Effects of cadmium on the intestinal health of the snail Bradybaena ravida Benson.

The heavy metal cadmium (Cd) is a toxic and bioaccumulative metal that can be enriched in the tissues and organs of living organisms through the digestive tract. However, more research is needed to determine whether food-sourced Cd affects the homeostasis of host gut microflora. In this study, the snail Bradybaena ravida (Benson) was used as a model organism fed with mulberry leaves spiked with different concentrations of Cd (0, 0.052, 0.71, and 1.94 mg kg-1). By combining 16S rRNA high-throughput sequencing with biochemical characterization, it was found that there were increases in the overall microbial diversity and abundances of pathogenic bacteria such as Corynebacterium, Enterococcus, Aeromonas, and Rickettsia in the gut of B. ravida after exposure to Cd. However, the abundances of potential Cd-resistant microbes in the host's gut, including Sphingobacterium, Lactococcus, and Chryseobacterium, decreased with increasing Cd concentrations in the mulberry leaves. In addition, there was a significant reduction in activities of energy, nutrient metabolism, and antioxidant enzymes for gut microbiota of snails treated with high concentrations of Cd compared to those with low ones. These findings highlight the interaction of snail gut microbiota with Cd exposure, indicating the potential role of terrestrial animal gut microbiota in environmental monitoring through rapid recognition and response to environmental pollution.

Regulation of potential denitrification rates in sediments by microbial-driven elemental coupled metabolisms.

Microbial driven coupled processes between denitrification and methane/sulfur metabolism play a very substantial role in accelerating nitrogen removal in river sediments. Until now, little is known about how element coupling processes alter nitrogen metabolism by the microbial functional communities. The primary objective of this research was to clarify the contributory role of microbial-mediated coupled processes in controlling denitrification. Specifically, the study sought to identify the key bioindicators (or metabolic pathway) for preferably regulating and predicting potential denitrification rate (PDR). Here, a total of 40 sediment samples were collected from the inflow rivers of Chaohu Lake under nitrogen stress. The results revealed the ecological importance of methanogens and sulfate reducing bacteria in the microbial interaction network. Correlations between quantitative or predicted genes showed that the methanogenic gene (mcrA) was synergistic with denitrifying genes, further unraveling that the key role of methanogenesis in denitrification process for facilitating nitrogen removal. The PDR of sediments ranged from 0.03 to 133.21 µg N·g-1·h-1. The study uncovered specific environmental factors (NH4+ and OM) and microbial indicators (nosZ, mcrA, Paracoccus, Thauera, Methanobrevibacter and Desulfomicrobium) as potential contributors to the variations in PDR. Structural Equation Model (SEM) analysis revealed a significant direct effect of NH4+ on PDR, evidenced by a standardized coefficient (λ) of 0.77 (P < 0.001). Additionally, the findings also emphasized the salient role of methanogens (Methanobrevibacter) and methanogenic gene (mcrA) in indicating PDR. The research's aforementioned findings shed light on the substantial consequences of methanogenesis on nitrogen metabolism in coupled processes, enabling improved control of nitrogen pollution in river sediments. This study provided fresh perspectives on the effects of multiple functional taxa on denitrification, and reinforces the significance of coupling processes for nitrogen removal.

Seasonal variation in soil algal community structure in different forest plantations in subtropic China.

Algae exert great impact on soil formation and biogeochemical cycling. However, there is no full understanding of the response of soil algal community structure to the seasonal fluctuations in temperature and moisture and changes of soil physicochemical properties across different forests. Here, based on 23S rRNA gene sequencing, we analyzed soil algal community structure in four different forest plantations in two seasons and examined soil physiochemical properties. The results showed the significantly seasonal variation in soil algal community structure, with the higher overall diversity in summer than in winter. In addition, there existed significant correlations between soil algae (species composition, relative abundance, diversity index) and physicochemical properties (pH, total phosphorus, organic matter and nitrate nitrogen), suggesting that edaphic characteristics are also largely responsible for the variation in soil algal community. Nevertheless, the seasonal variation in algal community structure was greater than the variation across different forest plantations. This suggest temperature and moisture are more important than soil physicochemical properties in determining soil algal community structure. The findings of the present study enhance our understanding of the algal communities in forest ecosystems and are of great significance for the management and protection of algal ecosystem.

Regulation of gut bacteria in silkworm (Bombyx mori) after exposure to endogenous cadmium-polluted mulberry leaves.

