Microbial Community Structure Research Articles

Impact of microplastics on microbial community structure in the Qiantang river: A potential source of N2O emissions

This study aimed to investigate the spatial distribution of microplastics (MPs) and the features of the bacterial community in the Qiantang River urban river. Surface water samples from the Qiantang River were analyzed for this purpose. The results of the 16S high-throughput sequencing indicated that the microbial community diversity of MPs was significantly lower than in natural water but higher than in natural substrates. The biofilm of MPs was mainly composed of Enterobacteriaceae (28.00%), Bacillaceae (16.25%), and Phormidiaceae (6.75%). The biodiversity on MPs, natural water, and natural substrates varied significantly and was influenced by seasonal factors. In addition, the presence of MPs hindered the denitrification process in the aquatic environment and intensified N2O emission when the nitrate concentration was higher than normal. In particular, polyethylene terephthalate (PET) exhibited a 12% residue of NO3−-N and a 4.2% accumulation of N2O after a duration of 48 h. Further findings on gene abundance and cell viability provided further confirmation that PET had a considerable impact on reducing the expression of nirS (by 0.34-fold) and nosZ (by 0.53-fold), hence impeding the generation of nicotinamide adenine dinucleotide (NADH) (by 0.79-fold). Notably, all MPs demonstrated higher the nirK gene abundances than the nirS gene, which could account for the significant accumulation of N2O. The results suggest that MPs can serve as a novel carrier substrate for microbial communities and as a potential promoter of N2O emission in aquatic environments.

Synergistic changes in bacterial community composition, function, and soil characteristics of tomato rhizosphere soil under long-term monoculture conditions

Tomato is widely cultivated all over the world, and long-term monoculture has resulted in decreased tomato yields and stunted plant growth. Soil bacterial communities have a profound effect on plant growth and health, and the effect of different planting years on rhizosphere soil microorganisms of tomato is not clear. In this study, metagenomic sequencing was used to analyze the rhizosphere soil microorganisms of tomatoes cultivated continuously for 3, 6 years (short-term continuous cropping), 9, and 12 years (long-term continuous cropping) (LZ3, LZ6, LZ9, LZ12). The results showed that the pH in LZ9 was significantly higher than that in the other treatments, the relative abundance of Planctomycetes and Candidatus Rokubacteria in LZ3 were higher than those in the other treatments, the relative abundance of Proteobacteria was significantly higher in LZ6 and LZ9 than that in the other treatments, and the relative abundance of Chloroflexi and Bacteroidetes in LZ12 were higher than those in the other treatments. At the genus level, the relative abundance of Nocardioides, Sphingomonas, Pseudolabrys were lower in LZ3 than that in other treatments, and the relative abundance of Gaiella was significantly higher in short-term continuous cropping than that in LZ9. The pH, hydrolyzable nitrogen (HN), and available potassium (AK) were the most important factors driving the changes in microbial communities. The relative abundance of amino acid metabolism, terpenoid and polyketide metabolism decreased significantly with years of continuous cropping, and that total nitrogen (TN), HN, and available phosphorus (AP) were significantly correlated with translation, amino acid metabolism, and cell growth and death. Continuous cropping leads to nutrient imbalance in tomato soils, which affects the structure and functional composition of soil microbial communities, providing insights into microbial community response to continuous tomato cropping, but further in-depth studies are needed.

Long-chain fatty acids facilitate acidogenic fermentation of food waste: Attention to the microbial response and the change of core metabolic pathway under saturated and unsaturated fatty acids loading

Long-chain fatty acids (LCFAs) are recognized as a significant inhibitory factor in anaerobic digestion of food waste (FW), yet they are inevitably present in FW due to lipid hydrolysis. Given their distinct synthesis mechanism from traditional anaerobic digestion, little is known about the effect of LCFAs on FW acidogenic fermentation. This study reveals that total volatile fatty acids (VFAs) production increased by 9.98 % and 4.03 % under stearic acid and oleic acid loading, respectively. Acetic acid production increased by 20.66 % under stearic acid loading compared to the control group (CK). However, the LCFA stress restricted the degradation of solid organic matter, particularly under oleic acid stress. Analysis of microbial community structure and quorum sensing (QS) indicates that LCFA stress enhanced the relative abundance of Lactobacillus and Klebsiella. In QS system, the relative abundance of luxS declined from 0.157 % to 0.116 % and 0.125 % under oleic acid and stearic acid stress, respectively. LCFA stress limited the Autoinducer-2 (AI-2) biosynthesis, suggesting that microorganisms cannot use QS to resist the LCFA stress. Metagenomic sequencing showed that LCFA stress promoted acetic acid production via the conversion of pyruvate and acetyl-CoA to acetate. Direct conversion of pyruvate to acetic acid increased by 47.23 % compared to the CK group, accounting for the enhanced acetic acid production under stearic acid loading. The abundance of β-oxidation pathway under stearic acid loading was lower than under oleic acid loading. Overall, the stimulating direct conversion of pyruvate plays a pivotal role in enhancing acetic acid biosynthesis under stearic acid loading, providing insights into the effect of LCFA on mechanism of FW acidogenic fermentation.

