普生轮藻浸提液对两种淡水藻类的化感抑制作用及其数学模型

利用大型水生植物的化感作用抑制水华藻类是水域生态学研究的热点课题之一。探讨了不同浓度普生轮藻浸提液对产毒铜绿微囊藻和斜生栅藻(单纯以及混合藻类)的抑制作用,并根据实验过程中得到的数据和数据特征,在传统的Logistic模型和Lotka-Volterra模型基础上,通过微元法建立了普生轮藻浸提液对单纯产毒铜绿微囊藻、单纯斜生栅藻抑制的数学模型以及两藻混合时抑制的数学模型。结果表明,(1)普生轮藻浸提液无论对单独的毒性铜绿微囊藻或斜生栅藻还是共生状态的毒性铜绿微囊藻和斜生栅藻均有很强抑制作用,且对毒性铜绿微囊藻的抑制作用要显著高于对斜生栅藻;(2)所建立的抑藻模型可有效表征和预测在一定范围内的产毒铜绿微囊藻、斜生栅藻及其混合藻在普生轮藻浸提液胁迫下藻密度随时间变化的规律;通过这些模型可方便地计算出实验期间任何时间节点上普生轮藻浸提液的半抑制浓度(EC50)、最小有效浓度(MIC)等指标的预测值、混合藻在小生境中相对稳定时的预测值等等。该研究可为实际抑藻的方案制定和实施提供有价值的数据支撑和参考,具有一定的理论与应用意义。     

不同藻类对大型溞存活和生殖的影响

通过生命表技术观察了大型溞（Daphnia magna）在实验室恒定温度（25 ℃）下分别以梅尼小环藻、铜绿微囊藻905、铜绿微囊藻469和斜生栅藻为饵料时的存活率和生殖量变化,并据此探讨了不同藻类对大型溞生活史特征的影响。结果表明：大型溞食用梅尼小环藻和铜绿微囊藻469后生长良好,大型溞在斜生栅藻中也能较好生长,而铜绿微囊藻905对大型溞的生长和繁殖均有不良影响;大型溞对不同藻类的净生殖率(R₀)、世代历期(T)和内禀增长率(r_m)及存活率有不同的影响,梅尼小环藻分别为44.35、11.86、0.32、5%;铜绿微囊藻469分别为48.20、14.25、0.27、30%;斜生栅藻分别为8.10、12.47、0.17、15%;铜绿微囊藻905分别为0、0、0、0。     

铜锈环棱螺对水华中常见藻类的抑制效应

藻类水华频发已成为全球性的水环境问题,近年来,生物控藻法因具有环境友好的特点而备受关注。本研究以我国富营养化湖泊中常见大型底栖动物铜锈环棱螺为操纵生物,通过室内培养试验,研究了其对水华水体中常见蓝藻铜绿微囊藻、绿藻普通小球藻和斜生栅藻生长及光合活性的影响,以期阐明螺-藻间相互作用关系,探究铜锈环棱螺作为生物操纵物种的可行性。结果表明: 铜锈环棱螺能在短时间内大量摄食藻细胞,其对铜绿微囊藻产毒株和不产毒株以及斜生栅藻的去除率均在12 h内达到最大值,分别为73.7%、73.2%和51.1%;其对普通小球藻的摄食强于其他藻类,至试验结束时去除率达到99.2%。产毒铜绿微囊藻产生的微囊藻毒素会在铜锈环棱螺体内累积并促发其肝脏病理学变化,进而阻碍铜锈环棱螺的摄食。试验后期各处理组藻细胞光合活性均显著低于对照组,表明铜锈环棱螺的摄食作用对藻细胞造成了损伤,抑制了其大量增殖。此外,当不产毒铜绿微囊藻与斜生栅藻混合时,铜锈环棱螺的选择摄食性导致微囊藻的优势地位被斜生栅藻所取代。因此,铜锈环棱螺可以通过摄食作用抑制藻类的光合活性并降低其生物量,从而在一定程度上抑制或减缓水华的形成。     

微囊藻和栅藻共培养实验及其竞争参数的计算

以Ｌｏｔｋａ－Ｖｏｌｔｅｒｒａ的双种竞争模型为基础,进行试验设计。共培养试验中,两种藻类的增长行为是不同的,培养前期共培养中栅藻的数量大于纯培养中栅藻的数量,而在后期则相反,微囊藻则是在整个共培养过程中的数量都小于纯培养中的数量。通过纯培养取得参数Ｋ和ｒ,变模型的微分形式为差分形式,以生长曲线拐点（密度制约起始点）出现的时间作为计算竞争参数的起始时间。经模拟计算获得参数,表明微囊藻的抑制能力是栅藻     

