天山一号冰川前沿生态系统真菌群落结构演替及分布格局

【目的】分析真菌群落结构和多样性随着一号冰川退缩前沿年代序列的变化,揭示真菌群落的演替轨迹及环境因子对群落组成的影响。【方法】采用宏基因组学研究方法,结合生物信息学和统计学分析技术,对取自一号冰川末端表面冰尘,底部和前沿14个样品进行总DNA的提取,ITS基因的扩增并使用Illumina Miseq平台测序,通过相关生物地理化学特性综合分析在不同年代序列下真菌群落结构及其演替规律。【结果】经测序,筛选和质控分析获得185103条rawreads,占78.3%的非单序列在97%的相似度聚类分析共得到300个操作分类单元(OTU),共划分为6个门:子囊菌门(Ascomycota,52.7%)、担子菌门(Basidiomycota,16.9%)、壶菌门(Chytridiomycota,15.1%)、接合菌门(Zygomycota,2.4%)和球囊菌门(Glomeromycota,1.2%)。从演替初期到后期阶段虽然子囊菌的序列数逐渐下降而担子菌出现缓慢上升趋势,但子囊菌随着土壤年代序列的增加始终为优势类群,壶菌在冰川底部和前沿基层普遍存在且丰度仅次于子囊菌和担子菌。我们在缺乏植被的最新退缩基层发现依靠自养型宿主存活的活体营养菌,如Taphrinomycetes、Urediniomycetes和Ustilaginomycetes。从冰川底部和前沿基层检测到丰度较高的酵母菌,而粪生真菌(coprophilous fungi)仅仅出现在冰川前沿基层,共23个操作分类单元。球囊菌仅在前沿部分样品中存在,有着十分狭小的生态位分布。【结论】一号冰川前沿随着年代序列的增加真菌群落存在明显的演替轨迹和多样性的显著变化,不同生态位真菌类群组成的相似性较低且都存在明显的指示性真菌类群。     

Spatial distribution of discrete RAPD phenotypes of a root endophytic fungus, Phialocephala fortinii, at a primary successional site on a glacier forefront

Phialocephala fortinii is among the few identified hyphomycetes belonging to the Mycelium radicis atrovirens complex. This 'dark-septate endophyte' has a global distribution and colonizes a wide variety of host plants. In this study, the spatial distribution of discrete genets of P. fortinii on the forefront of a receding glacier was analysed using the randomly amplified polymorphic DNA (RAPD) technique to determine plants colonized and patterns of colonization. In two consecutive years of sampling, a total of 74 isolates of P. fortinii were obtained from nine plant species, typically ectomycorrhizal, ericoid mycorrhizal or non-mycorrhizal. The isolates showed substantial variation, sharing on average approx. half the RAPD markers. In the first year, three isolates belonging to a single genet were obtained from two plants separated by a distance of nearly 1.5 m. The continuity of this genet was assessed by a sampling the following year. No isolates similar to that, or any of the genets collected the year before were observed. Consequently, the identical isolates from the previous year were concluded to represent discontinuous ramets. Two additional large genets were observed during the second year of sampling, which inhabited roots of several plants representing three different species. These data suggest that the sharing of P. fortinii genets among plant species might play a fundamental role in adaptation and interaction within the whole plant community in a system undergoing primary succession.     

Vertical distribution of the soil microbiota along a successional gradient in a glacier forefield

