Different genotypes regulate the microbial community structure in the soybean rhizosphere

The soybean rhizosphere has a specific microbial community,but the differences in microbial community structure between different soybean genotypes have not been explained.The present study analyzed the structure of the rhizosphere microbial community in three soybean genotypes.Differences in rhizosphere microbial communities between different soybean genotypes were verified using diversity testing and community composition,and each genotype had a specific rhizosphere microbial community composition.Co-occurrence network analysis found that different genotype plant hosts had different rhizosphere microbial networks.The relationship between rhizobia and rhizosphere microorganisms in the network also exhibited significant differences between different genotype plant hosts.The ecological function prediction found that different genotypes of soybean recruited the specific rhizosphere microbial community.These results demonstrated that soybean genotype regulated rhizosphere microbial community structure differences.The study provides a reference and theoretical support for developing soybean microbial inoculum in the future.

Characterization of the microbial community response to replant diseases in peach orchards

This study attempted to monitor the development of microbial communities and reveal the correlation between the soil microbial community and soil nutrient factors over different years following the replanting of peach trees.The replanted soil(RS)and nonreplanted soil(NRS)were collected from peach orchards with different growth years(1,3,5,7,9,11,and 13 years)in the same region.The soil bacterial and fungal community diversities were analyzed by high-throughput sequencing technology.Redundancy analysis(RDA)was used to show the correlation between the soil microbial community and environmental variables.The alpha diversities of the bacterial and fungal communities indicated that RS contained a higher abundance of bacterial and fungal operational taxonomic units(OTUs)than NRS.NMDS and ANOSIM analyses showed that the soil bacterial and fungal communities were significantly(P<0.01)affected by planting years,and that the main changes occurred in the first and ninth planting years.The presence of the bacterial orders Sphingobacteriales,Burkholderiales and Actinomycetales changed significantly after replanting.Some bacteria associated with bioremediation,such as Burkholderiales and Intrasporangiaceae,and some harmful pathogens,such as Penicillium and Ophiostomatales,significantly increased after replanting(LDA score>3.0).In addition,the soil nutrient contents were lower in RS than in NRS in the early stage(1–5 years),and the RDA showed that bacterial and fungal phyla are closely associated with environmental variables,including the potential of hydrogen(pH),ammonium nitrogen(AN),available phosphorus(AP)and available potassium(AK).These results lead to a deeper understanding of the microbial responses to replanting in peach orchards.

Effects of nitrogen and phosphorus additions on soil microbial community structure and ecological processes in the farmland of Chinese Loess Plateau

Microorganisms regulate the responses of terrestrial ecosystems to anthropogenic nutrient inputs.The escalation of anthropogenic activities has resulted in a rise in the primary terrestrial constraining elements,namely nitrogen(N)and phosphorus(P).Nevertheless,the specific mechanisms governing the influence of soil microbial community structure and ecological processes in ecologically vulnerable and delicate semi-arid loess agroecosystems remain inadequately understood.Therefore,we explored the effects of different N and P additions on soil microbial community structure and its associated ecological processes in the farmland of Chinese Loess Plateau based on a 36-a long-term experiment.Nine fertilization treatments with complete interactions of high,medium,and low N and P gradients were set up.Soil physical and chemical properties,along with the microbial community structure were measured in this study.Additionally,relevant ecological processes such as microbial biomass,respiration,N mineralization,and enzyme activity were quantified.To elucidate the relationships between these variables,we examined correlation-mediated processes using statistical techniques,including redundancy analysis(RDA)and structural equation modeling(SEM).The results showed that the addition of N alone had a detrimental effect on soil microbial biomass,mineralized N accumulation,andβ-1,4-glucosidase activity.Conversely,the addition of P exhibited an opposing effect,leading to positive influences on these soil parameters.The interactive addition of N and P significantly changed the microbial community structure,increasing microbial activity(microbial biomass and soil respiration),but decreasing the accumulation of mineralized N.Among them,N24P12 treatment showed the greatest increase in the soil nutrient content and respiration.N12P12 treatment increased the overall enzyme activity and total phospholipid fatty acid(PLFA)content by 70.93%.N and P nutrient contents of the soil dominate the microbial community structure and the corresponding changes in hydrolytic enzymes.Soil microbial biomass,respiration,and overall enzyme activity are driven by mineralized N.Our study provides a theoretical basis for exploring energy conversion processes of soil microbial community and environmental sustainability under long-term N and P additions in semi-arid loess areas.

