Diversity Of Soil Bacteria Research Articles

Comparative Analyses of Rhizosphere Bacteria Along an Elevational Gradient of Thuja sutchuenensis.

Thuja sutchuenensis Franch. is an endangered species in southwestern China, primarily distributed in 800–2,100 m of inaccessible mountainous areas. Rhizosphere soil physicochemical properties and bacterial communities play an essential role in managing plant growth and survival. Nonetheless, the study investigating rhizosphere soil properties and bacterial communities of T. sutchuenensis is limited. The present study investigated soil properties, including soil pH, organic matter, water content, nitrogen, phosphorus, and potassium contents, and bacterial communities in nearly all extant T. sutchuenensis populations at five elevational gradients. Our results demonstrated that the increase in elevation decreased rhizosphere and bulk soil phosphorus content but increased potassium content. In addition, the elevational gradient was the dominant driver for the community composition differentiation of soil bacterial community. Proteobacteria and Acidobacteria were the dominant bacterial phyla distributed in the rhizosphere and bulk soils. Co-occurrence network analysis identified key genera, including Bradyrhizobium, Acidicapsa, Catenulispora, and Singulisphaera, that displayed densely connected interactions with many genera in the rhizosphere soil. The dominant KEGG functional pathways of the rhizosphere bacteria included ABC transporters, butanoate metabolism, and methane metabolism. Further correlation analysis found that soil phosphorus and potassium were the dominant drivers for the diversity of soil bacteria, which were distinctively contributed to the phylum of Planctomycetes and the genera of Blastopirellula, Planctomycetes, and Singulisphaera. Collectively, this comprehensive study generated multi-dimensional perspectives for understanding the soil bacterial community structures of T. sutchuenensis, and provided valuable findings for species conservation at large-scale views.

Advancing the spring rest-grazing time until the critical period when soil thaws promotes soil recovery and bacterial diversity in alpine meadows

The management strategy of the Qinghai–Tibet Plateau (QTP) alpine meadows is “conservation + use”. Scientific management of grazing and sustainable use of alpine meadows is essential for maintaining the ecological health of the region. An optimal rest-grazing period in spring can protect the pasture and prevent trampling during soil freeze-thawing and plant re-greening stages. The treatment methods investigated in this study were: 1) rest-grazing when soil surface began to thaw until the grass withered (R1); 2) rest-grazing when soil thawing depth was >10 cm until the grass withered (R2); 3) rest-grazing when plant upper ground re-greening (coverage reached 30–40%) until the grass withered (R3); 4) rest-grazing when re-green plant coverage reached 80% until the grass withered (R4); and 5) rest-grazing when dominant plant height was approximately 5 cm until the grass withered (R5, traditional rest-grazing, CK). The soil physicochemical properties, enzyme activities, and microbial diversity of each treatment were determined. The results demonstrated that advancing the time of rest-grazing increased the soil water content (SWC) and decreased the soil temperature (ST). There was no significant change in the total soil nutrients between the treatments. However, there were significant differences in the available nutrients and enzyme activities (p < 0.05). Compared with R5, R1 significantly increased SWC by 15.90–56.22%, NO3––N content increased by 7.91%–7.94%, available phosphorus (AP) content increased by 5.3–15.0%, and soil organic matter (SOM) content increased 1.40 –7.72%. R1 and R2 had higher soil β-glucosidase (BG) activity and alkaline phosphatase (ALP) activity, while R3 and R4 had higher sucrose (SUC) activity. R3, R4, and R5 increased soil bacterial metabolism and energy conversion; in particular, it promoted the carbon cycle, resulting in a significant increase in SUC activity (R4 > R3 > R5). The abundance and diversity of soil bacteria showed that R1 was significantly higher than R2, R3, and R4, but not significantly different from R5, while R5 enhanced soil spatial heterogeneity. Thus, the optimal period for grazing in alpine meadows on the QTP is before soil thawing. This treatment could increase the utilization of available nutrients, SOM content, and soil bacterial diversity.

Effects of Litter and Root Manipulations on Soil Bacterial and Fungal Community Structure and Function in a Schrenk's Spruce (Picea schrenkiana) Forest.

