生长阶段及环境因子对东海原甲藻氨基酸氧化酶活性的影响

以中国沿海典型赤潮藻东海原甲藻为实验材料, 研究了不同生长阶段以及温度、光照和氮源对其氨基酸氧化酶活性的影响。结果表明, 在缺氮条件下东海原甲藻显示较高的氨基酸氧化酶活性。在15-30℃温度范围均检测出氨基酸氧化酶活性, 较低温度下(15-20℃)的氨基酸氧化酶活性显著高于高温处理组(25-30℃)(p<0.05), 其中20℃时的酶活最高。在50-100 μmol/(m²·s)的光强下, 氨基酸氧化酶活性较高(0.38-0.47 fmol/(h·cell)), 而在2 μmol/(m²·s)的低光强下, 虽然酶活受到显著抑制, 但仍达到0.28 fmol/(h·cell)。氮源组成对氨基酸氧化酶活性具有显著影响, 以丙氨酸为唯一氮源时的酶活最高(0.44 fmol/(h·cell)), NH₄⁺+丙氨酸为氮源时的酶活最低(0.22 fmol/(h·cell))。研究显示, 光照、温度和氮源是东海原甲藻氨基酸氧化酶活性的关键调控因子。东海原甲藻不仅能够有效利用游离氨基酸, 而且适应较广的温度和较低的光照条件, 这可能是东海原甲藻赤潮形成和持续的重要原因。     

不同光照条件下米氏凯伦藻和东海原甲藻生长的温度生态幅

米氏凯伦藻和东海原甲藻是我国东南沿海地区赤潮的主要优势种。为定量获取米氏凯伦藻和东海原甲藻生长的温度生态幅,根据3个光照水平(28.32,75.06,111.66μmol m~(-2)s~(-1))条件下4个温度水平(18,22,25,28℃)对米氏凯伦藻和东海原甲藻生长特性的室内培养实验结果,并结合Shelford耐受性定律建立了基于温度的米氏凯伦藻和东海原甲藻比生长率的耐受性模型,最后根据前期的研究成果分别获取了米氏凯伦藻和东海原甲藻生长的最适温度、适温范围及耐受温度范围。结果表明,无论是米氏凯伦藻还是东海原甲藻,在相同培养光照条件下,在设定的温度水平范围内,分别存在一个适宜米氏凯伦藻和东海原甲藻的最适生长温度T_(opt),且当T≤T_(opt)时,米氏凯伦藻和东海原甲藻细胞密度和比生长率随着温度的升高而显著增大;而当T≥T_(opt)时,米氏凯伦藻和东海原甲藻细胞密度和比生长率随着温度的升高而显著减小。随着培养光照强度的升高,米氏凯伦藻和东海原甲藻细胞密度和比生长率均呈现"先升后降"的变化趋势。建立的藻类生长温度耐受性模型与谢尔福德耐受定律较为吻合,定量获取米氏凯伦藻在3个光照水平(28.32,75.06,111.66μmol m~(-2)s~(-1))下的最适生长温度分别为22.48,22.37,22.33℃;适温范围分别为17.93—27.03,17.82—26.92,17.78—26.88℃;耐受温度范围分别为13.38—31.58,13.27—31.47,13.23—31.43℃;东海原甲藻在3个光照水平(28.32,75.06,111.66μmol m~(-2)s~(-1))下的最适生长温度分别为22.10,21.99,21.93℃;适温范围分别为17.59—26.61,17.48—26.5,17.42—26.44℃;耐受温度范围分别为13.08—31.12,12.97—31.01,12.91—30.95℃。     

南麂列岛海域原甲藻种群动态及其环境影响因子分析

研究了2006年4月至2007年3月之间,南麂海域原甲藻种群的种类组成、季节动态、空间分布及其与水温、盐度、氮磷营养盐等环境因子的关系。原甲藻种类有三角棘原甲藻、东海原甲藻、海洋原甲藻和反曲原甲藻,前两者是南麂海域最为优势的种类,它们的分布季节集中在春季（4－6月）,并先后于5月12日和5月25日形成赤潮。原甲藻细胞数量在表层水体中的数量显著高于底层,这与原甲藻种类能够自主运动,具有明显的昼夜垂直移动特性有关。三角棘原甲藻较高细胞数量则相对集中出现在水温为18.5－19.5,盐度为29.58‰－30.95‰的水体中;东海原甲藻较高细胞数量则相对集中出现在水温为18.5－21.3℃,盐度为29.03‰－30.92‰的水体中。氮盐和磷酸盐浓度与原甲藻细胞数量之间呈负相关,磷营养盐浓度的高低对原甲藻种群动态影响更甚。对原甲藻细胞数量和环境因子之间进行相关性分析,发现原甲藻细胞数量与N:P值之间存在显著的正相关性,并与磷酸盐浓度之间存在显著的负相关性。原甲藻细胞具有较强储备氮磷营养物质能力的生物学特性使其能够在低营养条件下取得生长竞争的优势。     