Effects of heavy metals on soil microbial community of different land use types

To evaluate soil environmental quality of introduced new crops and other traditional crops,and to understand the importance of response of soil microbial community to heavy metal stress,rhizosphere soil samples of different land use types(Sphagnum farming,rice field,grassland and bare land) in Dading Village,Duyun City,Guizhou Province of China were selected as research objects.The differences of soil chemical properties,heavy metal concentration and microbial community among different land use types were compared.The abundance and structural diversity of microbial communities in soil samples were analyzed by 16S rDNA sequencing,the relationship between soil pollution characteristics and microbial community in farmland was studied.The results showed that the different land use types planting different agricultural products under the same growing environment were subject to different heavy metal pollution.Soil chemical properties and heavy metals had significant effects on the soil microbial community.Proteobacteria,Actinobacteriota and Acidobacteriota were the most dominant groups of bacteria.The soil microorganisms responded more actively to the variability of pH,SOM and AK contents,although the variability was not high.With the increase of pH value,the abundance of the dominant species Proteobacteria also increased.Verrucomicrobiota had a better tolerance to the heavy metal Hg.Verrucomicrobiota and Firmicutes had strong resistance to the heavy metal Cd.These results deepen our understanding of the changes and aggregation of microorganisms under different land use patterns in heavy-metal contaminated farmland soils.

Effects of Different Chinese Hickory Husk Returning Modes on Soil Nutrition and Microbial Community in Acid Forest Soil

Chinese hickory(Carya cathayensis Sarg.)is an important economic forest in Southeastern China.A large amount of hickory husk waste is generated every year but with a low proportion of returning.Meanwhile,intensive management has resulted in soil degradation of Chinese hickory plantations.This study aims to investigate the effects of three Chinese hickory husk returning modes on soil amendment,including soil acidity,soil nutrition,and microbial community.The field experiment carried out four treatments:control(CK),hickory husk mulching(HM),hickory husk biochar(BC),and hickory husk organic fertilizer(OF).The phospholipid fatty acid(PLFA)biomarker method was employed to determine the soil microbial community.After one year of treatment,the results showed that:(i)HM and BC significantly increased soil pH by 0.33 and 1.71 units,respectively;(ii)HM,BC and OF treatments significantly increased the soil organic carbon,alkaline nitrogen,available phosphorous,and available potassium.The OF treatment demonstrated the most significant improvement in the soil nutrient;(iii)The soil microbial biomass significantly increased in the HM,BC and OF treatments,and all microbial groups showed an increasing trend.HM treatment increased the fungal/bacterial ratio(F/B).The OF treatment significantly decreased the Shannon-Wiener diversity(H’)and evenness index(J)of the microbial community(P<0.05).Considering the treatments effects,costs,and ease of operation,our recommended returning modes of Chinese hickory husk are mulching and organic fertilizer produced by composting with manure.

Effects of Sweet Potato Rotation and Intercropping on the Microbial Community of Rhizosphere Soil

