抗病性不同大豆品种根面及根际微生物区系的变化 Ⅰ.非连作大豆(正茬)根面及根际微生物区系的变化

采用平板计数法测定了3个抗病性不同的大豆品种在生育期内根面和根际微生物区系的变化情况,并应用荧光计数法直接测定了根际细菌和真菌的生物量。结果表明,土体的微生物种类最丰富、根际的次之、根面的较单一。播种后从三叶期到鼓粒初期,根面和根际的可培养细菌总数随生育期逐渐增加,鼓粒初期达最大值,而成熟期则有明显的下降;大豆根际细菌生物量也存在相同的变化规律。抗病性不同的大豆品种其根面、根际可培养细菌总数存在差异;抗病品种大豆的根瘤重明显高于感病品种。种植一季后感病品种根际积累的病原生物(镰孢霉Fusarium.sp.和大豆胞囊线虫Heterodera.glycines的胞囊数)明显高于抗病品种。说明大豆根系分泌物对微生物具有选择性的促进或抑制作用,不同大豆品种以及同一大豆品种在不同生育时期根系分泌物的组成和数量不同,从而使大豆根面及根际形成了特定的微生物区系组成。     

Rhizosphere effects on soil bacterial abundance and diversity in the Yellow River Deltaic ecosystem as influenced by petroleum contamination and soil salinization

In this study, we compared the differences of bacterial abundance and diversity between rhizosphere and surrounding bulk soils under soil salinization and petroleum contamination in the Yellow River Delta on a 110-km-distance scale. In comparison with bulk soils, rhizosphere soils were mainly characterized by lower salinity and higher water content in saline soils. For bacterial abundance, the numbers of total bacteria and hydrocarbon degraders were significantly higher in rhizosphere soils than those in bulk soils. Although there was no significant difference in total petroleum hydrocarbon (TPH) concentration between the two types of soils, TPH had distinctly different effects on bacterial abundance in rhizosphere and bulk soils. TPH concentration was the major determinant of total bacterial abundance and had positive effects on abundances of hydrocarbon degraders. However, the abundances of total bacteria and hydrocarbon degraders in bulk soils were primarily determined by soil salinity and water content. Great abundance of rhizosphere bacteria suggested that plant roots could alleviate the stresses from soil salinization and provide more favorable microhabitats for bacterial growth. TPH had positive effects on bacterial diversity of both rhizosphere and bulk soils. Our results support the view that petroleum in the environments functions as both toxic chemicals and carbon sources to soil bacteria. Great abundance and diversity of total bacteria in plant rhizospheres would potentially improve the roles of bacteria in maintaining ecosystem functioning in the degraded ecosystems. Our results would improve our understanding of the relationships between rhizosphere effects and multiple environmental stresses that control the development of bacterial community in fragile anthropologically-affected ecosystems.     

Rhizosphere microbial communities and organic acids secreted by aluminum-tolerant and aluminum-sensitive soybean in acid soil

This study aimed to investigate the correlation between organic acids secreted by two soybeans genotypes, BX10 [aluminum (Al) tolerant] and BD2 (Al sensitive) and rhizosphere microbial communities in acid soil. The organic acids secreted by BX10 and BD2 were significantly different at each growth stage. Both fungi/bacteria and gram-negative bacteria/gram-positive bacteria ratio values were affected by the two soybean genotypes at different growth periods. Compared with BD2, phospholipid fatty acid of BX10 showed higher Shannon diversity at the seedling and flowering stages, but had lower Shannon diversity at the pod-setting stage. Redundancy analysis and canonical correspondence analysis revealed that the organic acids including tartaric acid, lactic acid, and citric acid significantly affected rhizosphere bacterial communities. Sequence analysis indicated that uncultured Acidobacterium, Chloroflexi, and actinomycete enriched in BD2, whereas some uncultured bacteria enriched in BX10. The two soybean genotypes exhibit distinct rhizosphere microbial communities; root organic acid exudates may affect composition of microbial communities of rhizosphere soil: tartaric acid may negatively affect rhizosphere bacteria at the seedling stage, lactic acid may positively affect rhizosphere actinomycetes at the flowering stage, and succinic acid may stimulate fungi at the pod-setting stage.     

