尖峰岭热带天然林不同土层细菌群落多样性和组成的海拔变异规律

土壤微生物群落结构沿海拔梯度的变异是微生物生物地理学分异和群落空间分布的重要内容,然而,热带森林土壤微生物多样性及其群落特征的海拔模式尚不明确。研究海南省尖峰岭自然保护区0—20cm和20—40cm土壤细菌多样性和群落组成沿海拔梯度(400—1410m)的变化及其与环境因子的关系。结果表明：在0—20cm土壤微生物生物量碳、生物量氮和生物量磷随海拔升高(峰顶降低)而增加,20—40cm土壤微生物生物量碳、生物量氮和生物量磷随海拔升高呈先升高后降低趋势;整体上,变形菌门、放线菌门、酸杆菌门、拟杆菌门、厚壁菌门在0—20cm中占优势,丰度总和占该层细菌总量的88.17%;变形菌门、放线菌门、酸杆菌门、厚壁菌门、绿弯菌门在20—40cm中占优势,丰度总和占该层细菌总量的90.82%;随海拔增加,0—20cm细菌多样性线性减少,20—40cm细菌多样性变化不显著;沿海拔梯度,0—20cm细菌群落组成可分为低(409—1018m),中(1018—1357m)和高(1410m)三个海拔聚集群落,20—40cm细菌群落组成随海拔无显著性变化;两土层细菌多样性与土壤pH显著正相关,土壤细菌群落组成在0...     

祁连山中部4种典型植被类型土壤细菌群落结构差异

土壤微生物参与土壤生态过程,在土壤生态系统的结构和功能中发挥着重要作用。2013年7月采集了祁连山中段4种典型植被群落(垫状植被、高寒草甸、沼泽草甸和高寒灌丛)的表层土壤,分析了表层土壤微生物生物量碳氮和采用Illumina高通量测序技术研究了土壤细菌群落结构及多样性,并结合土壤因子对土壤细菌群落结构和多样性进行了相关性分析。结果表明:(1)土壤微生物生物量碳氮的大小排序为:沼泽草甸高寒草甸高寒灌丛垫状植被;(2)土壤细菌群落相对丰度在5%以上的优势类群是放线菌门、酸杆菌门、α-变形菌、厚壁菌门和芽单胞菌门5大门类;(3)沼泽草甸土壤细菌α多样性(物种丰富度和系统发育多样性)显著高于其它3种植被类型(P0.05),而垫状植被土壤细菌α多样性最低;(4)冗余分析和Pearson相关性分析表明,土壤pH、土壤含水量、土壤有机碳和总氮是土壤细菌群落结构和α多样性的主要影响因子。研究结果可为祁连山高寒生态系统稳定和保护提供理论依据。     

西藏色季拉山垂直植被带土壤细菌群落组成及功能潜势

研究青藏高原土壤微生物群落组成和功能的空间分布特征有助于深入理解典型高寒生态系统中土壤微生物的重要生态功能。本研究采用16S rDNA高通量测序方法,分析了西藏色季拉山4个不同海拔土壤细菌群落物种组成和功能潜势的变化特征及其驱动因子。结果表明: 随着海拔的升高,土壤细菌的丰富度和Shannon多样性指数显著降低;酸杆菌门、绿弯菌门、芽单胞菌门和硝化螺旋菌门的相对丰度显著增加,而变形菌门、放线菌门和拟杆菌门的相对丰度则显著降低。KEGG二级代谢通路中,膜运输及氨基酸、脂类、萜类和聚酮类化合物代谢相关基因的相对丰度在高海拔显著降低,而碳水化合物代谢、信号转导、复制与修复、酶家族等基因丰度则显著升高。不同海拔土壤细菌群落组成和功能潜势的变化受到植被和土壤因子的显著影响,并且pH值是关键驱动因子。群落功能潜势与放线菌门、拟杆菌门、纤维杆菌门等种群丰度显著相关。不同海拔下群落KEGG代谢通路基因组成的差异(β多样性)与土壤细菌群落结构的差异呈显著正相关,说明微生物群落组成与功能潜势之间可能存在紧密关联。     