Spatial patterns of microbial communities have been extensively surveyed in well‐developed soils, but few studies investigated the vertical distribution of micro‐organisms in newly developed soils after glacier retreat. We used 454‐pyrosequencing to assess whether bacterial and fungal community structures differed between stages of soil development (SSD) characterized by an increasing vegetation cover from barren (vegetation cover: 0%/age: 10 years), sparsely vegetated (13%/60 years), transient (60%/80 years) to vegetated (95%/110 years) and depths (surface, 5 and 20 cm) along the Damma glacier forefield (Switzerland). The SSD significantly influenced the bacterial and fungal communities. Based on indicator species analyses, metabolically versatile bacteria (e.g. Geobacter) and psychrophilic yeasts (e.g. Mrakia) characterized the barren soils. Vegetated soils with higher C, N and root biomass consisted of bacteria able to degrade complex organic compounds (e.g. Candidatus Solibacter), lignocellulolytic Ascomycota (e.g. Geoglossum) and ectomycorrhizal Basidiomycota (e.g. Laccaria). Soil depth only influenced bacterial and fungal communities in barren and sparsely vegetated soils. These changes were partly due to more silt and higher soil moisture in the surface. In both soil ages, the surface was characterized by OTUs affiliated to Phormidium and Sphingobacteriales. In lower depths, however, bacterial and fungal communities differed between SSD. Lower depths of sparsely vegetated soils consisted of OTUs affiliated to Acidobacteria and Geoglossum, whereas depths of barren soils were characterized by OTUs related to Gemmatimonadetes. Overall, plant establishment drives the soil microbiota along the successional gradient but does not influence the vertical distribution of microbiota in recently deglaciated soils.     

Microbial dynamics in glacier forefield soils show succession is not just skin deep

All over the world, glaciers are receding. One key consequence of glacier area loss is the creation of new terrestrial habitats. This presents an experimental opportunity to study both community formation and the implications of glacier loss for terrestrial ecosystems. In this issue of Molecular Ecology, Rime et al. ( 2015 ) describe how microbial communities are structured according to soil depth and development in the forefield of Damma glacier in Switzerland. The study provides insights into the contrasting structures of microbial communities at different stages of soil development. An important strength of the study is the integration of soil depth into the paradigm of primary succession, a feature which has rarely been considered by other studies. These findings underscore the importance of studying the interactions between microbial communities and glaciers at a time when Earth's glacial systems are experiencing profound change.     

Effects of transgenic potatoes with an altered starch composition on the diversity of soil and rhizosphere bacteria and fungi

The aim of this study was to investigate potential effects on the composition of the bacterial and fungal diversity in rhizosphere and soil of a transgenic potato line (SIBU S1) which was modified in its starch composition by RNA anisensing, compared to the non-transgenic parental cultivar (SIBU) at the flowering stage in 2000. Furthermore a second non-transgenic cultivar (SOLANA) was included in the study. To avoid artefacts derived from cultivation depending approaches, molecular techniques based on 16S-(bacteria) and 18S-(fungi) rDNA respectively were used to describe the microbial community structure. Comparing 16S- and 18S-rDNA DGGE fingerprints from the different bulk soil samples, it could be shown that no significant differences between the two cultivars and the transgenic line were found. Similar results were obtained for the rhizosphere samples using the eubacterial, α-and β-proteobacterial and fungal specific primers with the exception of, the eubacterial DGGE patterns obtained for the rhizosphere of SOLANA. These patterns revealed that the relative abundance of one band was enhanced compared with the patterns of SIBU and SIBU S1 and the sequence of the differentiating band showed the highest similarity with Enterobacter amnigenus. When Pseudomonas specific primers were used, relevant differences were found between the rhizosphere patterns of the transgenic potato line (SIBU S1) and the parental cultivar (SIBU). However, clear effects of the cultivar SOLANA on the structure of the Pseudomonas community compared to SIBU were also detected.     

