造礁石珊瑚共附生固氮微生物的固氮活性

造礁石珊瑚是珊瑚礁生态系统的主要建造者,其共附生微生物参与的生物固氮过程可以缓解寡营养海域的氮素限制,从而维持珊瑚礁生态系统较高的初级生产力。本研究以位于海南三亚鹿回头和西沙南沙洲两地的造礁石珊瑚为对象,采用乙炔还原法测定了不同季节及不同物种的珊瑚共附生固氮微生物的固氮活性;同时测定了海水营养盐含量,分析了珊瑚固氮活性与环境因子之间的关系。结果表明:三亚鹿回头海域的鹿角杯形珊瑚(Pocillopora damicornis)、澄黄滨珊瑚(Porites lutea)和芽枝鹿角珊瑚(Acropora gemmifera)的固氮活性无季节性差异;但相同季节3种珊瑚的固氮活性具有显著的物种间差异,其中鹿角杯形珊瑚的固氮活性最高(P0.05),夏季为5.925×10~(-11)mol C_2H_4·g~(-1)·h~(-1),冬季为6.471×10~(-11)mol C_2H_4·g~(-1)·h~(-1);西沙寡营养条件下的澄黄滨珊瑚的固氮活性在夏季为5.401×10~(-11)mol C_2H_4·g~(-1)·h~(-1),显著高于同一季节三亚鹿回头的澄黄滨珊瑚的固氮活性(1.971×10~(-11)mol C_2H_4·g~(-1)·h~(-1))(P0.01)。研究表明,在营养盐浓度较高的背景下,珊瑚的固氮活性受环境因子和季节变化的影响较小。西沙南沙州海水中溶解性营养盐浓度的升高可能会减弱珊瑚共附生固氮微生物的固氮能力。     

涠洲岛2种造礁珊瑚共附生可培养潜在耐热细菌多样性

【背景】珊瑚适应环境的能力与机体内共附生细菌有关,然而,这些细菌在珊瑚宿主适应环境变化过程中所起的作用尚不清楚。对珊瑚共附生细菌进行纯培养,探究其生物功能和生态作用,是解析珊瑚宿主环境适应机理的重要途径。【目的】研究热耐受性不同的2种造礁珊瑚共附生可培养潜在耐热细菌多样性和功能,为理解珊瑚适应环境的能力提供新的认识。【方法】从涠洲岛选取2种热耐受性差异显著的霜鹿角珊瑚(Acropora pruinosa)和丛生盔形珊瑚(Galaxea fascicularis)为研究对象,采用2216E、海水R₂A和海水GYP这3种琼脂培养基,于32℃(珊瑚热耐受阈值)培养条件下对珊瑚共附生潜在耐热细菌进行分离培养,对分离菌株进行16S rRNA基因测序和序列相似性分析。选取代表菌株进行热耐受性检验,并利用平板对峙法进行抗菌活性检测。【结果】2种造礁珊瑚共附生可培养潜在耐热细菌的多样性存在显著差异。从热敏型的霜鹿角珊瑚中获得44株细菌,隶属于4个门22个属,其中弧菌属(Vibrio)、假交替单胞菌属(Pseudoalteromonas)和Tenacibaculum为优势属;从热耐...     

南海鹿角杯形珊瑚(Pocillopora damicornis)的低遗传多样性凸显了环境变化下的脆弱性

珊瑚礁是典型的环境敏感性的海洋生态系统之一,其对环境变化的响应及适应机制的相关研究得到越来越多的关注。了解南海广布型物种鹿角杯形珊瑚(Pocillopora damicornis)的遗传特征有利于深入理解南海珊瑚礁的环境适应机制。本研究基于南海2个典型海域4个调查站点共84个鹿角杯形珊瑚样品,使用7个微卫星标记表征其遗传多样性和遗传结构。遗传多样性指标统计结果显示,南海鹿角杯形珊瑚的遗传多样性水平较低(H_o为0.090～0.567,H_e为0.137～0.458),海南岛海区与西沙海区的遗传多样性水平差别不大,其中海南岛的鹿回头群体的遗传多样性较高,西沙的银屿群体的遗传多样性最低。遗传结构分析结果显示,南海鹿角杯形珊瑚形成2个遗传分离的谱系：(鹿回头群体、七连屿群体、永兴群体)和银屿群体。曼特尔检验结果表明鹿角杯形珊瑚群体间的遗传分化与平均海表温度(sea surface temperature, SST)(R²=0.312 5,P=0.290)、 SST变异度(R²=0.066 8,P=0.680)...     

