源于微生物的海鞘天然产物

海洋动物是具有生物活性海洋天然产物的重要来源。海鞘中含有丰富的微生物类群,如细菌、放线菌、真菌和蓝细菌。越来越多的直接或间接证据表明,一些从海鞘中分离的天然产物并不是海鞘本身产生的,而是由其共生微生物产生的。本文对近些年来的海鞘天然产物的微生物来源的研究方法进行综述,包括可培养细菌的分离、不可培养细菌的粗提物检测、宏基因组学、全基因组测序等直接方法,以及化合物结构比对的间接方法。通过对海鞘-微生物共生体中天然产物生物合成来源的研究,不仅可以从根本上解决动物药源的问题,而且可为研究海鞘与微生物共生关系提供有力证据。     

氮胁迫下共生蓝藻的分离纯化及生理响应机制

目的：揭示氮胁迫逆境下共生蓝藻的生理响应机制。方法：采用藻细胞分离纯化技术获得了一株共生蓝藻,测定其光合色素含量并分析了氮胁迫下的生理响应机制。结果：新分离藻株的细胞形态与其他念珠藻属相似,具有典型的营养细胞和异型胞;该藻室温吸收光谱中叶绿素蓝区相对含量减少,类胡萝卜素相对含量增加;氮胁迫时,藻细胞在pH8.4和160μmol·m-2·s-1光强组合下的细胞增长率最高,同时藻细胞叶绿素a含量增加值也最高,对共生藻生理响应机制有着显著性影响（P〈0.05）。结论：该共生蓝藻为念珠藻属蓝藻,在氮胁迫下有较强的叶绿素合成能力,对碱性条件及高光强有着显著的生理响应。     

病毒与宿主互利共生的研究

在病毒与其宿主的相互作用中,病毒所扮演的角色不仅仅是病原体,它们也是宿主保持健康的重要共生体。病毒与微生物、植物、昆虫和哺乳动物之间存在互利共生作用,有的甚至涉及共生功能体的多个生物体。随着新病毒的不断发现,越来越多的互利共生关系被发掘,也还有许多有待发掘。本文旨在突出一些近年来关于有益病毒的典型例子,阐明为何需要重新认识病毒——病毒不仅是病原体,同时也是共生功能体中的一个完整个体。     

中国玻璃海鞘属一新纪录种——萨氏海鞘Ciona savignyi

海鞘(尾索动物亚门Urochordata,海鞘纲Ascidiacea)是与脊椎动物亲缘关系最近的分支1,是研究动物进化和发育的重要材料。其中玻璃海鞘(Ciona intestinalis)在世       

松树蜂与其共生真菌的互利共生关系

松树蜂Sirex noctilio Fabricius是一种重要的国际林业检疫性害虫,主要危害针叶树,原产欧亚大陆和北非。近100多年来,先后入侵大洋洲(新西兰和澳大利亚)、南美洲(乌拉圭、阿根廷、巴西和智利)、北美洲(加拿大和美国),以及南非。2013年8月,在中国黑龙江省内首次发现松树蜂,目前发现其主要危害樟子松。松树蜂能与一种淀粉韧革菌属Amylostereum的真菌Amylostereum areolatum(Fr.)Boidin形成严格的互利共生关系,该虫除直接钻蛀树木外,还能通过产卵行为将自身毒素腺体分泌的毒素和体内共生真菌随同虫卵一起注入寄主树木体内,形成"虫-毒-菌"3个致害因子相互协作的特殊危害方式,加速树势的衰弱并造成寄主树木死亡。本文就国内外松树蜂与其共生菌互利共生关系的研究进行了综述,分别从结构与功能的层次上对其互利共生关系进行了梳理和总结,重点阐释了松树蜂与共生菌的营养共生关系,松树蜂携带传播共生菌的机制,共生菌的种群遗传学以及松树蜂毒素和共生菌在危害寄主树木时的协同关系等。以期为开展关于松树蜂的专项研究提供一些合理的建议,同时为积极有效地防控该害虫提供科学依据。     

