海洋褐藻多糖的复杂结构、降解酶系以及生物学功能

海洋大型藻类(包括褐藻、红藻和绿藻)具有生物质资源产量高、生长过程中不占用耕地和淡水资源等优点,是未来生物炼制的优良原料。2021年,中国褐藻产量为190万吨,远高于其他经济藻类。但是与绿藻相比,褐藻所含的褐藻酸盐和红藻所含的3,6-脱水-L-半乳糖等多糖组分不容易发酵,极大地限制了其高值转化的进程。本文针对褐藻多糖的高效降解与高值转化这一研究热点,总结了褐藻的系统发育与褐藻多糖(褐藻胶、岩藻多糖以及昆布多糖)的复杂结构组成,分析了3类海洋多糖降解酶系的家族、空间结构及其特异性识别专一底物的活性架构等特征,并对褐藻多糖降解产物及其衍生寡糖的生物学功能进行了构效分析,以期揭示海洋多糖降解酶系的高效催化机制和特异性识别机理,推动褐藻的高效生物降解转化,为精准定制生物活性寡糖,构建绿色低碳工业化生产工艺提供参考。     

中国北方燕山盆地长城纪生物群落和古环境关系探讨

长城纪（１８－１４亿年）是燕山盆地发生和发展的初期阶段,它经历了河口湾,局限海湾和陆表海的发展阶段,在河口湾期与外海沟通顺畅,正常盐度海水带来了大量的浮游生物并逐步地沉积下来,此后海盆进一步封闭,由淡化而咸化,浮游藻类减少,发育底栖藻群,有亚宏观的丝状绿藻和直立生长的宏观膜状绿藻或褐藻,在陆表海阶段海水咸化,发育以蓝藻为主体的耐盐低级菌藻类和见有线形底栖动物的遗迹,这些表明长城纪是早期生命进化的快速发展时期,它与生态环境有密切的关系,多细胞动植物的出现多与咸化环境有关,偏高的盐度可能是早期生物进化的推动力,富盐、含氧,透光的浅水环境是蕴育多细胞底栖生物的温床     

几种绿藻、褐藻和红藻的吸收光谱的比较研究

1.用乳白玻璃法测定了我国黄海常见的属于绿藻门、褐藻门和红藻门的十种海藻的吸收光谱。讨论了这三门海藻的吸收光谱的特点。通过对吸收光谱及红藻、褐藻相对于绿藻的差异光谱的分析,讨论了各种色素在活体中的吸收峰和吸收带的位置。2.根据褐藻与绿藻的吸收光谱的差异及差异光谱的比较分析,认为绿藻吸收光谱中位于485(或480)毫微米的吸收峰是叶绿素 b 的蓝光吸收峰。叶绿素 b 的红光吸收峰位于655毫微米附近。岩藻黄素的吸收峰位于525毫微米附近。根据红藻吸收光谱及其同绿藻的差异光谱中的红光吸收峰和负峰的特点,初步认为红藻中的叶绿素 d 的红光吸收峰比叶绿素 a 的红光吸收峰位于较长波长处。3.对几种红藻的吸收光谱进行了比较。观察到原始红藻纲的条斑紫菜(Porphyra yezoen-sis)的藻胆素与真红藻纲的藻类有显著的差异。这种差异及条斑紫菜的藻胆素的含量和组成上的易变性值得进一步研究。     

山西永济白草坪组具刺疑源类的发现及其地质意义

该文着重报道了山西永济白草坪组(一般认为系中元古界上部相当于蓟县系的层位),以具刺疑源类为主的微化石群,计有4类6属15种,其中包括1新属,4新种,1新组合,1亲近种,2未定种,新属是具细网状纹饰的复杂具刺疑源类Shuiyousphaeridium Yan gen.nov.,4新种是Shuiyousphaeridium membraniferum Yan sp.nov.,Dictyosphaera incrassate Yan sp.nov.,Foliomorpha stipuliferaYan sp.nov.,Manicosiphoninema shuiyouense Yan sp.nov.。本微化石群以球形疑源类为主体,以具刺疑源类的大量发育为特征,并伴生有推测是绿藻和褐藻的化石,其组合面貌与蓟县上前寒武系各组皆有明显区别,具有更高的进化程度,从生物地层标志推测白草坪组所在的汝阳群应归入震旦系。白草坪组具刺疑源类可能是横裂甲藻的原始分子,它在地层对比和藻类进化方面皆具有重要意义。     