Soil microorganisms are the key driver of the geochemical cycle in forest ecosystem. Changes in litter and roots can affect soil microbial activities and nutrient cycling; however, the impact of this change on soil microbial community composition and function remain unclear. Here, we explored the effects of litter and root manipulations [control (CK), doubled litter input (DL), litter removal (NL), root exclusion (NR), and a combination of litter removal and root exclusion (NI)] on soil bacterial and fungal communities and functional groups during a 2-year field experiment, using illumina HiSeq sequencing coupled with the function prediction platform of PICRUSt and FUNGuild. Our results showed that litter and root removal decreased the diversity of soil bacteria and fungi (AEC, Shannon, and Chao1). The bacterial communities under different treatments were dominated by the phyla Proteobacteria, Acidobacteria, and Actinomycetes, and NL and NR reduced the relative abundance of the first two phyla. For the fungal communities, Basidiomycetes, Ascomycota, and Mortierellomycota were the dominant phyla. DL increased the relative abundance of Basidiomycetes, while NL and NR decreased the relative abundance of Ascomycota. We also found that litter and root manipulations altered the functional groups related to the metabolism of cofactors and vitamins, lipid metabolism, biosynthesis of other secondary metabolites, environmental adaptation, cell growth, and death. The functional groups including ectomycorrhizal, ectomycorrhizal-orchid mycorrhizal root-associated biotrophs and soil saprotrophs in the fungal community were also different among the different treatments. Soil organic carbon (SOC), pH, and soil water content are important factors driving changes in bacterial and fungal communities, respectively. Our results demonstrate that the changes in plant detritus altered the soil microbial community structure and function by affecting soil physicochemical factors, which provides important data for understanding the material cycle of forest ecosystems under global change.

Responses of Soil Microbial Metabolic Activity and Community Structure to Different Degraded and Restored Grassland Gradients of the Tibetan Plateau.

Climate change and land-use disturbances are supposed to have severely affected the degraded alpine grasslands on the Tibetan Plateau. Artificial grassland establishment has been implemented as a restoration tool against grassland degradation. However, the impact of such degradation and restoration processes on soil microbial communities and soil quality is not clearly understood. Here, we aim to investigate how the dynamics of microbial community and soil quality of alpine grasslands respond to a gradient of degradation and that of restoration, respectively. We conducted a randomised experiment with four degradation stages (light, moderate, heavy, and extreme degradation) and three restoration stages (artificial restoration for 1, 5, and 10 years). We analysed the abundance and diversity of soil bacteria and fungi, and measured soil nutrients, enzymatic activity and microbial biomass. The concentration of soil nitrogen (TN), soil organic matter (OM) in heavy degraded grassland decreased significantly by 37.4 and 45.08% compared with that in light degraded grassland. TN and OM in 10-years restored grassland also increased significantly by 33.10 and 30.42% compared to that in 1-year restored grassland. Four soil enzymatic activity indicators related to microbial biomass decreased with degradation gradient and increased with recovery time (i.e., restoration gradient). Both bacterial and fungal community structure was significantly different among grassland degradation or restoration successional stages. The LEfSe analysis revealed that 29 fungal clades and 9 bacterial clades were susceptible to degraded succession, while16 fungal clades and 5 bacterial clades were susceptible to restoration succession. We conclude that soil quality (TN, OM, and enzymatic activity) deteriorated significantly in heavy degraded alpine grassland. Soil microbial community structure of alpine is profoundly impacted by both degradation and restoration processes, fungal communities are more sensitive to grassland succession than bacterial communities. Artificial grasslands can be used as an effective method of restoring degraded grassland, but the soil functions of artificial grassland, even after 10 years of recovery, cannot be restored to the original state of alpine grassland.

Effects of Cotton Stalk Returning on Soil Enzyme Activity and Bacterial Community Structure Diversity in Cotton Field with Long-term Saline Water Irrigation