Effect of Capsicum annuum cultivated in sub-alkaline soil on bacterial community and activities of cultivable plant growth promoting bacteria under field conditions

In literature, it remains little explored the soil–plant relationships within Capsicum agroecosystem. We studied how chili peppers plants contribute to influence microbial diversity. Across the bulk and rhizosphere soils of three genotypes of Capsicum annuum, the structure, the diversity and the abundance of bacteria was evaluated by means of DNA-based culture-independent approach. Furthermore, 515 bacterial strains isolated from the bulk and rhizosphere soil, were used to investigate the effect of C. annuum on four plant growth promoting bacteria (PGPB) abilities. Our results indicated that the three genotypes influence differently the physical-chemical and microbial properties of soil around the roots. Bacterial abundance resulted in increasing with different trend rhizospheres to bulk soil ratio; however, bacterial diversity was significantly higher only in the rhizosphere of one genotype. Only the indolic compounds production was stimulated in the rhizosphere of the three cultivars. Inhibition of Fusarium oxysporum was stimulated just with one genotype, where 53 of rhizosphere isolates showed more than 10% of inhibition. 165 of isolates produced siderophores and the major part belonged to the high production level. Interactions between PGPB features revealed that anti-phytopathogenic activity was not associated with the others characteristics; however, phosphate solubilization was associated with both siderophores and indolic compounds productions.     

不同作物根际土壤微生物的群落结构特征分析

为探究根际微生物群在支持植物生长、发育和健康方面的重要作用,本研究在2017年7月采集同一农田中大豆[Glycine max (L.) Merr.]、玉米[Zea mays)、花生(Arachis hypogaea L.]、四季豆[Phaseolus vulgaris L.]、豇豆[Vigna unguiculata (L.) Walp]、番薯[Ipomoea batatas (L.) Lam.]和芋艿[Colocasia esculenta (L.) Schoot]7种不同作物,通过Illumina MiSeq测序技术和磷脂脂肪酸(PLFA)对这7种不同作物的根际微生物群落结构和组成进行了分析。结果显示,不同作物根际土壤微生物的PLFA种类和组成差异显著,但均以表征革兰氏阴性菌、革兰氏阳性菌和真菌的特征脂肪酸为主。花生根际土中微生物的PLFAs含量最高,花生根际土中的真菌细菌比(F/B)显著高于其他作物,且其革兰氏阳性菌与革兰氏阴性菌比(G⁺/G^-)最低。尽管在门水平,变形菌门、放线菌门、酸杆菌门和厚壁菌门是7种作物根际微生物的主要优势门,但是在纲水平和目水平不同作物根际微生物组成存在差异。Alpha多样性分析表明,大豆根际的OTU丰富度(Chao1,P<0.001)和细菌群落多样性(Shannon,P<0.001)在7种作物中最高。非度量多维尺度分析(NMDS)表明,根际微生物群落结构在OTU和PLFAs水平下均以不同作物形成聚类,不同聚类间的差异显著。根际敏感微生物的筛选和比较进一步说明不同作物对根际微生物的选择具有差异性,群落中某些特定菌群优势度存在区别,不同作物具有不同敏感微生物的选择倾向。本研究为构建健康的植物根际微生物群落以促进植物育种提供了基础。     

Rhizosphere microbiota assemblage associated with wild and cultivated soybeans grown in three types of soil suspensions

Soil microbial community composition is determined by the soil type and the plant species. By sequencing the V3-V4 region of the bacterial 16S rRNA gene amplicons, the current study assessed the bacterial community assemblage in rhizosphere and bulks soils of wild (Glycine soja) and cultivated (Glycine max) soybeans grown in the suspensions of three important soil types in China, including black, red and soda-saline-alkali soils. The alpha-diversity of the bacterial community in the rhizosphere was significantly higher than that of the bulk soils suggesting that bulk soil lacks plant nurturing effect under the current study conditions. Black and red soils were enriched with nitrifying and nitrogen-fixing bacteria but the soda-saline-alkali soil suspension had more denitrifying bacteria, which may reflect agronomic unsuitability of the latter. We also observed a high abundance of Bradyrhizobium and Pseudomonas, enriched cellulolytic bacteria, as well as a highly connected molecular ecological network in the G. soja rhizosphere soil. Taken all, the current study suggest that wild soybeans may have evolved to recruit beneficial microbes in its rhizosphere that can promote nutrients requisition, biostasis and disease-resistance, therefore ecologically more resilient than cultivated soybeans.     

