东海原甲藻和海洋异养细菌对磷酸盐的竞争吸收

在水生生态系统的研究中, 微型藻类与海洋细菌的相互关系越来越引起人们的重视。微型藻类是引起赤潮的主要生物, 其与海洋细菌的关系主要表现在藻、菌既可相互促进生长, 又可相互抑制以至于杀灭对方。这种复杂的生态关系因藻种及菌种的不同而异, 并受到环境等因素的影响。     

溶藻细菌

利用溶藻细菌防治水华和赤潮,作为富营养化水体藻类生物防治的方法已经受到广泛关注.多项研究表明,许多溶藻细菌能分泌胞外活性物质,对宿主藻类的生长起抑制作用.因此,分离筛选环保、高效、专一的溶藻活性代谢产物,最终开发安全、高效的生物杀藻剂已经日渐成为治理藻类水华和赤潮问题的方法之一.近年来,国内外相关人员和机构对溶藻细菌的溶藻机理以及溶藻活性物质的分离、提纯和鉴定进行了较为深入的基础性研究.     

海水实验围隔中桡足类对海洋原甲藻摄食的研究

现场研究了发生严重海洋原甲藻（Ｐｒｏｒｏｃｅｎｔｒｕｍｍｉｃａｎｓ）水华后海水实验围隔中桡足类火腿许水蚤（Ｓｃｈｍａｃｋｅｒｉａｐｏｐｌｅｓｉａ）和长腹剑水蚤（Ｏｉｔｈｏｎａｓｐ．）的摄食强度．结果表明,体长在１２５ｍｍ以上的火腿许水蚤成体及其部分桡足幼体对海洋原甲藻的摄食率平均为１２１４０ｃｅｌｓ·ｉｎｄ－１·ｄ－１;体长不到１２５ｍｍ的部分火腿许水蚤桡足幼体和长腹剑水蚤成体及其桡足幼体的摄食率仅为１１３３ｃｅｌｓ·ｉｎｄ－１·ｄ－１．实验期间围隔中海洋原甲藻的浓度为８５０～１６１７０ｃｅｌｓ·ｍｌ－１,该藻的种群增长率为－０．００２～０．１５０．当海洋原甲藻细胞处于生长期时,桡足类的摄食不足以抑制该藻种群的增长,因此围隔中桡足类不可能阻止海洋原甲藻水华发生或使水华发生后迅速消退     

几株赤潮甲藻的摄食能力

采用荧光标记的方法,在营养盐限制条件下,对6株赤潮甲藻对荧光标记的海洋细菌(FLB)、金藻(FLA)和两种粒径分别为0.5μm和2.0μm的荧光微球(FM0.5和FM2.0)4种摄食对象的摄食进行了比较研究。研究结果表明,除了东海原甲藻对4种摄食对象均没有摄食外,其它5株甲藻,微小亚历山大藻、链状亚历山大藻、塔玛亚历山大藻、海洋原甲藻和微小原甲藻均具有摄食能力,但对摄食对象的选择和摄食率有差异,多数摄食率是在4 h达到最大,白天的摄食能力强于夜间。研究说明了在营养盐限制环境中,有些具有兼性营养能力的甲藻对细菌和/或更小浮游植物的摄食能力可能对维持和促进其生长具有不可忽视的作用。     

慢原甲藻――南海热带附生甲藻新记录

从海南陵水新村港分离出1株附生原甲藻,在光学显微镜和扫描电子显微镜下进行形态学特征分析,并结合核糖体18S rRNA基因序列分析,鉴定为慢原甲藻(Prorocentrum rhathymum),为国内首次报道.国内曾将该种与墨西哥原甲藻(Prorocentrum mexicanum)归为同种异名.     