To reveal the response mechanism of soil microbial community in different planting systems of sweet potato,the effects of rotation and intercropping on microbial community structure and carbon source utilization capacities of sweet potato rhizosphere soil were studied by using phospholipid fatty acid(PLFA)and ecological board(BIOLOG ECO)through field positioning experiments.In this study,three treatments were sweet potato continuous cropping,sweet potato-wheat rotation,and sweet potato-corn intercropping.The main results showed that compared with the sweet potato continuous cropping treatment,sweet potato rotation and intercropping changed the PLFA biomass of soil microorganisms;the contents of bacteria increased by 21.82%and 38.77%,respectively(P<0.05);the contents of actinomycetes increased by 6.98%and 12.77%,and the biomass of Gram-positive bacteria increased by 28.60%and 63.44%,respectively;and the biomass of Gram-negative bacteria increased by 18.21%and 22.29%,and the fungal contents decreased by 16.60%and 13.03%,respectively.With the extension of culture time,the average well color development(AWCD value)of sweet potato-corn intercropping was significantly higher than other two treatments.The utilization capacities of carboxylic acid compounds,polymers,carbohydrates,amino acids,and amines in the sweet potato-corn intercropping treatment were significantly increased by 17.28%,14.67%,54.17%,36.62%,and 20.00%,respectively,compared with the sweet potato continuous cropping treatment.The results of the multivariate analysis(RDA)showed that the changes of soil microbial community structure and functional diversity were controlled by many factors,and the soil available potassium and total nitrogen were the main driving factors.However,sweet potato-wheat rotation and sweet potato-corn intercropping could optimize the soil microbial community structure and enhance the microbial functional diversity,and the effect of sweet potato-corn intercropping treatment was better.

Effects of Bamboo Charcoal-based Biochar on Soil Enzyme Activity and Microbial Community Structure

[Objectives]This study was conducted to reveal the effects of bamboo charcoal-based biochar(or bamboo charcoal for short)on soil enzyme activity and microbial community structure.[Methods]The field experiment was carried out at the Modern Agriculture Demonstration Base of Gaoping Village,Gaoping Town,Suichang County,Zhejiang Province.Bamboo charcoal was applied at four different levels:T_(0)(no bamboo charcoal),T_(1)(1125 kg/hm^(2)bamboo charcoal),T_(2)(2250 kg/hm^(2)bamboo charcoal)and T_(3)(3375 kg/hm^(2)bamboo charcoal).Soil physicochemical properties and enzyme activities in different treatments were measured.[Results]The soil fungal,bacterial and actinomycete populations increased significantly in the soils surrounding capsicum roots.The bacterial population,fungal population and fungus/bacterium ratio peaked in Treatment T_(2),up to 7.32×10^(6)cfu/g,2.65×10^(4)cfu/g and 0.36×10^(-2),respectively.The effect of bamboo charcoal in promotingβ-glucoside,catalase,acid phosphatase and sucrase activities was T_(2)>T_(3)>T_(1)>T_(0).With bamboo charcoal increasing,the bacterium population,fungus population,fungus/bacterium ratio,β-glucoside,catalase,acid phosphatase and sucrase activities all increased at first and then decreased.T_(2)treatment showed the best effects in improving soil physicochemical properties and microbial community structure.[Conclusions]Bamboo charcoal significantly improves soil enzyme activity and increases soil microbial population,and thus has important positive effects on the soil ecosystem.

Inuence of oxytetracycline on the structure and activity of microbial community in wheat rhizosphere soil

The microbial community composition in wheat rhizosphere was analyzed by detecting colony forming units （CFUs） in agar plates. The total CFUs in rhizosphere were 1.04×10^9/g soil with 9.0×10^8/g bacteria, 1.37×10^8/g actinomyces and 3.6×10^6/g fungi. The 10 dominant bacteria were isolated from wheat rhizosphere and were grouped into genus Bacillus according to their full length 16S rRNA gene sequences. Although belonging to the same genus, the isolated strains exhibited different sensitivities to oxytetracycline. When a series of the rhizosphere soil was exposed under various concentrations of oxytetracycline, the microbial community structure was highly affected with significant decline of CFUs of bacteria and actinomyces （22.2% and 31.7% at 10 mg/kg antibiotic, respectively）. This inhibition was clearly enhanced with the increase exposure dosage of antibiotic and could not be eliminated during 30 d incubation. There was no obvious influence of this treatment on fungi population. Among the four soil enzymes （alkaline phosphatase, acidic phosphatase, dehydrogenase and urease）, only alkaline phospbatase was sensitive to oxytetracycline exposure with 41.3% decline of the enzyme activity at 10 mg/kg antibiotic and further decrease of 64.3%-80.8% when the dosage over 30 mg/kg.