重金属铅与两种淡水藻的相互作用

为了研究重金属铅与淡水藻类之间的相互作用,采用不同Pb2+浓度处理铜绿微囊藻(Microcysis aeruginosa Kutz.)和斜生栅藻[Scenedesmus obliquus(Turp.)Kutz.],分别对两种藻的生物量、藻液电导率、O-·2含量、过氧化物酶(POD)、过氧化氢酶(CAT)活性以及藻对Pb2+的吸收作用等进行了测定,并通过扫描电镜观察了不同Pb2+浓度处理下两种藻细胞的表面结构。结果显示:(1)Pb2+浓度低于3 mg/L促进铜绿微囊藻生长,高于9 mg/L抑制其生长;但在3—12 mg/L范围内,Pb2+均明显抑制了斜生栅藻的生长,说明斜生栅藻对Pb2+毒性的敏感程度要高于铜绿微囊藻。(2)受到铅离子的胁迫,两种藻细胞膜通透性均有一定改变,扫描电子显微镜的照片观察,两种藻细胞表面的絮状物随着Pb2+的升高而增多,尤其是斜生栅藻细胞结构改变明显,多数细胞变形破裂;同时,O-·2含量升高,POD、CAT活性早期均可随Pb2+的增加而上升,表明氧自由基的产生增多以及由其引起的细胞生理生化改变可能是铅离子作用于藻细胞的主要机制。(3)两种淡水藻对Pb2+均有吸收作用,单位量藻细胞内,斜生栅藻对Pb2+的吸收能力好于铜绿微囊藻。所有结果提示:斜生栅藻不仅可以作为对重金属敏感的指示生物来监测水体Pb2+污染程度;同时由于斜生栅藻比铜绿微囊藻具有更好的Pb2+吸收能力,因此还可以利用斜生栅藻作为处理水体Pb2+的生物材料。     

水生花卉对铜绿微囊藻、斜生栅藻和小球藻生长的影响

选择黄菖蒲(Iris pseudacorus)、溪荪(I.sanguinea)、梭鱼草(Pontederia cordata)、白花水龙(Jussiaea repens)、水罂粟(Hydrocleys nymphoides)和大藻(Pistia stratiotes)6种具有较高观赏价值的水生花卉,通过将植物种植水与藻类共同培养的方式研究了不同种植时间的种植水对铜绿微囊藻(Microcystis aeruginosa)、斜生栅藻(Scenedesmus obliqnus)和小球藻(Chlorella vulgaris)生长的影响.结果表明:6种水生花卉种植水对3种藻类的化感作用具有选择性.通过6d的处理,种植水对铜绿微囊藻生长的抑制率为31.22％ ～ 96.53％,除白花水龙外,其余5种花卉的种植水对铜绿微囊藻生长的抑制率均超过70％,表现出很好的抑藻效果;种植水对斜生栅藻生长的抑制率为23.15％～77.25％;而种植水对小球藻有抑制也有促进,抑制率为-26.07％ ～75.70％,大藻、梭鱼草和溪荪抑制小球藻的生长,黄菖蒲、白花水龙表现为低促高抑,水罂粟表现为促进作用.随着种植时间的延长,种植水对3种藻类的抑制作用增强.6种水生花卉种植水对铜绿微囊藻生长的抑制作用由大到小依次为水罂粟＞黄菖蒲＞梭鱼草＞大藻＞溪荪＞白花水龙;对斜生栅藻生长的抑制作用由大到小依次为梭鱼草＞溪荪＞黄菖蒲＞水罂粟＞白花水龙＞大藻;对小球藻生长的抑制作用由大到小依次为大藻＞梭鱼草＞溪荪＞黄菖蒲、白花水龙＞水罂粟.试验表明,6种水生花卉在控制城市景观水体中的藻类水华有一定的推广价值.     