慢原甲藻——南海热带附生甲藻新记录

从海南陵水新村港分离出1株附生原甲藻,在光学显微镜和扫描电子显微镜下进行形态学特征分析,并结合核糖体18S rRNA基因序列分析,鉴定为慢原甲藻(Prorocentrum rhathymum),为国内首次报道。国内曾将该种与墨西哥原甲藻(Prorocentrum mexicanum)归为同种异名。     

北部湾海洋原甲藻的形态特征及其系统进化分析

为探讨广西北部湾海洋原甲藻(Prorocentrum micans)的形态特征及其系统进化意义,利用光学显微镜、分子生物学方法,对海洋原甲藻BBW-01 藻株的形态特征进行了描述,并分析了其分子系统进化关系.结果表明,各地理株系的海洋原甲藻的形态特征相似,仅在细胞大小上存在差异.海洋原甲藻BBW-01 与采自于广东大亚湾的海洋原甲藻形态特征最为接近,其壳板后端的7 个呈“V”字形对称排列的大孔可作为海洋原甲藻鉴定的重要指标.18S rDNA 序列同源检索和系统进化分析表明,海洋原甲藻BBW-01 与源自中国南海的海洋原甲藻的亲缘关系最近,并与其他2 株海洋原甲藻聚成一支,属于浮游、兼性浮游类原甲藻.因此,对赤潮原因种的准确识别有助于预防和减轻赤潮对海洋环境和人类带来的危害.     

细菌溶藻技术的研究

近年来水体富营养化而导致的藻类水华爆发事件,对人类健康及水生生态系统产生了严重危害。在利用物理、化学等防治方法都不甚理想的情况下,利用微生物处理作为水华治理的潜在手段已得到学界的广泛关注。通过实验经验和查阅大量文献,对一些细菌溶藻技术进行综述。     

东海原甲藻修订及与相关原甲藻的分类学比较

分析了东海原甲藻(Prorocentrum donghaiense Lu)显微结构,并与具齿原甲藻(Prorocentrum dentatum Stein)模式种和Schiller的钝头原甲藻的描述等进行了比较,结果表明,它们之间的形态结构和个体大小具有很大的差别,这些差异远超出了同种个体因环境不同所造成的形态变化范围．从细胞形态及其表面结构可以判断,日本、韩国海区所记录并报道的“P．dentatum”与我国东海的东海原甲藻应属同一种．因此可以认为,我国东海赤潮高发区以及在韩国、日本海区的出现的高生物量(high biomass bloom—forming species)赤潮原甲藻不是Stein所发表的具齿原甲藻。而是东海原甲藻,并对其进行了进一步修订,其种名应为东海原甲藻Prorocentrum donghaiense Lu．     

溶藻细菌胞外活性物质对蛋白核小球藻的毒性效应

为了探索分离到的溶藻细菌L7胞外活性物质对蛋白核小球藻的毒性效应和致毒机理, 采用不同质量浓度的L7胞外活性物质冻干粉(L7-LPEAC)处理蛋白核小球藻(Chlorella pyrenoidosa), 测定藻细胞的光合作用效率(EPR)以及蛋白质、叶绿素a和丙二醛(MDA)的含量。L7-LPEAC溶液浓度较低(0.80 g/L和1.25 g/L)时促进蛋白核小球藻的生长, 其96 h、120 h的EC50分别为5.75 g/L和2.55 g/L。当L7-LPEAC溶液浓度≥2.00 g/L时, 叶绿素a和蛋白质含量变化同步呈现先增加后减少的趋势; 处理72 h后, L7-LPEAC溶液浓度分别为2.00 g/L, 3.13 g/L, 4.90 g/L的浓度组中, 藻细胞MDA含量与对照组相比差异显著(P<0.05), 浓度组7.67 g/L和12.00 g/L则与对照组差异极显著(P<0.01); 处理120 h后, 各浓度组藻细胞叶绿素a含量的相对抑制率均大于60%。使用L7-LPEAC修复富营养化水体时, 选择适当的投加浓度, 既能杀灭引起水体富营养化的目标藻类, 又能避免对其他藻类产生抑制作用, 可以较好地维持水生生态系统的平衡。     