黄河三角洲刺槐根际与非根际细菌结构及多样性

为精确分析黄河三角洲刺槐根际与非根际土壤细菌群落定殖情况,本研究采用高通量测序方法对刺槐根际与非根际土壤细菌结构及多样性进行了研究。研究表明,根际土壤细菌共有36门214属,非根际土壤细菌共有33门153属。变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)细菌丰度超过15%,是根际与非根际土壤中的优势菌落。根际与非根际土壤中酸杆菌门、硝化螺旋菌门(Nitrospirae)丰度差异显著。根际土壤中红游动菌属(Rhodoplanes)、溶杆菌属(Lysobacter)、热单胞菌属(Thermomonas)、链霉菌属(Streptomyces)及非根际土壤中红游动菌属、溶杆菌属、链霉菌属、Kaistobacter细菌丰度超过4%。根际土壤中固氮菌丰度显著高于非根际土壤,解磷、解钾细菌丰度差异不显著。根际与非根际土壤细菌Chao丰富度分别为2 054、2 376,差异显著。根际与非根际土壤细菌之间的权重(Weighted Unifrac)距离在0.12~0.25之间。综上所述,黄河三角洲刺槐根际与非根际土壤细菌结构具有一定差异,多样性差异显著。     

盐沼湿地中植物根围土壤细菌群落结构和多样性的16S rDNA分析

The structure and diversity of the bacterial communities in rhizosphere soils of native Phragmites australis and Scirpus rnariqueter and alien Spartina alterniflora in the Yangtze River Estuary were investigated by constructing 16S ribosomal DNA （rDNA） clone libraries. The bacterial diversity was quantified by placing the clones into operational taxonomic unit （OTU） groups at the level of sequence similarity of 〉 97%. Phylogenetic analysis of the resulting 398 clone sequences indicated a high diversity of bacteria in the rhizosphere soils of these plants. The members of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria of the phylum Proteobacteria were the most abundant in rhizobacteria. Chao 1 nonpaxametric diversity estimator coupled with the reciprocal of Simpson＇s index （l/D） was applied to sequence data obtained from each library to evaluate total sequence diversity and quantitatively compare the level of dominance. The results showed that Phragmites, Scirpus, and Spartina rhizosphere soils contained 200, 668, and 382 OTUs, respectively. The bacterial communities in the Spartina and Phragraites rhizosphere soils displayed species dominance revealed by 1/D, whereas the bacterial community in Scirpus rhizosphere soil had uniform distributions of species abundance. Overall, analysis of 16S rDNA clone libraries from the rhizosphere soils indicates that the changes in bacterial composition may occur concomitantly with the shift of species composition in plant communities.     

连作对再植枸杞根际细菌群落多样性和群落结构的影响研究

受枸杞道地产区土地资源等因素限制,连作障碍已成为影响枸杞产业发展的重要原因之一,导致严重的经济损失.研究连作条件下枸杞农田土壤生态系统微生物群落的演替规律对枸杞产业的可持续发展具有重要的理论意义.以宁夏银川市南梁农场连作多年的枸杞地为研究对象,利用Illumina MiSeq测序技术分析了连作对再植枸杞根际/非根际细菌群落的影响.结果表明,连作地显著抑制再植枸杞苗地径的增加,且其土壤pH较对照样地显著降低(p<0.05).测序结果证实,与对照样地相比,连作地再植枸杞根际土壤细菌物种数显著降低(p<0.05),细菌群落α多样性下降(p>0.05).主坐标分析表明,连作和对照样地间枸杞非根际细菌群落结构无明显差异,但连作显著改变再植枸杞根际细菌的群落结构.对细菌群落丰度的统计分析发现,连作地枸杞根际浮霉菌门、非根际假单胞菌门的相对丰度较对照样地显著降低(p<0.05).此外,冗余分析结果表明:枸杞园土壤pH和有效磷含量是影响枸杞非根际土壤细菌群落结构变化的主要因素,分别解释了41.8%和35.4%的群落结构变化(p<0.05),其他土壤因子无统计学意义,但土壤理化因子对再植枸杞根际细菌群落结构变化的影响均未达显著水平.这些结果证实连作能够显著抑制再植枸杞生长、影响再植枸杞根际细菌群落结构和多样性,干扰枸杞与土壤细菌群落间的互作关系.这些研究结果将为解析枸杞连作障碍机制提供理论基础.     

