Analysis of cultivable aerobic bacterial community composition and screening for facultative sulfate-reducing bacteria in marine corrosive steel

Anaerobic, aerobic, and facultative bacteria are all present in corrosive environments. However, as previous studies to address corrosion in the marine environment have largely focused on anaerobic bacteria, limited attention has been paid to the composition and function of aerobic and facultative bacteria in this process. For analysis in this study, ten samples were collected from rust layers on steel plates that had been immersed in seawater for diff erent periods (i.e., six months and eight years) at Sanya and Xiamen, China. The cultivable aerobic bacterial community structure as well as the number of sulfate-reducing bacteria (SRB) were analyzed in both cases, while the proportion of facultative SRB among the isolated aerobic bacteria in each sample was also evaluated using a novel approach. Bacterial abundance results show that the proportions are related to sea location and immersion time;abundances of culturable aerobic bacteria (CAB) and SRB from Sanya were greater in most corrosion samples than those from Xiamen, and abundances of both bacterial groups were greater in samples immersed for six months than for eight years. A total of 213 isolates were obtained from all samples in terms of CAB community composition, and a phylogenetic analysis revealed that the taxa comprised four phyla and 31 genera. Bacterial species composition is related to marine location;the results show that Firmicutes and Proteobacteria were the dominant phyla, accounting for 98.13% of the total, while Bacillus and Vibrio were the dominant genera, accounting for 53.06% of the total. An additional sixfacultative SRB strains were also screened from the isolates obtained and were found to encompass the genus Vibrio (four strains), Staphylococcus (one strain), and Photobacterium (one strain). It is noteworthy that mentions of Photobacterium species have so far been absent from the literature, both in terms of its membership of the SRB group and its relationship to corrosion.

The bacterial diversity and community composition altered in the oxygen minimum zone of the Tropical Western Pacific Ocean

The oxygen minimum zones(OMZs)are globally expanding,yet the variation pattern of microbial communities related to dissolved oxygen levels remain unclear.Spatial variability of bacterial diversity and community composition(repre sented by 16 S rRNA)of six stations was investigated within the water column in the seamount area of Tropical Western Pacific Ocean(TWPO)in May 2019.The seawater has dissolved oxygen(DO)concentration of 3.01-6.68 mg/L and the core of the oxygen minimum zones was located between the depths of 650 m and 1750 m.The bacterial alpha-diversity showed unimodal pattern with the decreasing DO with depths and peaked in the upper oxycline(UO)of OMZs.The bacterial community structure of the mixed layer(ML)and the bottom layer clustered and separated from each other,while those of UO and the OMZ core(OM)clustered and overlapped.Overall,bacterial community composition transitioned from being Alphaproteobacteria and Gammaproteobacteria-dominant in ML to being Gammaproteobacteria and Nitrososphaeria/Deltaproteobacteria-dominant in UO and OM,and then changed to being Clostridia and unidentified Actinobacteria-dominant in the bottom layer.Moreover,both bacterial alpha-diversity and the abundant classes fitted varying sectioned functions with DO.The DO solely explained 40.37%of the variation of bacterial community composition among layers(P<0.001).The predicted function profiling showed that the water column was predominant by chemoheterotrophy,cyanobacteria,and photoautotrophy in ML,by chemoheterotrophy and nitrate/sulfide cycling in UO and OM,and by chemoheterotrophy and ferme ntation in the bottom layer.Our findings revealed the DO-associated variation in bacterial diversity and community composition,and help to clarify the potential responses of microbes and their involved biogeochemical processes to the expansion and intensification of OMZs.

Soil fungistasis and its relations to soil microbial composition and diversity:A case study of a series of soils with different fungistasis

Fungistasis is one of the important approaches to control soil-borne plant pathogens.Some hypotheses about the mechanisms for soil fungistasis had been established,which mainly focused on the soil bacterial community composition,structure,diversity as well as function.In this study,the bacterial community composition and diversity of a series of soils treated by autoclaving,which coming from the same original soil sample and showing gradient fungistasis to the target soil-borne pathogen fungi Fusarium grami...