脂肪酸对中华哲水蚤摄食两种海洋微藻的指示作用

在室内以饥饿培养为对照,以海洋原甲藻(Prorocentrum micans)和中肋骨条藻(Skeletonema costatum)培养中华哲水蚤(Calanus sinicus),研究了各脂肪酸标记对中华哲水蚤摄食不同饵料的指示作用。结果显示,海洋原甲藻中18 ∶ 4ω3、22 ∶ 6ω3含量较高,中肋骨条藻中16 ∶ 1ω7、20 ∶ 5ω3的含量较高。二者分别表现出典型的甲藻门和硅藻门的脂肪酸组成特征。中华哲水蚤的脂肪酸组成有两个特点:(1)20 ∶ 5ω3和22 ∶ 6ω3的含量均较高;(2)其体内表征桡足类浮游植物食性、由桡足类自身合成的20 ∶ 1和22 ∶ 1脂肪酸占有相当的比例。虽然中华哲水蚤对不同脂肪酸的吸收和转化效率不同,但以脂肪酸作为标记还是成功的指示了中华哲水蚤对微藻的摄食。在饥饿培养中,首先消耗的是那些浮游动物自身不能合成的多不饱和脂肪酸,而结构脂肪酸都表现出了较高的保守性。结合各脂肪酸标记变化趋势和Pearson相关性分析的结果认为,18 ∶ 4ω3、18 ∶ 4ω3/16 ∶ 1ω7、∑18/∑16能较好的指示中华哲水蚤对海洋原甲藻的摄食,仅16 ∶ 1ω7/18 ∶ 4ω3能指示中华哲水蚤对中肋骨条藻的摄食。     

三种甲藻对阳光紫外辐射响应机制的种间差异

<正>从发现南极臭氧空洞以来,光生物学的研究领域便出现了一个新的研究方向,即研究阳光紫外辐射(Ultraviolet radiation,UVR)对藻类的影响[1]。众多研究表明,阳光UVR对藻类具有明显的负面效应,如UVR抑制光合固碳和生长,并导致DNA和蛋白的损伤[2—4]。但也有少数研究发现,在一定条件下,阳光UVR具有正面效应,如紫外线A(UV-A)有利于DNA损伤后的修复[2],并     

东海原甲藻与中肋骨条藻的种间竞争数值模拟

研究探讨了两个零维箱式模型在东海典型赤潮藻东海原甲藻和中肋骨条藻竞争与演替研究中的应用。模型在采用不同接种密度下的单种培养实验数据进行参数校正后,被用来模拟不同N/P条件下单种培养实验以及两藻种共培养竞争实验,并以实验数据对其结果进行了验证。模拟结果表明,在单种培养条件下,模型能够较好地重现两种藻在不同N/P环境中的生长及对营养盐的利用;共培养实验的模拟结果显示,在所有初始细胞密度比例条件下,中肋骨条藻的最终密度均会超过东海原甲藻,且PO4的消耗主要源于中肋骨条藻的利用,与实验结果一致,表明模型能够很好地体现两种藻的竞争结果及对营养盐的竞争关系;由于模型不足以模拟除营养盐竞争以外的藻间相互作用,模拟结果未体现东海原甲藻细胞数迅速衰减这一现象,有待进一步研究。     

