Effects of enrichmemt planting with native tree species on bacterial community structure and potential impact on Eucalyptus plantations in southern China

Multi-generational planting of Eucalyptus species degrades soil quality but the introduction of legumes can improve soil fertility and microbial diversity.However,the effects of introducing non-legume native tree species on soil nutrients and bacterial community structure remain poorly understood.This study investigated the impacts of the conversion of third generation monoculture Eucalyptus plantations to mixed systems including Eucalyptus urograndis with Cinnamomum camphora(EC)and E.urograndis with Castanopsis hystrix(EH),on soil chemical and biochemical properties and bacterial community structure,diversity and functions.First generation E.urophylla plantations were the control.Results show that planting the third generation Eucalyptus led to a significant decrease in p H,organic matter,nutrient content,enzyme activities(invertin,acid phosphataes,and urease),and bacterialα-diversity compare to the controls.However,the mixed planting showed significant improvement in soil chemical and biochemical attributes and bacterialα-diversity,although the E.urograndis and C.hystrix planting had no improvement.Chloroflexi(oligotrophic bacteria)were significantly enriched in third generation Eucalyptus and Eucalyptus+C.hystrix,while proteobacteria increased significantly in the E.urograndis with C.camphora plantings.The relative abundance of multiple metabolic pathways increased significantly in the third generation Eucalyptus plantations whereas membrane transportrelated genes were enriched in soils of the mixed systems.The changes in bacterial community structures in the two mixed systems were driven by diversity,organic matter and acid phosphatase,while bacterial functions were affected by invertase,NO_(3)^(-)-N,diversity and urease.These results suggest that the transformation of successive monoculture Eucalyptus plantations into mixed plantations reduces the depletion of soil nutrients and enhances the ecological function of soil microorganisms.

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.

Changes in Cold and Hot Syndromes and Gastrointestinal Bacterial Community Structure in Mice by Intervention with Food of Different Nature

Objective:To reveal the effect of foods with different natures on cold or hot syndrome and gastrointestinal bacterial community structure in mice.Methods:Forty-five 6-week-old male ICR Kunming mice of clean grade were divided into 5 groups,9 per group,including the control(CK),hot nature herb medicine(HM),Hong Qu glutinous rice wine(RW),tea rice wine(TW),and cold nature herb medicine(CM)groups.Distilled water or corresponding herbs were administered to mice(0.01 mL/g body weight)in the 5 groups by gastric infusion respectively,once daily for 28 d.Appearance,behavior,and serum biochemical indicators,including 5-hydroxytryptamine(5-HT),thyroid stimulating hormone(TSH),noradrenaline(NE),cyclic adenosine monophosphate(cAMP)and cyclic guanosine monophosphate(cGMP),the hot nature index,as well as the gastrointestinal bacterial community structure were analyzed in all groups after treatment.Results:After supplementation for 28 d,CM and TW mice showed different degrees of cold syndrome,and HM and RW mice showed different degrees of hot syndrome.Compared with the HM and RW mice,the TSH,NE,cAMP levels and hot nature indices in the CM and TW mice were significantly decreased and 5-HT and cGMP levels were significantly increased(P<0.05).There was no obvious change in appearance or behavior in CK mice.Results of clustering analysis showed that the gastrointestinal bacterial community structures were highly similar in TW and CM mice as well as in RW and HM mice,and that they were from the same branch,respectively,when the distance was 0.02.The key microbes associated with cold syndrome were Lachnospiraceae uncultured,Lactococcus,etc.,and the key microbes associated with hot syndrome were S24-7 norank,Ruminococcaceae uncultured,etc.Conclusion:The interventions with different nature foods could change cold or hot syndrome in mice,leading to changes in gastrointestinal bacterial community structure.