皱瘤海鞘神经腺上皮细胞活动周期与性腺发育关系的研究

对皱瘤海鞘神经腺上皮细胞活动周期进行了组织学、超微结构和免疫细胞化学的研究。结果表明皱瘤海鞘神经腺细胞活动周期与性腺发育相关。在性发育早期,神经腺各小叶上皮细胞基本上属胞质致密形式。性腺Ⅱ－Ⅲ期,有些小叶腺细胞出现空泡化,空泡化小叶占统计总数的２３％,性腺Ⅳ,Ⅴ期,增至３５－３９％和６３％。产卵后大多数腺小叶为空泡形式,或网状形式。超微结构研究进一步证实组织学观察。免疫细胞化学定位首次证实了神经腺     

浅谈生物共生现象的分类

总结了生物共生现象的基本定义,从互利共生、偏利共生、原始协作角度对生物共生现象的分类方式进行总结,并对生物间共生关系的发展进行了简要总结.     

气候变化与太湖蓝藻暴发的关系

对太湖区域40多年来气温、降水量、日照时数随时间变化的特征进行了分析,并对太湖蓝藻的爆发时间、次数、等级进行了统计,采用对比分析法对气候变化与太湖蓝藻暴发的关系进行了分析。结果表明:太湖区域1961—2007年总的气候倾向率,年平均气温为0.35℃.10a-1,年累计降水量为31.33mm.10a-1,年累计日照时数为-69.00h.10a-1;而突变点,气温在1989年,降水量在1979年,日照时数在1999年,在突变点年份后,气温升高、降水量增加和日照时数减少的趋势更加明显。2000—2007年气候变得异常,主要表现为气温上升速度加快,约为1961—2007年的3.7倍,5月和10月的这种气候倾向性更明显;降水量减少,比1961—2007年减少了178.10mm.10a-1,日照时数增加,比1961—2007年增加了244.23h.10a-1。气候变暖速度加快为太湖蓝藻的生长发育提供了热量条件;降水量减少,加速了太湖水质恶化,为蓝藻暴发提供了有利的水质环境条件;日照时数增多,充足的光照为蓝藻生长发育提供了优良的光合条件;温度偏高、降水量偏少、日照时数偏多的气候变化趋势对应太湖蓝藻暴发的次数也偏多,造成了太...     

植物体中的互利共生

分析了植物体内主要的互利共生类型。     

Self and non-self recognition between gametes of the ascidian,Halocynthia roretzi

Summary The self-sterility ofHalocynthia roretzi from Mutsu Bay, Japan, was examined. This sterility is strict and not a single egg can be fertilized in self-sterile animals. Less than 2% of the animals were self-fertile (with 100% cross-fertility). All heterologous sperm can fertilize all eggs, although there are pairs of individuals in which the coelomocytes recognize each other as self. Eggs deprived of follicle cells cannot be fertilized by either autologous or heterologous spermatozoa. Detached autologous or heterologous follicle cells can reattach to the chorion in calcium-enriched sea water and the reconstituted eggs recover their ability to be fertilized. A mosaic egg can therefore be obtained, which consists of oocyte, test cells and chorion originating from one individual and follicle cells from another. The mosaic egg was used to determine the site of recognition of self and non-self. The results indicate that the recognition resides in the chorion and/or test cells, probably the chorion. The relationship between somatic alloreactivity, previously found in coelomocytes ofH. roretzi, and gamete reactivity is discussed.     