中国蓟县长城系团山子宏观藻群

团山子宏观藻群按形态类型分成４属６种,皆有上下之分,直立生长,群集于盆地的浅水部位,形成一繁盛的水下“草原”。大型宏观藻类宽１０－３６ｍｍ,长在１６５－１９０ｍｍ以上,叶状体的广度扩展到４０００ｍｍ＾２友上,与现代藻类大小相近,形态相似,相近于绿藻,乃至褐藻,藻体大型化,形态多样。     

有机磷培养下水体浮游植物竞争与群落结构演替

磷是浮游植物生长的必要元素,也是调控水体富营养化的重要因子之一。在无机磷缺乏的水域,能够有效利用有机磷的藻类有可能成为浮游植物群落的优势种。为了研究有机磷对浮游植物群落结构演替的影响,分别从3个水库采集表层水样,西陂水库(硅藻70.3%,甲藻19.1%,绿藻9.3%)、山美水库(硅藻31.3%,甲藻59.2%,绿藻3.5%)、三十六脚湖(硅藻43.1%,甲藻50.5%,绿藻5.0%),选用有机磷单磷酸腺苷(Adenosine monophosphate,AMP)作为磷源进行实验室模拟实验,并与无机磷(NaH_2PO_4·2H_2O)作为磷源实验组做同步对比,探讨有机磷源条件下浮游植物竞争及群落结构演替规律。结果显示:AMP培养20 d后,西陂水库、山美水库和三十六脚湖的浮游植物生物量分别增加了6.5倍,2.1倍和1.9倍,浮游植物群落结构都演替为以甲藻门和绿藻门为优势藻,所占比例分别为81.8%和16.7%、55.2%和33.5%、73.2%和24.3%,其中西陂水库甲藻门拟多甲藻对有机磷AMP的利用能力强,其所占比例达到81.8%。表明有机磷AMP能有效地促进甲藻门拟多甲藻属的增殖,进而改变水体浮游植物群落结构。     

烟台养马岛潮间带大型海藻分布特征及环境影响因素

2010年4月—2011年3月对烟台养马岛潮间带大型海藻进行了逐月调查.在养马岛潮间带共设置了A、B两个点,对大型海藻物种组成、生物量以及与环境变化的关系进行了研究.结果表明: 调查区域共有大型海藻35种,其中红藻24种,占总数的68.6%;绿藻6种,占总数的17.1%;褐藻5种,占总数的14.3%.夏季优势种以褐藻和绿藻为主,秋、冬、春季优势种以红藻和褐藻为主,鼠尾藻在各季节中均为优势种.大型海藻生物量呈现夏季高、冬季低的特点,生物量最高值出现在6月,A、B采样点大型海藻生物量最小值分别出现在1月和11月,具有温带海域藻类变化特点.温度、营养盐和pH对大型海藻生物量有显著影响.
     

藻类的前世今生——浅析内共生学说与藻类的进化

正什么是藻类?藻类是一类有趣的低等生物的统称。它们没有根茎叶分化,绝大多数能够进行光合作用。说它们低等,是因为在它们完整的生命周期内自始至终不会形成胚,而高等生物(例如种子植物和哺乳动物等)则会在繁殖发育过程中形成胚。藻类既包含能进行光合作用的细菌——蓝藻(蓝细菌),也包括能够进行光合作用的低等真核生物(灰胞藻、绿藻、红藻、隐藻、定鞭藻、异鞭藻、甲藻、裸藻和网绿藻等),还包括具有叶绿体但不能进行光合作用的     