Long-term saline water irrigation will increase soil salinity, adversely affect soil physical and chemical properties, and change the diversity of soil bacteria. Straw returning can improve the soil microenvironment and subsequently affect soil enzyme activity and bacterial community structure diversity. This experiment used two types of irrigation water salinity:fresh water (FW, 0.35 dS·m-1) and saline water (SW, 8.04 dS·m-1). Under each irrigation water salinity, the amount of cotton straw applied was 0 and 6000 kg·hm-2 (represented by FWST and SWST, respectively). The results showed that:compared with those under fresh water irrigation, saline water irrigation significantly increased the soil salt, bulk density, total carbon, and available phosphorus but significantly decreased available potassium content. Under saline water irrigation, straw returning significantly increased the soil total carbon, total nitrogen, available potassium, and available phosphorus but reduced soil bulk density. Compared with those under fresh water irrigation, soil sucrase, alkaline phosphatase, and catalase activities under saline water irrigation decreased by 57.24%, 35.15%, and 3.91%, respectively, whereas urease activity increased by 26.73%. However, straw returning significantly increased sucrase, alkaline phosphatase, and catalase activities but decreased urease activity. Saline water irrigation decreased the relative abundance of Acidobacteriota, Actinobacteriota, Bacteroidota, Verrucomicrobiota, and Firmicutes and increased the abundance of Gemmatimonadota and Myxococcota. Under saline water irrigation, straw returning significantly increased the relative abundance of Actinobacteriota, Bacteroidetes, Firmicutes, Crenarchaeota, Sphingomonas, Dongia, and Steroidobacter. NMDS results also showed that saline water irrigation and straw returning changed the bacterial community structure. In conclusion, straw returning can improve soil nutrient content, reduce soil bulk density and salinity, and then change soil enzyme activity and bacterial community structure diversity. The change in soil bacterial community composition was mainly affected by soil salinity and bulk density. Therefore, straw returning can improve soil fertility and help maintain the health of soil ecosystem. This study revealed a relationship between soil enzyme activities and bacterial communities, which provides a theoretical basis and mechanism for applying cotton stalk to regulate the soil enzyme and micro-ecological environment.

Effects of straw and straw-derived biochar on bacterial diversity in soda saline-alkaline paddy soil

PurposeIn order to provide a scientific basis for the improvement of soda saline-alkaline paddy soil, the pot experiment was performed to explore the effects of rice straw and straw-derived biochar on the diversity of soil bacteria and community structure in soda saline-alkaline soil.MethodsThe experiment was four gradients of straw return (3 (RS1), 7.5 (RS2), 12 (RS3), and 16.5 (RS4) t/hm2) and four gradients of biochar return (3 (RB1), 7.5 (RB2), 12 (RB3), and 16.5 (RB4) t/hm2), using 0 t/hm2 as a control (CK). After 5 consecutive years of measuring straw returns, high-throughput sequencing was used to determine the relative abundance, alpha diversity, and changes in the community structure of soil bacteria.ResultOur results demonstrated that straw return significantly increased the relative abundance of Bacteroidetes, Firmicutes, and Sphingomonas and significantly reduced the relative abundance of Acidobacteria, Actinobacteria, Gemmatimonadetes, Parcubacteria, Anaeromyxobacter, Pontibacter, uncultured_bacterium_f_Draconibacteriaceae, and Bryobacter. Straw-derived biochar return significantly increased the relative abundance of uncultured_bacterium_f_Draconibacteriaceae and significantly reduced the relative abundances of Actinobacteria, Gemmatimonadetes, Thiobacillus, and Anaeromyxobacter, indicating that both straw and its associated biochar return changed the relative abundance of the phyla and genera of some bacteria. Straw return affected bacteria phylum and genus more than straw-derived biochar. With the exception of the 16.5 t/hm2 straw return, which reduced bacterial richness, the treatments did not significantly impact alpha diversity. Compared with straw-derived biochar return, straw return significantly changed the bacterial community structure, and the higher the straw return, the higher the impact on the bacterial community structure. Redundancy analysis (RDA) demonstrated that there was a significant correlation between the physicochemical properties of the soil and the community structure of its bacteria. A Mantel test demonstrated that the content of available phosphorus, available potassium, and organic matter was all important environmental factors affecting community structure.ConclusionWe speculate that straw return regulates the physicochemical properties of the soil, which affects the bacterial community structure.

Effects of mulching film on soil microbial diversity and community of cotton

Different types of mulching film could variously influence soil properties and plant growth. Yet, surprisingly few studies have investigated the effects of mulching film upon soil microbial diversity and community structure. In this research, two kinds of mulching film, a traditional PE (polyethylene) mulching film and a degradable PBAT ((Poly [butyleneadipate-co-terephthalate])) mulching film, were applied to cotton (Gossypium spp.) plants grown in Xinjiang Province, China. The respective influence of the two mulching films on the cotton’s soil microbial (bacteria and fungi) diversity and community were investigated. The results showed that applying the PBAT mulching film could significantly alter the diversity of non-rhizosphere soil fungi when compared to using the PE mulching film. However, neither the PE nor PBAT mulching film had any significant influence on the diversity of soil bacteria and rhizosphere soil fungi. Nevertheless, soil microbial community composition differed under the PBAT mulching film treatment vis-à-vis the PE mulching film treatment. The abundance of Gibellulopsis was higher under the PBAT than PE mulching film treatment. Our study’s findings provided an empirical basis for the further application of degradable PBAT mulching film for the sustainable development of cotton crops.