海南新村湾泰来草内生细菌与内生固氮菌的多样性与群落结构研究

内生菌对宿主植物的生长、发育、健康状态具有重要影响。通过构建克隆文库解析泰来草不同营养器官中内生细菌、内生固氮菌的群落组成和结构。从表面消毒的不同泰来草组织中提取DNA, 基于16S rRNA和固氮基因nifH分别构建克隆文库, 分析泰来草不同营养器官内生细菌和内生固氮菌的群落结构特征。新村湾泰来草共获得内生细菌分类单元(Operational Taxonomic Units, OTUs) 162个, 根、地下匍匐茎、叶分别含有72、45、52个OTUs, 其中α-变形杆菌和γ-变形杆菌是优势类群, 其相对丰度分别约为48.34%—62.72%和8.41%—33.21%。内生固氮菌OTUs 90个, 根、地下匍匐茎、叶的OTUs数分别为59、19、27个, α-变形杆菌是优势类群, 在根、地下匍匐茎和叶中所占的比例分别约为47.73%、48.99%和67.65%。泰来草不同组织部位内生细菌和内生固氮菌具有丰富的多样性, 但是各个组织部位的优势菌存在差异, 其中, 根的内生细菌群落丰富度最高, 叶的多样性最高; 内生固氮菌群落的丰度和多样性最高的是根。另外, 层级聚类分析和非度量多维尺度分析结果显示, 泰来草根、地下匍匐茎和叶片三者的内生细菌、内生固氮菌群落结构均具有显著差异(R = 1, P ≤ 0.01。本初步研究成果可为挖掘海草功能微生物提供新的视野, 进一步将其应用于海草床的生态修复中。     

澄黄滨珊瑚和丛生盔型珊瑚非培养放线菌多样性

【目的】研究澄黄滨珊瑚(Porites lutea)和丛生盔型珊瑚(Galaxea fascicularis)联合放线菌物种多样性。【方法】实验提取两种珊瑚的总DNA,利用放线菌特异性引物对样品总DNA进行扩增,通过构建16S rRNA基因克隆文库和系统发育分析,对三亚鹿回头岸礁区优势物种澄黄滨珊瑚和丛生盔型珊瑚联合放线菌的多样性和群落结构进行研究。【结果】118个从澄黄滨珊瑚克隆文库中随机挑选的阳性克隆子归为58个OTUs,主要分布于酸微菌亚目、棒状杆菌亚目、微球菌亚目、丙酸杆菌亚目和未知类群。丛生盔型珊瑚克隆文库共获得96个序列,归为31个OTUs,主要分布于酸微菌亚目和未知的放线菌类群。多样性指数和稀疏度曲线分析结果显示澄黄滨珊瑚联合放线菌物种多样性比丛生盔型珊瑚更高。【结论】澄黄滨珊瑚和丛生盔型珊瑚拥有较高水平的放线菌物种多样性和复杂的群落结构,并隐藏着大量的高等级放线菌新分类单元。     

间作大豆对甘蔗根际土壤细菌及固氮菌多样性的影响

为探讨间作大豆(Glycine max)对甘蔗(Saccharum officinarum)根际土壤细菌及固氮细菌多样性的影响, 收集和开发固氮菌资源, 筛选高效甘蔗联合固氮体系, 选用3个甘蔗栽培品种‘ROC22’、‘GT21’、‘B8’与大豆品种‘Guizao 2’进行间种栽培, 采用巢式PCR特异扩增细菌16S rRNA基因片段和固氮细菌nifH基因片段, 并结合变性梯度凝胶电泳(DGGE)技术, 对间作大豆的甘蔗根际土壤细菌及固氮细菌进行系统演化和多样性分析。聚类分析结果显示, 间作大豆改变了甘蔗根际土壤细菌及固氮细菌原来的群落组成结构, 尤其对固氮菌群落组成的改变更大, 但对群落物种的优势度影响较小。Shannon-Wiener多样性指数和Simpson多样性指数分析结果表明, 甘蔗-大豆间作显著影响甘蔗根际土壤中细菌和固氮菌的多样性, 其中对固氮细菌多样性的影响较大。不同甘蔗品种的根际土壤细菌和固氮菌在间作大豆条件下表现出不同的多样性, ‘ROC22’和‘GT21’间作处理甘蔗根际土壤固氮细菌的Shannon-Wiener多样性指数显著高于单作处理, 而‘ROC22’与大豆间作处理的甘蔗根际土壤固氮菌多样性最为丰富。在大豆生长盛期, 间作处理的甘蔗根际土壤细菌多样性最为丰富, 不同处理间的差异也最大, 随后下降。总体来看, 甘蔗-大豆间作显著地影响根际土壤细菌和固氮菌的群落结构和群落多样性, 有助于对甘蔗合理间作栽培模式的认识和筛选高效甘蔗联合固氮体系。     