Can Functional Micro-organisms Associated with Pumpkin Sizes Be Sought Out from the Soil?-A Comparison of Soil Microbial Community Structures in Rhizospheres between Giant- and Small-Sized Pumpkin Varieties.

To elucidate the biological mechanisms driving the growth of various pumpkin varieties to different sizes under identical management conditions while in the same field, the soil microbial community structures in the rhizospheres of giant-pumpkin (GP) and small-pumpkin (SP) varieties were analyzed. The results revealed that a significantly higher abundance of bacterial communities could be detected in the rhizospheres of the giant pumpkin varieties, such as Gemmatimonadota, norank__f__norank__o_Gaiellales, norank__f__Gemmatimonadaceae, Bryobacter, Sphingomonas, norank__f__JG30-KF-AS9, and norank__f__norank__o___Elsterales, than in those of the small-sized pumpkins. Additionally, norank_f__norank_o__Elsterale, Ellin6067, norank_f__67-14, and Chujaibacter were unique dominant soil bacteria genera in the rhizospheres of the giant pumpkins. By contrast, Arthrobacter, norank_f__Roseiflexaceae, unclassified_f__Rhizobiaceae, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Nocardioides, Mycobacterium, norank_f__norank_o__Vicinamibacterales, and Burkholderia-Caballeronia-Paraburkholderia were the unique dominant soil bacterial genera in the rhizospheres of the small pumpkins. Moreover, at the fungal genus level, unclassified_c__Chytridiomycetes, Podosphaera, and Colletotrichum presented significant differences between the giant-pumpkin (GP) and small-pumpkin (SP) rhizospheres. In addition, unclassified__p__Rozellomycota, unclassified__c__Chytridiomycetes, Penicillium, and unclassified__f__Chaetomiaceae were unique dominant soil fungal genera in the rhizospheres of the giant pumpkins (GPs). By contrast, Podosphaera, Colletotrichum, unclassified__f__Plectosphaerellaceae, unclassified__o_Boletales, Scytalidium, unclassified__p__Rozellomycota, and unclassified__o_Agaricales were the unique dominant soil fungal genera in the rhizospheres of the small pumpkins (SPs). PICRUSt and FUNGuild functional prediction analyses revealed that the giant-pumpkin rhizosphere microbial community had significantly increased translation, ribosomal structure and biogenesis, nucleotide transport and metabolism, defense mechanisms, replication, recombination and repair, wood saprotroph, and undefined saprotroph levels. The above results suggest that the soil microbial compositions differed between the rhizospheres of the giant- (GP) and small-pumpkin (SP) varieties, even though the plants were grown in the same field under identical management conditions. Meanwhile, bacterial genera such as norank_f__norank_o__Elsterale, Ellin6067, norank_f__67-14, and Chujaibacter, in addition to fungal genera such as unclassified__p__Rozellomycota, unclassified__c__Chytridiomycetes, Penicillium, and unclassified__f__Chaetomiaceae, can be speculated as potential soil functional micro-organisms associated with improved pumpkin size.