营养盐限制条件下塔玛亚历山大藻对东海原甲藻的化感作用研究

为明确塔玛亚历山大藻(Alexandrium tamarense)对东海原甲藻(Prorocentrum donghaiense)生长的化感作用,研究了在N、P限制及正常营养盐条件下(又称富营养)塔玛亚历山大藻无细胞滤液对东海原甲藻生长的影响,并探讨了3种不同营养盐条件下两种藻共培养时的生长状况。结果表明,半连续培养时,营养盐限制下,塔玛亚历山大藻无细胞滤液对东海原甲藻的生长均有一定影响。N限制下,5 d后东海原甲藻藻密度显著低于未加滤液的对照组,藻密度为1.02×107 cells L-1,对照组为1.7×107 cells L-1;P限制下,东海原甲藻藻密度与对照组差异不显著,5 d后藻密度为1.44×107 cells L-1;富营养条件下,东海原甲藻藻密度与对照组无明显区别。共培养时,塔玛亚历山大藻对东海原甲藻生长的抑制作用更为显著,N、P限制下,4 d后东海原甲藻全部死亡,且聚集成团形成沉淀;富营养条件下,仍有少量东海原甲藻存活(藻密度3.3×104 cells L-1)。这表明,塔玛亚历山大藻对东海原甲藻的生长有一定的化感作用。营养盐限制可促进塔玛亚历山大藻化感物质的合成和释放,化感作用是塔玛亚历山大藻抑制东海原甲藻生长的原因之一。     

凤眼莲浸出液对东海原甲藻生长的抑制作用

研究了凤眼莲浸出液对赤潮藻东海原甲藻生长的影响。浸出液浓度以单位体积溶液中所含凤眼莲鲜重表示。结果显示,在浸出液浓度大于2g·L^-1时,活体凤眼莲浸出液和干凤眼莲浸出液对东海原甲藻的生长都有明显的抑制作用。在浸出液浓度达到8g·L^-1时,活体凤眼莲浸出液和干凤眼莲浸出液对东海原甲藻都具有杀灭作用,东海原甲藻全部死亡出现的时间分别为培养后的第4t和第5t。经121℃高温处理20min后的活体凤眼莲浸出液对东海原甲藻的抑制作用仍然存在,抑制作用并没有显著减弱。研究结果表明凤眼莲的抑藻物质具有用来控制赤潮生物东海原甲藻的潜在价值。     

大型海藻分泌物亚麻酸对东海原甲藻的化感效应

东海原甲藻是常见有毒有害赤潮藻。本文从种群生长、光合效率和抗氧化系统等角度研究大型海藻分泌物亚麻酸胁迫下东海原甲藻的生理生化响应。结果表明:低浓度亚麻酸(200μg·L~(-1))对东海原甲藻的生长具有促进作用,200~1000μg·L~(-1)浓度下,东海原甲藻的生长受到显著抑制,当亚麻酸浓度为1000μg·L~(-1)时,抑藻率达90%;200~1000μg·L~(-1)亚麻酸胁迫下,藻细胞光合色素含量显著降低,最大光能转化效率Fv/Fm降低,当亚麻酸浓度为1000μg·L~(-1)时,F_v/F_m为对照组的33.87%;随着亚麻酸浓度的增大,抗氧化酶活性(过氧化氢酶CAT、超氧化物歧化酶SOD和谷胱甘肽过氧化物酶GPx)与抗氧化非酶物质(还原型谷胱甘肽GSH、氧化型谷胱甘肽GSSG、抗坏血酸As A和脱氢抗坏血酸DHA)含量呈现出先升高后降低趋势;亚麻酸胁迫下丙二醛含量显著升高,表明膜脂过氧化程度加剧。以上结果说明,低浓度亚麻酸对东海原甲藻的生长具有促进作用,高浓度亚麻酸主要通过降低光合效率和细胞过氧化损害抑制东海原甲藻的生长。研究结果为生物法防控以东海原甲藻为优势藻种的赤潮提供了理论基础。     