Inclusion of peanut in wheat–maize rotation increases wheat yield and net return and improves soil organic carbon pool by optimizing bacterial community

Improving soil quality while achieving higher productivity is the major challenge in the agricultural industry. Wheat(Triticum aestivum L.)–maize(Zea mays L.)(W–M) rotation is the dominant planting pattern in the Huang-HuaiHai Plain and is important for food security in China. However, the soil quality is deteriorating due to the W–M rotation’s long-term, intensive, and continuous cultivation. Introducing legumes into the W–M rotation system may be an effective way to improve soil quality. In this study, we aimed to verify this hypothesis by exploring efficient planting systems(wheat–peanut(Arachis hypogaea L.)(W–P) rotation and wheat rotated with maize and peanut intercropping(W–M/P)) to achieve higher agricultural production in the Huang-Huai-Hai Plain. Using traditional W–M rotation as the control, we evaluated crop productivity, net returns, soil microorganisms(SMs), and soil organic carbon(SOC) fractions for three consecutive years. The results indicated that wheat yields were significantly increased under W–P and W–M/P(382.5–579.0 and 179.8–513.1 kg ha-1, respectively) compared with W–M. W–P and W–M/P provided significantly higher net returns(58.2 and 70.4%, respectively) than W–M. W–M/P and W–M retained the SOC stock more efficiently than W–P, increasing by 25.46–31.03 and 14.47–27.64%, respectively, in the 0–20 cm soil layer. Compared with W–M, W–M/P improved labile carbon fractions;the sensitivity index of potentially mineralizable carbon, microbial biomass carbon(MBC), and dissolved organic carbon was 31.5, 96.5–157.2, and 17.8% in 20–40, 10–40, and 10–20 cm soil layers, respectively. The bacterial community composition and bacteria function were altered as per the soil depth and planting pattern. W–M/P and W–M exhibited similar bacterial community composition and function in 0–20 and 20–40 cm soil layers. Compared with W–P, a higher abundance of functional genes, namely, contains mobile elements and stress-tolerant, and a lower abundance of genes, namely,potentially pathogenic, were observed in the 10–20 cm soil layer of W–M and the 0–20 cm soil layer of W–M/P. SOC and MBC were the main factors affecting soil bacterial communities, positively correlated with Sphingomonadales and Gemmatimonadales and negatively correlated with Blastocatellales. Organic input was the main factor affecting SOC and SMs, which exhibited feedback effects on crop productivity. In summary, W–M/P improved productivity, net returns, and SOC pool compared with traditional W–M rotation systems, and it is recommended that plant–soil–microbial interactions be considered while designing high-yield cropping systems.

Effects of Tillage Depth on Nutrients and Microbial Communities in Tobacco-Planting Soil

The implementation of appropriate tillage practices is of great significance for agricultural production. However, the effects of different tillage depths on soil nutrients content and microbial communities in tobacco-planting soils are still lacking systematic research. In this study, three different tillage depths of 15 cm (T1), 20 cm (T2), and 30 cm (T3) were set up for field experiments in Liupanshui, Guizhou Province, to explore the effects of tillage depth on tobacco-planting soil nutrients and bacterial and fungal communities based on 16S rRNA and ITS sequencing and figure out the key factors affecting soil microbial communities. The results showed that T2 and T3 increased the contents of organic matter, total nitrogen, total phosphorus, available phosphorus, and available potassium in tobacco-planting soil, and increased the diversity of bacterial communities compared with T1. There was no significant difference in the structure of bacterial and fungal communities in different tillage depth treatments, but some dominant genera were significantly enriched in T2 and T3. Desulfobacter, Setophoma, Humicola, and Acremonium were significantly enriched in T2. Chthonomonas and Fusarium were significantly enriched in T3. These genera favor the decomposition of organic matter and the cycling of nutrients, and control soil pests and diseases. Redundancy analysis indicated that TP and AK were the key factors influencing the dominant genera of bacteria and fungi. This study provides a scientific basis for the selection of soil tillage depth for tobacco production in this region.