Microbial community structure and function in a sandy soil column under dynamic hydrologic regimes

The capillary fringe (CF) exhibits steep chemical and redox gradients, representing a critical reactive interface in the subsurface. The spatial extent of the CF is temporally dynamic because of water table and soil moisture fluctuations. To simulate the spatio-temporal responses of the CF’s microbial community structure and activity, a 91 cm long sandy soil column experiment was conducted by imposing three different sequential hydrologic regimes: a stable water table separating the unsaturated and saturated zones (static regime), periodic pulse infiltration events with a constant water table position (infiltration regime), and water table fluctuations under three drainage-imbibition cycles of 6, 12, and 18 days (fluctuating regime). The investigation focused on the microbially-mediated turnover of nitrogen (N) and carbon (C). Geochemical profiles in the soil column were monitored continuously, while microbial DNA was extracted for 16S rDNA sequencing at the start, middle and end of the experiment. The observed microbial community compositions corresponded to five categories: (1) initial soil, (2) near-surface and (3) CF and saturated soil under the infiltration regime, (4) unsaturated and (5) saturated soil in the fluctuating regime. Based on co-occurrence network analysis, microbial physiologies matched the predominant geochemical conditions, and relatively stable community structures prevailed throughout the experiment. NO3- and NH4+ were more available to the microbes in the fluctuating regime’s alternating oxic/anoxic zone, leading to a more flexible network. The prevalent microbial metabolic pathways predicted using FAPROTAX were mainly associated with N and C metabolisms and significantly correlated with the taxonomic compositions. However, the dominant microbial groups were shared among all the soil samples. The limited spatial differences in microbial community structure under the fluctuating regime were likely due to a more pronounced role of microbial activity than microbial diversity, and similar drying-wetting conditions between the soil column and the filed site. Internally consistent geochemical and microbial depth stratifications were identified by (1) the redox potential and nitrogen species distributions, (2) spatial moment analysis of NO3- and NH4+ concentrations, (3) microbial community composition and (4) function. The five imposed hydrologic regimes generated distinct and coupled geochemical and microbial signatures. These signatures resulted from variations in the soil microbial community’s activity, rather than diversity or abundance.

Effects of Wildfire on Soil CO2 Emission and Bacterial Community in Plantations.

In order to study the effects of wildfires on soil carbon dioxide (CO2) emissions and microbial communities in planted forests, Pinus massoniana Lamb. and Cunninghamia lanceolata (Lamb.) Hook. forests were selected as the research subjects. Through a culture test with 60 days of indoor constant temperature, the soil physical and chemical properties, organic carbon mineralization, organic carbon components, enzyme activity, and microbial community structure changes of the two plantations after fire were analyzed. The results showed that wildfires significantly reduced soil CO2 emissions from the Pinus massoniana forests and Cunninghamia lanceolata forests by 270.67 mg·kg-1 and 470.40 mg·kg-1, respectively, with Cunninghamia lanceolata forests exhibiting the greatest reduction in soil CO2 emissions compared to unburned soils. Bioinformatics analysis revealed that the abundance of soil Proteobacteria in the Pinus massoniana and Cunninghamia lanceolata forests decreased by 6.00% and 4.55%, respectively, after wildfires. Additionally, redundancy analysis indicated a significant positive correlation between Proteobacteria and soil CO2 emissions, suggesting that the decrease in Proteobacteria may inhibit soil CO2 emissions. The Cunninghamia lanceolata forests exhibited a significant increase in soil available nutrients and inhibition of enzyme activities after the wildfire. Additionally, soil CO2 emissions decreased more, indicating a stronger adaptive capacity to environmental changes following the wildfire. In summary, wildfire in the Cunninghamia lanceolata forests led to the most pronounced reduction in soil CO2 emissions, thereby mitigating soil carbon emissions in the region.

Physiological Function of Gut Microbiota and Metabolome on Successful Pregnancy and Lactation in the Captive Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis).

The gestation period in captive Yangtze finless porpoise (YFP) is a well-coordinated and dynamic process that involves both systemic and local alterations. The gut microbiota and its connection to fecal metabolites are crucial in supporting fetal development and ensuring maternal health during reproductive stages. This study evaluates changes in the gut microbiota and their correlation with fecal metabolites in captive YFPs during different reproductive stages. The results reveal that microbial community structure changed significantly during reproductive stages, while gut microbial diversity remained stable. The genus unclassified Peptostrptococcaceae, Corynebacterium, and norank KD4-96 were significantly greater in non-pregnancy (NP), Terrisporobacter was significantly greater in lactating (LL), and Clostridium was significantly higher in early-pregnancy (EP) compared to the other groups. The host fecal metabolome exhibited significant alterations during the reproductive stages. Indoxyl sulfate, octadecatrienoic acid, and methionyl-methionine were significantly higher in the NP; galactosylglycerol, chondroitin 6-sulfate, and lumichrome were significantly higher in the EP and mid-pregnancy (MP); and valylleucine and butyryl-l-carnitine were significantly higher in the LL. The altered metabolites were mostly concentrated in pathways associated with arachidonic acid metabolism (significantly altered in NP), leucine, valine, and isoleucine biosynthesis (significantly altered in EP and MP), and glycerophospholipid metabolism (significantly altered in LL compared to others stages). Additionally, we found a strong link between variations in the host metabolism and alterations in the fecal bacteria of captive YFP. In conclusion, this study provides detailed insights into host metabolic and fecal bacterial changes in captive YFP during reproduction stages, providing important knowledge for improving the reproductive management in the captive YFP.