Effects of Nutrient Levels and Rice Cultivation on Taxonomic and Functional Diversity of Bacterial Communities in Flooded Soils of the Hanon Maar Crater, Korea

Agricultural land use may deteriorate soil bacterial diversity and function in an agroecosystem. This study aimed to explore the impact of agricultural disturbance on the taxonomic and functional diversity of soil bacteria using a high-throughput sequencing method. We examined the bacterial community diversity in five types of flooded soils in the Hanon Maar Crater from two types of canals characterized by different nutrient levels and three field types with a different rice cultivation history. Proteobacteria (43.2%), Chloroflexi (19.8%), Acidobacteria (15.8%), Actinobacteria (5.1%), and Nitrospirae (5.0%) were the dominant phyla (&gt;5%). The relative abundance of Actinobacteria was 7.1 times greater in the abandoned fields than in the polluted canal. Alpha diversity indices of taxonomic diversity showed strong negative correlations with C, N, and NH4+ levels. The 1.7-fold greater number of operational taxonomic units (OTUs) in abandoned fields than in paddy fields may be caused by factors other than nutrients. Functional analysis revealed that 11 putative functions, including cellulolysis and ligninolysis, were significantly affected by soil management. Functional diversity indices showed negative correlations with electrical conductivity (EC) and NH4+. Nitrogen input had a greater effect on bacterial taxonomic diversity than on functional diversity. Available P was positively correlated with the diversity indices. Taken together, these results suggest that keeping land fallow for more than 5 years and monitoring of C, N, and P levels are practical approaches for restoring taxonomic diversity but not functional diversity of soil bacteria. Our study demonstrated a decoupled response of taxonomic and functional diversity to rice cultivation, highlighting the necessity of further studies on the impact of decoupling on the stability of ecosystem functioning.

Effects of balanced and unbalanced fertilisation on tea quality, yield, and soil bacterial community

Unbalanced fertilisation with nitrogen (N), phosphorus (P), or potassium (K) deficiencies suppresses tea growth and is common in tea production. Balanced fertilisation based on the optimal nutrient requirements of tea plants improves tea yield and quality. However, the effects of unbalanced fertilisation on the yield and quality of tea, soil chemical properties, and bacterial community have not been investigated, and the mechanisms affecting the tea yield and quality remain unclear. Therefore, we conducted a five-year field experiment in tea orchards using four combinations of N, P, and K fertiliser and an unfertilised control. Compared with balanced fertilisation, N, P, and K deficiencies led to a 27.3%, 12.9%, and 11.3% reduction in annual tea yield, respectively. In general, N deficiency had a greater impact on the tea quality than P and K deficiencies. Nutrient contents in tea leaves correlated positively and significantly with tea quality (free amino acid and polyphenol contents). Alpha diversity of soil bacteria was lower in N addition treatments. The addition of N altered the soil bacterial community structure significantly and resulted in a lower Bray–Curtis dissimilarity with respect to the unfertilised treatment. Compared to balanced fertilisation, N deficiency inhibited Chloroflexi but favoured Thaumarchaeota growth. P deficiency resulted in a lower relative abundance of Acidobacteria but a higher relative abundance of Proteobacteria. Fertilisation indirectly influenced soil bacteria with the mediation of pH and soil organic carbon and NH4+ contents. This study indicates that N fertiliser input and pH are the main factors affecting tea yield and quality, respectively. Understanding the effects of unbalanced fertilisation on both tea and soil will help to guide fertilisation strategies, improve tea yield and quality, and reduce the environmental impacts of cultivation.

Tropical Soil Bacterial Diversity in Sabah, Malaysia

Bacteria are an essential biological component of soil function that plays fundamental roles in biogeochemical cycling, soil quality improvement, habitat-shaping, and ecosystem conservation. It is therefore important to have a good record of soil bacteria in the tropics in order to monitor future changes that may occur due to global warming and other factors. However, extremely limited data are available on the diversity of bacteria in soils in some tropical Borneo regions such as Sabah, Malaysia. This research, therefore, was undertaken to determine the bacterial diversity of soils from various locations in Sabah, Malaysia. Ten soil samples (n=10) were collected around Sabah. 16S rDNA of bacterial DNA extracted from soils were amplified and analysed using the Denaturing Gradient Gel Electrophoresis (DGGE). A total of 100 dominant and well-defined DNA fragments observed in the DGGE gel were extracted, sequenced, and aligned. The results indicated that 93 different bacterial operational taxonomic units (OTUs) representing bacteria from 8 different phyla were present. The most abundant phyla in the analysed Sabah soils were Proteobacteria followed by Acidobacteria, Firmicutes, Actinobacteria, Planctomycetes, Verrucomicrobia, Chloroflexi, and Bacteroidetes. The examined soils of Sabah and Peninsular Malaysia had similar dominant phyla in general, except that the most dominant phylum in Peninsular Malaysia soils is the Acidobacteria instead of Proteobacteria. These baseline data generated from this work are important and can be used to track bacterial diversity shifts due to soil or environmental changes in the future.