青藏铁路沿线唐古拉山口土壤微生物的ARDRA分析

通过构建16S rDNA文库及文库的限制性片段长度多态性分析（ARDRA）,对青藏铁路沿线唐古拉山口的土壤微生物多样性进行了研究。采用限制性内切酶HaeIII和RsaI对克隆文库中的90个克隆子进行了酶切分型,根据ARDRA酶切图谱的不同,可将其分为23个OTUs。16SrDNA序列分析结果表明,该克隆文库中主要包括变形菌门（Proteobacteria）的alpha、beta、detla亚类、厚壁菌门（Firmicutes）、放线菌门（Actinobacteria）、拟杆菌门（Bacteroidetes）、酸杆菌门（Acidobacteria）及浮霉菌门（Planctomycetes）等8类细菌及未培养细菌。Alpha变形细菌为该文库中的主要菌群,占克隆总数的33.3%;其次为未培养细菌,占克隆总数的22.2%,Bradyrhizobium为优势菌属。研究结果揭示,青藏铁路唐古拉山口的土壤微生物种群不仅具有丰富的多样性,还存在丰富的潜在新菌种。     

三亚两种常见珊瑚健康与白化状态反射率特征分析

对三亚海域常见风信子鹿角珊瑚(Acropora hyacinthus)和疣状杯形珊瑚(Pocillopora verrucosa)健康与白化状态的反射率进行分析。结果表明: 健康状态下风信子鹿角珊瑚与疣状杯形珊瑚反射率波形相似, 在575 nm、605 nm、650 nm 处均出现特征波峰; 白化状态下风信子鹿角珊瑚与疣状杯形珊瑚反射率高于健康状态珊瑚反射率, 波形较平缓,其中白化风信子鹿角珊瑚反射率在675 nm 处出现显著波谷, 为叶绿素对光吸收导致。大型多元统计软件PRIMER 6对健康与白化状态珊瑚反射率进行Bray-Curtis 相似聚类(CLUSTER)分析, 显示在80%相似水平上可以对健康与白化状态珊瑚反射率进行区分。一阶导数表明, 风信子鹿角珊瑚敏感波段为490 nm-570 nm, 疣状杯形珊瑚敏感波段为550 nm-575 nm, 不同种类珊瑚敏感波段具有差异性。     

药用植物凤丹(Paeonia suffruticosa)根际土壤细菌群落16S rRNA基因的ARDRA分析

凤丹(Paeonia suffruticosa Andr.)为芍药科多年生植物,是一种重要的传统中药资源。在其生长发育的周期中与土壤微生物尤其是根际土壤微生物有密切的关系。通过构建16S rRNA基因克隆文库及文库的限制性片段长度多态性分析(ARDRA),对中国药用植物凤丹5大主要分布区域的根际土壤细菌群落多样性进行了研究。采用限制性内切酶HinfI和Csp6I对克隆文库中随机挑选的1000个白色克隆子进行了酶切分型,根据酶切图谱的不同,将其分为324个OTUs,并对38个优势OTUs进行了测序和系统发育分析。16S rRNA基因序列分析结果表明,凤丹根际土壤细菌种群主要包括:变形菌门(包括alpha、beta、gamma、detla亚门)、酸杆菌门、放线菌门、拟杆菌门及厚壁菌门等11类细菌,此外还包含了3个未归类的细菌。变形菌门和酸杆菌门为文库中的主要菌群,分别占克隆总数的47.34%和14.36%,其中Pseudomonas sp.、Burkholderia sp.和Arthrobacter sp.为优势菌属。研究结果表明,我国药用植物凤丹5大主要分布区域的根际土壤细菌种群不仅具有丰富的多样性,还存在丰富的潜在新菌种。     