Conversion of pure Chinese fir plantation to multi-layered mixed plantation enhances the soil aggregate stability by regulating microbial communities in subtropical China

Background:Soil aggregates are the basic units of soil structure,and their stability is a key indicator of soil quality and capacity to support ecosystem functions.The impacts of various environmental factors on soil aggregates have been widely studied.However,there remains elusive knowledge on the synergistic effects of changing forest stand structure on soil aggregate stability(SAS),particularly in subtropical China where soil erosion remains a critical issue.Methods:We investigated variations in the components of soil humus(HS),including humic acids(HAs),fulvic acids(FAs),and humins(HMs),under pure Chinese fir(Cunninghamia lanceolata)plantation(PP)and multilayered mixed plantation(MP)comprising C.lanceolata,Castanopsis hystrix,and Michelia hedyosperma.The state of soil aggregate stability,was determined by three separate methods,i.e.,dry-sieving,wet-sieving,and the Le Bissonnais.High-throughput sequencing was used to determine the diversity and composition of microbial communities under PP and MP.We then built partial least squares path models(PLS-PM)for assessing the responses of SAS to the variations in soil microorganisms and HS components.Results:The MP stands had significantly greater SAS(P<0.05),higher content of HAs and more rapid organic matter humification within aggregates,than the PP stands.High-throughput sequencing confirmed that the Pielou andα-diversity index values(Chao1 and Shannon)for fungi were all significantly higher under MP than under PP,while no marked difference was found in bacterialα-diversity between the two plantation types.Moreover,there were markedly greater abundance of three bacterial phyla(Verrucomicrobia,Chloroflexi,and Gemmatimonadetes)and three fungal phyla(Ascomycota,Kickxellomycota,and Glomeromycota),and significantly less abundance of two bacterial phyla(Planctomycetes and Firmicutes)and four fungal phyla(Basidiomycota,Mortierellomycota,Mucoromycota,and Rozellomycota)under MP than under PP.The Chloroflexi and Ascomycota phyla appeared to be the primary drivers of soil aggregate distribution.Our findings revealed that the promotion of SAS under MP was mainly driven by increased soil organic matter(SOM)content,which altered bacterial communities and enhanced fungal diversity,thereby increasing HAs content and the rate of organic matter humification.Conclusions:Considering the combined effects of enhanced soil quality,productivity,and relevant economic costs,introducing broadleaved tree species into Chinese fir plantations can be an effective strategy for stabilizing soil structure against erosion in subtropical China.Our study elucidated the controls on variations of SAS in Chinese fir-dominated plantations and demonstrated the benefit of converting pure Chinese fir plantation to multi-layered mixed plantations in increasing soil structural stability and improving site quality.

Different mechanisms underlying divergent responses of autotrophic and heterotrophic respiration to long-term throughfall reduction in a warm-temperate oak forest

Background:There are many studies on disentangling the responses of autotrophic(AR)and heterotrophic(HR)respiration components of soil respiration(SR)to long-term drought,but few studies have focused on the mechanisms underlying its responses.Methods:To explore the impact of prolonged drought on AR and HR,we conducted the 2-year measurements on soil CO_(2) effluxes in the 7th and 8th year of manipulated throughfall reduction(TFR)in a warm-temperate oak forest.Results:Our results showed long-term TFR decreased HR,which was positively related to bacterial richness.More importantly,some bacterial taxa such as Novosphingobium and norank Acidimicrobiia,and fungal Leptobacillium were identified as major drivers of HR.In contrast,long-term TFR increased AR due to the increased fine root biomass and production.The increased AR accompanied by decreased HR appeared to counteract each other,and subsequently resulted in the unchanged SR under the TFR.Conclusions:Our study shows that HR and AR respond in the opposite directions to long-term TFR.Soil microorganisms and fine roots account for the respective mechanisms underlying the divergent responses of HR and AR to long-term TFR.This highlights the contrasting responses of AR and HR to prolonged drought should be taken into account when predicting soil CO_(2) effluxes under future droughts.