角突网纹溞培养滤液对铜绿微囊藻和栅藻形态及生长率的影响

在藻类中,随着环境条件的变化而产生相应的单细胞和群体之间的形态转化是一种广泛存在的现象,称为表型可塑性。例如,栅藻属成员就是这些藻类的代表,在野外具有典型的群体特征,但在室内纯培养条件下栅藻常较少形成群体而是保持以单细胞形态为主。     

铜绿微囊藻和斜生栅藻非稳态营养盐限制条件下的生长竞争特性

采用“脉冲”添加方法进行了非稳态条件下铜绿微囊藻（M.）和斜生栅藻（S.）分别在氮磷单营养盐和双营养盐限制时的共培养试验。试验结果显示：当添加频率为1d时,无论何种营养盐限制,M.均成为优势藻种。氮限制条件下,氮时均浓度范围在0.3—2.4 mg/L时,M.始终具有竞争优势。磷限制条件下,磷浓度范围在0.018—0.035 mg/L时,S.只在生长初期阶段占优。氮磷双营养盐限制条件下,添加液的氮磷质量比为35:1（设定为最优比）,添加频率为8 d时,两种藻表现出共生特征;而偏离最优比时（N:P=70:1,17:1）,在不同的添加频率下均未出现共生现象,且氮的时均浓度为0.6—4.8 mg/L时（70:1）,M.具有竞争优势,而降低为0.15—0.3 mg/L时（17:1）,S.占优。随着添加频率的变化,两种藻的细胞大小也会随之改变,S.随着营养盐浓度的降低而增大,且在双营养盐限制条件下变化更显著。上述试验结果分析表明：两种藻竞争能力与添加频率相关,在藻种浓度的变化上,按照‘拾遗－机会’交替竞争理论,M.表现出机会主义者特征,而S.则表现出拾遗者的特征,两者的共生特征也符合‘中度干扰’假说。藻细胞大小变化表明,两种藻均可以改变大小实现最大限度争夺受限营养盐。在低浓度时,S.细胞大小的变化同样也变现出了“拾遗者”的特征。     

三聚氰胺对藻类的毒性效应研究

以近头状伪蹄形藻(Pseudokirchneriella subcapitata)和斜生栅藻(Scenedesmus obliquus)为材料,利用藻类生长抑制试验测定了三聚氰胺对藻类的毒性效应。结果表明,三聚氰胺对两种藻的生长存在不同程度的抑制效应,浓度越高,抑制效应越强;对斜生栅藻的毒性效应还随处理时间的延长而增强。以生物量计,三聚氰胺抑制近头状伪蹄形藻和斜生栅藻生长的72h EbC50值分别是537.67和485.17mg/L,均为较低的毒性效应。两种藻的生长率均随处理浓度的增加而逐渐降低;依据估算的EC20和EC10值推断,斜生栅藻对三聚氰胺较为敏感,而且还具有明显的慢性毒性效应。       

绿藻栅藻对微囊藻的抑制效应及评价

为筛选具有控制微囊藻水华潜力的绿藻, 研究基于藻类之间的化感作用, 对34株绿藻开展筛选及评价工作。结果发现, 栅藻FACHB-1229的抑制率最高, 其滤液对微囊藻FACHB-3550和FACHB-905的抑制率分别为53.95%和48.39%; 通过对滤液中的物质进行GC-MS检测, 推测该藻株的效应物质可能为邻苯二甲酸二(2-甲氧基乙基)酯。进一步对FACHB-1229生长和光合放氧、氨氮耐受等指标进行评价, 结果发现: 该藻株在孔板中的生长速率(0.38±0.06)/d高于微囊藻生长速率(0.13±0.03)/d; 栅藻FACHB-1229的光合放氧速率高于同期测定的其他绿藻光合放氧速率, 可达(229.91±10.49) μmol O₂/(mg Chl.a·h); 同时该藻株对氨氮的耐受能力最强, 在氨氮浓度为1888.60 mg/L时其生长速率可达(0.30±0.08)/d。此外, 在与微囊藻FACHB-3550进行共培养时, 栅藻FACHB-1229所占比例持续升高。综上, 栅藻FACHB-1229具备与微囊藻竞争的优势, 有望成为微囊藻水华生物控制的优选材料。     

Isolation and identification of phenols in oil of vetiver

Several rare phenols, including 4-vinylphenol, 4-vinyl-2-methoxyphenol and trans-isoeugenol, were identified in oil of vetiver.     

