Endosymbiotic sulphate-reducing and sulphide-oxidizing bacteria in an oligochaete worm

Stable associations of more than one species of symbiont within a single host cell or tissue are assumed to be rare in metazoans because competition for space and resources between symbionts can be detrimental to the host. In animals with multiple endosymbionts, such as mussels from deep-sea hydrothermal vents and reef-building corals, the costs of competition between the symbionts are outweighed by the ecological and physiological flexibility gained by the hosts. A further option for the coexistence of multiple symbionts within a host is if these benefit directly from one another, but such symbioses have not been previously described. Here we show that in the gutless marine oligochaete Olavius algarvensis, endosymbiotic sulphate-reducing bacteria produce sulphide that can serve as an energy source for sulphide-oxidizing symbionts of the host. Thus, these symbionts do not compete for resources but rather share a mutalistic relationship with each other in an endosymbiotic sulphur cycle, in addition to their symbiotic relationship with the oligochaete host.     

Symbiosis insights through metagenomic analysis of a microbial consortium

Symbioses between bacteria and eukaryotes are ubiquitous, yet our understanding of the interactions driving these associations is hampered by our inability to cultivate most host-associated microbes. Here we use a metagenomic approach to describe four co-occurring symbionts from the marine oligochaete Olavius algarvensis, a worm lacking a mouth, gut and nephridia. Shotgun sequencing and metabolic pathway reconstruction revealed that the symbionts are sulphur-oxidizing and sulphate-reducing bacteria, all of which are capable of carbon fixation, thus providing the host with multiple sources of nutrition. Molecular evidence for the uptake and recycling of worm waste products by the symbionts suggests how the worm could eliminate its excretory system, an adaptation unique among annelid worms. We propose a model that describes how the versatile metabolism within this symbiotic consortium provides the host with an optimal energy supply as it shuttles between the upper oxic and lower anoxic coastal sediments that it inhabits.     

Mealybug beta-proteobacterial endosymbionts contain gamma-proteobacterial symbionts

Some insects have cultivated intimate relationships with mutualistic bacteria since their early evolutionary history. Most ancient 'primary' endosymbionts live within the cytoplasm of large, polyploid host cells of a specialized organ (bacteriome). Within their large, ovoid bacteriomes, mealybugs (Pseudococcidae) package the intracellular endosymbionts into 'mucus-filled' spheres, which surround the host cell nucleus and occupy most of the cytoplasm. The genesis of symbiotic spheres has not been determined, and they are structurally unlike eukaryotic cell vesicles. Recent molecular phylogenetic and fluorescent in situ hybridization (FISH) studies suggested that two unrelated bacterial species may share individual host cells, and that bacteria within spheres comprise these two species. Here we show that mealybug host cells do indeed harbour both beta- and gamma-subdivision Proteobacteria, but they are not co-inhabitants of the spheres. Rather, we show that the symbiotic spheres themselves are beta-proteobacterial cells. Thus, gamma-Proteobacteria live symbiotically inside beta-Proteobacteria. This is the first report, to our knowledge, of an intracellular symbiosis involving two species of bacteria.     

具角斯氏线虫共生菌的分子鉴定

在我国的云南和贵州省进行昆虫病原线虫(Entomopathogenic nematodes)资源调查时从不同地区采集到4个品系的具角斯氏线虫Steinernema ceratophorum,以16S rDNA部分序列为分子标记对从这4个品系线虫中分离到的4株共生菌进行了初步的鉴定.测序结果显示,4株菌的16S rDNA部分序列完全一样.基于该段序列所构建的系统发育树表明,具角斯氏线虫共生菌属异杆菌属Xenorhabdus,很可能是该属的一个新种.     

西藏札达、噶尔地区侏罗—白垩纪双壳类化石新材料

文章描述了西藏最西南部札达、噶尔地区双壳类化石2新种和1新亚种,并刊出部分双壳类化石图版。     

胃肠道微生物区系在宿主体内共生作用的研究进展

宿主与肠道微生物区系长期共同进化的结果是宿主与细菌间的互利共生.在人的消化系统中拥有成千上万的共生细菌,这些共生细菌对宿主肠道的营养加工、粘膜免疫耐受和一些其它功能具有重要的作用.现行的分子生物学技术和无菌动物模型为研究宿主与共生细菌之间的分子机制提供了前所未有的机遇,有助于我们更深入地理解肠道的共生细菌对人正常生理功能的作用,从而发展新的治疗策略.     