Does the Use of an Intercropping Mixture Really Improve the Biology of Monocultural Soils?—A Search for Bacterial Indicators of Sensitivity and Resistance to Long-Term Maize Monoculture

The choice of appropriate agricultural practices has a significant impact on soil quality, crop productivity, or soil microbial community. Ten representative soil samples were collected in Wierzchucin Królewski (Kujawsko-Pomorskie Province, NW Poland), an agricultural area belonging to the Potulicka Foundation Group. The cropping systems included a maize monoculture grown continuously for over 30 years and an intercropping mixture (Gorzow mixture) applied in 2020. The study aimed to determine the effect of the intercropping system on the quality and biodiversity of the studied soils and to identify bacterial indicators of sensitivity and resistance to long-term maize monoculture. Therefore, in this study, the impact of the intercrop mixture application on the chemical and biological soil properties and on the diversity of the bacterial community was evaluated by amplifying the 16S rRNA gene sequences and indicators of sensitivity and resistance to long-term maize monoculture were recommended. The results showed that intercropping had a positive effect on soil features and increased the richness and diversity of soil bacteria at the taxonomic level of genera compared to the maize monoculture. Massilia and Haliangium were proposed to be bacterial indicators of sensitivity, while Sphingomonas was recommended to be an indicator of resistance to long-term maize monoculture. Overall, our results evidenced that using an intercropping system may be a sustainable agricultural practice in this area and in north-western Poland.

Deep incorporation of corn straw benefits soil organic carbon and microbial community composition in a black soil of Northeast China

Abstract‘Deep incorporation of corn straw’ (CSDI) is to concentrate the burial of corn straw into the subsurface soil layer (20–40 cm) and to break the plough pan, thereby creating a loosened plough layer (0–20 cm) and a fertile subsurface soil layer. However, its impacts on soil organic carbon (SOC) and the microbial community remain poorly understood. A field experiment was conducted to investigate the effects of 1‐year CSDI (CD1), 3‐year CSDI (CD3) and 5‐year CSDI (CD5) on soil aggregates and aggregate‐associated SOC, as well as bacterial and fungal community characteristics (examined by the high‐throughput gene sequencing method). The results demonstrated that SOC and soil fungal diversity were decreased by CD1, but increased by CD3 and CD5. Compared with the control, CD5 promoted 2–0.25 mm soil macroaggregation, significantly increased SOC by 8.94% and aggregate‐associated SOC by 5.96%–8.84%, consequently improving the physical protection of SOC by soil aggregates. CD3 and CD5 enhanced the richness and diversity of soil bacteria and fungi, and altered community composition. For soil bacteria, the relative abundance of Acidobacteria and Chloroflexi was increased, while that of Firmicutes, Gemmatimonadetes, Sphingomonas and Bacillus was decreased. For soil fungi, the relative abundance of Ascomycota, Zygomycota, Mortierella and Fusarium was greatly improved, but that of Basidiomycota was reduced. These obvious variations in microbial community structure were beneficial to straw degradation and SOC accumulation. Overall, the optimization of microbial community with CSDI plays a positive role in promoting soil organic matter, nutrient cycling and carbon sequestration, and thus improving soil fertility.

Microbiology combined with metabonomics revealing the response of soil microorganisms and their metabolic functions exposed to phthalic acid esters

As microplastics became the focus of global attention, the hazards of plastic plasticizers (PAEs) have gradually attracted people's attention. Agricultural soil is one of its hardest hit areas. However, current research of its impact on soil ecology only stops at the microorganism itself, and there is still lack of conclusion on the impact of soil metabolism. To this end, three most common PAEs (Dimethyl phthalate: DMP, Dibutyl phthalate: DBP and Bis (2-ethylhexyl) phthalate: DEHP) were selected and based on high-throughput sequencing and metabolomics platforms, the influence of PAEs residues on soil metabolic functions were revealed for the first time. PAEs did not significantly changed the alpha diversity of soil bacteria in the short term, but changed their community structure and interfered with the complexity of community symbiosis network. Metabolomics indicated that exposure to DBP can significantly change the soil metabolite profile. A total of 172 differential metabolites were found, of which 100 were up-regulated and 72 were down-regulated. DBP treatment interfered with 43 metabolic pathways including basic metabolic processes. In particular, it interfered with the metabolism of residual steroids and promoted the metabolism of various plasticizers. In addition, through differential labeling and collinear analysis, some bacteria with the degradation potential of PAEs, such as Gordonia, were excavated.