肿柄菊挥发油的化学成分分析及其化感作用

采用水蒸气蒸馏法提取肿柄菊地上部分的挥发油,利用GC-MS技术对肿柄菊地上部分的挥发油进行分析,以假臭草、巴西含羞草、含羞草、蝶豆和鬼针草5种肿柄菊伴生植物为供试植物,用半密闭容器法对肿柄菊挥发油的化感效应进行生物测定。GC-MS分析结果显示,从肿柄菊挥发油中鉴定出50个化合物,占总出峰面积的94.79%,肿柄菊挥发油中主要含有α-蒎烯(63.81%)、柠檬烯(7.07%)、β-石竹烯(4.85%)、双环大香烯(2.95%)、香桧烯(2.78%)、斯巴醇(2.70%)等萜类和醇类化合物,占挥发油总量的94.15%,其中萜类化合物含量占总挥发油的86.01%。生测结果显示,肿柄菊挥发油对5种受试植物的种子萌发和幼苗生长均产生抑制作用,其中对巴西含羞草的抑制作用最为显著,而对含羞草和蝶豆影响较小。说明肿柄菊挥发油在其入侵扩散中发挥一定的化感作用。     

Studies on oil palm trunks as sources of infection in the field

Diseases of oil palm caused by Ganoderma boninense are of major economic importance in much of South-East Asia. This paper describes results from an ongoing field trial concerning the spread of the pathogen from artificially inoculated trunks used to simulate spread from windrowed trunks. Three planting distances for bait seedlings revealed that the closer the seedling was planted to the source of inoculum the sooner it succumbed to the disease. However, infection only occurred when the trunks were mounded (covered with soil), and seedlings planted around uncovered trunks (at any distance) have showed no symptoms of disease to date. Isolates are being collected from infected plants and molecular analysis is being undertaken to give more information on the spread of the pathogen.     

Synergy effects of the antibiotics gentamicin and the essential oil of Croton zehntneri

The leaves of Croton zehntneri Pax et Hoffm (Euphorbiaceae) were subjected to hydrodistillation, and the essential oil extracted was examined with respect to antibacterial and antibiotic modifying activity by gaseous contact. The gaseous component of the oil inhibited the bacterial growth of Staphylococcus aureus and Pseudomonas aeruginosa with a MID of 0.5 and<1 mg/l air, respectively. The activity of the antibiotic gentamicin was increased by 42,8% against P. aeruginosa after contact with the gaseous component, showing that this oil influences the activity of the antibiotic and may be used as an adjuvant in the antibiotic therapy of respiratory tract bacterial pathogens.     

Use of clove oil to anaesthetize freshwater amphipods

The use of clove oil as a potential anaesthetic for freshwater amphipods was examined at 20 °C. Individuals of Gammarus minus, a common species in southern Illinois, USA, spanning the entire body size range (4.3–14.3 mm), were used to test four anaesthetic concentrations varying from 1.48 × 10⁻⁴ ml ml⁻¹ to 5.9 × 10⁻⁴ ml ml⁻¹. Small-bodied individuals (mean size = 5.4 mm ± 0.27SE) were used to test additional concentrations, up to 14.7 × 10⁻⁴ ml ml⁻¹, a 10-fold span, to identify potential lethal concentrations. At the lowest concentration, time to anaesthesia and recovery was constant at all body sizes. For the three next higher concentrations, time to anaesthesia decreased with increasing concentration while recovery time increased. Activity of amphipods was not affected by the ethanol carrier. In addition, activity did not differ between amphipods that had recovered from anaesthesia and unexposed amphipods. At clove oil concentrations of 8.84 × 10⁻⁴ ml ml⁻¹ and 14.7 × 10⁻⁴ ml ml⁻¹, mortality was 7 and 40%, respectively, indicating, that 5.9 × 10⁻⁴ ml ml⁻¹ was a safe working concentration. No mortality was observed with Gammarus acherondytes, a federally endangered cave amphipod on which the protocol with 80 μl of stock was used in the field. The method enabled us to obtain information on the endangered amphipod which normally would have required the sacrifice of individuals. Thus, research can continue on species for which population numbers are low and for which basic information is needed to formulate meaningful recovery plans.     