艾比湖湿地三种植物根际土壤氨氧化细菌群落的多样性

摘要:【目的】以艾比湖湿地盐节木(Halocnemum strobilaceum)、芦苇(Reed)及盐角草(Salicornia)三种植物为对象,研究其根际土壤氨氧化细菌(AOB)的群落多样性。【方法】利用PCR-RFLP的方法,构建氨氧化细菌amoA基因克隆文库,进行系统发育分析。结合三种植物根际理化因子特点,探讨三种植物根际AOB群落结构组成的特点。【结果】通过序列多态性分析表明,三种植物根际土壤AOB amoA基因克隆文库中的所有序列均属于β亚纲(β-Proteobacteria)中的亚硝化单胞菌属(Nitrosomonas)及Nitrosomonas-like,未发现亚硝化螺菌属(Nitrosospira)。三个AOB amoA基因克隆文库分别包括9个OTUs、12个OTUs和7个OTUs,其文库覆盖度均达99%以上,代表性强。三个文库的丰富度、Chao1指数、ACE指数、Shannon指数均为R＞H＞S。【结论】三种植物的AOB多样性为芦苇＞盐节木＞盐角草,并且其最优氨氧化菌群各不相同。本研究为系统认识艾比湖湿地植物根际氨氧化细菌群落多样性和结构组成提供了基础。     

Identification key for European strand-forming house-rot fungi

An identification key for 20 common strand-forming indoor wood decay fungi is given. The key is based on observations of material from affected buildings and on wood samples that have been incubated in the laboratory. The key is with macro- and microscopic photographs.     

Semicircular canal system in early primates

Mammals with more rapid and agile locomotion have larger semicircular canals relative to body mass than species that move more slowly. Measurements of semicircular canals in extant mammals with known locomotor behaviours can provide a basis for testing hypotheses about locomotion in fossil primates that is independent of postcranial remains, and a means of reconstructing locomotor behaviour in species known only from cranial material. Semicircular canal radii were measured using ultra high resolution X-ray CT data for 9 stem primates (“plesiadapiforms”; n = 11), 7 adapoids (n = 12), 4 omomyoids (n = 5), and the possible omomyoid Rooneyia viejaensis (n = 1). These were compared with a modern sample (210 species including 91 primates) with known locomotor behaviours. The predicted locomotor agilities for extinct primates generally follow expectations based on known postcrania for those taxa. “Plesiadapiforms” and adapids have relatively small semicircular canals, suggesting they practiced less agile locomotion than other fossil primates in the sample, which is consistent with reconstructions of them as less specialized for leaping. The derived notharctid adapoids (excluding Cantius) and all omomyoids sampled have relatively larger semicircular canals, suggesting that they were more agile, with Microchoerus in particular being reconstructed as having had very jerky locomotion with relatively high magnitude accelerations of the head. Rooneyia viejaensis is reconstructed as having been similarly agile to omomyids and derived notharctid adapoids, which suggests that when postcranial material is found for this species it will exhibit features for some leaping behaviour, or for a locomotor mode requiring a similar degree of agility.     

Bacterial flora in the alimentary tract of chickens infected with Eimeria brunetti and in chickens immunized with Eimeria maxima and cross-infected with Eimeria brunetti

Differential bacterial counts were made on the intestinal and caecal contents of chickens after inoculation with a standard dose of 320 000 freshly sporulated oocysts of Eimeria brunetti.     

Parasites, emerging disease and wildlife conservation

In this review some emerging issues of parasite infections in wildlife, particularly in Australia, are considered. We discuss the importance of understanding parasite biodiversity in wildlife in terms of conservation, the role of wildlife as reservoirs of parasite infection, and the role of parasites within the broader context of the ecosystem. Using a number of parasite species, the value of undertaking longitudinal surveillance in natural systems using non-invasive sampling and molecular tools to characterise infectious agents is illustrated in terms of wildlife health, parasite biodiversity and ecology.     

Phylogenetic relationships among Southeast Asian climbing bamboos (Poaceae: Bambusoideae) and the Bambusa complex

A phylogenetic analysis of Bambusa and allies based on the plastid DNA non-coding regions rps16-trnQ, trnC-rpoB, trnH-psbA and trnD-T, and a partial nuclear GBSSI gene, was carried out. This included representatives from all four Bambusa subgenera (including type species), a group of segregate Southeast Asian genera distinctive by their climbing–scrambling culms (Dinochloa, Holttumochloa, Kinabaluchloa, Maclurochloa, Soejatmia, Sphaerobambos), and two other Bambusinae genera (Dendrocalamus, Gigantochloa). The results do not support the present subgeneric classification of Bambusa. The climbing Southeast Asian genera, all of which include species previously placed in Bambusa, are distinct from the “core Bambusa group” (type species and alliance) and the Bambusa complex generally.     