Diversity of soil bacteria in some sacred patches of Purba Bardhaman District, West Bengal, India

Diversity of soil bacteria in some sacred patches of Purba Bardhaman District, West Bengal, India

When microclimates meet soil microbes: Temperature controls soil microbial diversity along an elevational gradient in subtropical forests

Climatic variability along elevational gradients affects biodiversity and produces a natural range of conditions for realistic experiments. Soil biodiversity is expected to respond to the general climatic conditions, as well as microclimatic effects. With the Illumina MiSeq high-throughput sequencing technique, we systematically examined the taxonomic and phylogenetic diversity of soil bacteria and fungi along a 320-1350 m elevational gradient in subtropical forests. Microclimate data under continuous in-situ monitoring, soil physicochemical properties, and plant composition attributes were collected in the forest sites. We found a contrasting pattern in soil bacterial and fungal taxonomic diversity, with monotonically decreasing bacteria populations and no obvious change in fungi taxonomic richness but increased Shannon-Wiener index with increasing elevation. However, the analysis of the richness-dependent phylogenetic index showed no bacterial phylogenetic variability across the elevation gradient, whereas fungal phylogenetic variability increased with greater elevation. Soil temperature and pH were strongly associated with bacterial diversity, but less well correlated with fungal diversity. Microbial community structure differed taxonomically and phylogenetically along the elevation gradient and was most strongly related to soil temperature, followed by soil variables such as soil pH and N content. We conclude that microclimates are ecologically significant in mediating soil microbial community assembly.

Soil Acidification Under Long-Term N Addition Decreases the Diversity of Soil Bacteria and Fungi and Changes Their Community Composition in a Semiarid Grassland.

Soil microorganisms play key roles in terrestrial biogeochemical cycles and ecosystem functions. However, few studies address how long-term nitrogen (N) addition gradients impact soil bacterial and fungal diversity and community composition simultaneously. Here, we investigated soil bacterial and fungal diversity and community composition based on a long-term (17years) N addition gradient experiment (six levels: 0, 2, 4, 8, 16, 32 gN m-2year-1) in temperate grassland, using the high-throughput Illumina MiSeq sequencing. Results showed that both soil bacterial and fungal alpha diversity responded nonlinearly to the N input gradient and reduced drastically when the N addition rate reached 32gNm-2year-1. The relative abundance of soil bacterial phyla Proteobacteria increased and Acidobacteria decreased significantly with increasing N level. In addition, the relative abundance of bacterial functional groups associated with aerobic ammonia oxidation, aerobic nitrite oxidation, nitrification, respiration of sulfate and sulfur compounds, and chitinolysis significantly decreased under the highest N addition treatment. For soil fungi, the relative abundance of Ascomycota increased linearly along the N enrichment gradient. These results suggest that changes in soil microbial community composition under elevated N do not always support the copiotrophic-oligotrophic hypothesis, and some certain functional bacteria would not simply be controlled by soil nutrients. Further analysis illustrated that reduced soil pH under N addition was the main factor driving variations in soil microbial diversity and community structure in this grassland. Our findings highlight the consistently nonlinear responses of soil bacterial and fungal diversity to increasing N input and the significant effects of soil acidification on soil microbial communities, which can be helpful for the prediction of underground ecosystem processes in light of future rising N deposition.