贡嘎山冰川退缩区植物-土壤反馈与植物间相互作用

植物-土壤反馈是揭示陆地生物群落动态变化的关键环节,为理解植物间相互作用及植被群落变化过程奠定基础。本研究以贡嘎山冰川退缩区原生演替早(5~10年)、中(30~40年)和晚期(80~100年)3个阶段典型土壤以及各阶段优势植物为对象,采用盆栽控制试验,比较优势植物在不同土壤条件下的生物量,并量化植物间相互作用以及植物-土壤反馈的方向与强度,为探究贡嘎山冰川退缩区植被群落演替规律提供依据。结果表明:(1)植物-土壤反馈作用显著影响植物在本土中的生物量,早期沙棘(Hippophae rhamnoides)在本土中生长最差,沙棘的植物-土壤反馈系数为负值;演替中期冬瓜杨(Populus purdomii)的反馈系数趋于零;晚期峨眉冷杉(Abies fabri)在本土中生长最好,峨眉冷杉的反馈系数为正值。(2)混种时,早期沙棘与演替中、晚期植物间相互作用指数为负值;中期冬瓜杨、川滇柳(Salix rehderiana)与演替早、晚期植物的相互作用指数接近于零,晚期植物峨眉冷杉、麦吊云杉(Picea brachytyla)与演替早、中期植物相互作用指数为正值。从植物-土壤反馈的方向来看,贡嘎山植被演替从早期负反馈,中期中性反馈,过渡到晚期正反馈。此外,演替早期沙棘促进演替中晚期植物生长,演替中期冬瓜杨、川滇柳对演替早晚期植物无显著影响,晚期峨眉冷杉、麦吊云杉更利于与演替早中期植物相互竞争。结果显示,植物-土壤反馈与植物间相互作用共同驱动了贡嘎山冰川退缩区植被快速演替,直至顶极群落。     

不同连作年限草莓根际细菌和真菌多样性变化

【目的】以不同连作年限草莓根际土壤为材料,探讨不同连作年限土壤细菌、真菌多样性的变化,以期为草莓连作障碍调控提供理论依据。【方法】将没有连作(CK)、连作1年(1Y)、连作8年(8Y)的土壤分别与珍珠岩以3:1的体积充分混匀装盆,"宁玉"草莓苗于2016年9月10日定植于盆栽土壤中,定植后50 d时(开花前)进行土壤取样,提取基因组DNA,通过PCR扩增建立文库,利用Mi Seq平台Illumina第二代高通量测序技术并结合相关生物信息学方法,分析土壤细菌16S rRNA基因V4+V5区域和真菌ITS1+ITS2区域的丰富度和多样性指数以及群落结构。【结果】从9个草莓根际土壤样本中获得3 192个细菌分类操作单元OTU和762个真菌OTU,其中,变形菌门、厚壁菌门、放线菌门、拟杆菌门和蓝藻门为草莓根际土壤的优势菌种,在CK、1Y、8Y草莓根际土壤中分别占细菌总数的87.86%、64.83%和61.79%;子囊菌门和担子菌门为优势真菌,在CK、1Y、8Y草莓根际土壤中分别占真菌群落的69.17%、69.06%和76.18%。从门的分类水平看,酸杆菌门、放线菌门、拟杆菌门、厚壁菌门、绿弯菌门、蓝菌门、浮霉菌门、芽单胞菌门、变形菌门以及真菌担子菌门、接合菌门、壶菌门的比例在不同连作年限的草莓根际土壤中显著改变(P0.05)。属水平的分析也表明,共有29个细菌属和19个真菌属的比例发生改变(P0.05)。【结论】随连作年限的延长,草莓根际土壤生态系统中细菌和真菌群落各门类组成的比例会发生显著变化。     

The last 50 years of climate‐induced melting of the Maliy Aktru glacier (Altai Mountains,Russia) revealed in a primary ecological succession

In this article, we report and discuss the results obtained from a survey of plants, microorganisms (bacteria and fungi), and soil elements along a chronosequence in the first 600 m of the Maliy Aktru glacier's forefront (Altai Mountains, Russia). Many glaciers of the world show effects of climate change. Nonetheless, except for some local reports, the ecological effects of deglaciation have been poorly studied and have not been quantitatively assessed in the Altai Mountains. Here, we studied the ecological changes of plants, fungi, bacteria, and soil elements that take the form of a primary ecological succession and that took place over the deglaciated soil of the Maliy Aktru glacier during the last 50 year. According to our measurements, the glacier lost about 12 m per year during the last 50 years. Plant succession shows clear signs of changes along the incremental distance from the glacier forefront. The analysis of the plant α‐ and β‐diversity confirmed an expected increase of them with increasing distance from the glacier forefront. Moreover, the analysis of β‐diversity confirmed the hypothesis of the presence of three main stages of the plant succession: (a) initial (pioneer species) from 30 to 100 m; (b) intermediate (r‐selected species) from 110 to 120–150 m; and (c) final (K‐selected species) from 150 to 550. Our study also shows that saprotrophic communities of fungi are widely distributed in the glacier retreating area with higher relative abundances of saprotroph ascomycetes at early successional stages. The evolution of a primary succession is also evident for bacteria, soil elements, and CO₂ emission and respiration. The development of biological communities and the variation in geochemical parameters represent an irrefutable proof that climate change is altering soils that have been long covered by ice.     