春季海南岛近岸海域尿素与浮游生物的脲酶活性

2011年春季(4-5月),对海南岛的海口湾、澄迈湾、文昌八门湾、陵水新村湾和大东海5个海湾的尿素浓度及浮游生物的脲酶活性开展调查研究,结合其它理化环境因子,分析海南岛近岸海域尿素的可利用性及其对该海区浮游植物生长可能产生的影响.结果表明,海南岛近岸水体中尿素平均浓度为2.07-3.30 μmol/L,占总溶解态氮TDN含量的14％-38％,尿素占TDN比例由北向东、南方向递增.浮游生物脲酶活性为0.30-0.84 μmolN· L-1· h-1,海口湾最高,从北部向东、南部逐渐减少.各海湾较高水平的尿素和脲酶活性主要分布在排污口、养殖区或旅游区的近岸海域.硅藻为优势种,甲藻种类少且密度低,部分甲藻密度达到104-105个/L的水体,尿素和脲酶活性也处于较高水平.海区浮游植物细胞密度与脲酶活性或尿素占TDN比例等因子存在相关性,表明尿素是海南海域浮游植物生长不可忽略的重要氮源.尿素在一定程度上促进春季海南岛近岸海域甲藻等浮游植物的生长,可能对浮游植物群落结构的改变产生重要影响.     

温度、盐度对海月水母碟状体生长及存活的影响

海月水母为我国近海主要大型灾害水母种类之一,当自然环境适宜其生长与繁殖时,易出现暴发性的增殖现象,严重破坏了我国近岸海洋生态系统的稳点与平衡。采用实验生态学方法,研究了温度(2.5、5、7.5、10、15、20、25、27.5、30℃)和盐度(15、20、25、30、35、40)对海月水母碟状体存活与生长的影响,实验共进行30d。结果显示,在实验设置的温盐范围内,温度、盐度均显著影响碟状体的存活与生长。在盐度15-35条件下,海月水母碟状体可以在温度2.5-25℃存活,在15-25℃范围内可正常生长;在温度20-25℃和盐度20-30条件下适宜海月水母碟状体生长,其中温度20℃和盐度25条件下海月水母碟状体特定生长率达到最大。与盐度相比,温度对碟状体的影响较大,在盐度15-35条件下,随着温度的升高,碟状体的伞径逐渐增大,其碟状体形态向水母体形态的转变速度加快。在达到临界点25℃时,若继续升高温度,碟状体的生存率与生长率显著下降。温度与盐度对海月水母碟状体的生存与生长具有明显的交互效应,碟状体在实验过程中表现出在较低温度条件下提高了对较高盐度的适应性。研究表明,温度、盐度的变化显著影响碟状体的生长与存活,直接导致碟状体种群数量变动,进而影响成熟水母体种群数量。结论为进一步探索大型水母暴发的生态环境机理提供重要科学依据。     

不同无机氮源对东海原甲藻生长的影响

在实验室条件下,研究了不同浓度、不同形态的氮(NaNO₃、NH₄Cl和NaNO₂)对东海原甲藻(Prorocentrum donghaiense)生长的影响。结果表明:在NH₄Cl浓度为5.20μmol·L^-1(N/P为8)时藻的比生长率最高,而N/P为32和100时,藻的生长明显受到抑制。在NaNO₃为氮源时,最适N/P为12(氮浓度为7.80μmol·L^-1)。而NaNO₂作氮源,N/P为16(10.40μmol·L^-1)时藻的比生长率最高,N/P为32和100时藻的生长也明显受到抑制。研究显示,东海原甲藻对无机氮NH₄Cl和NaNO₃和NaNO₂都可以利用,最适生长的N/P比范围在8～20之间,相对高的N/P(32、100)不利于东海原甲藻的生长。     

温、光、盐对硅藻STR01生长、总脂、脂肪酸的影响

为了优化新分离STR01的生态培养条件, 采用单因子试验和正交试验研究了不同温度、光照强度、盐度和温、光、盐三因素三水平对该藻的生长、总脂和脂肪酸组成影响。结果表明: 温、光、盐对STR01的生长、总脂和脂肪酸组成影响显著(P<0.05)。生长的适宜温度为15—35℃, 最适25—30℃(K值达0.679—0.682), 总脂含量积累的最适温度是25℃(总脂可达17.23%), 温度20℃时有利于该藻PUFA的积累, 可达34.23%。STR01生长的适宜光照强度为40—120 μmol/(m2·s), 最适光强为60 μmol/(m2·s), 光照强度40 μmol/(m2·s)有利于该藻的PUFA积累, 可达34.29%。STR01生长的适宜盐度为10—35, 最适盐度25, 盐度25时PUFA含量较高(43.42%)。正交试验结果表明温度对STR01的平均相对生长速率和总脂含量影响显著, 生长的最优组合: 温度30℃、光照强度60 μmol/(m2·s)、盐度25, 该组合下的生长速率达0.756; 总脂含量积累的最优组合: 温度30℃、光照强度60 μmol/(m2·s)、盐度20, 该组合下的总脂含量为20.00%。PUFA的最优组合: 温度25℃、光照强度60 μmol/(m2·s)、盐度20, 该组合下PUFA的含量为35.37%。综上所述: 该藻生长迅速, 总脂含量较高, PUFA丰富, 是一种可开发利用的耐高温浮游硅藻。     