丹江口水库浮游植物时空动态及影响因素

2007年7月至2008年6月对丹江口水库浮游植物进行了为期一年的调查和分析,共采集到浮游植物8门、60属、110种及变种.种类组成以绿藻门、硅藻门和蓝藻门为主,其中绿藻门占优势,共计46种(42％),其次为硅藻35种(32％).藻类年平均密度为4.17×106 celVL,最高密度为6.10×107 cell/L,最低密度为5.16×103 cell/L.各季节浮游植物优势种差异显著,春季为一种颤藻(Oscillatoria sp.)和尖针杆藻(Synedra acus),夏秋两季为啮蚀隐藻(Cryptomonas erosa),冬季转为倪氏拟多甲藻(Peridiniopsis niei).空间分布上,丹江、汉江库区以及取水口3个区域浮游植物优势种为尖针杆藻,五青入库区则以倪氏拟多甲藻占优势.磷浓度是驱动丹江口水库藻类密度的主要影响因子.根据建库几十年来的对丹江口水库较为全面的4次调查资料,分析了丹江口水库的浮游植物群落演替及变化趋势.自1958年以来,50年间,整个水库浮游植物密度增加了16倍,水库富营养化程度有增加的趋势.种类组成由适应河流的固着型硅藻,经过硅藻-绿藻-蓝藻型逐渐发展为硅藻-甲藻-隐藻-蓝藻型.     

北京怀沙河、怀九河自然保护区藻类组成及时空分布动态研究

于2004年3月至2005年3月,首次对北京怀沙河、怀九河自然保护区的藻类植物进行实地调查研究,通过对区内10个采样点360余份水生藻类植物标本鉴定、统计,分析了该区藻类植物的区系组成、藻类时空分布特点.研究表明,该区共分布有藻类植物9门105属226种,其中以硅藻、蓝藻、绿藻3门为主,并有少量裸藻、甲藻、黄藻、红藻、金藻等分布;藻类植物由于受水体化学物质组成和物理性质的影响,各采样点及不同月份的种类组成和数量均有差异.怀九河源头的物种丰度和硅藻多度均最大,洞台、黄坎丝状蓝藻占优势,怀柔水库绿藻占优势;在时间分布上,7月物种丰度和藻类多度最大.通过对区内藻类分布规律及大量污染指示藻类的分析表明,该保护区的水体已经受到了一定程度的污染.     

Fungal remains from the Late Riphean

The paper describes organic remains of one billion years old from the Lakhanda microbiota of the Uchur-Maya Region of southeastern Siberia. The microfossils were discovered on organic sapropelic films. The preserved morphological characters and some developmental stages of the ancient organisms, which are fixed in fossil state, suggest that some of them resembled zygomycetes. Other microfossils under consideration are comparable to reproductive structures of myxomycetes in the type of fusion of spheroid cells and formation of various types of aggregation (sori). Colonies of unicellular microfossils that are arranged in a branching pseudomycelium superficially resemble yeasts. The presence in the same biota of fungal remains belonging to the Myxomycota and Mycota, as well as members of xanthophyte vaucherian algae, indicates that various branches of eukaryotes might have developed in parallel even earlier than the Late Riphean.     

A discovery of riphean heterotrophs in the Lakhanda group of Siberia

New fossil remains have been discovered from the well-known Lakhanda Microbiota (1015–1025 Ma, Uchur-Maya Region, Southeastern Siberia). The microfossils have characters observed in microscopic fungi, such as a reticulate mycelium, formed by anastomizing hyphae of non-cellular structure and of variable width. The fungal mycelium shows that hyphae grew in a certain direction, both forwards and backwards. As their length increased, the hyphae became curved and merged with neighboring hyphae to form enclosed spaces. The presence on hyphae of knoblike trapping structures and secretion of adhesive enzymes suggest a similarity with modern nematophagous fungi. Microorganisms associated with the adhesive hyphae consist of colonial green unicellular algae and thin bacterial sheaths, which may indicate mutually beneficial relationships between morphologically and biologically different partners. Microfossils of fungal origin are systematically described. They include Aimonema ramosa gen. et sp. nov. and the green unicellular alga Eoprotoderma neruenica gen. et sp. nov., forming a symbiotic association.     