Short-term microbial community dynamics induced by 13C-labeled maize root, its derived biochar and NPK in long-term amended soil

Crop residues and their derived biochar are frequently used for their potential to improve grain yield, soil fertility and carbon (C) sequestration. However, the effects of root are often overlooked, and the effects of chemical fertilizer (NPK) combined with root or its biochar on microbial community structure need further study. This study used 13C-labeled maize root, its biochar and soil with different fertilization for 8 years as materials and substrates. A 112-day incubation experiment was conducted to explore the effects of microbial community on the C processing. During incubation, the root-C (54.9%) mineralized significantly more than biochar-C (12.8%), while NPK addition significantly increased the root-C mineralization. Adding biochar alone did not significantly change the microbial community. Compared to the biochar treatment (BC), the root treatment (R) notably increased the contents of total phospholipid fatty acids (PLFAs), 13C-PLFA and the proportion of fungi and Gram-negative bacteria, but reduced the proportion of actinomycetes. The root mineralization was significantly correlated with the relative content of 13C-Gram-positive bacteria and 13C-fungi, while biochar mineralization was significantly correlated with the relative content of 13C-Gram-positive bacteria and 13C-actinomycetes. Notably, NPK addition significantly increased the contribution of biochar-C to PLFA-C pool, while decreasing the contribution of root-C. In summary, due to microbial adaptation to the lack of bioavailable C in biochar-amended soil, biochar can act as a buffer against the significant disturbance caused by NPK to microbial communities and native soil organic carbon (SOC), which contributes to the steady enhancement in soil C storage.Graphical

Microbial C and N Metabolism Alterations Based on Soil Metagenome and Different Shrub Invasion Stages in Sanjiang Plain Wetlands.

Shrub invasion affects plant growth and soil physicochemical properties, resulting in soil microbiota metabolic pathway changes. However, little is known about the shrub expansion intensity of microbial metabolic pathway processes. In this study, we used metagenome sequencing technology to investigate changes in soil microbial C and N metabolic pathways and community structures, along with different shrub invasion intensities, in the Sanjiang Plain wetlands. Different shrub invasion intensities significantly affected the soil microbial composition (β diversity), with no significant effect on the α diversity compared to CK. AN, pH, and TP were the major factors influencing the microbial community's structures. Compared to CK, the shrub expansion intensity did not significantly affect C fixation and central metabolism but significantly reduced methanogenesis, which involves the CO2-to-methane transition that occurs in methane metabolism, and denitrification, the nitrite to nitric oxide (nirK or nirS) transition that occurs in N metabolism. This study provides an in-depth understanding of the biogeochemical cycles of wetland ecosystems in cold northern regions undergoing shrub invasion.

Effects of different adding methods of fermentation medium on the quality of cigar.

Background: To investigate the effects of different media and media addition methods on the fermentation of tobacco. Methods: A plant extract and a bacterial agent are used for fermenting cigar tobacco leaves in a different order of addition. The chemical composition, cellulose, and pectin content, as well as changes in the microbial community, were measured. Results: The addition method of the fermentation medium affects the quality of fermented tobacco. The optimal medium formula and addition method involve first adding plant extracts and then microbial agents. The medium formula and addition method can significantly reduce cellulose in tobacco, with a reduction rate of 46%, and significantly increase the content of β-carotene, thereby enhancing the aroma of cigarettes. There is an increase in aroma components, such as alcohols, alkanes, and olefins, in tobacco. By reducing the proportion of Aspergillus, it can alter the microbial community structure of tobacco. Conclusion: Adding plant extracts before introducing microbial agents can significantly improve the quality and alter the microbial community structure of Dexue No.1 tobacco.