Taxonomic status of the species of the green algal genusNeochloris

Komárek has recently reviewed the various species assigned to the green algal genusNeochloris Starr (Chlorococcales, Chlorococcaceae) and removed those with uninucleate vegetative cells to a new genus,Ettlia. Watanabe & Floyd, unaware ofKomárek's work, also reviewed the species ofNeochloris and distributed them among three genera—Neochloris, Chlorococcopsis gen. nov., andParietochloris gen. nov.—on the basis of details of the covering of the zoospore and the arrangement of the basal bodies of the flagellar apparatus. This paper reconciles these two treatments and makes additional recommendations at the ranks of genus, family, order, and class.     

Hectorella: A member of the betalain-suborderChenopodiineae of the orderCentrospermae

Roots ofHectorella caespitosa Hook. f. were induced to produce a red pigment which was shown to be a betalain and not an anthocyanin. These data indicate thatHectorella belongs to theChenopodiineae, the betalain suborder of theCentrospermae, and excludes alignment with the anthocyanin family theCaryophyllaceae.     

Succession in the southern part of the Canadian boreal forest

Forest succession following fire in a forest mosaic of northwestern Quebec has been studied in order to: (1) describe the successional pathways using communities of different ages and (2) evaluate convergence of successional pathways and possible effect of fire suppression on the establishment of steady-state communities. As a first step, ordination and classification techniques were used in order to remove changes in forest composition which are related to abiotic conditions. Then, ordinations based on tree diameter distributions were used to study shifts in species composition in relation to time since the last fire.Even under similar abiotic conditions, successional pathways are numerous. However, regardless of forest composition after fire, most stands show convergence toward dominance of Thuja occidentalis and Picea mariana on xeric sites and dominance of Abies balsamea and Thuja occidentalis on more mesic sites. Stable communities of >300 yr occur on xeric sites while on mesic sites directional succession still occurs after 224 yr. Nearly all species involved in succession are present in the first 50 yr following fire. Only Abies balsamea and Thuja occidentalis increase significantly in frequency during succession. Following initial establishment, successional processes can generally be explained by species longevity and shade tolerance. Early successional species may be abundant in the canopy for more than 200 yr while the rapid decrease of Picea glauca, a late successional species could be related to spruce budworm outbreaks. Considering the short fire rotation observed (about 150 yr), a steady-state forest is unlikely to occur under natural conditions, though it may be possible if fire is controlled.     

The purification of the three trimannosyl-N-acetylchitobiose pentasaccharides from the urine of swainsonine-intoxicated sheep

A simple method for the preparative resolution of three Man₃GlcNAc₂ isomers called Ia, Ib and II has been designed. It consists mainly of the use of concanavalin A-Sepharose which allowed the total purification of Man₃GlcNAc₂-Ia, and then of anion-exchange resin in borate buffer-gradient to separate the Ib and II isomers. The purity of each oligosaccharide was checked by two HPLC methods. The use of these oligosaccharides for different analytical and biosynthetic purposes is discussed, and the unexpected resistance of one of the Man₃GlcNAc₂ alditols to the action of endo--N-acetylglucosaminidase H is noted.     

Evaluation of the Pro-Lab ID ring system for the identification of medically important yeasts

We evaluated 151 coded isolates of medically important yeast species belonging to the genera Candida, Cryptococcus, Geotrichum, Rhodoturula, Saccharomyces and Torulopsis using the newly developed rapid Pro-Lab Identification Ring, PL 960 system (PLID-Ring). All isolates were concurrently identified by the API 20C and conventional procedures comprising macro- and micromorphology, assimilation and fermentation of various carbon and nitrogen compounds. The PLID-Ring system identified isolates of Candida albicans, C. kefyr, C. krusei, C. lusitaniae, C. parapsilosis, Rhodotorula rubra, and Torulopsis glabrata with 100% accuracy in 24 h. This system identified C guilliermondii and S. cerevisiae isolates with an accuracy of 90% and 86%, respectively, while those belonging to Cr. neoformans, T. candida (= C. famata), C. rugosa and C. tropicalis were identified with 38.4%, 50%, 12.5% and 50% accuracy, respectively. Three isolates of Cr. laurentii were not identified by the PLID-Ring system. The overall accuracy of the PLID-Ring system was 81.45% (123 of 151 isolates). However, the system does not include species such as Cr. laurentii in its data base. When these three Cr. laurentii isolates were excluded from the evaluation, the accuracy of the PLID-Ring system increased from 81.45% to 83.1%.     