二叠纪末大灭绝后双壳类新的辐射

研究了二叠纪未生物大灭绝事件后双壳类的首次辐射,辐射的代表是贵州青岩地区中三叠世Anisian晚期的青岩生物群,共50余属100余种,归在5亚纲10目18超科32科。以往通常认为双壳类的辐射发生在晚三叠世,以阿尔卑斯地区圣·卡息安生物群为最早代表;但根据研究,大灭绝后双壳类的首次辐射时代比以往认为的圣·卡息安生物群早约1000万年。     

Xenoturbella is a deuterostome that eats molluscs

Xenoturbella bocki, first described in 1949 (ref. 1), is a delicate, ciliated, marine worm with a simple body plan: it lacks a through gut, organized gonads, excretory structures and coelomic cavities. Its nervous system is a diffuse nerve net with no brain. Xenoturbella's affinities have long been obscure and it was initially linked to turbellarian flatworms. Subsequent authors considered it variously as related to hemichordates and echinoderms owing to similarities of nerve net and epidermal ultrastructure, to acoelomorph flatworms based on body plan and ciliary ultrastructure (also shared by hemichordates), or as among the most primitive of Bilateria. In 1997 two papers seemed to solve this uncertainty: molecular phylogenetic analyses placed Xenoturbella within the bivalve molluscs, and eggs and larvae resembling those of bivalves were found within specimens of Xenoturbella. This molluscan origin implies that all bivalve characters are lost during a radical metamorphosis into the adult Xenoturbella. Here, using data from three genes, we show that the samples in these studies were contaminated by bivalve embryos eaten by Xenoturbella and that Xenoturbella is in fact a deuterostome related to hemichordates and echinoderms.     

西藏聂拉木县聂聂雄拉地区早、中侏罗世双壳类动物群

西藏聂拉木县聂聂雄拉地区，早、中侏罗世地层较发育，地层中化石属 种繁多。地层划分为下侏罗统“普普嘎组”，中侏罗统聂聂雄拉组和拉弄拉组。作者研究了该区旱、中侏罗世的双壳类动物群40多属80多种。描述双壳类化石8新种：Tancredia(T.)nyalamensis,Hiatellasubtrigona,Pronoella(P.)minima,Opis(O.)curvus,Costigeruillia tetracostata,Weyla costalliformisa,Entolium obliquus,E.subfilosus,刊出部分化石图版，简述双壳类化石组合特征。它的研究对该地区旱、中侏罗世地层划分对比，生物地理分区和动物群特征的认识都具有一定的理论与实践意义。     

Nitrogen fixation. Endocrine disrupters and flavonoid signalling

Nitrogen fixation is a symbiotic process initiated by chemical signals from legumes that are recognized by soil bacteria. Here we show that some endocrine-disrupting chemicals (EDCs), so called because of their effect on hormone-signalling pathways in animal cells, also interfere with the symbiotic signalling that leads to nitrogen fixation. Our results raise the possibility that these phytochemically activated pathways may have features in common with hormonal signalling in vertebrates, thereby extending the biological and ecological impact of EDCs.     

颤蚓及其生物扰动对表层沉积物微环

以颤蚓为扰动生物, 通过室内模拟实验, 借助微电极研究颤蚓孔穴附近沉积物微环境pH和溶解氧(DO)的高分辨率分布及变化规律. 结果表明: 沉积物的pH值随扰动时间延长先升高后降低, 颤蚓扰动对pH值的降低有抑制作用; 当扰动时间相同时, 颤蚓使沉积物表面的pH值以颤蚓孔穴为中心出现下降（最多达0.3 pH单位）, 该下降
作用可影响孔穴周围半径1 mm的范围; 无生物体系中的水 沉积物界面附近DO值随时间延长逐渐降低, 但颤蚓的扰动作用使孔穴附近沉积物表面的DO值在水平方向上升高（可升高9.2~17.0 μmol/L）, 并增加DO的渗透深度, 使最大渗透深度从3 mm增加到5 mm. 因此, 沉积物中的颤蚓可通过改变沉积物微环境pH和DO的分布特征, 进而影响水 沉积物界面附近污染物的环境行为.     