Disruption of bacterial balance in the gut of Portunus trituberculatus induced by Vibrio alginolyticus infection

A bstract Gut microbiota impacts the health of crustaceans. V ibrio alginolyticus is a main causative pathogen that induces the vibriosis in farmed swimming crabs, Portunus trituberculatus. However, it remains unknown whether gut bacteria perform functions during the progression of vibriosis. In this study, 16 SrRNA gene amplicon sequencing was used to investigate temporal alteration of gut bacterial community in swimming crabs in response to 72-h V. alginolyticus challenge. Our results show that V. alginolyticus infection resulted in dynamic changes of bacterial community composition in swimming crabs. Such changes were highlighted by the overwhelming overabundance of V ibrio and a significant fluctuation in the gut bacteria including the bacteria with high relative abundance and especially those with low relative abundance. These findings reveal that crab vibriosis gradually develops with the infection time of V. alginolyticus and tightly relates to the dysbiosis of gut bacterial community structure. This work contributes to our appreciation of the importance of the balance of gut bacterial community structure in maintaining the health of crustaceans.

Soil pH and dissolved organic carbon shape microbial communities in wetlands with two different vegetation types in Changdu area,Tibet

Soil microorganisms play pivotal roles in element biogeochemical cycling and ecological functions in wetland ecosystem,which may affect global climate change.Variations in biotic and abiotic factors are known to affect soil microbial diversity,community structure and the corresponding functions.However,the relative importance of these biotic and abiotic factors on wetland soil microbial diversity and community structure on the QinghaiTibet Plateau remains poorly understood.In this study,we explored soil bacterial and fungal diversity and composition of five wetlands under two vegetation types(herbs vs Hippophae thibetana)in Changdu area,Tibet,through Illumina high throughput sequencing analysis of 16S rRNA for bacteria and internal transcribed spacer(ITS)for fungi.Results showed that soil bacterial alpha diversity was higher in H.thibetana dominated wetlands and was significantly and positively correlated with soil pH.No difference was detected in the soil fungal alpha diversity among samples and between vegetation types.The dominant soil bacterial phyla were Proteobacteria,Actinobacteria,Acidobacteria,and Firmicutes.While Ascomycota,Basidiomycota and Mucoromycota were the dominant fungal phyla.Soil bacterial and fungal community structures were significantly distinct by vegetation types.In addition,redundancy analysis indicated that soil pH was the key factor shaping soil bacterial community structure.Nevertheless,soil p H showed no effect on fungal community.Instead,soil dissolved organic carbon was the major factor contributing to soil fungal community structure.This study emphasized that wetland soil microbial communities were distinct by vegetation types and the driving factors of microbial beta diversity between bacterial and fungal community were also different in wetlands in Changdu area.

The Effect of Organic Carbon on Soil Bacterial Diversity in an Antarctic Lake Region

This study assessed the effects of changes in organic carbon content on soil bacterial community composition and diversity in the Antarctic Fildes Peninsula.16 S rRNA gene sequencing was performed to investigate bacterial community composition.Firstly,we found that organic carbon(OrC)and nutrients showed an increasing trend in the lake area.Secondly,soil geochemistry changes affected microbial composition in the soil.Specifically,we found 3416 operational taxonomical units(OTUs)in 300 genera in five main phyla:Proteobacteria,Actinobacteria,Acidobacteria,Chloroflexi,and Bacteroidetes.Although the diversity was similar among the four sites,the composition was different.Among them,Hungateii content changed very significantly,from 16.67% to 33.33%.Canonical correspondence analysis showed that most measured geochemical factors were relevant in structuring microbiomes,and organic carbon concentration showed the highest correlation,followed by NO3^--N.Hungateii was significantly correlated with the content of organic carbon.Our finding suggested organic carbon played an important role in soil bacterial communities of the Antarctic coastal lake region.