冰川前缘土壤微生物原生演替的生态特征——以乌鲁木齐河源1号冰川为例

为了解冰川前缘土壤微生物在原生演替过程中的生态特征及其影响因素,用空间距离代替时间序列,以乌鲁木齐河源1号冰川终碛堤为起点,沿6个不同演替时期(0,4,15,31,43a和对照)的样带采集土样,以冰川附近发育良好的土壤为对照,测定土壤酶活性、微生物氮矿化与脱氨作用以及微生物生物量。结果表明,土壤脲酶、蛋白酶、酸性磷酸酶、芳基硫酸酯酶、蔗糖酶活性、微生物氮矿化及脱氨作用随演替时间而增加,微生物生物量碳和氮变化呈波动状,趋势不明显。相关分析表明,土壤有机质与酶活、微生物生物量存在极显著正相关(P0.01)。1号冰川前缘微生物多样性指数随着演替时间持续增加,但目前仍未达稳定状态。     

Pioneer dwarf willow may facilitate tree succession by providing late colonizers with compatible ectomycorrhizal fungi in a primary successional volcanic desert

To advance understanding of the contribution of ectomycorrhizal (ECM) fungi to tree successional processes, natural establishment patterns of secondary colonizing hosts and their ECM fungal communities were investigated with special reference to pioneer hosts. In the volcanic desert on Mount Fuji, Japan, vegetation is sparsely distributed, resembling islands in a sea of scoria. Of 509 vegetation islands in the research area, 161 contained Salix reinii (Salix), the first colonizing ECM host species. The spatial coincidence between secondary colonizing timber species and Salix was analysed, and ECM fungal communities were studied using molecular identification methods. I found 39 and 26 individuals of Betula ermanii and Larix kaempferi, respectively. Without exception, these individuals were all accompanied by Salix. The ECM fungal communities of these timber species showed high similarity to that of Salix and were dominated by generalists that were compatible with two or more plant families. In this desert, available ECM propagules are limited. Pioneer Salix may contribute to tree succession by providing adjacent late colonizers with compatible ECM fungal symbionts.     

丛枝菌根真菌对黄瓜枯萎病的影响

盆栽条件下播种黄瓜Cucumis sativus同时接种丛枝菌根真菌Glomus etunicatum,4周后对接种处理和对照黄瓜苗分别浇灌Fusairum oxysporum f.sp.cucumerinum分生孢子悬液,2周后测定幼苗生物量、根内丙二醛、可溶性糖与游离脯氨酸含量及根围真菌和细菌数量。结果表明:接种Glomus etunicatum根系干重增加了9.3%,提高了根内可溶性糖和游离脯氨酸含量,显著减少了根围真菌数量,降低了黄瓜枯萎病的发病率和病情指数。而不接种Glomus etunicatum的黄瓜苗根系干重减少了28.0%。研究认为AM真菌Glomus etunicatum对黄瓜枯萎病具有一定的生防价值。     