Effects of Bacillus amyloliquefaciens QSB-6 on the Growth of Replanted Apple Trees and the Soil Microbial Environment

Apple replant disease (ARD), caused largely by soil-borne fungal pathogens, has seriously hindered the development of the apple industry. The use of antagonistic microorganisms has been confirmed as a low-cost and environmentally friendly means of controlling ARD. In the present study, we assessed the effects of Bacillus amyloliquefaciens QSB-6 on the growth of replanted apple saplings and the soil microbial environment under field conditions, thus providing a theoretical basis for the successful use of microbial biocontrol agents. Four treatments were implemented in three apple orchards: untreated replant soil (CK1), methyl bromide fumigation (CK2), blank carrier treatment (T1), and QSB-6 bacterial fertilizer treatment (T2). The plant height, ground diameter, and branch length of apple saplings treated with T2 in three replanted apple orchards were significantly higher than that of the CK1 treatment. Compared with the other treatments, T2 significantly increased the number of soil bacteria, the proportion of actinomycetes, and the activities of soil enzymes. By contrast, compared with the CK1 treatments, the phenolic acid content, the number of fungi, and the abundance of Fusarium oxysporum, Fusarium moniliforme, Fusarium proliferatum, and Fusarium solani in the soil were significantly reduced. PCoA and cluster analysis showed that soil inoculation with strain QSB-6 significantly decreased the Mcintosh and Brillouin index of soil fungi and increased the diversity of soil bacteria in T2 relative to CK1. The soil bacterial community structure in T2 was different from the other treatments, and the soil fungal communities of T2 and CK2 were similar. In summary, QSB-6 bacterial fertilizer shows promise as a potential bio-inoculum for the control of ARD.

Effects of biofertilizer on soil microbial diversity and antibiotic resistance genes

Spread of antibiotic resistance or the presence of antibiotic resistance genes (ARGs) in pathogens is a globally recognized threat to human health. Numerous studies have shown that application of organic fertilizers may increase the risk of ARGs, however, the risk of resistance genes associated with biofertilizers is largely unknown. To investigate whether biofertilizer application introduces ARGs to the soil, we used high-throughput quantitative polymerization chain reaction (HT-qPCR) to explore the effect of biofertilizer application over three years on soil ARGs in three orchards with different locations in China. Redundancy analysis showed specific and significant differences in the beta diversity of soil bacteria and fungi between treatments (fertilizer vs. no fertilizer). One-way ANOVA analysis revealed findings of the main driver of the significant difference in microbial community structure between fertilizer and control treatment was the change in soil properties following the application of biofertilizer. A total of 139 ARGs and 27 MGEs (mobile genetic elements), and 46 ARGs and 6 MGEs from 11 major taxa were detected in biofertilizer and soil samples, respectively. Only the samples from Guangxi had significant differences in the detected number of ARGs and MGEs between fertilization and control. Through structural equation modeling (SEM), we found that soil properties indirectly affected ARGs by shaping bacterial diversity, while bacterial abundance directly affected ARGs. Biofertilizer application did not significantly alter the relative abundance of ARGs in soil due to the complexity of the soil environment and competition between exogenous and native microorganisms. This study provided new insights into the spread of the antibiotic resistome of the soil through biofertilizer applications.

Filtered mud improves sugarcane growth and modifies the functional abundance and structure of soil microbial populations.

BackgroundExploring high-quality organic amendments has been a focus of sustainable agriculture. Filtered mud (FM), a sugar factory waste derived from sugarcane stems, could be an alternative organic amendment for sugarcane production. However, the effects of its application proportions on soil fertility, nutrient cycling, structure of soil bacterial and fungal communities, and the growth of sugarcane in clay-loam soils remain unexplored.MethodsThree application proportions of FM: (FM1-(FM: Soil at 1:4), FM2-(FM: Soil at 2:3), and FM3-(FM: Soil at 3:2)) were evaluated on sugarcane growth and soil nutrient cycling. High throughput sequencing was also employed to explore soil microbial dynamics.ResultsWe observed that FM generally increased the soil’s nutritional properties while improving NO3− retention compared to the control, resulting in increased growth parameters of sugarcane. Specifically, FM1 increased the concentration of NH4+−N, the N fraction preferably taken up by sugarcane, which was associated with an increase in the plant height, and more improved growth properties, among other treatments. An increase in the proportion of FM also increased the activity of soil nutrient cycling enzymes; urease, phosphatase, and β-glucosidase. High throughput sequencing revealed that FM reduced the diversity of soil bacteria while having insignificant effects on fungal diversity. Although increasing FM rates reduced the relative abundance of the phyla Proteobacteria, its class members, the Gammaproteobacteria and Betaproteobacteria containing some N-cycling related genera, were stimulated. Also, FM stimulated the abundance of beneficial and lignocellulose degrading organisms. These included the bacterial phyla Actinobacteria, Bacteroidetes, Acidobacteria, Chloroflexi, and the fungal phylum Ascomycota. The distribution of the soil microbial community under FM rates was regulated by the changes in soil pH and the availability of soil nutrients. Since FM1 showed more promise in improving the growth properties of sugarcane, it could be more economical and sustainable for sugarcane production in clay-loam soils.