Plant property regulates soil bacterial community structure under altered precipitation regimes in a semi-arid desert grassland, China

Variations of precipitation have great impacts on soil carbon cycle and decomposition of soil organic matter.Soil bacteria are crucial participants in regulating these ecological processes and vulnerable to altered precipitation.Studying the impacts of altered precipitation on soil bacterial community structure can provide a novel insight into the potential impacts of altered precipitation on soil carbon cycle and carbon storage of grassland.Therefore,soil bacterial community structure under a precipitation manipulation experiment was researched in a semi-arid desert grassland in Chinese Loess Plateau.Five precipitation levels,i.e.,control,reduced and increased precipitation by 40%and 20%,respectively(referred here as CK,DP40,DP20,IP40,and IP20)were set.The results showed that soil bacterial alpha diversity and rare bacteria significantly changed with altered precipitation,but the dominant bacteria and soil bacterial beta diversity did not change,which may be ascribed to the ecological strategy of soil bacteria.The linear discriminate analysis(LDA)effect size(LEfSe)method found that major response patterns of soil bacteria to altered precipitation were resource-limited and drought-tolerant populations.In addition,increasing precipitation greatly promoted inter-species competition,while decreasing precipitation highly facilitated inter-species cooperation.These changes in species interaction can promote different distribution ratios of bacterial populations under different precipitation conditions.In structural equation model(SEM)analysis,with changes in precipitation,plant growth characteristics were found to be drivers of soil bacterial community composition,while soil properties were not.In conclusion,our results indicated that in desert grassland ecosystem,the sensitive of soil rare bacteria to altered precipitation was stronger than that of dominant taxa,which may be related to the ecological strategy of bacteria,species interaction,and precipitation-induced variations of plant growth characteristics.

Strong partitioning of soil bacterial community composition and co-occurrence networks along a small-scale elevational gradient on Zijin Mountain

The elevational distributions of bacterial communities in natural mountain forests,especially along large elevational gradients,have been studied for many years.However,the distributional patterns that underlie variations in soil bacterial communities along small-scale elevational gradients in urban ecosystems are not yet well understood.Using Illumina MiSeq DNA sequencing,we surveyed soil bacterial communities at three elevations on Zijin Mountain in Nanjing City:the hilltop(300 m a.s.l.),the hillside(150 m a.s.l.),and the foot of the hill(0 m a.s.l.).The results showed that edaphic properties differed significantly with elevation.Bacterial community composition,rather than alpha diversity,strongly differed among the three elevations(Adonis:R2=0.12,P<0.01).Adonis and DistLM analyses demonstrated that bacterial community composition was highly correlated with soil pH,elevation,total nitrogen(TN),and dissolved organic carbon(DOC).The degree scores,betweenness centralities,and composition of keystone species were distinct among the elevations.These results demonstrate strong elevational partitioning in the distributions of soil bacterial communities along the gradient on Zijin Mountain.Soil pH and elevation together drove the smallscale elevational distribution of soil bacterial communities.This study broadens our understanding of distribution patterns and biotic co-occurrence associations of soil bacterial communities from large elevational gradients to short elevational gradients.