Impacts of methamidophos, copper, and their combinations on bacterial community structure and function in black soil

The potential ecotoxicologial risks of methamidophos, copper, and their combinations on microbial community of black soil ecosystem in the Northeast China were assessed in species richness and structures by using 16S rDNA-PCR-DGGE analysis approach, and functional characteristics at community levels by using BIOLOGGN system analysis method as well as two conventional methods(DHA and SIR). All results of DGGE banding fingerprint patterns(amplified by bacterial specific 16S rDNA V3 high variable region universal primer) indicated that the species richness of bacterial community in tested soil was significantly decreased to different extents by using different concentrations of single methamidophos, copper, especially some of their combinations had worse effects than their corresponding single factors. In addition,the structures of soil bacterial community had been disturbed under all stresses applied in this study because of the enrichment of some species and the disappearance of other species from the bacterial community. The effects of the single factors with lower concentrations on the communiy structure were weaker than those with higher concentrations. Moreover, the bacterial community structures under the combined stresses of methamidophos and copper were significantly different from those of control and their corresponding single factors. The change of DHA and carbon source substrate utilizing fingerprint patterns based on BIOLOGGNsystem were two relatively sensitive directors corresponding to the stress presented in this study. Between methamodophos and copper, there happened the significant joint-toxic actions when they were used in combination on DHA and carbon source substrate utilizing fingerprint patterns of soil bacterial communities. The DHA of soil under the combined stresses was lower than that of the control and that under the single factors, and the BIOLOGGN substrate utilizing patterns of soil treated by combinations were distinctively differentiated from the control and their corresponding single factors. From all of above, the methamidophos, copper, especially their combinations had the clearly potential ecotoxicological risks to influence the natural soil microbial ecological system by changing the structure, richness, and the functional characteristics of microbial community.

Wheat, maize and sunflower cropping systems selectively influence bacteria community structure and diversity in their and succeeding crop's rhizosphere

Wheat and maize are increasingly used as alternative crops to sunflower monocultures that dominate the Hetao Irrigation District in China.Shifts from sunflower monocultures to alternate cropping systems may have significant effects on belowground microbial communities which control nutrient cycling and influence plant productivity.In this research,rhizosphere bacterial communities were compared among sunflower,wheat and maize cropping systems by 454 pyrosequencing.These cropping systems included 2 years wheat(cultivar Yongliang 4) and maize(cultivar Sidan 19) monoculture,more than 20 years sunflower(cultivar 5009) monoculture,and wheat-sunflower and maize-sunflower rotation.In addition,we investigated rhizosphere bacterial communities of healthy and diseased plants at maturity to determine the relationship between plant health and rotation effect.The results revealed taxonomic information about the overall bacterial community.And significant differences in bacterial community structure were detected among these cropping systems.Eight of the most abundant groups including Proteobacteria,Bacteroidetes,Acidobacteria,Gemmatimonadetes,Chloroflexi,Actinobacteria,Planctomycetes and Firmicutes accounted for more than 85%of the sequences in each treatment.The wheat-wheat rhizosphere had the highest proportion of Acidobacteria,Bacteroidetes and the lowest proportion of unclassified bacteria.Wheat-sunflower cropping system showed more abundant Acidobacteria than maize-sunflower and sunflower monoculture,exhibiting some influences of wheat on the succeeding crop.Maize-maize rhizosphere had the highest proportion of γ-Proteobacteria,Pseudomonadales and the lowest proportion of Acidobacteria.Sunflower rotation with wheat and maize could increase the relative abundance of the Acidobacteria while decrease the relative abundance of the unclassified phyla,as was similar with the health plants.This suggests some positive impacts of rotation with wheat and maize on the bacterial communities within a single field.These results demonstrate that different crop rotation systems can have significant effects on rhizosphere microbiomes that potentially alter plant productivities in agricultural systems.