Soil cadmium (Cd) pollution presents a severe pollution burden to flora and fauna due to its non-degradability and transferability. The Cd in the soil is stressing the silkworm (Bombyx mori) out through a soil-mulberry-silkworm system. The gut microbiota of B.mori are reported to shape host health. However, earlier research had not reported the effect of endogenous Cd-polluted mulberry leaves on the gut microbiota of B.mori. In the current research, we compared the phyllosphere bacteria of endogenous Cd-polluted mulberry leaves at different concentrations. The investigation of the gut bacteria of B.mori fed with the mulberry leaves was done to evaluate the impact of endogenous Cd- polluted mulberry leaves on the gut bacteria of the silkworm. The results revealed a dramatic change in the gut bacteria of B.mori whereas, the changes in the phyllosphere bacteria of mulberry leaves in response to an increased Cd concentration were insignificant. It also increased the α-diversity and altered the gut bacterial community structure of B. mori. A significant change in the abundance of dominant phyla of gut bacteria of B.mori was recorded. At the genus level, the abundance of Enterococcus, Brachybacterium and Brevibacterium group related to disease resistance, and the abundance of Sphingomonas, Glutamicibacter and Thermus related to metal detoxification was significantly increased after Cd exposure. Meanwhile, there was a significant decrease in the abundance of the pathogenic bacteria Serratia and Enterobacter. The results demonstrated that endogenous Cd-polluted mulberry leaves caused perturbations in the gut bacterial composition of B.mori, which may driven by Cd content rather than phyllosphere bacteria. A significant variation in the specific bacterial community indicated the adaptation of B. mori gut for its role in heavy metal detoxification and immune function regulation. The results of this study help to understand the bacterial community associated with endogenous Cd-polluted resistance in the gut of B.mori, which proves to be a novel addition in describing its response in activating the detoxification mechanism and promoting its growth and development. This research work will help to explore the other mechanisms and microbiota associated with the adaptations to mitigate the Cd pollution problems.

Changes of DOM and its correlation with internal nutrient release during cyanobacterial growth and decline in Lake Chaohu, China.

The seasonal changes in dissolved organic matter (DOM), and its correlation with the release of internal nutrients during the annual cycle of cyanobacteria in the eutrophic Lake Chaohu, China, were investigated from four sampling periods between November 2020 and July 2021. The DOM fluorescence components were identified as protein-like C1, microbial humic-like C2, and terrestrial humic-like C3. The highest total fluorescence intensity (FT) of DOM in sediments during the incubation stage is due to the decomposition and degradation of cyanobacteria remains. The lowest humification of DOM and the highest proportion of C1 in waters during the initial cyanobacterial growth indicate that fresh algae are the main source. The highest molecular weight of DOM and FT of the C2 in sediments during cyanobacterial outbreaks indicate the concurrent deposition of undegraded cyanobacterial remains and microbial degradation. The components of DOM are affected mainly by the dissolved total phosphorus in waters, while the temperature drives the annual cycle of cyanobacteria. The decreasing C1 in sediments and increasing nutrients in waters from the cyanobacterial incubation to outbreak indicate that mineralization of algal organic matter contributes importantly to the release of internal nutrients, with the strongest release of phosphorus observed during the early growth of cyanobacteria. The humic-like C2 and C3 components could also affect the dynamics of internal phosphorus through the formation of organic colloids and organic-inorganic ligands. The results show that the degradation of DOM leads to nutrients release and thus supports the continuous growth of cyanobacteria in eutrophic Lake Chaohu.

Unveil of the role of fungal taxa in iron(III) reduction in paddy soil.

Hitherto, research on iron(III)-reduction has mainly focused on bacteria rather than fungal communities. To acquire insight into fungi involved in iron(III) reduction, typical organic matters (containing cellulose, glucose, lactate, and acetate) and ferrihydrite were used as electron donors and acceptors, respectively, in the presence of antibiotics. After antibiotic addition, microbial iron(III) reduction was still detected at quite high rates. In comparison, rates of iron(III) reduction were significantly lower in cellulose-amended groups than those with glucose, lactate, and acetate under the antibiotic-added condition. Patterns of intermediate (e.g., acetate, pyruvate, glucose) turnover were markedly different between treatments with and without antibiotics during organic degradation. A total of 20 genera of potential respiratory and fermentative iron(III)-reducing fungi were discovered based on ITS sequencing and genome annotation. This study provided an insight into the diversity of iron(III)-reducing fungi, indicating the underestimated contribution of fungi to iron and the coupled carbon biogeochemical cycling in environments.

Effects of soil properties on heavy metal bioavailability and accumulation in crop grains under different farmland use patterns.