Aerenchyma in emergent plants and rhizospheric microbial communities promote methane fluxes in wetlands

AbstractWetlands are the largest natural source of CH4 globally, yet our understanding of how environmental parameters and microorganisms affect the production and emission of CH4 in emergent plant–sediment systems remains limited. In this study, CH4 fluxes were investigated in a wetland with Canna indica for 42 d, as well as nutrients and microbial community. It was found that the chimney effect formed by aerenchyma in roots, stems, and leaves of C. indica promoted the emission and oxidation of CH4 in the wetland and reduced the CH4 concentration in sediments. Canna indica reduced the nutrient release from surface sediments into the overlying water. Pearson correlation analysis showed that temperature, pH, and oxidation–reduction potential were the main influencing factors for CH4 production and oxidation in the wetland. Canna indica inhibited the diversity of archaeal community but promoted the diversity of bacterial community in the rhizosphere. Stochastic processes had a greater impact on bacterial and archaeal succession trajectories in wetland sediments. Network analysis showed that C. indica promoted interactions among bacteria and archaea that enhanced their ability to resist environmental interference. The well‐developed aerenchyma of C. indica provided an important passage for the transport of CH4 from sediments to the atmosphere and shaped the microbial community structure in the rhizosphere. Meanwhile, CH4 emissions were also constrained by several variables, such as temperature and physiological adaptation in the long term. Thus, it is necessary to plant emergent plants in areas with low CH4 emissions and optimize plant configuration in the context of global warming.

The influence of vermicompost on atrazine microbial degradation performance and pathway in black soil, Northeast China

The atrazine (ATR) is extensively used in dryland crops like corn and sorghum in black soil region of Northeast China, posing ecological risks due to toxic metabolites. Vermicompost are known for soil organic pollution remediation but their role in pesticide degradation in black soil remains understudied. The influence of vermicompost on the microbial degradation pathway of atrazine was assessed in this study. Although vermicompost didn't significantly boost atrazine removal, they notably aided in primary metabolite degradation, hydroxyatrazine (HYA), deisopropylatrazine (DIA), and deethylatrazine (DEA), reducing their content by 38.67 %. They also altered the soil microbial community structure, favoring atrazine-degrading bacteria like Proteobacteria, Firmicutes, and Actinobacteria. Five secondary degradation products were identified in vermicompost treatments. Atrazine degradation occurred via dechlorination, dealkylation, and deamination pathways mainly by Nocardioidacea, Streptomycetaceae, Bacillaceae, Sphingomonadaceae, Comamonadaceae and Nitrososphaeraceae. pH and available nitrogen (AN) influenced microbial community structure and atrazine degradation, correlating with vermicompost application rates. Future black soil remediation should optimize application rates based on atrazine content and soil properties.

Effects of tomato straw fermentation on nutrients and bacterial community structure

Unsustainable straw treatment methods detrimentally affect the environment and ecology. Aerobic fermentation (AE) and anaerobic fermentation (AN) are environmentally friendly treatments that better utilise straw resources. In this study, high-throughput sequencing was used to investigate the effects of AE and AN on nutrient content and microbial community structure during tomato straw fermentation. Nitrate nitrogen, available phosphorus, available potassium, and fulvic acid contents following AE were 1250.04 mg/kg, 80.34 %, 161.39 %, and 49.31 %, respectively, which were higher than those following AN. Ammonium nitrogen, humic acid, and humic substance levels following AN were 309.07 %, 31.18 %, and 17.38 %, respectively, which were higher than those following AE. Firmicutes (24.76 %) and Actinobacteria (12.93 %) were more abundant following AE, whereas Proteobacteria (33.82 %) and Bacteroidetes (33.82 %) exhibited higher abundance following AN. AE more effectively eliminated pathogenic bacteria (22.01%–0.26 %) and encouraged stronger interactions between dominant bacterial genera. Redundancy and Mantel test analyses revealed that electrical conductivity and temperature were the most important environmental factors affecting bacterial communities in AE and AN, respectively. AE had a stronger effect on effective nutrient release from tomato straw, implying its greater application potential as a fertiliser. Overall, our study provides a theoretical basis for the optimisation of fermentation methods and processes.

Effects of Deep Tillage on Wheat Regarding Soil Fertility and Rhizosphere Microbial Community.