共生理论视角下创业教育与专业教育融合的实践研究——以电子商务专业为例

通过共生理论来探讨创业教育和专业教育的融合是一个全新的视角,创建课程这个共生单元成为两者融合的基本单位;按照共生体在共生单元融合的紧密度,形成了创业教育和专业教育之间的一体化共生、间断共生和点共生的融合发展关系;课程实施条件形成了共生环境。同时以此为视角,对电子商务专业实现两者融合发展进行了案例阐述。     

灰飞虱Wolbachia群体生物学的遗传特性研究

Ｗｏｌｂａｃｈｉａ是存在于多种昆虫生殖器官的一类共生菌,它可能在宿 主群体中引起细菌质不亲和性而给宿 主带来生殖优势。对灰飞虱体内的Ｗｏｌｂａｃｈｉａｆｊｔｆｄｇｐｗ,ｖ ｇｍ ｐｇｃｆｍｗ ｑｎｎｋｕｄｙｊｒ ｄｏ ｎｕｉ     

环境胁迫对禾草—内生真菌共生体的影响

Neotyphodium属内生真菌与禾本科植物之间的共生关系因其与农牧业的密切关系而受到研究者们的广泛关注。Neotyphodium属内生真菌长期生活在植物体内的特殊环境中,并与宿主协同进化,在演化过程中二者形成互惠共生关系,一方面内生真菌可从宿主中吸收营养供自己生长需要,另一方面内生真菌可增强宿主植物的抗旱性、抗病性和抗虫性,促进宿主植物生长并提高其竞争能力,但也对家畜产生毒性。     

西藏侏罗纪双壳类化石组合特征

该文详细论述了西藏侏罗纪双壳类化石组合特征、地理分布和共生生物的关系,并划分为喜马拉雅和冈底斯-念青唐古拉-三江两生物地理区。     

Genome sequence of the endocellular bacterial symbiont of aphids Buchnera sp. APS

Almost all aphid species (Homoptera, Insecta) have 60-80 huge cells called bacteriocytes, within which are round-shaped bacteria that are designated Buchnera. These bacteria are maternally transmitted to eggs and embryos through host generations, and the mutualism between the host and the bacteria is so obligate that neither can reproduce independently. Buchnera is a close relative of Escherichia coli, but it contains more than 100 genomic copies per cell, and its genome size is only a seventh of that of E. coli. Here we report the complete genome sequence of Buchnera sp. strain APS, which is composed of one 640,681-base-pair chromosome and two small plasmids. There are genes for the biosyntheses of amino acids essential for the hosts in the genome, but those for non-essential amino acids are missing, indicating complementarity and syntrophy between the host and the symbiont. In addition, Buchnera lacks genes for the biosynthesis of cell-surface components, including lipopolysaccharides and phospholipids, regulator genes and genes involved in defence of the cell. These results indicate that Buchnera is completely symbiotic and viable only in its limited niche, the bacteriocyte.     

菌丝内生细菌及其宿主真菌共生体系研究进展

微生物共生普遍存在于自然界中，真菌-细菌联合体能以多种方式相互作用，共同发挥各种生态功能。有些细菌驻留在真菌菌丝内部，借以调控真菌的生长、发育、分布和次级代谢过程，这些细菌被称为菌丝内生细菌（endohyphal bacteria, EHB）。EHB的研究揭开了微生物生态学的一个新篇章，是真菌与细菌共生关系中最紧密的代表。在逆境条件下，EHB可以调节寄主生殖机制相关的关键成分或步骤，诱导植物激素类物质的产生，对寄主真菌具有辅助性保护作用。研究最深入的真菌-EHB共生体系是植物致病性根霉菌Rhizopus sp.与伯克霍尔德氏菌Burkholderia sp.，引起水稻幼苗枯萎病所必需的植物毒素——根霉素是由伯克霍尔德氏菌所产生的，而非寄主根霉菌本身产生的。EHB也会影响定殖于高等植物的内生真菌的生态和多样性。在某些情况下，EHB还有助于激活参与识别、转录调节和初级代谢蛋白合成过程的相关基因。目前已开发出了无菌培养分离EHB的方法，然而对真菌-EHB共生体系的研究尚不够深入。综述了菌丝内生细菌EHB及其与宿主真菌的共生体系，阐述这些伴侣之间复杂微妙的相互关系，以及EHB对宿主真菌和宿主植物生长和发育的影响，并对该领域的研究方向提出了建议。     