毛竹林集约经营对土壤固碳细菌群落结构和多样性的影响

为揭示毛竹集约经营对土壤固碳细菌的影响,分别采集集约经营时间为0、10、15、20年和25年的毛竹林土壤(0—20 cm和20—40 cm)土壤,应用实时荧光定量PCR、T-RFLP以及cbbL基因文库方法,分析毛竹林长期集约经营过程中土壤固碳细菌丰度和群落结构多样性的变化,通过冗余分析(RDA)探讨影响土壤固碳细菌群落的主要环境因素。结果表明,长期的集约经营显著提高了毛竹林表层和亚表层土壤的养分含量,土壤pH值却明显降低。集约经营毛竹林土壤固碳微生物数量并未表现出与SOC的相关性,而与N素水平的变化显著相关。具体表现为:随着集约经营的进行表层cbbL基因丰度呈先上升(10年)后下降的规律,与氮素水平呈正相关(P0.05);亚表层土壤cbbL基因丰度则呈直线下降的趋势,与C∶N呈正相关(P0.05)。集约经营导致表层和亚表层土壤微生物群落结构改变,表层固碳细菌多样性指数下降。由系统发育分析可知,不可培养固碳细菌占56%比例,土壤中共同的优势种类多为变形菌和放线菌,以兼性自养为主。RDA分析结果表明土壤酸化和养分积累是毛竹林土壤固碳细菌群落和多样性变化的重要原因。     

基于高通量测序的两种高寒草甸土壤原核生物群落特征研究

土壤微生物在生态系统中具有重要的生态功能,研究青藏高原高寒草甸的土壤原核生物群落组成及其主要影响因子,对揭示青藏高原独特的微生物地理区系和预测全球环境变化的影响有重要意义。利用Illumina Miseq高通量测序技术,结合分子生态网络,对青藏高原高寒沼泽化草甸和高寒草甸的土壤原核生物的群落组成特征进行了分析。结果共检测到23145个OTUs,可分为2个古细菌类群和33个已知的细菌类群;其中变形菌门、酸杆菌门、放线菌门和拟杆菌门为土壤的优势菌群,相对丰度累计超过79%;高寒草甸原核生物的多样性高于高寒沼泽化草甸,两种草甸类型原核生物群落特征具有显著差异性(P0.001)。分子生态网络分析表明,高寒草甸网络具有较长的平均路径距离和较高的模块性,使其比高寒沼泽化草甸网络更能抵抗外界环境变化,在应对气候变化时具有更高的稳定性;典范对应分析(CCA)和分子生态网络的分析结果均表明,土壤p H值是影响土壤原核生物群落特征的主要影响因子。综上所述,土壤微生物群落的组成变化对于评估其对全球气候变化的响应具有重要的指示作用,土壤原核生物群落特征在不同的高寒草甸土壤中具有显著差异,了解其变化规律和影响因子,能为高寒草甸生态系统的适应性管理和应对气候变化提供理论依据。     

土壤细菌群落特征对高寒草甸退化的响应

为明确高寒草甸土壤细菌物种组成及功能结构对草地环境恶化的响应规律, 本文采用高通量基因测序技术对高寒草甸未退化、轻度退化、中度退化、重度退化和极重度退化草地土壤细菌的组成、格局和功能进行了研究。结果表明: 高寒草甸土壤优势细菌为酸杆菌门、放线菌门、浮霉菌门、变形菌门和疣微菌门, 在土壤细菌中占比分别为16%‒18%、9%‒12%、12%‒14%、23%‒29%和11%‒12%。退化草地中土壤细菌物种组成明显改变, 变形菌门细菌丰度降低, 酸杆菌门和浮霉菌门丰度增加, 不同草地科水平细菌丰度差异因土层而异。草地退化对细菌Chao1指数无影响, 轻度退化提高了细菌Simpson指数, 重度退化草地土壤细菌Shannon-Wiener指数最高。Faprotax细菌功能分组以化能异养、硝化作用、亚硝酸盐氧化及硫代谢作用为主, 草地退化改变了微生物介导的碳循环、氮循环、硫循环、铁循环和锰循环。重度及极重度退化提高了细菌氨氧化功能作用, 降低了硫化物、亚硝酸盐氧化及尿素水解作用; 草地退化过程中细菌化能异养、芳香族化合物降解及反硝化作用功能等均呈先降低后升高的变化趋势, 中度退化阶段是微生物群落生态功能结构转变的拐点。高寒草甸退化改变了土壤细菌的群落及功能结构, 土壤含水量、pH、总有机碳、全氮、全钾和有效氮磷比是土壤细菌群落及功能结构变化的主要驱动因子。     