Soil enzymatic activities and microbial community structure with different application rates of Cd and Pb

This study focused on the changes of soil microbial diversity and potential inhibitory effects of heavy metals on soil enzymatic activities at different application rates of Cd and/or Pb. The soil used for experiments was collected from Beijing and classified as endoaquepts. Pots containing 500 g of the soil with different Cd and/or Pb application rates were incubated for a period of 0, 2, 9, 12 weeks in a glasshouse and the soil samples were analyzed for individual enzymes, including catalase, alkaline phosphatase and dehydrogenase, and the changes of microbial community structure. Results showed that heavy metals slightly inhibited the enzymatic activities in all the samples spiked with heavy metals. The extent of inhibition increased significantly with increasing level of heavy metals, and varied with the incubation periods. The soil bacterial community structure, as determined by polymerase chain reaction- denaturing gradient gel electrophoresis techniques, was different in the contaminated samples as compared to the control. The highest community change was observed in the samples amended with high level of Cd. Positive correlations were observed among the three enzymatic activities, but negative correlations were found between the amounts of the heavy metals and the enzymatic activities.

Effect of cypermethrin insecticide on the microbial community in cucumber phyllosphere

Cucumber (Cucumis sativus) is one of the most widely used vegetable in the world,and different pesticides have been extensively used for controlling the insects and disease pathogens of this plant.However,little is known about how the pesticides affect the microbial community in cucumber phyllosphere.This study was the first attempt to assess the impact of pyrethroid insecticide cyperemethrin on the microbial communities of cucumber phyllosphere using biochemical and genetic approaches.Phospholipid fatty ac...

Process of rice straw degradation and dynamic trend of pH by the microbial community MC1

The process of the rice straw degradation in the fermentor with aeration at 290 ml/h was studied. The results of dissolved oxygen （DO） indicated that the optimum DO during cellulose degradation by microbial community MC1 ranged from 0.01 to 0.12 mg/L. The change model ofpH values was as follows： irrespective of the initial pH of the medium, pH values decreased rapidly to approximate 6.0 after being inoculated within 48 h when cellulose was strongly degraded, and then increased slowly to 8.0--9.0 until cellulose was degraded completely. During the degradation process, 15 kinds of organic compounds were checked out by GC-MS. Most of them were organic acids. Quantity analysis was carried out, and the maximum content compound was ethyl acetate which reached 13.56 g/L on the day 4. The cellulose degradation quantity and ratio analyses showed that less quantity （under batch fermentation conditions） and longer interval （under semi-fermentation conditions） of rice straw added to fermentation system were contributed to matching the change model of pH, and increasing the quantity and ratio of rice straw degradation during cellulose degrading process. The highest degradation ratio was observed under the condition office straw added one time every five days （under semi-fermentation conditions）.

Comparative study of microbial community structure in different filter media of constructed wetland

Comparisons of microbial community structure, in eight filter media of zeolites, anthracite, shale, vermiculite, ceramic filter media, gravel, steel slag and bio-ceramic, were undertaken by analyzing the phospholipid fatty acid （PLFA） composition. A total of 20 fatty acids in the range of C18to C20 were determined but only 13 PLFAs were detected in steel slag. They consist of saturated fatty acids, branched fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids. The variation of fatty acids was revealed in the relative proportions of these fatty acids in different media. The aerobic prokaryotes were the predominant group in all media. The PLFA composition showed significant differences among the eight different media by Tukey＇s honestly test. It was found that steel slag was significantly different in the microbial community as compared to other filter media, probably due to its alkaline effluent. Steel slag alone is probably not a good choice of substratum in constructed wetlands. The principle components analysis （PCA） showed that zeolites, bio-ceramic, shale and vermiculite had a similar microbial community structure while steel slag and ceramic filter media were distinct from other media.