抗病性不同大豆品种根面及根际微生物区系的变化 Ⅱ.连作大豆(重茬)根面及根际微生物区系的变化

采用平板计数法测定了两个抗根腐病连作大豆品种生育期间根面和根际微生物区系动态变化。结果表明,两个品种大豆根面细菌随生育期增加呈递减趋势,品种间无差异。合丰25(H25)的根际细菌数量随生育期呈递减趋势,绥农10号(S10)根际细菌数量从三叶期到鼓粒初期不断增加,到成熟期又急剧减少。感病品种H25根瘤重明显低于抗病品种S10。H25根面真菌和镰孢霉总数在三叶期和成熟期均高于S10,苗期是根腐病的主要发病期。总之,在连作条件下,无论抗病品种还是感病品种大豆成熟期其根面和根际细菌减少,真菌和主要病原菌(镰孢霉Fusarium)都会大量富集,表明根系分泌物对根面和根际的微生物种群有选择性地促进或抑制作用。     

Bacterial communities in soybean rhizosphere in response to soil type, soybean genotype, and their growth stage

Three experiments were conducted in this study in order to investigate the impacts of soil type, soybean genotype, and the reproductive growth stage on bacterial communities in the soybean rhizosphere. Communities were evaluated by principal component analysis of denaturing gradient gel electrophoresis (DGGE) banding patterns and sequencing of partial 16S rDNA polymerase chain reaction (PCR) amplicons. A pot experiment analyzing three soybean genotypes grown in two different types of soil (Black soil and Dark Brown soil) indicated that soil type was the major factor in influencing the bacterial communities in the soybean rhizosphere, with a more significant effect observed in the Black soil samples than in the Dark Brown soil samples. A field experiment was conducted in Dark Brown soil using three soybean genotypes, and the results gleaned from both pot and field experiments indicated that bacterial communities in the soybean rhizosphere changed with growth stages, and higher number of DGGE bands observed in early reproductive growth stages, while surprisingly, a significant impact of genotype on the bacterial communities was not observed in these experiments. However, a plate culture experiment targeting the culturable bacterial communities detected a remarkable difference in the community structures of the rhizosphere between the two soybean genotypes, suggesting that a small portion of the total bacteria was influenced by genotype. Sequence analysis of DGGE bands indicated that bacterial phyla of Proteobacteria, Actinobacteria, Bacteroidetes, Nitrospirae, Firmicutes, Verrucomicrobia and Acidobacteria commonly inhabit the soybean rhizosphere.     

Density,metabolic activity,and identity of cultivable rhizosphere bacteria on Salix viminalis in disturbed arable and landfill soils