短期牦牛放牧强度对川西北高原高寒草甸土壤细菌群落的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 短期牦牛放牧强度对川西北高原高寒草甸土壤细菌群落的影响 DOI: 10.5846/stxb202011273042 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（42001055）；中央引导地方-自由探索项目（20ZYZYTS0020）；西南民族大学中央高校基本科研业务费专项（2020NQN27）和研究生创新型科研项目（CX2020SZ22） Effects of short-term yak grazing intensity on soil bacterial communities in an alpine meadow of the Northwest Sichuan Plateau Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:气候变化和人类干扰使青藏高原的草地退化日趋严重，特别是过度放牧导致的草地退化现象尤为突出；然而，牦牛作为青藏高原分布广且数量多的重要家畜，其不同放牧强度对高寒草甸土壤理化性质与细菌群落的影响仍不明晰。在川西北高原典型高寒草甸开展牦牛放牧强度试验，设置了对照组（禁牧）、轻度放牧（1头牦牛/hm2）、中度放牧（2头牦牛/hm2）和重度放牧（3头牦牛/hm2）4个放牧强度，每个强度设置3个重复。两年放牧实验后的结果表明：短期的重度放牧导致土壤有效磷显著增加，而其它土壤性质在各放牧强度变化不显著；随着放牧强度的增加，土壤细菌α多样性呈先增加后减少的趋势，其主要原因是牦牛活动为细菌的生长繁殖提供了有利的营养条件，但由于放牧的持续时间较短，变化不显著；就优势菌而言，土壤绿弯菌门中存在光合自养细菌，在重度放牧下显著高于对照组，其它各菌门在不同放牧强度下无显著差异；土壤氮与硝化螺旋菌门呈正相关，速效磷与酸杆菌门也呈显著正相关，均说明放牧强度对土壤细菌类群的影响是通过土壤性质间接实现的。本实验通过研究不同牦牛放牧强度下的土壤细菌群落结构，为放牧策略的制定提供了基础数据支持，为草地退化的防治提供理论依据。 Abstract:As an important part of China, the Qinghai-Tibetan Plateau plays a vital role in the balance of global ecosystems. Climate change and human activities have led to grassland degradation on the Qinghai-Tibetan Plateau, especially overgrazing-induced grassland degradation. However, as one of the most dominated livestock on the Qinghai-Tibetan Plateau, the effects of different yak grazing intensities on soil physicochemical properties and microbial communities and structures still remain unclear. To address yak grazing effect on soil bacterial communities, we conducted a yak grazing intensity experiment in a typical alpine meadow of the Northwest Sichuan Plateau. According to local investigations and previous experiment, we set four grazing intensities, including control group (no grazing), light grazing (1 yak/hm2), moderate grazing (2 yak/hm2), and heavy grazing (3 yak/hm2). After two years of grazing experiments, we found that heavy grazing significantly increased soil available phosphorus and short term grazing reduced the bulk density in the 0-10cm soils, while other soil properties showed no responses to different grazing intensities. The possible reason may be that the effect of grazing on soil physicochemical properties was long-term, and the short-term grazing intensity of yak was difficult to change soil properties. The α diversity of soil bacteria increased firstly and then decreased with the increasing grazing intensity, but the changes were not statistically significant due to the short duration of grazing experiment. On the one hand, yak grazing could provide available nutrients for the growth of bacteria through dung and urine. On the other hand, high grazing intensity changed the root distribution and root exudates of plants, and increased ultraviolet radiation reduced the diversity of bacteria. In terms of the dominant bacteria, the Chloroflexi was significantly higher under no-grazing than that under heavy grazing, which has photosynthetic autotrophic bacteria. In contrast, other phylum had no significant differences among grazing intensities. With the increase of grazing intensity, the relative abundance of Actinobacteri and Firmicutes increased firstly and then decreased, while Acidobacteria and Gemmatimonadetes showed reverse trends. The β diversity of soil bacteria showed that grazing intensity had no significant effect on bacterial community structure. Soil total nitrogen is positively correlated with Nitrospira. There was a significantly negative correlation between soil total phosphorus and Acidobacteria, but soil available phosphorus was also significantly positive related to Acidobacteria, indicating that grazing intensity indirectly affect soil bacteria may be through changing soil properties. This study provides basic data to grazing managements and a theoretical basis to the restoration of degraded grasslands. 参考文献 相似文献 引证文献