高寒草甸鼠兔活动对土壤微生物群落特征的影响

高原鼠兔活动严重影响了高寒草甸生态系统的多样性及稳定性, 土壤微生物对环境变化高度敏感, 其群落特征受到了高原草甸鼠兔活动的显著影响。为探究鼠兔活动对土壤微生物群落结构及多样性的影响, 本实验以青海湖高寒草甸鼠兔活动干扰下的土壤微生物为研究对象, 基于细菌16s rRNA进行高通量测序。不同处理下的土壤细菌的优势菌群相似, 主要包括变形菌门和酸杆菌门。与自然状态下的高寒草甸相比, 鼠兔活动下的土壤细菌群落丰富度显著增加, 多样性指数显著降低 (P < 0.05)。鼠兔活动显著影响了土壤细菌的群落结构 (P < 0.05), 对照与鼠兔活动分组间存在104个差异菌群, 鼠兔活动下的亚表层土壤 (10—20 cm) 仅有3个菌群相对丰度显著升高, 鼠兔活动下的表层土壤 (0—10 cm) 则存在52个差异菌群。FAPROTAX预测分析表明, 土壤细菌群落功能基团多为碳氮代谢相关的功能基团, 另有部分与无氧呼吸途径及人类疾病有关。总体而言, 鼠兔活动显著影响了高寒草甸土壤细菌的群落结构及多样性特征, 且表层土壤的细菌群落对鼠兔活动的响应更为明显。     

青藏高原高寒草甸不同海拔梯度下土壤微生物群落碳代谢多样性

土壤微生物群落功能多样性对维持生态系统功能和稳定性具有非常重要的意义。为探究青藏高原高寒草甸不同海拔梯度下土壤微生物碳源利用差异以及影响机制,运用Biolog微平板技术,研究了西藏当雄县草原站4300—5100 m的6个不同海拔梯度下土壤微生物群落碳源代谢多样性。研究结果表明:(1)不同海拔下高寒草甸土壤微生物碳源的利用程度均随培养时间的延长而升高;微生物代谢活性和群落多样性指数均随海拔升高呈现先上升后下降的单峰变化趋势,整体表现4800 m4950 m4400 m4650 m5100 m4300 m;(2)主成分分析表明不同海拔显著影响了土壤微生物群落碳源代谢多样性,其中碳水化合物类、氨基酸类和胺类碳源是各海拔土壤微生物的偏好碳源;碳水化合物类、羧酸类、氨基酸类和胺类碳源的利用强度受海拔影响较大;(3)分类变异分析表明,土壤、植物和气候因素是影响不同海拔碳源利用变异的主要影响因子,可解释不同海拔的碳源利用差异的79.0%;排除环境因子之间的多重及交互作用,偏曼特尔检验表明土壤含水量、植被丰富度和年均降水量是影响不同海拔微生物碳源利用多样性的最重要的环境因子。综上,研究表明青藏高寒草甸不同海拔土壤微生物碳源代谢多样性呈现显著的海拔差异趋势,其海拔差异主要受到土壤含水量、植被丰富度和年均降水量的影响。     

纳木错湖水体固碳微生物数量、群落结构及其驱动因子

湖泊是微生物固碳的主要生态系统之一,但青藏高原湖泊水体固碳微生物群落的研究还罕见报道。以纳木错为例,采用定量PCR和克隆文库方法,研究湖水中cbbL ID基因丰度和固碳微生物群落组成,并分析其与环境参数的关系。结果显示:纳木错湖水中存在较高丰度的cbbL ID类型固碳微生物,从表层到底层呈增加趋势,T2点底层达到最高值(6.37×10~8拷贝L~(-1)湖水)。cbbL ID类型固碳微生物共分四个类群,即不等鞭毛类(Stramenopiles),定鞭藻纲(Haptophyceae),蓝藻(Cyanobacteria)和隐藻门(Cryptophyta)。其中占主要的是Stramenopiles和Haptophyceae。Stramenopiles类群的多样性较高(含7个纲,13个科),其他类群只有1个科。相关性分析表明Stramenopiles和Haptophyceae出现频率存在显著的负相关关系(P0.01)。湖水深度和pH与湖水cbbL ID基因丰度显著相关(P0.05,P0.01)。叶绿素含量与Stramenopiles和Haptophyceae出现频率显著相关(P0.01)。     