丛枝菌根真菌对黄瓜枯萎病的影响

Pot experiment was conducted to explore whether nursery inoculation of cucumber with Glomus etunicatum could alleviate fusarium wilt caused by Fusarium oxysporum f. sp. cucumerinum. Four-week-old seedlings inoculated with Glomus etunicatum were infected with F. oxysporum f. sp. cucumerinum by pouring conidial suspension. Biomass, contents of malonaldehyde (MDA), soluble sugar and free proline in roots, as well as the quantity of bacteria and fungi in rhizosphere were determined. The results indicated that the root dry weight of seedlings preinoculated with Glomus etunicatum increased by 9.3%; contents of soluble sugar and free proline in roots increased, and the quantity of fungi in rhizosphere decreased significantly. The disease incidence and disease index of Fusarium wilt were reduced. On the contrary, root dry weight of seedlings without inoculation with Glomus etunicatum was reduced by 28.0%. It is concluded that Glomus etunicatum is beneficial to biocontrol of Fusarium wilt of cucumber seedlings.     

Comparison of coal solubilization by bacteria and fungi

Coal-solubilizing agents produced byTrametes versicolor, Phanerochaete chrysosporium, Aspergillus sp., a bacterial consortium, and a bacterial isolate,Arthrobacter sp., from that consortium were compared in terms of pH dependence, thermostability, molecular mass, mechanism of action, and product diversity. The thermostability and low molecular weights exhibited by the coal-solubilizing agents indicated a non-enzymatic mechanism of action. Competition studies using cupric copper indicated that coal solubilization by these agents involved metal chelation. Results demonstrated that oxalate could account for some but not all of the coal solubilization observed forT.versicolor andP.chrysosporium. The very low levels of oxalate detected inAspergillus sp. and the bacterial cultures indicated that oxalate is not an important factor in coal solubilization by these microbes. When subjected to gel permeation chromatography, the soluble coal products generated by each microbial coal-solubilizing agent yielded unique molecular mass profiles suggesting substantial product diversity. Such diversity increases the possibility of identifying potentially valuable compounds and extending the commercial utilization of coal.Abbreviations A₄₅₀, A₂₆₀ absorbances respectively at 450 nm and 260 nm - CSA coal-solubilizing agent - CSU coal-solubilizing unit - GPC gel permeation chromatography - MEA malt extract agar - PDA potato dextrose agar - SDA Sabouraud dextrose agar - SDB Sabouraud dextrose broth - SEM standard error of the mean - Tris tris(hydroxymethyl)aminomethane - TSA trypticase soy agar - TSB trypticase soy broth     

Habitat selection and ecology of Xanthoria elegans (Link) Th. Fr. in glacier forefields: implications for lichenometry

Habitats occupied by the largest Xanthoria elegans (Link) Th. Fr. thalli at seven glacier forefields in the Canadian Rockies were studied to investigate the lichenometric assumption that large thalli occupy ideal sites for growth. The largest thalli were found on steep or overhanging facets at the base of grey limestone clasts that were embedded in moraines. These thalli were unfragmented, had nearly circular outlines, were bordered by barren rock and had SSE to S orientations. This is consistent with the general expectation that south-facing sites offer high solar input and a long snow-free season. Orientations other than south could result by chance or may reflect the importance of microscale factors (e.g. reflected rather than direct solar input). Closure of X. elegans communities and coalescence of thalli was only found at sites that were naturally fertilized with dung. It is concluded that all clasts do not afford homogeneous or ideal environments for lichen growth and do not have an equal chance of being colonized. This raises doubts concerning the validity of statistical normality assumptions in lichenometry and the use of grids to assess closure in lichen communities.     

丛枝菌根真菌伴生细菌的研究进展

在丛枝菌根真菌（Arbuscular mycorrhizal fungi,AMF）的孢子、菌丝的表面或内部栖息着细菌,称之为AMF伴生细菌。AMF伴生细菌种类多样、分布广泛,生态位点包括孢子壁的表面或内部、细胞质、菌丝、孢子果等。其可能的生物学意义包括影响AMF孢子萌发、菌丝生长、菌根形成等过程。由于伴生细菌与AMF联系紧密,其对AMF和土壤微生物生态学具有重要的意义。国际上在该领域的研究已有30多年的历史,就其研究进展进行综述。     