Wheat production is intrinsically linked to global food security. However, wheat cultivation is constrained by the progressive degradation of soil conditions resulting from the continuous application of fertilizers. This study aimed to examine the effects of deep tillage on rhizosphere soil microbial communities and their potential role in improving soil quality, given that the specific mechanisms driving these observed benefits remain unclear. Soil fertility in this research was evaluated through the analysis of various soil parameters, including total nitrogen, total phosphorus, total potassium, available phosphorus, and available potassium, among others. The high-throughput sequencing technique was utilized to examine the rhizosphere microbial community associated with deep tillage wheat. The findings indicated that deep tillage cultivation of wheat led to reduced fertility levels in the 0-20 cm soil layer in comparison with non-deep tillage cultivation. A sequencing analysis indicated that Acidobacteria and Proteobacteria are the dominant bacterial phyla, with Proteobacteria being significantly more abundant in the deep tillage group. The dominant fungal phyla identified were Ascomycota, Mortierellomycota, and Basidiomycota. Among bacterial genera, Arthrobacter, Bacillus, and Nocardioides were predominant, with Arthrobacter showing a significantly higher presence in the deep tillage group. The predominant fungal genera included Mortierella, Alternaria, Schizothecium, and Cladosporium. Deep tillage cultivation has the potential to enhance soil quality and boost crop productivity through the modulation of soil microbial community structure.

Antibiotic Pollution and Its Effects on the Spatiotemporal Variation in Microbial Community Structure and Functional Genes in Sediment of Baiyangdian Lake

Microbial communities play an important role in water quality regulation and biogeochemical cycles in lakes, and their community structure and function are affected by environmental factors. Therein, antibiotics affect the abundance, diversity, composition, and function of microbial communities. In this study, Baiyangdian Lake was selected as the study area. Sediment samples of 16 sites were collected in August 2018 and April 2019, respectively. Ultra-high performance liquid chromatography-mass spectrometry （HPLC-MS/MS） was used to determine the content of typical antibiotics-quinolones （QNs） in sediment. Through high-throughput sequencing technology, the structure and function of microbial communities was analyzed in the sediments to explore the spatiotemporal variation. Thereinto, redundancy analysis （RDA） was used to identify the key influencing factors of spatiotemporal variation of microbial communities. The results showed that： ① From August to April, the average ω（QNs） showed an increasing trend, and its mean value changed from 3.91 ng·g-1 to 6.34 ng·g-1, with significant seasonal differences in oxolinic acid （OXO） and total QNs content （P < 0.05）. ② In terms of temporal variation, the dominant bacteria were Proteobacteria and Chloroflexi. The relative abundance of Proteobacteria showed a decreasing trend, whereas Chloroflexi showed an increasing trend； at the genus level, the dominant bacteria genera in August were norank_ f__Anaerolineaceae and Thiobacilus, and the dominant bacteria genera in April were Acinetobacter and norank_ f_Anaerolineaceae, and the dominant bacteria genera had significant seasonal differences （P < 0.05）. ③ In terms of temporal variation, the index of Simpson, Chao, Ace, and OTU number all showed an increasing trend, and the seasonal differences were significant （P < 0.05）. ④ In terms of spatial variation, there were no significant spatial differences among functional genes of COG. In terms of temporal variation, there were significant seasonal differences in functional genes of energy production and conversion, carbohydrate transport and metabolism, transcription, cell wall/membrane/envelope biogenesis, and signal transduction mechanisms （P < 0.01 and P < 0.05）. ⑤ Microbial community structure and functional genes were significantly correlated with QNs （P < 0.01 and P < 0.05）, and QNs were the main influencing factors. Therefore, QNs were the main factor affecting the changes in microbial community structure and functional genes in sediments of Baiyangdian Lake. Thus, comprehensive control of antibiotic pollution in sediments should be further strengthened.

Impact of Intercropping Five Medicinal Plants on Soil Nutrients, Enzyme Activity, and Microbial Community Structure in Camellia oleifera Plantations.