干旱区高寒湿地逆行演替下土壤微生物群落结构的研究

【目的】探究高寒湿地逆行演替对土壤性质与微生物群落结构的影响。【方法】以新疆巴音布鲁克天鹅湖高寒湿地为研究对象,依托逆行演替典型样带(沼泽-沼泽化草甸-草甸),利用高通量测序技术分析各演替区土壤微生物群落结构。【结果】高寒湿地逆行演替改变了土壤微生物在分类操作单元(operational taxonomic unit,OTU)水平上的物种组成,致使草甸区的微生物ACE、Chao1、Simpson、Shannon多样性指数显著低于沼泽区和沼泽化草甸区(P<0.05);随着演替发生,变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)、拟杆菌门(Bacteroidetes)、子囊菌门(Ascomycota)的相对丰度均减少,放线菌门(Actinobacteria)、芽单胞菌门(Gemmatimonadetes)、担子菌门(Basidiomycota)、被孢霉门(Mortierellomycota)的相对丰度增加;主坐标法分析(principal coordinates analysis,PCoA)排序分析显示,土壤微生物群落在各逆行演替都出现不同程度的离散...     

Vermicomposting in the management of pig-waste in Hong Kong

The treatment and disposal of pig-waste in Hong Kong has received much attention in recent years but, following any of the presently used treatment processes, solids remain to be further stabilized. Vermicomposting is a waste stabilization technique which converts waste into potentially recyclable materials such as worm protein and worm casts. The earthworm, Pheretima asiatica, can stabilize most of the solids arising from the treatment of pig-waste, including raw pig manure, suggesting that vermicomposting has a high potential as a unit process in the management of pig-waste in Hong Kong.S.H. Wong is with the Environmental Protection Department, Hong Kong; and D.A. Griffiths is with the Department of Botany, University of Hong Kong, Hong Kong.     

Removal of wastewater pathogen indicators in a constructed wetland in Leon, Spain

This paper studies the seasonal presence and removal of the pathogenous micro-organisms Escherichia coli, total coliforms (TC), Clostridium perfringens (Cp), faecal streptococci (FS), Giardia cysts, Cryptosporidium oocysts and helminth eggs, in a constructed wetland treatment system. The removal efficiency of this system with respect to the indicator micro-organisms achieved maximum values in spring and autumn at 99.9% for E. coli and TC, respectively, in winter at 97.0% for FS, in summer at 100% for Clostridium and throughout the year, also at 100%, in the case of Giardia cysts, Cryptosporidium oocysts and helminth eggs. In general, very low protozoan and helminth egg counts were found, and the system demonstrated efficient reduction of the wastewater indicator pathogens.     

Inbreeding in a french peasant population

Genealogical pedigrees were collected from 976 farming couples who lived in a canton of central France in the XIXth and XXth century. Several methods (genealogical, isonymic and probability of origin of genes) were used to appraise the evolution of the biological structure of this population, which has gone through two phases. The first phase from 1800 to the World War I, shows gene flows between the farming population of the canton and those of neighbouring rural districts which are linked to an increase in consanguineous marriages. The second phase, from 1920 onwards, shows important gene flow from distant areas. This trend implies a decrease in consanguineous marriages.     

Lactic acid bacteria in fermented foods in Thailand

Traditional fermented foods (fish, meat and vegetable products), produced by many different processes, are eaten in many parts of Thailand. Lactic acid bacteria are responsible for the souring and ripening of these foods. Homofermentative strains of Lactobacillus pentosus, L. plantarum and Pediococcus pentosaceus are dominant in foods with low salt concentrations whereas P. halophilus strains are present in foods containing high salt. Strains of Lactobacillus sake, other Lactobacillus spp., P. acidilactici and P. urinaeequi are frequently found. Heterofermentative strains of L. brevis, L. confusus, L. fermentum, L. vaccinostercus, other Lactobacillus spp., and of Leuconostoc spp. are distributed as minor bacteria and strains of Staphylococcus, Enterococcus and Halobacterium are occasionally isolated.S. Tanasupawat is with the Department of Microbiology, Faculty of Pharmaceutical Sciences. Chulalongkorn University, Bangkok 10330, Thailand; K. Komagata is with the Department of Agricultural Chemistry, Tokyo University of Agriculture, Sakuragaoka 1-1-1, Setagaya-ku, Tokyo 156, Japan.     

New species and new combinations in Peruvian Orchidaceae

seventeen new species and combinations are proposed in the generaChondrorhyncha, Cischweinfia, Cochlioda, Eloyella, Encyclia, Kefersteinia, Koellensteinia, Macroclinium, Rodriguezia, Solenidiopsis, andStenia. All new species are illustrated. A key is provided for 2-flowered species ofMacroclinium, PeruvianSigmatostalix, and PeruvianStenia. Solenidium (Solenidiopsis) peruvianum Schltr. is lectotypified.     