Zebrafish msxB, msxC and msxE function together to refine the neural-nonneural border and regulate cranial placodes and neural crest development

The zebrafish muscle segment homeobox genes msxB, msxC and msxE are expressed in partially overlapping domains in the neural crest and preplacodal ectoderm. We examined the roles of these msx genes in early development. Disrupting individual msx genes causes modest variable defects, whereas disrupting all three produces a reproducible severe phenotype, suggesting functional redundancy. Neural crest differentiation is blocked at an early stage. Preplacodal development begins normally, but placodes arising from the msx expression domain later show elevated apoptosis and are reduced in size. Cell proliferation is normal in these tissues. Unexpectedly, Msx-deficient embryos become ventralized by late gastrulation whereas misexpression of msxB dorsalizes the embryo. These effects appear to involve Distal-less (Dlx) protein activity, as loss of dlx3b and dlx4b suppresses ventralization in Msx-depleted embryos. At the same time, Msx-depletion restores normal preplacodal gene expression to dlx3b-dlx4b mutants. These data suggest that mutual antagonism between Msx and Dlx proteins achieves a balance of function required for normal preplacodal differentiation and placement of the neural-nonneural border.     

SNS: Adhesive properties, localization requirements and ectodomain dependence in S2 cells and embryonic myoblasts

The body wall muscles in the Drosophila larva arise from interactions between Duf/Kirre and Irregular chiasm C-roughest (IrreC-rst)-expressing founder myoblasts and sticks-and-stones (SNS)-expressing fusion competent myoblasts in the embryo. Herein, we demonstrate that SNS mediates heterotypic adhesion of S2 cells with Duf/Kirre and IrreC-rst-expressing S2 cells, and colocalizes with these proteins at points of cell contact. These properties are independent of their transmembrane and cytoplasmic domains, and are observed quite readily with GPI-anchored forms of the ectodomains. Heterotypic interactions between Duf/Kirre and SNS-expressing S2 cells occur more rapidly and to a greater extent than homotypic interactions with other Duf/Kirre-expressing cells. In addition, Duf/Kirre and SNS are present in an immunoprecipitable complex from S2 cells. In the embryo, Duf/Kirre and SNS are present at points of contact between founder and fusion competent cells. Moreover, SNS clustering on the cell surface is dependent on Duf/Kirre and/or IrreC-rst. Finally, although the cytoplasmic and transmembrane domains of SNS are expendable for interactions in culture, they are essential for fusion of embryonic myoblasts.     

Gene expression in spider appendages reveals reversal of exd/hth spatial specificity, altered leg gap gene dynamics, and suggests divergent distal morphogen signaling

Leg development in Drosophila has been studied in much detail. However, Drosophila limbs form in the larva as imaginal discs and not during embryogenesis as in most other arthropods. Here, we analyze appendage genes in the spider Cupiennius salei and the beetle Tribolium castaneum. Differences in decapentaplegic (dpp) expression suggest a different mode of distal morphogen signaling suitable for the specific geometry of growing limb buds. Also, expression of the proximal genes homothorax (hth) and extradenticle (exd) is significantly altered: in the spider, exd is restricted to the proximal leg and hth expression extends distally, while in insects, exd is expressed in the entire leg and hth is restricted to proximal parts. This reversal of spatial specificity demonstrates an evolutionary shift, which is nevertheless compatible with a conserved role of this gene pair as instructor of proximal fate. Different expression dynamics of dachshund and Distal-less point to modifications in the regulation of the leg gap gene system. We comment on the significance of this finding for attempts to homologize leg segments in different arthropod classes. Comparison of the expression profiles of H15 and optomotor-blind to the Drosophila patterns suggests modifications also in the dorsal-ventral patterning system of the legs. Together, our results suggest alterations in many components of the leg developmental system, namely proximal-distal and dorsal-ventral patterning, and leg segmentation. Thus, the leg developmental system exhibits a propensity to evolutionary change, which probably forms the basis for the impressive diversity of arthropod leg morphologies.