Bacterial community succession in response to dissolved organic matter released from live jellyfish

Jellyfish blooms have increased worldwide, and the outbreaks of jellyfish population not only affect the food web structures via voracious predation but also play an important role in the dynamics of nutrients and oxygen in planktonic food webs. However, it remains unclear whether specific carbon compounds released through jellyfish metabolic processes have the potential to shape bacterial community composition. Therefore, in this study, we aimed to investigate the compositional succession of the bacterioplankton community in response to the dissolved organic matter (DOM) released by the live Scyphomedusae Cyanea lamarckii and Chrysaora hysoscella collected from Helgoland Roads of the North Sea. The bacterial community was significantly stimulated by the DOM released form live jellyfish and different dominant phylotypes were observed for these two Scyphomedusae species. Furthermore, the bacterial community structures in the different DOM sources, jellyfish-incubated media, Kabeltonne seawater, and artificial seawater (DOM-free) were significantly different, as revealed by automated ribosomal intergenic spacer analysis fingerprints. Catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH) revealed a rapid species-specific shift in bacterial community composition. Gammaproteobacteria dominated the community instead of the Bacteroidetes community for C. lamarckii, whereas Gammaproteobacteria and Bacteroidetes dominated the community for C. hysoscella. The significant differences in the bacterial community composition and succession indicate that the components of the DOM released by jellyfish might differ with jellyfish species.

Soil bacterial and fungal community successions under the stress of chlorpyrifos application and molecular characterization of chlorpyrifos-degrading isolates using ERIC-PCR

Chlorpyrifos is a widely used insecticide in recent years,and it will produce adverse effects on soil when applied on crops or mixed with soil.In this study,nested polymerase chain reaction（PCR） and denaturing gradient gel electrophoresis（DGGE） were combined to explore the bacterial and fungal community successions in soil treated with 5 and 20 mg/kg of chlorpyrifos.Furthermore,isolates capable of efficiently decomposing chlorpyrifos were molecular-typed using enterobacterial repetitive intergenic consensus-PCR（ERIC-PCR）.Under the experimental conditions,degradation of chlorpyrifos in soil was interpreted with the first-order kinetics,and the half-lives of chlorpyrifos at 5 and 20 mg/kg doses were calculated to be 8.25 and 8.29 d,respectively.DGGE fingerprint and principal component analysis（PCA） indicated that the composition of the fungal community was obviously changed with the chlorpyrifos treatment,and that samples of chlorpyrifos treatment were significantly separated from those of the control from the beginning to the end.While for the bacterial community,chlorpyrifos-treated soil samples were apparently different in the first 30 d and recovered to a similar level of the control up until 60 d,and the distance in the PCA between the chlorpyrifos-treated samples and the control was getting shorter through time and was finally clustered into one group.Together,our results demonstrated that the application of chlorpyrifos could affect the fungal community structure in a quick and lasting way,while only affecting the bacterial community in a temporary way.Finally,nine typical ERIC types of chlorpyrifos-degrading isolates were screened.

酒精含量对快速发酵醉椒风味物质及微生物群落组成的影响研究

醉椒是以高酒精度白酒(30%以上)和辣椒为主要原料,低盐慢速发酵的西南特色鲜辣、低刺激调味品。其发酵周期长,且发酵原理、风味特征和微生物群落组成不明,制约品质和安全性控制。文章研究发现15%以上白酒(60%)显著抑制醉椒发酵过程,6%白酒发酵过快,酸味明显,质构变软;9%和12%为最适白酒添加范围,发酵30 d后pH稳定在3.5,总酸含量为13.93~15.92 g/kg,无酸味,无霉变,有清香味,咀嚼感良好;亚硝酸盐含量低于0.8 mg/kg,大肠菌群未检出。GC-MS结合16S rDNA、ITS高通量测序显示,真菌多样性高于细菌,克鲁维毕赤酵母、膜醭毕赤酵母、皱枝孢霉为优势真菌,黄曲霉、赭曲霉未检出,植物乳杆菌、肠膜明串珠菌为优势细菌;乳酸酯、萜类、糖醇、寡糖和鲜味氨基酸为醉椒特征风味物质。

Short-Term Effects of Experimental Warming and Precipitation Manipulation on Soil Microbial Biomass C and N, Community Substrate Utilization Patterns and Community Composition