Phylogenetic relationships in theCampanulales based onrbcL sequences

Phylogenetic relationships within the angiosperm orderCampanulales were investigated by comparative sequencing of the chloroplast generbcL. CompleterbcL sequences were obtained for ten species in six families within the order. These data were analyzed along with previously publishedrbcL sequences from other taxa (for a total of 117 species) within the subclassAsteridae and outgroups, producing 32 equally parsimonious trees. A subset consisting of 44 of these taxa was then chosen and more rigorous analyses performed, resulting in four equally parsimonious trees. Results indicate that two major clades roughly corresponding to traditionally circumscribedAsterales andCampanulales exist as sister taxa. In particular, therbcL trees indicate thatSphenoclea is not a member ofCampanulales orAsterales, thatPentaphragma is more closely allied toAsterales thanCampanulales, that theCyphiaceae are not monophyletic, thatCampanulaceae andLobeliaceae are not sister taxa, and thatStylidiaceae are correctly placed withinCampanulales.     

Mycoflora of Argentinian corn harvested in the main production area in 1990

Corn (Zea mays) is the main cereal produced in and exported from Argentina. The risk of contamination by mycotoxins is related to the mycoflora associated with the corn kernels. This paper reports on the identification of internal and external mycoflora of corn kernels harvested in the main production area in Argentina in 1990. A mycological survey was carried out on 178 corn samples, from five locations in that area and the isolation frequency and relative density of the prevalent fungal genera compared. GenusFusarium was the most prevalent component of the internal seedborne mycoflora in the five locations.Penicillium was prevalent in all locations, taking into account the frequency. However, this genus was predominant only in two locations, when the relative density was considered. The predominantFusarium wasF. moniliforme and the most frequently isolated species ofAlternaria, Aspergillus andPenicillium wereA. alternata, A. flavus andP. decumbens, respectively.Diplodia species were not isolated from any of the samples.     

Nectary structure and nectar characteristics in someBignoniaceae

The nectary structure and chemical nectar composition of 15 species belonging to 12 genera ofBignoniaceae are analyzed. All taxa bear a conspicuous nuptial nectary surrounding the ovary base. The secretory tissue is mostly supplied by phloem branches. The stomata are located in the middle and upper part of the nectary epidermis with an homogeneous distribution. The nuptial nectary is proportionally large in relation to the ovary (15–30%), disregarding the nectary volume. Most species have extranuptial nectaries in both inner and outer surfaces of the calyx. Both kinds of nectaries lack a vascular tissue that straightly supplies them. Nuptial nectar concentration (wt/wt) ranges from 19 to 68%. Sugars and amino acids are found in all species. Half of the species have hexose predominant nectars, the remaining sucrose predominant. Phenols are detected in only three species, whereas reducing acids exclusively inTecoma stans. Alkaloids and lipids were never detected. Extranuptial nectar chemical composition is analyzed in two species:Dolichandra cynanchoides andPodranea ricasoliana. Bees constitute the main flower visitors of the species studied whereas hummingbirds were seen visiting three species. A correlation analysis is performed with the data obtained. There are a few significant correlations which indicate a parallel increase of three parameters: the longer the flower length, the more voluminous the nectary and the higher stomata number, independently of the floral biotype. Phenograms are obtained using 24 floral characters including nectary and nectar data. The clusters obtained do not reflect taxonomic relationships but are useful in the understanding of animal-plant interactions when the flower biotype is considered.This paper is based on a chapter of a doctoral thesis presented at the University of Córdoba (Argentina).     

Synthetic oligonucleotide probes for detection of mercury-resistance genes in environmental freshwater microbial communities in response to pollutants

Mercury-resistance genes were detected byin situ hybridization using new synthetic oligonucleotide probes specific formerA andmerB genes according to the published sequences of the corresponding enzymes. These DNA probes were used for the detection of specific mercury-resistant microorganisms isolated from the Rhine River which had been polluted 3 years previously in 1986. Mercuric reductase and organomercurial lyase genes persist in the bacterial genome even after the disappearance of the pollutant but are absent in axenic amoebae. A total of 49 bacterial isolates showed DNA homologies with the³²P-labelled DNA probes and 15 free-living amoebae were selected due to their harboured symbiotic mercury-resistant bacteria.