Bayesian relaxed clock estimation of divergence times in foraminifera

Accurate and precise estimation of divergence times during the Neo-Proterozoic is necessary to understand the speciation dynamic of early Eukaryotes. However such deep divergences are difficult to date, as the molecular clock is seriously violated. Recent improvements in Bayesian molecular dating techniques allow the relaxation of the molecular clock hypothesis as well as incorporation of multiple and flexible fossil calibrations. Divergence times can then be estimated even when the evolutionary rate varies among lineages and even when the fossil calibrations involve substantial uncertainties. In this paper, we used a Bayesian method to estimate divergence times in Foraminifera, a group of unicellular eukaryotes, known for their excellent fossil record but also for the high evolutionary rates of their genomes. Based on multigene data we reconstructed the phylogeny of Foraminifera and dated their origin and the major radiation events. Our estimates suggest that Foraminifera emerged during the Cryogenian (650-920 Ma, Neo-Proterozoic), with a mean time around 770 Ma, about 220 Myr before the first appearance of reliable foraminiferal fossils in sediments (545 Ma). Most dates are in agreement with the fossil record, but in general our results suggest earlier origins of foraminiferal orders. We found that the posterior time estimates were robust to specifications of the prior. Our results highlight inter-species variations of evolutionary rates in Foraminifera. Their effect was partially overcome by using the partitioned Bayesian analysis to accommodate rate heterogeneity among data partitions and using the relaxed molecular clock to account for changing evolutionary rates. However, more coding genes appear necessary to obtain more precise estimates of divergence times and to resolve the conflicts between fossil and molecular date estimates.     

Plant histones. Relevance to the evolution of prokaryotes to eukaryotes

There are many procaryotic and eucaryotic organisms in plant kingdom. It is hoped that the study of plant histones will be useful in evolutionary studies. The histones of great variety of animal species have been studied and well characterized. Less information is available concerning plant histones. The general conclusion drawn from these investigations is that most organisms of eucaryotic plant and animal species contain the same five major histone fractions. Recently the histone-like proteins were found in some primitive eucaryotes and procaryotes. Data on histones from higher and lower eucaryotes and histone-like proteins of procaryotes are reviewed. Evolution of histones and their appearance prior to that of eucaryotic cell is postulated. The role of histones in evolution of nucleosomes is discussed.     

Streptophyte algae and the origin of embryophytes

Background

Land plants (embryophytes) evolved from streptophyte green algae, a small group of freshwater algae ranging from scaly, unicellular flagellates (Mesostigma) to complex, filamentous thalli with branching, cell differentiation and apical growth (Charales). Streptophyte algae and embryophytes form the division Streptophyta, whereas the remaining green algae are classified as Chlorophyta. The Charales (stoneworts) are often considered to be sister to land plants, suggesting progressive evolution towards cellular complexity within streptophyte green algae. Many cellular (e.g. phragmoplast, plasmodesmata, hexameric cellulose synthase, structure of flagellated cells, oogamous sexual reproduction with zygote retention) and physiological characters (e.g. type of photorespiration, phytochrome system) originated within streptophyte algae.

Recent Progress

Phylogenetic studies have demonstrated that Mesostigma (flagellate) and Chlorokybus (sarcinoid) form the earliest divergence within streptophytes, as sister to all other Streptophyta including embryophytes. The question whether Charales, Coleochaetales or Zygnematales are the sister to embryophytes is still (or, again) hotly debated. Projects to study genome evolution within streptophytes including protein families and polyadenylation signals have been initiated. In agreement with morphological and physiological features, many molecular traits believed to be specific for embryophytes have been shown to predate the Chlorophyta/Streptophyta split, or to have originated within streptophyte algae. Molecular phylogenies and the fossil record allow a detailed reconstruction of the early evolutionary events that led to the origin of true land plants, and shaped the current diversity and ecology of streptophyte green algae and their embryophyte descendants.

Conclusions

The Streptophyta/Chlorophyta divergence correlates with a remarkably conservative preference for freshwater/marine habitats, and the early freshwater adaptation of streptophyte algae was a major advantage for the earliest land plants, even before the origin of the embryo and the sporophyte generation. The complete genomes of a few key streptophyte algae taxa will be required for a better understanding of the colonization of terrestrial habitats by streptophytes.Key words: Chlorophyta, Streptophyta, Embryophyta, Charales, Coleochaetales, Zygnematales, viridiplant phylogeny, land plants, genome evolution, freshwater adaptation, sporophyte origin, diversification, extinction     