Soil microorganisms are major drivers of soil carbon(C) cycling;however,the response of these microorganisms to climate change remains unclear.In the present study,we investigated how 18 months of multifactor climate treatments(warmed air temperature by 3℃ and decreased or increased precipitation manipulation by 30%) affected soil microbial biomass C and nitrogen(N),community substrate utilization patterns,and community composition.Decreased and increased precipitation significantly reduced microbial biomass C by 13.5% and 24.9% and microbial biomass N by 22.9% and 17.6% in unwarmed plots,respectively(P<0.01).Warming enhanced community substrate utilization by 89.8%,20.4%,and 141.4% in the natural,decreased,and increased precipitation plots,respectively.Particularly,warming significantly enhanced the utilization of amine and carboxylic acid substrates among all precipitation manipulation plots.Compared with the natural air temperature with natural precipitation treatment,other treatments affected fungal community richness by -0.9% to 33.6% and reduced the relative abundance of the dominant bacterial and fungal groups by 0.5% to 6.8% and 4.3% to 10.7%,respectively.The warming and/or precipitation manipulation treatments significantly altered Zygomycota abundance(P<0.05).Our results indicate that climate change drivers and their interactions may cause changes in soil microbial biomass C and N,community substrate utilization patterns,and community composition,particularly for the fungal community,and shifts in the microorganism community may further shape the ecosystems function.

Effects of flue gas desulfurization gypsum and clover planting on qualities of soil and winter jujube in coastal saline-alkali orchard of north China

Flue gas desulfurization gypsum and clover planting alleviated the soil salinization stress.Soil pH and total phosphorus affected the bacterial communi-ties.Total phosphorus affected the fungal communities.Flue gas desulfurization gypsum and clover planting improved jujube quality.The coastal area of Shandong Province,characterized by coastal saline tidal soil,is one of the main production areas of winter jujube in China.However,the low soil fertility and poor soil structure in jujube orchard restricted the development of the jujube industry.The objectives of this study were to 1)evaluate the effect of application of flue gas desulfurization(FGD)gypsum and clover planting on soil quality improvement and soil microbial community structure of jujube orchard;2)investigate the effects of two measures on the nutrition and quality of winter jujube.The results showed that FGD gypsum reduced the soil total salt content by 65.6%,and clover planting increased the soil organic matter content by 30.7%,which effectively alleviated the soil salinization stress and improved the soil structure.Soil pH and total phosphorus(TP)were the main determinants influencing bacterial community composition,and TP was the dominant factor of the fungal community composition in the saline-alkali soils.Meanwhile,FGD gypsum addition and clover planting significantly increased the sugar degree and Vc content of winter jujube,thus improved jujube quality,and further contributed to the ecological sustainable development of winter jujube industry.

Drying-rewetting cycles reduce bacterial diversity and carbon loss in soil on the Loess Plateau of China

With global climate change, soil drying-rewetting(DRW) events have intensified and occurred frequently on the Loess Plateau of China. However, the extent to which the DRW cycles with different wetting intensities and cycle numbers alter microbial community and respiration is barely understood. Here,indoor DRW one and four cycles treatments were implemented on soil samples obtained from the Loess Plateau, involving increase of soil moisture from10% water-holding capacity(WHC) to 60% and 90% WHC(i.e., 10%–60% and 10%–90% WHC, respectively). Constant soil moistures of 10%, 60%,and 90% WHC were used as the controls. The results showed that bacterial diversity and richness decreased and those of fungi remained unchanged under DRW treatments compared to the controls. Under all moisture levels, Actinobacteriota and Ascomycota were the most dominant bacterial and fungal phyla,respectively. The bacterial network was more complex than that of fungi, indicating that bacteria had a greater potential for interaction and niche sharing under DRW treatments. The pulse of respiration rate declined as the DRW cycle increased under 10%–60% WHC, but remained similar for different cycles under 10%–90% WHC. Moreover, the DRW treatments reduced the overall carbon loss, and the direct carbon release under 10%–60% WHC was larger than that under 10%–90% WHC. The cumulative CO_(2) emissions after four DRW cycles were significantly positively correlated with microbial biomass carbon and negatively correlated with fungal richness(Chao 1).