The objective of this study was to provide fundamental data for a subsequent selection of willow growth and soil remediation promoting bacterial strains. The rhizosphere of willows (Salix viminalis) was screened for cultivable bacteria with high enzymatic activity (proteolytic, pectolytic, cellulolytic, amylolytic) and production of siderophores at four test sites with broad spectrum of anthropogenic soil disturbance: sewage‐sludge application, impoverishment by unfavorable arable use, ash dumping, and household‐waste depositing. The density of bacteria in the rhizosphere ranged from 7.92 to 8.56 log₁₀ of colony‐forming units per gram dry weight of soil and varied in a site‐ and willow‐clone‐specific manner. Within the 240 bacterial strains, a high diversity of metabolic activities was observed but was rarely combined in one strain (1.2% having six and 5.8% having five out of seven metabolic activities, respectively). The majority of strains (79.2%) revealed just one or two metabolic activities. Most common was a combination of lipolytic, proteolytic activities, and siderophore production as found in 13.8% of the bacterial strains. The 50 strains with the highest metabolic activity belonged predominantly to the Gammaproteobacteria (66%), the others to Flavobacteria (18%), Betaproteobacteria (8%), Actinobacteria (4%), and Bacilli (4%). The highest portion of cultivable strains of rhizosphere bacteria with high metabolic activities belonged to the genera Pseudomonas, Serratia, and Flavobacterium. We hypothesize that these genera include strains that support willow growth and soil remediation. Therefore, the described strain collection from the rhizosphere of S. viminalis provides a valuable basis for a subsequent selection of these candidates for applications in improvement of site adaptation of plants or remediation of soils.     

间套作玉米对线辣椒根际土壤微生物生态特征的影响

采用常规稀释平板法、氯仿熏蒸法、BIOLOG GN微平板反应系统及种间根系分隔技术, 以线辣椒单作(SC)为试验对照, 研究了间套作处理[玉米/线辣椒套作+根部塑料膜分隔(ICP)、玉米/线辣椒套作+根部尼龙网分隔(ICM)、玉米/线辣椒套作根部无分隔(ICN)]对线辣椒根际土壤微生物生态特征的影响。结果表明: 整个线辣椒生育期内, 各套作处理线辣椒根际土壤微生物总数与细菌总数具有相同的变化趋势, ICN和ICM处理的真菌、细菌、放线菌数量和细菌/真菌(B/F)、放线菌/真菌(A/F)比值均大于ICP与SC处理。盛果期, ICN处理根际土壤微生物量碳和微生物量氮比同处理其他生育期增加14.2%~54.0%和10.6%~54.7%。各处理土壤微生物群落AWCD的变化随培养时间呈现明显的"S"型曲线。间套作玉米显著提高了线辣椒根际土壤微生物群落的Shannon-Wiener指数(P<0.05)、Simpson指数、种间相遇几率和McIntosh指数(P<0.05), 并改变了土壤微生物对单一碳源的利用能力。线辣椒根际土壤微生物的不同多样性指数分别与其生物学产量之间存在显著或极显著正相关。说明间套作改善了土壤微生态环境。     

Search of environmental descriptors to explain the variability of the bacterial diversity from maize rhizospheres across a regional scale

The regional scale variability of the bacterial community inhabiting the rhizosphere was studied with soil collected from maize fields located in the Santo Domingo Valley (SDV; Baja California Sur, Mexico), a semi-arid agricultural ecosystem of approximately 200 km². The bacterial community structure was visualized by single-strand conformation polymorphism (SSCP) profiles of PCR-amplified partial 16S rRNA genes of directly extracted rhizosphere soil DNA. SSCP profiles of different SDV sites and an external field site in Germany were evaluated for their similarities and the contributing bacteria were characterized by DNA sequence analyses. SSCP profiles from each site were significantly different from the others, as revealed by permutation of pairwise similarities (P < 0.05). In comparison to the German site, SSCP profiles from SDV were more similar to each other despite contrasting soil salinity levels. Correspondence analysis revealed that among SDV sites, salinity levels, soil organic carbon and calcium (Ca²⁺) were most influential on the bacterial community structure. Depending on the phylogenetic group analyzed (Bacteria, Alphaproteobacteria, Pseudomonas), the importance of these soil variables varied. Interestingly, the East–West direction also revealed an effect, suggesting that future explorations of bacterial diversity patterns should also consider landscape topography in search of explaining patterns of bacterial diversity in soils.     