In vitro fungitoxicity of the essential oil of Syzygium aromaticum

The in vitro antifungal activity of clove oil was studied against four test fungi namely Alternaria alternata, Fusarium chlamydosporum, Helminthosporum oryzae and Rhizoctonia bataticola by the agar well diffusion method. These test fungi were found to be highly sensitive to clove oil at a concentration of 100 μl/well. The inhibition zone diameter was found to be in the range of 55–65 mm. The toxicity of clove oil on the germination and growth of A. alternata was further examined in liquid medium. Concentration- and time-dependent toxicity was recorded from 0.05 to 20% (v/v) concentration. The minimum fungistatic concentration was found to be 0.05%. Above this concentration, lysis of conidia and inhibition of mycelial growth were detected. Microscopic analysis showed 20–40% lysis of conidia after 72 h of incubation at 5% concentration. However at higher clove oil concentration (10%), up to 20% of conidia were lysed within 24 h of incubation. Similar concentration- and time-dependent toxicity was observed at different concentrations and time intervals. The findings indicated that clove oil possesses fungicidal activity against phytopathogenic fungi. Further study is required to determine whether it could have value in the management of plant infectious diseases. This revised version was published online in July 2006 with corrections to the Cover Date.     

Filamentous green algae in freshwater streams on Signy Island,Antarctica

The streams of Signy Island are varied and extremely seasonal environments. Water flows from November/December to March/April; streams are frozen for the rest of the year. Streams usually flow through small, barren catchments and are nutrient poor, though they may be enriched by dense summer populations of seabirds and seals. Temperatures are consistently low. Stream depth is maximal during the spring melt period, declining over the course of the summer. Vegetation is exclusively algal, and filamentous chlorophytes from a particularly conspicuous component. Small numbers of vegetative cells survive the long frozen period in situ. A steady increase in standing crop results in a maximum 2 to 3 months after flow begins. Sloughing is the major loss mechanism and grazers are effectively absent. Three taxa of filamentous algae are common in Signy streams, species of Zygnema, Mougeotia and Klebsormidium. The distributions of these algae are described and related to physical and chemical features of their environment.     

Occurrence and diversity of mesophilic Shewanella strains isolated from the North-West Pacific Ocean

Although bacteria of the genus Shewanella belong to one of the readily cultivable groups of "Gammaproteobacteria", little is known about the occurrence and abundance of these microorganisms in the marine ecosystem. Studies revealed that of 654 isolates obtained from marine invertebrates (ophiuroid Amphiopholis kochii, sipuncula Phascolosoma japonicum, and holothurian Apostichopus japonicus, Cucumaria japonica), seawater and sediments of the North-West Pacific Ocean (i.e. the Sea of Japan and Iturup Is, Kurile Islands), 10.7% belonged to the genus Shewanella. The proportion of viable Shewanella species varied from 4% to 20% depending on the source of isolation. From the isolation study, representative strains of different phenotypes (from seventy presumptive Shewanella strains) were selected for detailed characterization using phenotypic, chemotaxonomic, and phylogenetic testing. 16S rDNA sequence-based phylogenetic analysis confirmed the results of tentative identification and placed the majority of these strains within only a few species of the genus Shewanella with 98-99% of 16S rDNA sequences identity mainly with S. japonica and S. colwelliana, suggesting that the strains studied might belong to these species. Numerically dominant strains of S. japonica were metabolically active and produced proteinases (gelatinases, caseinases), lipases, amylases, agarases, and alginases. Shewanella strains studied demonstrated weak antimicrobial and antifungal activities that might be an indication of their passive role in the colonization on living and non-living surfaces.     

Studies on the characterization of rat prostate androgen receptors

Summary Choline used as the sole carbon or carbon and nitrogen source induces in Pseudomonas aeruginosa an active transport system. The induction of the choline uptake is repressed by succinate independently of the presence of ammonium ion in the culture medium. The repression mediated by succinate was insensitive to cyclic AMP. Substitution for dibutyryl-cyclic AMP was without effect. Choline metabolites that also support the growth of Pseudomonas aeruginosa were poor inducer agents of the choline transport. Kinetic evidence and the employment of choline metabolites as effectors indicated that the choline uptake system of this bacterium is formed by at least two components: one of high affinity (Km=3 µM) and another of low affinity (Km=400 µM). Contrary to what occurs in the synaptosome system, the high affinity form for the choline uptake was not dependent on Na⁺ ions and is not inhibited by hemicholinium-3. Since Pseudomonas aeruginosa can utilize choline as the sole carbon and nitrogen source, the induction of the choline transport with two components in this bacterium may be related to its own strategy to survive and grow in an adverse environment.