同步脱氮除磷系统中两种颜色好氧颗粒污泥的微生物群落特征

为研究同步脱氮除磷系统中出现的WG(白色好氧颗粒污泥)外形特点及微生物群落特征,探究其成因,利用SEM(扫描电子显微镜)表征了系统中的WG与YG(黄色好氧颗粒污泥)的微观形态,并采用Illumina Hi Seq 2500高通量测序平台对两种好氧颗粒污泥中细菌与真菌的群落组成进行研究.结果表明:WG结构疏松外形不规则,颗粒表面分布大量杆菌;而YG饱满紧实轮廓清晰,颗粒表面分布大量球菌.WG与YG的细菌群落组成相似,但真菌组成差异较大.与YG相比,WG具有更高的细菌和真菌多样性.变形菌门(Proteobacteria)和拟杆菌门(Bacteroidetes)为WG和YG中的细菌优势门,其在WG中的相对丰度分别为68.85%和26.61%,在YG中的相对丰度分别为82.52%和12.30%.Candidatus competibacter、Candidatus accumulibacter和Chiayiivirga为WG中的优势属,相对丰度分别为22.13%、8.95%和7.37%;Candidatus competibacter、Chiayiivirga和Xanthomonas为YG中的优势属,相对丰度分别为47.94%、6.95%和7.06%.子囊菌门(Ascomycota)和Rozellomycota分别为WG与YG中真菌优势门,其在两个样品中的相对丰度分别为50.10%和81.77%.在属水平,WG中存在大量青霉属(Penicillium)和假丝酵母属(Candida)等丝状真菌,为WG的形成提供了框架.研究显示,当YG破碎成为小菌胶团后,附着在真菌框架上,造成了WG的快速形成,同时WG中Candidatus competibacter的相对丰度较低,使其外形疏松、透光性较好,呈现出白色.

有机物料施用对潮土活性有机碳及微生物群落组成的影响

土壤活性有机碳是土壤中周转较快,对管理措施反应较为敏感的碳组分,但不同有机物料的影响效应及其微生物机制尚不清楚。比较小麦-玉米轮作条件下,麦季秸秆还田(R)和木本泥炭(MT)连续施用2年对玉米收获期潮土可矿化有机碳(PCM)、微生物生物量碳(MBC)、可溶性有机碳(DOC)、易氧化有机碳(ROC)、颗粒有机碳(POC)的影响,评估其与细菌和真菌群落组成之间的关系。结果表明:与不施用任何有机物料的CK相比,R处理及秸秆和木本泥炭联合施用(RMT)的DOC含量分别显著增加30.33%和31.46%;MT和RMT处理的POC含量分别显著增加104.86%和64.78%;而PCM、MBC、ROC在处理之间无显著变化。高通量测序发现,4个处理之间的细菌群落组成无显著变化,而真菌发生显著变化,并主要受制于POC、DOC、NH_(4)^(+)-N变化。相关性分析发现,DOC和POC均与转化酶活性显著正相关。DOC和转化酶均在R处理中显著增加,与Trichoderma peltatum和Trichoderma aerugineum丰度显著正相关;DOC同时与能促进根系分泌物生成的Pyrenochaeta unidentified丰度显著正相关,它在RMT处理中显著增加。POC和转化酶均与Cladorrhinum flexuosum和Basidiobolus ranarum显著负相关,该俩微生物在MT处理中显著降低,而在RMT中仅Cladorrhinum flexuosum显著降低;POC和转化酶均与Chaetothyriales unidentified显著正相关,它们在RMT处理中显著升高。施用秸秆或木本泥炭分别改变了潮土不同活性有机碳的含量,可能是因为两种有机物料施用分别产生了不同的真菌群落组成,进而改变了功能微生物丰度及相关酶活性。