Intercropping medicinal plants plays an important role in agroforestry that can improve the physical, chemical, and biological fertility of soil. However, the influence of intercropping medicinal plants on the Camellia oleifera soil properties and bacterial communities remains elusive. In this study, five intercropping treatment groups were set as follows: Curcuma zedoaria/C. oleifera (EZ), Curcuma longa/C. oleifera (JH), Clinacanthus nutans/C. oleifera (YDC), Fructus Galangae/C. oleifera (HDK), and Ficus simplicissima/C. oleifera (WZMT). The soil chemical properties, enzyme activities, and bacterial communities were measured and analyzed to evaluate the effects of different intercropping systems. The results indicated that, compared to the C. oleifera monoculture group, YDC and EZ showed noticeable impacts on the soil chemical properties with a significant increase in total nitrogen (TN), nitrate nitrogen (NN), available nitrogen (AN), available phosphorus (AP), and available potassium (AK). Among them, the content of TN and AK in the rhizosphere soil of Camellia oleifera in the YDC intercropping system was the highest, which was 7.82 g/kg and 21.94 mg/kg higher than CK. Similarly, in the EZ intercropping system, the content of NN and OM in the rhizosphere soil of Camellia oleifera was the highest, which was higher than that of CK at 722.33 mg/kg and 2.36 g/kg, respectively. Curcuma longa/C. oleifera (JH) and Clinacanthus nutans/C. oleifera (YDC) had the most effect on soil enzyme activities. Furthermore, YDC extensively increased the activities of hydrogen peroxide and acid phosphatase enzymes; the increase was 2.27 mg/g and 3.21 mg/g, respectively. While JH obviously increased the urease activity, the diversity of bacterial populations in the rhizosphere soil of the intercropping plants decreased, especially the Shannon index of YDC and HDK. Compared with the monoculture group, the bacterial community abundance and structure of JH and YDC were quite different. The relative abundance of Actinobacteriota and Firmicutes was increased in YDC, and that of Acidobacteriota and Myxococcota was increased in JH. According to the redundancy analysis (RDA), pH, total potassium, and soil catalase activity were identified as the main factors influencing the microbial community structure of the intercropping systems. In conclusion, intercropping with JH and YDC increased the relative abundance of the dominant bacterial communities, improved the microbial community structure, and enhanced the soil nutrients and enzyme activities. Therefore, in the future, these two medicinal plants can be used for intercropping with C. oleifera.

Response of Water-Vallisneria natans-Sediment System to Polyethylene Microplastics

The microplastics in aquatic ecosystems pose a serious threat to ecological security and environmental health, which have received widespread attention. To reveal the response of a water-Vallisneria natans-sediment system to microplastics exposure, the V. natans was exposed to polyethylene microplastics （PE-MPs） with different mass fractions （1%-5%, sediment wet mass fraction）, and the effects of PE-MPs on the physiochemical indicators of water quality, morphological characteristics of submerged plants, physiological characters, antioxidant system, and microbial community structure in sediments were studied respectively. The results showed that the physiochemical properties of the water body were not significantly changed in the PE-MPs treatment group, whereas the plant height, oxidative stress index, and antioxidant system were significantly inhibited. For the plant height, the 1% PE-MPs treatment group height was only 47.44% of that in the control group. Chlorophyll a content was 81.04% of that in the control group, and the activities of catalase （CAT）, malondialdehyde （MDA）, and peroxidase （POD） increased by 233.70%, 117.82%, and 61.62%, respectively. Different mass fractions of PE-MPs had a certain impact on microbial community structure in sediments. The above results are helpful to improve the evaluation system of PE-MPs ecological risk in the water-submerged plant-sediment system.

Characteristics of inter-root soil bacterial community structure and diversity of different sand-fixing shrubs at the southeastern edge of the Mu Us Desert, China

PurposeThis study aimed to investigate the effects of different shrub plants on the structure and diversity of inter-root soil bacterial communities, in order to provide scientific support for ecological restoration and revegetation of the Mu Us Desert.MethodsThree major shrub plants (Artemisia ordosica, Salix psammophila, Caragana microphylla) in the Mu Us Desert were selected for this study. Using high-throughput sequencing technology, the bacterial community structure and diversity in the inter-root soils of these plants were analysed in depth, and combined with the determination of soil physicochemical and microbiological properties, the response characteristics of the bacterial diversity in the inter-root soils of the different plants were assessed comprehensively.ResultsIt was found that although the soil pH did not show significant differences among different plant growths, the SOC, TN and TP contents were higher in Salix psammophila sample plot and Artemisia ordosica sample plot, which indicated that the plant growths had a positive effect on the soil nutrient contents. Through Venn diagram analysis, it was observed that the number of OTUs of bacteria in the soils of different shrubland sites varied, and all of them were higher than those in the soils of the sample sites where no plants grew, which indicated that plants had an effect on soil bacterial diversity. The bacterial Chao1 index were higher in the Artemisia ordosica sample plot sample site, suggesting that the growth of Artemisia ordosica contributes to the enhancement of soil bacterial richness. Soil bacterial communities showed compositional differences among different sample plots, especially the higher relative abundance of Betaproteobacteria in the Artemisia ordosica sample plot sample plot, which may be related to the increase of soil organic matter content.ConclusionThe results of the study revealed that specific plants, such as Artemisia ordosica, can significantly improve the soil nutrient status of windy sandy soils, increase soil organic matter and nitrogen content, and thus enhance the diversity and abundance of soil microorganisms. The bacterial community structure in the inter-root soils of different plants differed significantly, with changes in the relative abundance of the dominant phyla, such as Alphaproteobacteria, Betaproteobacteria and Actinobacteria, reflecting the differences in soil nutrient status. These findings emphasise the important role of plants on soil chemical properties and microbial community structure, providing an important basis for soil management and ecological restoration.