Effect of Different Vegetation Types on the Rhizosphere Soil Microbial Community Structure in the Loess Plateau of China

The Loess Plateau in China is one of the most eroded areas in the world. Accordingly, vegetation restoration has been implemented in this area over the past two decades to remedy the soil degradation problem. Understanding the microbial community structure is essential for the sustainability of ecosystems and for the reclamation of degraded arable land. This study aimed to determine the effect of different vegetation types on microbial processes and community structure in rhizosphere soils in the Loess Plateau. The six vegetation types were as follows：two natural grassland （Artemisia capillaries and Heteropappus altaicus）, two artificial grassland （Astragalus adsurgens and Panicum virgatum）, and two artificial shrubland （Caragana korshinskii and Hippophae rhamnoides） species. The microbial community structure and functional diversity were examined by analyzing the phospholipid fatty acids （PLFAs） and community-level physiological profiles. The results showed that rhizosphere soil sampled from the H. altaicus and A. capillaries plots had the highest values of microbial biomass C, average well color development of carbon resources, Gram-negative （G-） bacterial PLFA, bacterial PLFA, total PLFA, Shannon richness, and Shannon evenness, as well as the lowest metabolic quotient. Soil sampled from the H. rhamnoides plots had the highest metabolic quotient and Gram-positive （G＋） bacterial PLFA, and soil sampled from the A. adsurgens and A. capillaries plots had the highest fungal PLFA and fungal：bacterial PLFA ratio. Correlation analysis indicated a signiifcant positive relationship among the microbial biomass C, G- bacterial PLFA, bacterial PLFA, and total PLFA. In conclusion, plant species under arid climatic conditions signiifcantly affected the microbial community structure in rhizosphere soil. Among the studied plants, natural grassland species generated the most favorable microbial conditions.

Changes in Transformation of Soil Organic C and Functional Diversity of Soil Microbial Community Under Different Land Uses

Changes in soil biological and biochemical properties under different land uses in the subtropical region of China were investigated in order to develop rational cultivation and fertilization management. A small watershed of subtropical region of China was selected for this study. Land uses covered paddy fields, vegetable farming, fruit trees, upland crops, bamboo stands, and forestry. Soil biological and biochemical properties included soil organic C and nutrient contents, mineralization of soil organic C, and soil microbial biomass and community functional diversity. Soil organic C and total N contents, microbial biomass C and N, and respiration intensity under different land uses were changed in the following order： paddy fields （and vegetable farming） 〉 bamboo stands 〉 fruit trccs （and upland）. The top surface （0-15 cm） paddy fields （and vegetable farming） were 76.4 and 80.8% higher in soil organic C and total N contents than fruit trees （and upland） soils, respectively. Subsurface paddy soils （15-30 cm） were 59.8 and 67.3% higher in organic C and total N than upland soils, respectively. Soil microbial C, N and respiration intensity in paddy soils （0-15 cm） were 6.36, 3.63 and 3.20 times those in fruit tree （and upland） soils respectively. Soil microbial metabolic quotient was in the order： fruit trees （and upland） 〉 forestry 〉 paddy fields. Metabolic quotient in paddy soils was only 47.7% of that in fruit tree （and upland） soils. Rates of soil organic C mineralization during incubation changed in the order： paddy fields 〉 bamboo stands 〉 fruit trees （and upland） and soil bacteria population： paddy fields 〉 fruit trees （and upland） 〉 forestry. No significant difference was found for fungi and actinomycetes populations. BIOLOG analysis indicated a changing order of paddy fields 〉 fruit trees （and upland） 〉 forestry in values of the average well cell development （AWCD） and functional diversity indexes of microbial community. Results also showed that the conversion from paddy fields to vegetable farming for 5 years resulted in a dramatic increase in soil available phosphorus content while insignificant changes in soil organic C and total N content due to a large inputs of phosphate fertilizers. This conversion caused 53, 41.5, and 41.3% decreases in soil microbial biomass C, N, and respiration intensity, respectively, while 23.6% increase in metabolic quotient and a decrease in soil organic C mineralization rate. Moreover, soil bacteria and actinomycetes populations were increased slightly, while fungi population increased dramatically. Functional diversity indexes of soil microbial community decreased significantly. It was concluded that land uses in the subtropical region of China strongly affected soil biological and biochemical properties. Soil organic C and nutrient contents, mineralization of organic C and functional diversity of microbial community in paddy fields were higher than those in upland and forestry. Overuse of chemical fertilizers in paddy fields with high fertility might degrade soil biological properties and biochemical function, resulting in deterioration of soil biological quality.