Soil bacterial characteristics between surface and subsurface soils along a precipitation gradient in the Alxa Desert, China

Bacteria in desert soil have unique phylogeny and important ecological functions, and theirresponses to changes in precipitation need further attention. However, relevant studies have mainlyfocused on the surface soil, and studies on the responses of bacteria at different soil depths to variationsin precipitation are rare. Thus, we used 16S rDNA high-throughput sequencing to investigate the changesin soil bacterial distribution along a mean annual precipitation gradient (50–150 mm) in the Alxa Desert,China, and compared the variation characteristics in the surface soil layer (0–10 cm) and subsurface soillayer (10–20 cm). Results showed that soil bacterial communities significantly changed along theprecipitation gradient in both soil layers. However, the subsurface soil layer could support bacterialcommunities with higher diversity and closer internal relationships but more internal competition than thesurface soil layer. Additionally, compared with the surface soil layer, variations in diversity andco-occurrence patterns in the subsurface soil layer were more in line with the changes in the mean annualprecipitation, while bacterial community structure was less variable in the subsurface soil layer. Comparedwith the mean annual precipitation, soil moisture had little influence on the structure and diversity of soilbacterial community but had a high correlation with intercommunity connectivity. Therefore, soilmoisture might play a complex role in mediating environmental conditions and soil bacterial communitycharacteristics. Due to the different responses of surface and subsurface soil bacteria to the changes inprecipitation, it is necessary to distinguish different soil layers when predicting the trends in desert soilbacterial conditions associated with precipitation, and prediction of subsurface soil bacteria may be moreaccurate.

Enhanced nitrogen removal at low temperature with mixed anoxic/oxic process

Different hydraulic retention times(HRTs)were tested in a mixed anoxic/oxic(A/O)system at 5C and 10C to investigate the effects of HRT and carrier on nitrogen removal in wastewater at low temperatures.The results showed that the addition of the fillers improved the treatment effect of each index in the system.With an optimal HRT of 7.5 h at 5C,the removal efficiencies of NHþ4-N and total nitrogen(TN)reached 91.2%and 75.6%,respectively.With an HRT of 6 h at 10C,the removal efficiencies of NHþ4-N and TN were 96.7%and 82.9%,respectively.The results of high-throughput sequencing showed that the addition of the suspended carriers in the aerobic zone could improve the treatment efficiency of nitrogen at low temperatures.The microbial analysis indicated that the addition of the suspended carriers enhanced the enrichment of nitrogen removal bacteria.Nitrospira,Nitrotoga,and Nitrosomonas were found to be the bacteria responsible for nitrification,and their relative concentrations on the biofilm at 5C and 10C accounted for 98.11%,92.79%,and 69.98%of all biological samples,respectively.

Influence of cadmium and copper mixtures to rhizosphere bacterial communities

To study the effects of combined Cd and Cu pollution on rhizosphere bacterial community.High-throughput sequencing was used to examine the response of rhizosphere bacterial communities to heavy-metal stress under single and mixed pollution of cadmium(Cd)and copper(Cu).With additions of Cd and Cu,the mean diversity index of rhizosphere bacterial community was in the order Cu alone>Cd-Cu mixtures>Cd alone.In all Cd and Cu treatments,the dominant phyla were Proteobacteria,Actinobacteria,Chloroflexi and Acidobacteria.In the additions with different concentrations of Cd-Cu mixtures,LEfSe indicated that there were differences in the predominant species of rhizosphere bacterial communities.Some genera such as Streptomyces and Microbacterium belonging to Actinobacteria as biomarkers were significantly enriched in both control and treatments,while some genera such as Pseudoxanthomonas and Rhodopseudomonas belonging to Proteobacteria as biomarkers were observed to be enriched in the additions with single and mixture of Cd and Cu.According to the Nonmetric multidimensional scaling(NMDS)analysis,the structure of rhizosphere bacterial community was different between treatments and the CK.Principal Component Analysis(PCA)and permutational multivariate analysis of variance(PERMANOVA)showed that there were significant differences among treatments(p<0.01),and that the addition of Cu might be the primary factor affecting the composition of rhizosphere bacterial communities.