滇池中溶藻细菌的分离鉴定及其溶藻效应

【背景】藻类水华或赤潮在世界范围内频发,带来各种危害,亟需找到有效途径控制水华或赤潮。溶藻细菌具有杀死藻类控制藻类生物量的能力,可以作为防治水华和赤潮的有效工具。【目的】分离并鉴定滇池中的铜绿微囊藻(Microcystisaeruginosa)及其溶藻细菌,对溶藻菌作用于铜绿微囊藻的溶藻效应进行研究,初步了解其溶藻特性与溶藻机制。【方法】采用LB平板稀释涂布,再经多次划线分离纯化细菌,测定16SrRNA基因序列以鉴定细菌种类;采用毛细管分离的方法分离铜绿微囊藻,并测定其cpcBA基因序列以鉴定蓝藻种类;采用热乙醇法提取叶绿素a,从而计算溶藻效率;基于过氧化氢酶(CAT)、还原型谷胱甘肽(GSH)和丙二醛(MDA)探究藻细胞在溶藻菌处理下的抗氧化系统响应。【结果】共分离获得11株微囊藻和17株针对铜绿微囊藻的高效溶藻菌。选取其中一株生长速度最快的铜绿微囊藻DCM4和一株溶藻效果最好的溶藻菌Sp37 (Bacillus siamensis)进行后续研究。Sp37对DCM4的4 d溶藻率达到92.4%±1.5%,且对微囊藻属的水华微囊藻(M. flos-aquae)和惠氏微囊藻(M.wesenbergii)均有溶藻效果,而对绿藻没有溶藻效果。Sp37的原菌液和无菌滤液对DCM4的4d溶藻率分别为86.8%±4.3%和81.1%±2.2%,两者没有显著差异(P0.05)。Sp37菌体对DCM4的溶藻率为25.4%±7.3%。Sp37无菌滤液经不同温度和pH处理之后的溶藻率与未经处理的无菌滤液的溶藻率无明显差异。Sp37无菌滤液处理藻细胞会使藻细胞的CAT、GSH和MDA含量发生变化。【结论】菌株Sp37对铜绿微囊藻DCM4具有高效的溶藻作用,而且对微囊藻属具有一定的溶藻特异性。Sp37是通过分泌胞外物质间接溶藻,且溶藻物质具有热稳定性和酸碱稳定性。Sp37无菌滤液处理藻细胞会触发藻细胞抗氧化系统,并且会损伤藻细胞膜。Sp37无菌滤液很可能是通过对藻细胞造成氧化胁迫,最终导致藻细胞死亡的。     

ent-Labdane glycosides from the aquatic plant Potamogeton lucens and analytical evaluation of the lipophilic extract constituents of various Potamogeton species

Two new ent-labdane glycosides, one known furano-ent-labdane and a new hydroxylated fatty acid were isolated from the dichloromethane extract of the freshwater aquatic plant Potamogeton lucens. The new compounds were assigned the structures of beta-d-glucopyranosyl-8(17),13-ent-labdadien-16,15-olid-18-oate, 18-beta-d-glucopyranosyloxy-8(17),13-ent-labdadien-16,15-olide and 13(R)-hydroxy-octadeca-(9Z,11E,15Z)-trien-oic acid by spectroscopic means. The algicidal activity of these compounds was tested against Raphidocelis subcapitata. Based on our previous study of Potamogeton pectinatus, other constituents were identified in P. lucens by LC-UV-MS, LC-NMR and GC-MS. The lipophilic extract profiles of both species are presented. Two other species, Potamogeton perfoliatus and P. crispus, were also investigated by analytical comparison of their non-polar extracts. The distribution of ent-labdanes characterized in Potamogeton is summarized.     

Algicidal activity of rhamnolipid biosurfactants produced by Pseudomonas aeruginosa