Analysis of bacterial communities on alkaline phosphatase genes in soil supplied with organic matter

Abstract

We studied the effects of the application of organic matter (OM) and chemical fertilizer (CF) on soil alkaline phosphatase (ALP) activity and ALP-harboring bacterial communities in the rhizosphere and bulk soil in an experimental lettuce field in Hokkaido, Japan. The ALP activity was higher in soils with OM than in soils with CF, and activity was higher in the rhizosphere for OM than in the bulk soil. Biomass P and available P in the soil were positively related to the ALP activity of the soil. As a result, the P concentration of lettuce was higher in OM soil than in CF soil. We analyzed the ALP-harboring bacterial communities using polymerase chain reaction based denaturing gradient gel electrophoresis (DGGE) on the ALP genes. Numerous ALP genes were detected in the DGGE profile, regardless of sampling time, fertilizer treatment or sampled soil area, which indicated a large diversity in ALP-harboring bacteria in the soil. Several ALP gene fragments were closely related to the ALP genes of Mesorhizobium loti and Pseudomonas fluorescens. The community structures of the ALP-harboring bacteria were assessed using principal component analysis of the DGGE profiles. Fertilizer treatment and sampled soil area significantly affected the community structures of ALP-harboring bacteria. As the DGGE bands contributing to the principal component were different from sampling time, it is suggested that the major bacteria harboring the ALP gene shifted. Furthermore, there was, in part, a significant correlation between ALP activity and the community structure of the ALP-harboring bacteria. These results raise the possibility that different ALP-harboring bacteria release different amounts and/or activity of ALP, and that the structure of ALP-harboring bacterial communities may play a major role in determining overall soil ALP activity.     

利用Illumina高通量测序对复合重金属污染下根际和非根际稻田土壤细菌的研究

There is an increasing concern about rice (Oryza sativa L.) soil microbiomes under the influence of mixed heavy metal contamination.We used the high-throughput Illumina MiSeq sequencing approach to explore the bacterial diversity and community composition of soils in four paddy fields,exhibiting four degrees of mixed heavy metal (Cd,Pb and Zn) pollution,and examined the effects of these metals on the bacterial communities.Our results showed that up to 2 104 to 4 359 bacterial operational taxonomic units (OTUs) were found in the bulk and rhizosphere soils of the paddy fields,with the dominant bacterial phyla (greater than 1％ of the overall community) including Proteobacteria,Actinobacteria,Firmicutes,Acidobacteria,Gemmatimonadetes,Chloroflexi,Bacteroidetes and Nitrospirae.A number of rare and candidate bacterial groups were also detected,and Saprospirales,HOC36,SC-I-84 and Anaerospora were rarely detected in rice paddy soils.Venn diagram analysis showed that 174 bacterial OTUs were shared among the bulk soils with four pollution degrees.Rice rhizosphere soils displayed higher bacterial diversity indices (ACE and Chao 1) and more unique OTUs than bulk soils.Total Cd and Zn in the soils were significantly negatively correlated with ACE and Chao 1,respectively,and the Mantel test suggested that total Pb,total Zn,pH,total nitrogen and total phosphorus significantly affected the community structure.Overall,these results provided baseline data for the bacterial communities in bulk and rhizosphere soils of paddy fields contaminated with mixed heavy metals.     

转BADH基因大豆对盐碱土壤氮素转化的影响

以转甜菜碱醛脱氢酶(betaine aldehyde dehydrogenase)基因(BADH)大豆、非转基因亲本‘黑农35’、野生大豆、当地栽培种‘抗线王’、耐盐碱性较差品种‘合丰50’等5种大豆品种为材料,在典型盐碱土封闭种植,于大豆苗期、花荚期、鼓粒期和成熟期取根际土,采用经典方法测定氮素转化过程相关的细菌数量、生化功能及速效氮含量等指标的动态变化,为揭示转BADH基因大豆对土壤氮素转化的影响机制提供理论支持。结果表明:与非转基因亲本相比,转BADH基因大豆对苗期和花荚期根际土壤固氮菌数量有促进作用,但抑制苗期和花荚期根际土壤氨化细菌数量,对硝化细菌数量无显著性影响;显著促进成熟期大豆根际土壤固氮作用强度,对大豆苗期、花荚期和鼓粒期根际土壤氨化作用强度有显著抑制作用,显著促进各生育时期硝化作用强度;转BADH基因大豆苗期和花荚期根际土壤铵态氮含量显著降低,对鼓粒期根际土壤铵态氮含量无显著性影响,成熟期根际土壤铵态氮含量显著增高,大豆苗期、鼓粒期和成熟期根际土壤硝态氮含量显著升高,花荚期根际硝态氮含量显著降低。研究结果说明,转BADH基因大豆通过调节苗期、花期根际土壤氮素转化功能菌数量和生化过程强度进而影响氮素转化。     