Antitumor drugs inhibit the growth of halophilic archaebacteria

Permeability mutants of Escherichia coli have been used to prescreen antitumor drugs. However, most compounds active against eucaryotic proteins have no effect on isofunctional proteins of eubacteria. In contrast, we show that growth of halophilic archaebacteria, procaryotes as distantly related to eubacteria as to eucaryotes, is inhibited by several drugs known to interact with tubulin, actomyosin and DNA topoisomerase II of eucaryotes. Actually, different types of evidence indicate the presence of analogous proteins in halophilic archaebacteria: (a) a yeast actin probe hybridizes with DNA restriction digests of Halobacterium halobium; (b) antibodies against tubulin and actin from chicken react in a crude extract of H. halobium with polypeptides having Mr of 55,000 and 80,000, respectively; (c) the epipodophyllotoxin VP16, a eucaryotic DNA topoisomerase II inhibitor, induces DNA strand breaks with DNA-protein covalent linkage in H. halobium as in eucaryotes. Besides the evolutionary implications, these data indicate that halophilic archaebacteria can be used to prescreen antitumor drugs active on eucaryotic proteins.     

THE CULTURE COLLECTION OF ALGAE AT INDIANA UNIVERSITY

A list is presented of cultures of algae available for purposes of research and teaching. The list includes 753 Chlorophyta; 94 Chrysophyta; 56 Cyanophyta; 55 Euglenophyta; 7 Pyrrophyta; 6 Rhodophyta; 1 species of Phaeophyta; and 5 residual flagellates. Formulae of culture media and directions for maintaining the cultures are included, as are instructions for evoking the sexual process in species of Chlamydomonas, Astrephomene, Pandorina, Eudorina, Cosmarium, Closterium, Oedogonium, Bulbochaete, and Vaucheria.     

Resistant macromolecules of extant and fossil microalgae

The occurrence and composition of macromolecular resistant walls of microalgae and their fossil macromolecular counterparts are reviewed. To date, several algal groups have been identified to produce fossilizable biomacromolecules. Only two biosynthetic pathways seem to be responsible for this, of which the acetate/malate pathway used by Chlorophyta, Eustigmatophyta and Dinophyta is considered to lead to a series of closely related resistant biomacromolecules, called algaenans. Algaenans consist of a network of predominantly linear carbon chains. A different, as yet unidentified, pathway is used by the Dinophyta to produce the aromatic walls of their cysts. The poly‐ketide or acetogenic pathway may have been responsible for resorcinol‐based algae or bacteria‐derived microfossils of the acritarch Gloeocapsamorpha prisca, either through synthesis of the biomacromolecule or through a third pathway, the post‐mortem polymerization of its resorcinol lipids. The postmortem polymerization of lipids also appears to be responsible for the formation of fatty acid‐based macromolecules in Eocene dinoflagellate‐shaped remains from Pakistan. Finally, there is a clear need for elucidating the chemical differences between the biomacromolecules produced by the algae and their fossil analogs in the sediments. This notably applies to the release and condensation of aliphatic and aromatic moieties both at normal and at elevated temperature and pressure conditions.     

PHYTOPLANKTON DISTRIBUTION AND WATER QUALITY INDICES FOR LAKE MEAD (COLORADO RIVER)1

Phytoplankton samples were collected in Lake Mead 6 times from September 1970 to June 1971 for 8 stations at depths of 0, 3, 5, 10, 20, and 30 m. These samples were processed through a Millipore filter apparatus and 79 planktonic algae were identified. Algal divisions represented were Bacillariophyta, 42 species; Chlorophyta, 18; Cyanophyta, 9; Chrysophyta, 3; Cryptophyta, 3; Pyrrophyta, 2; and Euglenophyta, 2. Blue-green algae were dominant in late summer and fall; green algae, diatoms, and cryptomonads in winter; and green algae in spring. The early summer flora was best represented by the Chlorophyta, Cryptophyta, and Chrysophyta. Palmer's pollution-tolerant algae indices and Nygaard's indices were calculated from, phytoplankton data. These indices suggest eutrophic conditions in Lake Mead, especially for Boulder Basin.     

陕西西乡灯影组顶部的瓶状微化石

瓶状微化石被认为是某种未知海相原生动物外壳化石,最早出现于９００－８５０Ｍａ以前。本文记述的该类化石,产自陕西西乡三郎铺小湾里下寒武统灯影组顶部杨家沟段,相当于梅树村阶中－上部,计１０属,１３种和２未定种。所获化石个体数量及形态类型丰富。保存良好,并见有大量具公共壳壁的连体壳。此类连体壳的连接程度呈系列变化。可能代表处于分裂状态的生物体,如是则可为其原生动物解释提供一佐证,瓶状微化石在国外的地层分