菌丝内生细菌及其宿主真菌共生体系研究进展

微生物共生普遍存在于自然界中，真菌-细菌联合体能以多种方式相互作用，共同发挥各种生态功能。有些细菌驻留在真菌菌丝内部，借以调控真菌的生长、发育、分布和次级代谢过程，这些细菌被称为菌丝内生细菌（endohyphal bacteria, EHB）。EHB的研究揭开了微生物生态学的一个新篇章，是真菌与细菌共生关系中最紧密的代表。在逆境条件下，EHB可以调节寄主生殖机制相关的关键成分或步骤，诱导植物激素类物质的产生，对寄主真菌具有辅助性保护作用。研究最深入的真菌-EHB共生体系是植物致病性根霉菌Rhizopus sp.与伯克霍尔德氏菌Burkholderia sp.，引起水稻幼苗枯萎病所必需的植物毒素——根霉素是由伯克霍尔德氏菌所产生的，而非寄主根霉菌本身产生的。EHB也会影响定殖于高等植物的内生真菌的生态和多样性。在某些情况下，EHB还有助于激活参与识别、转录调节和初级代谢蛋白合成过程的相关基因。目前已开发出了无菌培养分离EHB的方法，然而对真菌-EHB共生体系的研究尚不够深入。综述了菌丝内生细菌EHB及其与宿主真菌的共生体系，阐述这些伴侣之间复杂微妙的相互关系，以及EHB对宿主真菌和宿主植物生长和发育的影响，并对该领域的研究方向提出了建议。     

Subcloning and Sequencing of the Form II Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase from Rhodopseudomonas palustris

0　IntroductionRibulose 1,5 bisphosphate (RuBP)carboxylase/oxygenase(RubisCO)isoneofkeyenzymesofthere ductive pentose phosphate pathway ,orCalvin Bassham Bensoncycle .RubisCOisabifunctionalen zymethatcatalyzesthefirststepinthecarbondioxideassimilatorypathwayandphotorespiratorypathwayinallphotosyntheticorganisms ,includingplants ,algae ,cyanobacteria ,andmostphotosyntheticbacteria[16 ] .Thus ,itispositionedtoregulatetheflowofcellcar bonthroughtwocompetingmetabolicpathways .Itisreportedtha…     

A receptor kinase gene regulating symbiotic nodule development

Leguminous plants are able to establish a nitrogen-fixing symbiosis with soil bacteria generally known as rhizobia. Metabolites exuded by the plant root activate the production of a rhizobial signal molecule, the Nod factor, which is essential for symbiotic nodule development. This lipo-chitooligosaccharide signal is active at femtomolar concentrations, and its structure is correlated with host specificity of symbiosis, suggesting the involvement of a cognate perception system in the plant host. Here we describe the cloning of a gene from Medicago sativa that is essential for Nod-factor perception in alfalfa, and by genetic analogy, in the related legumes Medicago truncatula and Pisum sativum. The identified 'nodulation receptor kinase', NORK, is predicted to function in the Nod-factor perception/transduction system (the NORK system) that initiates a signal cascade leading to nodulation. The family of 'NORK extracellular-sequence-like' (NSL) genes is broadly distributed in the plant kingdom, although their biological function has not been previously ascribed. We suggest that during the evolution of symbiosis an ancestral NSL system was co-opted for transduction of an external ligand, the rhizobial Nod factor, leading to development of the symbiotic root nodule.