Ultrastructural and histochemical study of anural development in the ascidian Molgula pacifica (Huntsman)

Summary Tadpole development is eliminated in the life cycle of the ascidian Molgula pacifica. The elimination of a tailed larva is termed anural development, in contrast to urodele development which is exhibited by most ascidian species. In the present study, transmission electron microscopy and histochemistry were used to gain a better understanding of anural development in M. pacifica. The fine structure of M. pacifica oocytes and fertilized eggs was similar to urodele oocytes and eggs, except that a perivitelline space and test cells were absent. M. pacifica embryos exhibited the typical cleavage pattern of urodele embryos. Gastrulation was initiated at the vegetal pole, as in urodeles, and occurred at the same time as in two urodele species (Molgula manhattensis and Pyura haustor). However, changes in cell shapes and cell movements of the vegetal pole cells that participate in gastrulation were highly modified compared to commonly studied ascidians. The changes in shapes and movements of the vegetal pole cells were minimal and resulted in embryos having a very small archenteron and blastopore. The presence of large, yolky cells in the interior of the embryo likely restricted vegetal cell movements. Two ultrastructurally distinct types of epidermal cells were evident at the gastrula stage. When gastrulae were manually dechorionated from their surrounding mucous-follicular envelope layers, the embryos were already surrounded by a thin tunic. When day 1 juveniles in the process of hatching were sectioned along the anterior-posterior axis, regional differences in cell types were evident. Differentiated muscle cells in the posterior region were not evident. Day 1 M. pacifica juveniles, anural-developing M. provisionalis juveniles and tadpoles from three urodele species were tested for their abilities to express AchE activity. The highest levels of AchE activity were detected in the larval tail muscle cells of urodeles, low levels of activity were detected in the posterior region of M. provisionalis juveniles, whereas M. pacifica juveniles did not exhibit AchE activity. The results are discussed in terms of evolutionary mechanisms responsible for anural development in ascidians. Offprint requests to: W.R. Bates     

Epimeric methylsulfinyladenosine derivatives from the marine ascidian Herdmania momus

Investigation of the secondary metabolites of the ascidian Herdmania momus led to the isolation and characterization of four new nucleoside derivatives (1–4). Structural studies showed that these derivatives represent a series of rare methylsulfinyladenosine derivatives of interconvertible transesterification isomers and/or sulfinyl epimers. The antiviral activities of these rare nucleosides were evaluated against a series of human pathogenic viruses.     

Ultrastructure and differentiation of ascidian muscle

Summary The larval caudal musculature of the compound ascidian Diplosoma macdonaldi consists of two longitudinal bands of somatic striated muscle. Approximately 800 mononucleate cells, lying in rows between the epidermis and the notochord, constitute each muscle band. Unlike the caudal muscle cells of most other ascidian larvae, the myofibrils and apposed sarcoplasmic reticulum occupy both the cortical and the medullary sarcoplasm.The cross-striated myofibrils converge near the tapered ends of the caudal muscle cell and integrate into a field of myofilaments. The field originates and terminates at intermediate junctions at the transverse cellular boundaries. Close junctions and longitudinal and transverse segments of nonjunctional sarcolemmata flank the intermediate junctions, creating a transverse myomuscular (TMM) complex which superficially resembles the intercalated disk of the vertebrate heart.A perforated sheet of sarcoplasmic reticulum (SR) invests each myofibril. The sheet of SR spans between sarcomeres and is locally undifferentiated in relation to the cross-striations. Two to four saccular cisternae of SR near each sarcomeric Z-line establish interior (dyadic) couplings with an axial analogue of the vertebrate transverse tubular system. The axial tubules are invaginations of the sarcolemma within and adjacent to the intermediate junctions of the TMM complex.The caudal muscle cells of larval ascidians and the somatic striated muscle fibers of lower vertebrates bear similar relationships to the skeletal organs and share similar locomotor functions. At the cellular level, however, the larval ascidian caudal musculature more closely resembles the vertebrate myocardium.This investigation was supported by Developmental Biology Training Grant No. 5-T01-HD00266 from the National Institute of Child Health and Human Development, National Institutes of Health, by National Research Service Award No. 1-F32-GM05259 (M.J.C.) from the National Institute of General Medical Sciences, National Institutes of Health, and by Research Grant No. BMS 7507689 (R.A.C.) from the National Science Foundation. A portion of this study was carried out at the Friday Harbor Laboratories of the University of Washington, and the authors gratefully acknowledge the cooperation and advice extended by the former Director, Dr. Robert L. FernaldResearch facilities were provided in part by Douglas E. Kelly, Professor and Chairman, Department of Anatomy, University of Southern California School of Medicine, Los Angeles, California 90033, USA. The provisions and counsel are warmly acknowledged     