Responses of soil microbial communities to manure and biochar in wheat cultivation of a rice-wheat rotation agroecosystem in East China

Soil contamination in agroecosystems remains a global environmental problem. Biochar has been suggested as an organic amendment to alleviate soil pollution, sequester carbon(C), and improve soil fertility. However, information on how bacterial and fungal communities in acidic bulk and rhizosphere soils respond to swine manure and its biochar is still lacking. In this study, biochar and swine manure were applied at two rates of 1.5 and 3 t ha^-1 in a rice-wheat rotation field to assess ...     

菌肥对青稞根际土壤理化性质以及微生物群落的影响

应用化学分析、聚合酶链反应-变性梯度凝胶电泳(PCR-DGGE)技术和DNA测序技术,研究了西藏棕色砂壤土中微生物肥料不同施用量和施用期对青稞根际土壤理化性质和细菌群落多样性的影响。结果表明,施用谷特菌肥能显著提高土壤全氮、全磷、全钾、有机质、碱解氮、有效磷和速效钾的水平,如播前施用菌肥浓度750 ml hm-2的处理较不施用菌肥的处理上述指标分别提高13.32%、28.42%、16.20%、9.81%、21.36%、39.35%和30.48%,拔节期施用菌肥浓度2 250 ml hm-2的处理较不施用菌肥的处理分别提高7.25%、29.35%、18.04%、12.86%、15.90%、43.27%和53.99%。DGGE分析表明,相同施用方式中不同施用量土样中微生物的DGGE图谱相似。非加权组平均法(UPGMA)聚类分析将DGGE图谱分为2大类群。Shannon-Wiener指数表明,施用菌肥的土壤细菌多样性先增加后逐渐降低,播前以喷施谷特菌浓度750 ml hm-2时的细菌多样性最高;拔节期则以喷施谷特菌浓度2 250 ml hm-2处理的细菌多样性最高,且两种施用方式土壤养分的释放与Shannon指数的变化规律均为播前﹥拔节期。测序结果表明,不同施肥浓度土样微生物种群分布较为广泛,其中Actinobacteria纲细菌种类略多,少数菌种为未经培养菌种(Uncultured bacterium)。典型对应分析(CCA)表明,DGGE图谱条带分布与土壤理化性质密切相关,碱解氮、全磷和全氮是影响微生物群落的主要环境因子。研究结果表明,施用谷特菌肥可明显改善青稞根际土壤理化性状,提高土壤细菌多样性。     

基于高通量测序的两种植被恢复类型根际土壤细菌多样性研究

为研究库布齐沙地生态恢复过程中不同植被恢复类型土壤微生物细菌群落结构、多样性的变化特征,以流动沙地为对照,运用高通量测序技术,对自然恢复的油蒿群落、人工种植的中间锦鸡儿群落根际和非根际土壤细菌多样性进行了研究,并分析了土壤理化性质对其分布的影响。结果表明:(1)与流沙对照相比,两种植被恢复类型对细菌多样性产生了正效应,细菌群落丰度、多样性和均匀度明显增加。其中,自然恢复的油蒿群落土壤细菌丰度高于人工种植的中间锦鸡儿群落;(2)变形菌门、酸杆菌门和放线菌门为研究区土壤中的优势细菌类群,其中变形菌门在各样地丰度比例最高,变形菌的4个亚群变化趋势一致,α-变形菌相对含量在油蒿和中间锦鸡儿群落根际土壤中明显增加,尤其是自然恢复的油蒿群落根际土壤中α-变形菌得到了很好的恢复;(3)土壤有机质、全氮、速效氮、速效钾含量和土壤含水量是影响土壤细菌群落丰度和多样性的主要土壤因子,典型相关分析表明土壤有机质、全氮、全钾、速效钾、速效氮含量对于研究区土壤细菌群落遗传多样性的变化起着重要作用。