Progress on the genetics of the N2-fixing actinorhizal symbiont Frankia

The actinomycete Frankia is of fundamental and ecological interests for several reasons including its wide distribution, its ability to fix nitrogen, differentiate into sporangium and vesicle (specialized cell for nitrogen-fixation), and to nodulate plants from about 24 genera. Here, we present a review on the genetics performed so far on Frankia. At the end of July 2001, 293 kbp of Frankia DNA sequences were found in the databases. Thirty five percent of these sequences corresponded to full gene or gene cluster sequences. These genes could be divided according to their role into 6 key activities: gene translation (rrnA and tRNA ^pro gene), proteolysis (pcr genes), assimilation of ammonium (glnA and glnII), protection against superoxide ions (sodF), nitrogen fixation (nif cluster), and plasmid replication. We present a review of these genetic islands; their function, expression, localization and particular properties are discussed. A comparative analysis of Frankia nif genes from various strains and species is presented. An improved nomenclature for some of these genes is suggested to avoid conflicts. Frankia plasmids DNA sequences are also presented. The novel trends in Frankia genetics are described.     

Analysis of the genes of the OEE1 and OEE3 proteins of the photosystem II complex from Chlamydomonas reinhardtii

The sequences of the nuclear genes of the 33 kDa (OEE1) and the 16 kDa (OEE3) polypeptides of the oxygen evolving complex of Chlamydomonas reinhardtii have been established. Comparison between the OEE1 protein sequences of C. reinhardtii and higher plants and cyanobacteria reveals 67 and 47% homology. In contrast, C. reinhardtii and higher plants have only 28% overall homology for OEE3 which is mostly limited to the central portion of the protein. The transit peptides of the C. reinhardtii proteins consist of 52 (OEE1) and, most likely, 51 (OEE1) amino acids. They have a basic amino terminal region and, at least in the case of OEE1, a hydrophobic segment at their carboxy terminal end typical of thylakoid lumen proteins. Comparison of the genomic and cDNA clones indicates that the OEE1 and OEE3 genes contain five and four introns, respectively, some of which are located within the coding sequences of the transit peptides.     

Comparative analysis of the Kekkon molecules,related members of the LIG superfamily

Leucine-rich repeats (LRRs) and immunoglobulin (Ig) domains represent two of the most abundant sequence elements in metazoan proteomes. Despite this prevalence, comparatively few molecules containing both LRR and Ig (LIG) modules exist, and fewer still have been functionally defined. One LIG whose function has been investigated is the Drosophila protein Kekkon1 (Kek1). In vivo studies have demonstrated a role for Kek1 in Epidermal Growth Factor Receptor (EGFR) signaling and have suggested a role in neuronal pathfinding. Kek1 is the founding member of the Kek family, a group of six Drosophila transmembrane proteins that contain seven LRRs and a single Ig in their extracellular domains. While this arrangement of domains predicts a possible role as cell adhesion molecules (CAMs), to date little is known about the function or evolutionary relationship of these additional Kek molecules. Here we report that orthologs of Kek1, Kek2, Kek5, and Kek6 exist in the mosquito, Anopheles gambiae, and the honeybee, Apis mellifera, indicating that this family has been conserved for ~300 million years of evolutionary time. Comparative sequence analyses reveal remarkable identity among these orthologs, primarily in their extracellular regions. In contrast, the intracellular regions are more divergent, exhibiting only small pockets of conservation. In addition, we provide support for the general notion that these molecules may share common functions as CAMs, by demonstrating that Kek family members can form homotypic and heterotypic complexes.Edited by D. TautzChristina M. MacLaren, Timothy A. Evans and Diego Alvarado contributed equally to this work     

The history of the genusHomo

The genusHomo was established by Carolus Linnaeus in 1758. During the course of the past 150 years, the addition of fossil species to the genusHomo has resulted in a genus that, according to the taxonomic interpretation, could span as much time as 2.5 Myr, and include as many as ten species. This paper reviews the fossil evidence for each of the species involved, and sets out the case for their inclusion inHomo. It suggests that while the case for the inclusion of some species in the genus (e.g.Homo erectus) is well-supported, in the case of two of the species,Homo habilis andHomo rudolfensis, the case for their inclusion is much weaker. Neither the cladistic evidence, nor evidence about adaptation suggest a particularly close relationship with laterHomo.