Spatial and seasonal variations in bacterial communities of the Yellow Sea by T-RFLP analysis

Four typical coastal sites(rocky shore,sandy shore,mud flat shore,and artificial harbor)at the Yellow Sea were chosen to investigate the spatial and seasonal variations in bacterial communities.This was accomplished by using terminal restriction fragment length polymorphism(T-RFLP)analysis of PCR amplified 16S rDNA fragments.Two kinds of tetrameric restriction enzymes,HhaI and MspI,were used in the experiment to depict the bacterial community diversity in different marine environments.It was found that the community compositions digested by the two enzymes separately were different.However,the results of bacterial community diversity derived from them were similar.The MDA analysis results of T-RFLP profiles coming from HhaI and MspI both exhibited a significant seasonal community shift for bacteria and a relatively low spatial variation among the four locations.With HhaI as the sample,the pair wise Ttests also revealed that variations were minor between each pair of marine environments,with R ranging from 0.198 to 0.349.However,the bacterial community structure in the mud flat site depicted a larger difference than each of the other three sites(R ranging from 0.282 to 0.349).

Vertical distribution patterns and drivers of soil bacterial communities across the continuous permafrost region of northeastern China

Background:Soil microorganisms in the thawing permafrost play key roles in the maintenance of ecosystem function and regulation of biogeochemical cycles.However,our knowledge of patterns and drivers of permafrost micro-bial communities is limited in northeastern China.Therefore,we investigated the community structure of soil bacteria in the active,transition and permafrost layers based on 90 soil samples collected from 10 sites across the continuous permafrost region using high-throughput Illumina sequencing.Results:Proteobacteria(31.59%),Acidobacteria(18.63%),Bacteroidetes(9.74%),Chloroflexi(7.01%)and Actinobacteria(6.92%)were the predominant phyla of the bacterial community in all soil layers;however,the relative abundances of the dominant bacterial taxa varied with soil depth.The bacterial community alpha-diversity based on the Shannon index and the phylogenetic diversity index both decreased significantly with depth across the transition from active layer to permafrost layer.Nonmetric multidimensional scaling analysis and permutation multivariate analysis of variance revealed that microbial community structures were significantly different among layers.Redundancy analysis and Spearman’s correlation analysis showed that soil properties differed between layers such as soil nutrient content,temperature and moisture mainly drove the differentiation of bacterial communities.Conclusions:Our results revealed significant differences in bacterial composition and diversity among soil layers.Our findings suggest that the heterogeneous environmental conditions between the three soil horizons had strong influences on microbial niche differentiation and further explained the variability of soil bacterial community structures.This effort to profile the vertical distribution of bacterial communities may enable better evaluations of changes in microbial dynamics in response to permafrost thaw,which would be beneficial to ecological conservation of permafrost ecosystems.

Influence of pore structure on biologically activated carbon performance and biofilm microbial characteristics

Optimizing the characteristics of granular activated carbon(GAC)can improve the performance of biologically activated carbon(BAC)filters,and iodine value has always been the principal index for GAC selection.However,in this study,among three types of GAC treating the same humic acidcontaminated water,one had an iodine value 35%lower than the other two,but the dissolved organic carbon removal efficiency of its BAC was less than 5%away from the others.Iodine value was found to influence the removal of different organic fractions instead of the total removal efficiency.Based on the removal and biological characteristics,two possible mechanisms of organic matter removal during steady-state were suggested.For GAC with poor micropore volume and iodine value,high molecular weight substances(3500–9000 Da)were removed mainly through degradation by microorganisms,and the biodegraded organics(soluble microbial by-products,<3500 Da)were released because of the low adsorption capacity of activated carbon.For GAC with higher micropore volume and iodine value,organics with low molecular weight(<3500 Da)were more easily removed,first being adsorbed by micropores and then biodegraded by the biofilm.The biomass was determined by the pore volume with pore diameters greater than 100μm,but did not correspond to the removal efficiency.Nevertheless,the microbial community structure was coordinate with both the pore structure and the organic removal characteristics.The findings provide a theoretical basis for selecting GAC for the BAC process based on its pore structure.