The algicidal activity of the rhamnolipid biosurfactants (the mixture of Rha-Rha-C₁₀-C₁₀ and Rha-C₁₀-C₁₀) produced by Pseudomonas aeruginosa was investigated in the present paper. The results indicated that the biosurfactants had potential algicidal effects on the harmful algal bloom (HAB) species, Heterosigma akashiwo. The growth of H. akashiwo was strongly inhibited in medium containing rhamnolipids (0.4–3.0 mg L⁻¹); moreover, the rhamnolipids showed strong lytic activity toward H. akashiwo at higher concentrations (≥4.0 mg L⁻¹). In addition, the effects of the rhamnolipids on the growth of Gymnodinium sp. and Prorocentrum dentatum, another two kinds of HAB species, were also studied. Compared with the dramatic algicidal effect on H. akashiwo, the cells of P. dentatum were inhibited or lysed at higher concentrations (1.0–10.0 mg L⁻¹), while the cells of Gymnodinium sp. were not suppressed with the same treatment, indicating the rhamnolipids had the potential for the selective control of HABs.Morphometric analysis at ultrastructural level by transmission electron micrographs indicated that the extent of ultrastructural damage of the alga was severe at high concentrations of rhamnolipids and during extended periods of contact. The first response occurred in the plasma membrane which partly disintegrated. The lack of membrane facilitated the rhamnolipid biosurfactants into the cells and allowed damage to other organelles, which resulted in the injury of chloroplast, vacuolization of mitochondria and deformation of the cristae, disruption of nuclear membrane and condensation of chromatin in nucleus, suggesting that the lytic activity of rhamnolipids was mainly due to their powerful surfactivity and their tendency to cohere on the surface of phospholipids bimolecular layer of the cells and further destroyed the layers, and then the structure of quasi-membrane configurations inside the cells was disintegrated, following by the irreversible damage to the ultrastructure and the loss of the function of organelles, consequently leading the cells to lyse.     

Biochemical compositions of two dominant bloom- forming species isolated from the Yangtze River Estuary in response to different nutrient conditions

Variations of cellular total lipid, total carbohydrate and total protein content of two dominant bloom-forming species (Skeletonema costatum and Prorocentrum donghaiense) isolated from the Yangtze River Estuary were examined under six different nutrient conditions in batch cultures. Daily samples were collected to estimate the cell growth, nutrient concentration and three biochemical compositions content during 7 days for S. costatum and the same sampling procedure was done every other day during 10 days for P. donghaiense. Results showed that for S. costatum, cellular total lipid content increased under phosphorus (P) limitation, but not for nitrogen (N) limitation; cellular carbohydrate were accumulated under both N and P limitation; cellular total protein content of low nutrient concentration treatments were significantly lower than that of high nutrient concentration treatments. For P. donghaiense, both cellular total lipid content and total carbohydrate content were greatly elevated as a result of N and P exhaustion, but cellular total protein content had no significant changes under nutrient limitation. In addition, the capability of accumulation of three biochemical constituents of P. donghaiense was much stronger than that of S. costatum. Pearson correlation showed that for both species, the biochemical composition of three constituents (lipid, carbohydrate and protein) had no significant relationship with extracellular N concentration, but had positive correlation with extracellular and intracellular P concentration. The capability of two species to accumulate cellular total lipid and carbohydrate under nutrient limitation may help them accommodate the fluctuating nutrient condition of the Yangtze River Estuary. The different responses of two species of cellular biochemical compositions content under different nutrient conditions may provide some evidence to explain the temporal characteristic of blooms caused by two species in the Yangtze River Estuary.     

Isolation and distribution of iridescent Cellulophaga and other iridescent marine bacteria from the Charente-Maritime coast,French Atlantic

An intense colored marine bacterium, identified as Cellulophaga lytica, was isolated previously from a sea anemone surface on the Charente-Maritime rocky shore (Atlantic Coast, France), and iridescence of its colonies under direct light was recently described. In addition, iridescence intensities were found to differ strongly between C. lytica strains from different culture collections. However, importantly, the occurrence and distribution of iridescent bacteria in the marine environment were still unknown. Therefore, in this study, a search was undertaken for marine iridescent bacterial strains in different biotopes of the Charente-Maritime coast. Various marine samples (water, sediment, macroalgae, other macroorganisms and detritus) were collected from seven biotopes using a direct plate inoculation method. As a result, 34 iridescent strains related to the genus Cellulophaga, as well as 63 iridescent strains affiliated to the genera Tenacibaculum and Aquimarina, were isolated. Iridescent colors were different according to the genera but iridescent marine bacteria were widely distributed. However, a majority of strains were isolated from rocky shores and, in particular, red seaweed surfaces and mollusks. The data from the study suggested that isolates with iridescent properties were well conserved in stressful environments such as the coastal shoreline. This origin may provide an insight into the ecological and biological functions of iridescence.