冰川退缩区不同演替阶段土壤溶解性有机质光谱特征及环境响应

溶解有机质(DOM)作为土壤中最活跃的有机组分,在土壤生物地球化学过程中起着关键作用,探讨植被演替过程中DOM的来源、组成、环境响应与累积规律,对预测土壤碳循环过程具有重要意义。本研究从海螺沟冰川退缩区植被原生演替序列选取演替年龄分别为12、30、40、50、80、120年的样地采集表层和亚表层土壤样本,测定DOM浓度并进行紫外-可见光光谱和三维荧光光谱分析,研究原生演替过程中DOM含量和组成的变化特征及其影响因素。结果表明: 土壤DOM浓度随演替年龄的增加而显著增加。土壤DOM中类蛋白组分、荧光指数和生物指数随演替时间的增加而减小,类腐殖质组分和腐殖化程度随演替过程不断增加,土壤DOM芳香化程度先增加后减小。pH值、铵态氮含量解释了62.2%的表层土壤DOM组分变异,土壤含水率和pH值解释了64.3%的亚表层土壤DOM组分变异,说明环境因素是影响海螺沟冰川退缩区原生演替过程中土壤DOM数量和组成的重要因子。     

The ratio of fungi and bacteria in the biomass of different types of soil determined by selective inhibition

Tundra, chernozem (virgin and arable), soddy-podzolic (coniferous forest, meadow, and arable), and grey forest (larch forest) soils were used to separate the contributions of fungi and bacteria to substrate-induced respiration (SIR) with the help of antibiotics. For soils with a high content of organic matter (tundra and chernozem: 12 and 8%, respectively), the procedure of selective inhibition of SIR has been optimized. This procedure consists in application of high concentrations of streptomycin (50–120 mg/g of soil) and cycloheximide (50–80 mg/g of soil) and decreasing the weight of the analyzed soil sample. Soils under study have shown the predominant contribution of fungi (63–82%) to the total SIR. The fungal-bacterial ratio in the soils of natural ecosystems (0–5 cm, without litter) was 4.3, 2.2, 1.5, and 1.5 for tundra soil, virgin chernozem, coniferous (soddy-podzolic soil), and larch (grey forest soil) forests, respectively. The lower layers of soddy-podzolic (5–10 cm) and grey forest (48–58 cm) soils showed a decrease in the fungal and increase in the bacterial component in the total SIR.     

Interactions among endophytic bacteria and fungi: Effects and potentials

Plants benefit extensively by harbouring endophytic microbes. They promote plant growth and confer enhanced resistance to various pathogens. However, the way the interactions among endophytes influence the plant productivity has not been explained. Present study experimentally showed that endophytes isolated from rice (Oryza sativa) used as the test plant produced two types of interactions; biofilms (bacteria attached to mycelia) and mixed cultures with no such attachments. Acidity, as measured by pH in cultures with biofilms was higher than that of fungi alone, bacteria alone or the mixed cultures. Production of indoleacetic acid like substances (IAAS) of biofilms was higher than that of mixed cultures, fungi or bacteria. Bacteria and fungi produced higher quantities of IAAS than mixed cultures. In mixed cultures, the potential of IAAS production of resident microbes was reduced considerably. There was a negative relationship between IAAS and pH of the biofilms, indicating that IAAS was the main contributor to the acidity. However, such a relationship was not observed in mixed cultures. Microbial acid production is important for suppressing plant pathogens. Thus the biofilm formation in endophytic environment seems to be very important for healthy and improved plant growth. However, it is unlikely that an interaction among endophytes takes place naturally in the endophytic environment, due to physical barriers of plant tissues. Further, critical cell density dependant quorum sensing that leads to biofilm formation may not occur in the endophytic environment as there is a limited space. As suchin vitro production and application of beneficial biofilmed inocula of endophytes are important for improved plant production in any agro-ecosystem. The conventional practice of plant inoculation with monocultures or mixed cultures of effective microbes may not give the highest microbial effect, which may only be achieved by biofilm formation.