Research Note: Correlation between the reproductive tract microbiota and speckled eggs in laying hens

The microbiomes of the reproductive tract play a crucial role in the egg production and quality and reproductive health of laying hens. Speckled eggs are characterized by shells with brown spots of varying sizes and commonly produced by brown-shelled laying hens. Speckles reduce the economic value of eggs. However, the relationship between oviduct and cloacal microbiomes and the presence of speckled eggs in laying hens remains unclear. In this study, we collected samples from the reproductive tracts (uterus, vagina, and cloaca) of hens laying speckled eggs and those laying normal eggs and compared their microbial structures and relative abundances through 16S rRNA sequencing. We found that the microbial community structure in the reproductive tracts of the hens laying speckled eggs was similar to that in the reproductive tracts of the hens laying normal eggs; however, the relative abundances of Clostridium in the uterus and Turicibacter and Gallibacterium in the vagina of the hens from the speckled group (7.27%, 6.83% and 0.10%, respectively) were significantly higher than those in the normal group (2.00%, 0% and 0%, respectively [P < 0.05]). Additionally, 8, 24, and 11 bacterial taxa in the uterus, vagina, and cloaca were different between the groups of hens laying speckled and normal eggs. At the same time, Clostridium in the uterus may be associated with eggshell speckles. However, further investigations are necessary to understand the functions of these microbiota in the reproductive tracts of laying hens. This study provides novel insights into methods for reducing the occurrence of speckled eggs in laying hens.

Co-bioaugmentation with microalgae and probiotic bacteria: Sustainable solutions for upcycling of aquaculture wastewater and agricultural residues into microbial-rice bran complexes

Aquaculture farming generates a significant amount of wastewater, which has prompted the development of creative bioprocesses to improve wastewater treatment and bioresource recovery. One promising method of achieving these aims is to directly recycle pollutants into microbe-rice bran complexes, which is an economical and efficient technique for wastewater treatment that uses synergetic interactions between algae and bacteria. This study explores novel bioaugmentation as a promising strategy for efficiently forming microbial-rice bran complexes in unsterilized aquaculture wastewater enriched with agricultural residues (molasses and rice bran). Results found that rice bran serves a dual role, acting as both an alternative nutrient source and a biomass support for microalgae and bacteria. Co-bioaugmentation, involving the addition of probiotic bacteria (Bacillus syntrophic consortia) and microalgae consortiums (Tetradesmus dimorphus and Chlorella sp.) to an existing microbial community, led to a remarkable 5-fold increase in microbial-rice bran complex yields compared to the non-bioaugmentation approach. This method provided the most compact biofloc structure (0.50 g/L) and a large particle diameter (404 μm). Co-bioaugmentation significantly boosts the synthesis of extracellular polymeric substances, comprising proteins at 6.5 g/L and polysaccharides at 0.28 g/L. Chlorophyta, comprising 80% of the total algal phylum, and Proteobacteria, comprising 51% of the total bacterial phylum, are emerging as dominant species. These microorganisms play a crucial role in waste and wastewater treatment, as well as in the formation of microbial-rice bran complexes that could serve as an alternative aquaculture feed. This approach prompted changes in both microbial community structure and nutrient cycling processes, as well as water quality. These findings provide valuable insights into the transformative effects of bioaugmentation on the development of microbial-rice bran complexes, offering potential applications in bioprocesses for waste and wastewater management.