Changes in soil microbial community structure associated with two types of genetically engineered plants analyzing by PLFA

With the rapid expansion of GEPs(genetically engineered plants), people are more and more concerned about the ecological risks brought by their release. Assessing the effect of GEPs on soil microbial ecology is indispensable to study their ecological risks. In our study, the phospholipids fatty acid(PLFA) method was used to analyze the microbial community of soil samples collected from fields with two types of GEPs_Bt transgenic corn and PVY(potato virus Y) cell protein gene transgenic potato. The principal components analysis(PCA) showed all controls were on the right of related GEPs samples along the PC1 (the first principal component) axis, which means a decrease of fungi in soils with genetically engineered crop since most of PLFAs that are strongly positively correlated with PC1 represent fungi. For samples collected from Bt transgenic cornfield, the ratios of gram_positive to gram_negative bacteria were less than those of controls. For samples of transgenic potato field, these ratios were lower than those of controls when soils were collected from deep layer(20—40 cm), but were higher when soils collected from surface layer(0—20 cm). For soils collected from 0—20 cm, the ratios of fungi to bacteria for all GEPs samples were at the same level. So were such rations for all controls. Changes of soil microbial community in two types of GEPs fields were detected in our study, but the causes and more information still needs further study.

Phosphorus utilization and microbial community in response to lead/iron addition to a waterlogged soil

Constructed wetlands have emerged as a viable option for helping to solve a wide range of water quality problems. However, heavy metals adsorbed by substrates would decrease the growth of plants, impair the functions of wetlands and eventually result in a failure of contaminant removal. Typha latifolia L., tolerant to heavy metals, has been widely used for phytoremediation of Pb/Zn mine tailings under waterlogged conditions. This study examined effects of iron as ferrous sulfate （100 and 500 mg/kg） and lead as lead nitrate （0, 100, 500 and 1000 mg/kg） on phosphorus utilization and microbial community structure in a constructed wetland. Wetland plants （T. latifolia） were grown for 8 weeks in rhizobags filled with a paddy soil under waterlogged conditions. The results showed that both the amount of iron plaque on the roots and phosphorus adsorbed on the plaque decreased with the amount of lead addition. When the ratio of added iron to lead was 1：1, phosphorus utilized by plants was the maximum. Total amount of phospholipids fatty acids （PLFAs） was 23%-59% higher in the rhizosphere soil than in bulk soil. The relative abundance of Gram-negative bacteria, aerobic bacteria, and methane oxidizing bacteria was also higher in the rhizosphere soil than in bulk soil, but opposite was observed for other bacteria and fungi. Based on cluster analysis, microbial communities were mostly controlled by the addition of ferrous sulfate and lead nitrate in rhizosphere and bulk soil, respectively.

Intestinal Microbial Community Differs between Acute Pancreatitis Patients and Healthy Volunteers

A case control study including 45 acute pancreatitis and 44 healthy volunteers was performed to investigate the association between intestinal microbial community and acute pancreatitis. High-throughput 16S r RNA gene amplicon sequencing was used to profile the microbiological composition of the samples. In total, 27 microbial phyla were detected and the samples of pancreatitis patients contained fewer phyla. Samples from acute pancreatitis patients contained more Bacteroidetes and Proteobacteria and fewer Firmicutes and Actinobacteria than those from healthy volunteers. PCo A analyses distinguished the fecal microbial communities of acute pancreatitis patients from those of healthy volunteers. The intestinal microbes of acute pancreatitis patients are different from those of healthy volunteers. Modulation of the intestinal microbiome may serve as an alternative strategy for treating acute pancreatitis.