Characterization of cytochrome c-550 from cyanobacteria

Cytochrome c-550 has been purified from several cyanobacteria. It is a low-potential, auto-oxidizable cytochrome. This cytochrome should not be confused with a degradation product of cytochrome ? which may be formed during the isolation of the latter protein. Cytochromes c-550 are distinctive in size, amino-acid composition and N-terminal amino-acid sequence.     

Early specification of ascidian larval motor neurons

In the tadpole larvae of the ascidian Halocynthia roretzi, six motor neurons, Moto-A, -B, and -C (a pair of each), are localized proximal to the caudal neural tube and show distinct morphology and innervation patterns. To gain insights into early mechanisms underlying differentiation of individual motor neurons, we have isolated an ascidian homologue of Islet, a LIM type homeobox gene. Earliest expression of Islet was detected in a pair of bilateral blastomeres on the dorsal edge of the late gastrula. At the neurula stage, this expression began to disappear and more posterior cells started to express Islet. Compared to expression of a series of motor neuron genes, it was confirmed that early Islet-positive blastomeres are the common precursors of Moto-A and -B, and late Islet-positive cells in the posterior neural tube are the precursors of Moto-C. Overexpression of Islet induced ectopic expression of motor neuron markers, suggesting that Islet is capable of regulating motor neuron differentiation. Since early expression of Islet colocalizes with that of HrBMPb, the ascidian homologue of BMP2/4, we tested a role of BMP in specification of the motor neuron fate. Overexpression of HrBMPb led to expansion of Lim and Islet expression toward the central area of the neural plate, and microinjection of mRNA coding for a dominant-negative BMP receptor weakened the expression of these genes. Our results suggest that determination of the ascidian motor neuron fate takes place at late gastrula stage and local BMP signaling may play a role in this step.     

Attachment of the ascidian sperm surface egg receptor N-acetylglucosaminidase to the cell membrane

Ascidian sperm bind to vitelline coat N-acetylglucosamine groups of the egg bvia sperm surface N-acetylglucosaminidase. This sperm surface egg receptor remains anchored throughout penetration. Localization to the sperm surface was verified by biotinylation of intact sperm followed by solubilization in Triton X-100 and binding to streptavidin agarose. The enzyme was determined to be an integral membrane protein as judged by resistance to release by KI and high pH. Linkage of the enzyme to the sperm surface was probed through differential solubilization followed by measuring released enzymatic activity with a fluorogenic substrate. Nonionic detergents released 90% of the activity. Proteases released about 40%. No activity was released by a phosphatidyl–inositol specific phospholipase C. This finding, combined with the similarity of release level by all the detergents, including triton X-114 phase separation experiment. This observation, coupled with the finding of release by nonionic detergents, suggests that the protein is hydrophilic once released from the membrane. Thus, although clearly an integral membrane protein, the enzyme has limited bydrophobicity such as would be present in a single transmembrane sequence or extensive glycosylation. © 1994 Wiley-Liss, Inc.     

Survival of diazotrophic cyanobacteria in soil

The survival under drough conditions for one year of 12 heterocystous cyanobacterial strains inoculated in three different soil types (silt clay, calcareous clay and silt loam) gave the highest survival (50%) forScytonema 208L.Fischerella 288L andNostoc OP25 also showed significant survival. Moreover, the soils inoculated withFischerella 288L andScytonema 208L had a higher total N content than non-inoculated soils.