为铜绿假单胞菌(Pseudomonas aeruginosa)。该菌株以甲基对硫磷为唯一碳源时,30℃培养30h降解率达84.69%,其酶活性随培养时间的增加呈上升趋势。     

铜绿假单胞菌与长枝木霉对杂交竹梢枯病的协同增效生防研究

铜绿假单胞菌和长枝木霉均对杂交竹梢枯病菌具有明显的拮抗作用。通过室内抗生素、紫外诱变和杀菌剂胁迫培养,获得铜绿假单胞菌和长枝木霉突变菌株,此突变体在形态特征、平板抑菌活性上与原始菌株差异不显著,且具有长期稳定的抗药性。田间喷施突变菌株菌悬液或孢子悬液可以使其成功定殖到杂交竹叶表面。铜绿假单胞菌和长枝木霉的亲和性研究显示,二者浓度低于108 cfu/mL,均无明显抑制作用,具有高度亲和性,这有利于2菌株在杂交竹梢枯病生物防治中协同作用的发挥。利用铜绿假单胞菌悬液和长枝木霉孢悬液进行梢枯病菌田间协同防治试验,结果表明:预先接种拮抗菌防效最高,其次是同时接种,后施拮抗菌防效最低,说明铜绿假单胞菌和长枝木霉均有良好的防病作用。另外,2菌株的联合使用在3种处理中防效均最优,尤其是在先接种病原菌的处理中,协同防效得到很大提高,说明二者联合使用有良好的梢枯病治理作用。      

花生青枯病生防细菌的筛选与鉴定

【目的】筛选花生青枯病的生物防治菌株。【方法】利用平板对峙法筛选对花生青枯病有拮抗 作用的生物防治细菌菌株,利用盆栽试验筛选防治效果好的细菌菌株。【结果】从根际土壤中分离的 300 余 株细菌中筛选获得 7 株对花生青枯病有拮抗作用的菌株。其中菌株 Ab、A27 和 A38 的抑菌直径超过 10 mm, 且其分泌物对该菌有抑制效果。将这 3 个菌株进一步进行盆栽试验,结果表明 A38 的防治效果最好,达到 52.72%。通过生理生化及分子生物学鉴定,将 A38 菌株鉴定为绿脓假单胞杆菌（Pseudomonas aeruginosa）。【结 论】筛选到一种花生青枯病菌拮抗效果较好的生防细菌,鉴定为绿脓假单胞杆菌。