Effects of a decade of organic fertilizer substitution on vegetable yield and soil phosphorus pools, phosphatase activities, and the microbial community in a greenhouse vegetable production system

Partial substitution of chemical fertilizers by organic amendments is adopted widely for promoting the availability of soil phosphorus(P)in agricultural production.However,few studies have comprehensively evaluated the effects of longterm organic substitution on soil P availability and microbial activity in greenhouse vegetable fields.A 10-year(2009–2019)field experiment was carried out to investigate the impacts of organic fertilizer substitution on soil P pools,phosphatase activities and the microbial community,and identify factors that regulate these soil P transformation characteristics.Four treatments included 100%chemical N fertilizer(4 CN),50%substitution of chemical N by manure(2 CN+2 MN),straw(2 CN+2 SN),and combined manure with straw(2 CN+1 MN+1 SN).Compared with the 4 CN treatment,organic substitution treatments increased celery and tomato yields by 6.9-13.8%and 8.6-18.1%,respectively,with the highest yields being in the 2 CN+1 MN+1 SN treatment.After 10 years of fertilization,organic substitution treatments reduced total P and inorganic P accumulation,increased the concentrations of available P,organic P,and microbial biomass P,and promoted phosphatase activities(alkaline and acid phosphomonoesterase,phosphodiesterase,and phytase)and microbial growth in comparison with the 4 CN treatment.Further,organic substitution treatments significantly increased soil C/P,and the partial least squares path model(PLS-PM)revealed that the soil C/P ratio directly and significantly affected phosphatase activities and the microbial biomass and positively influenced soil P pools and vegetable yield.Partial least squares(PLS)regression demonstrated that arbuscular mycorrhizal fungi positively affected phosphatase activities.Our results suggest that organic fertilizer substitution can promote soil P transformation and availability.Combining manure with straw was more effective than applying these materials separately for developing sustainable P management practices.

Effect of CO_2 and N_2 on microbial community changes during column bioleaching of low-grade high pyrite-bearing chalcocite ore

Simulated heap bioleaching of low-grade high pyrite-bearing chalcocite ore was conducted at 40 °C with aeration of CO_2 and N_2.Ore samples were collected at day 43,64,85,106 and subjected to microbial community analysis by 16S rRNA gene clone library.Phylogenetic analyses of 16S rDNA fragments revealed that the retrieved sequences are mainly related to genus Acidithiobacillus,Leptospirillum and Sulfobacillus.Aeration of CO_2 and N_2 significantly impacted the microbial community composition.When CO_2 was aerated,the proportion of genus Acidithiobacillus considerably increased,whereas the proportion of genus Leptospirillum and genus Sulfobacillus declined.However,with the aeration of N_2,the proportion of genus Acidithiobacillus and Leptospirillum increased,but genus Sulfobacillus decreased.When there was no aeration,the microbial community was similar to the inocula with the proportion of genus Leptospirillum mounted.These results indicated that the limitation of oxygen could change the bioleaching microbial community and the aeration of CO_2 and N_2 was favourable for the growth of sulfur-oxidizer(At.caldus) and iron-oxidizer(L.ferriphilum) respectively,which could be used for the regulation of microorganisms' role in mineral bioleaching.

Analysis of effect of nicotine on microbial community structure in sediment using PCR-DGGE fingerprinting

Solid or liquid waste containing a high concentration of nicotine can pollute sediment in rivers and lakes, and may destroy the ecological balance if it is directly discharged into the environment without any treatment. In this study, the polymerase chain reaction （PCR） and denaturing gradient gel electrophoresis （DGGE） method was used to analyze the variation of the microbial community structure in the control and nicotinecontaminated sediment samples with nicotine concentration and time of exposure. The results demonstrated that the growth of some bacterial species in the nicotine-contaminated sediment samples was inhibited during the exposure. Some bacteria decreased in species diversity and in quantity with the increase of nicotine concentration or time of exposure, while other bacteria were enriched under the effect of nicotine, and their DGGE bands changed from undertones to deep colors. The microbial community structure, however, showed a wide variation in the nicotine- contaminated sediment samples, especially in the sediment samples treated with high-concentration nicotine. The Jaccard index was only 35.1% between the initial sediment sample and the sediment sample with a nicotine concentration of 0.030 μg/g after 28 d of exposure. Diversity indices showed that the contaminated groups had a similar trend over time. The diversity indices of contaminated groups all decreased in the first 7 d after exposure, then increased until day 42. It has been found that nicotine decreased the diversity of the microbial community in the sediment.