Mining activities have increased the accumulation of heavy metals in farmland soil and in food crops. To identify the key soil properties influencing heavy metal bioavailability and accumulation in food crops, 81 crop samples and 81 corresponding agricultural soil samples were collected from rape, wheat, and paddy fields. Heavy metal (copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd), iron (Fe), and manganese (Mn)) concentrations in soils and rape, wheat, rice grains were determined using inductively coupled plasma atomic emission spectroscopy, and soil physicochemical properties (pH, organic matter, total nitrogen, total phosphorus, available phosphorus, and available potassium (AK)) were analyzed. Soil extractable metals were extracted using various single extractants (DTPA, EDTA, NH4OAc, NH4NO3, and HCl). The average concentrations of Cu, Zn, Pb, Cd, and Mn in the soil samples all exceeded the local geochemical background value (background values of Cu, Zn, Pb, Cd, and Mn are 43.0, 81.0, 28.5, 0.196, and 616 mg/kg, respectively), and Cd over-standard rate was the highest, at 98%. Furthermore, soil total Cd concentrations (0.1-24.8 mg/kg) of more than 86% of the samples exceeded the soil pollution risk screening value (GB 15618-2018). The sources of Cu, Zn, Pb, Cd, and Mn in soils were mainly associated with mining activities. The key factors influencing heavy metal bioavailability were associated with the types of extractants (complexing agents or neutral salt extractants) and the metals. Cd and Pb concentrations in most wheat and rice grain samples exceeded the maximum allowable Cd and Pb levels in food, respectively, and Cd concentrations in approximately 10% of the rice grain samples exceeded 1.0 mg/kg. Furthermore, rice and wheat grains exhibited higher Cd accumulation capacity than rape grains, and despite the high soil Cd concentrations in the rape fields, the rape grains were safe for consumption. High soil pH and AK restricted Cd and Cu accumulation in wheat grains, respectively. Soil properties seemed to influence heavy metal accumulation in rice grains the most.

How microorganisms tell the truth of potentially toxic elements pollution in environment.

Potentially toxic elements (PTEs) posed a major hazard to microbial community in river sediments, but the way how different kinds of microorganisms responses to elements pollution has not been clearly understood. The target of this research was to discriminate the apposite indicators for diagnosing elements pollution based on the sensitivity of microbial abundance, biodiversity, predicted metabolic functions to PTEs (Cu, Cd, Cr, Ni, Pb, Zn, As and Hg). Considering Huaihe River Basin as the main subject, sediment samples were gathered from 135 sites. Ni, Zn and Cd significantly influenced the microbial communities and predicted functions. In general, the microbial sensitivity to PTEs was bacteria > archaea. Geo-accumulation index and potential ecological risk (PER) index suggested Hg and Cd were the significant contaminates and posed the most serious ecological risk in sediments. Structural Equation Model identified the bioindicators 1/nitrate reduction and rara taxa (Azoarcus) as reflect and speculate Hg and Cd pollution, respectively. PER was predicted by 1/nitrate reduction and rare taxa (Phaeodactylibacter and Illumatobacter). Results elucidated the rather role of rare taxa in indicating PTEs pollution. The findings contributed to provide useful reference for bioremediation of contaminated sediments under PTEs stress.

Effects of straw mulching on predatory myxobacterial communities in different soil aggregates under wheat-corn rotation.

Crop straw mulching is an important organic supplement in sustainable agriculture; however, the effect of increased organic matter on the diversity of micropredators such as myxobacteria and the correlation between myxobacteria and microorganisms have been little explored. In the current investigation, high-throughput sequencing was performed to analyze the myxobacterial community composition in a wheat-corn rotation experimental field with 6-year straw mulching and fertilization treatments. The results reveal no significant influence of straw mulch application on myxobacterial α-diversity (P < 0.05). NMDS (nonmetric multidimensional scaling) and perMANOVA results indicate the significant influence of straw mulching application on myxobacterial community composition (P < 0.05), and several groups, including Haliangiaceae, Polyangiaceae, and Archangiaceae, also varied in soil aggregates. RDA (redundancy analysis) results show that TOC (total organic carbon) was the most important factor affecting the myxobacterial community structure. In addition, RDA and random forest analysis results show the contribution of myxobacterial community structure to soil bacterial community α- and ß-diversity, especially in the 0.25-1 mm and < 0.25 mm soil aggregate fractions. In conclusion, we suggest that the variation in myxobacterial community structure may be a driver of bacterial α- and ß-diversity in soil microhabitats and might be a cause of soil microbial community changes. Our results are fruitful for finding more efficient ways to use straw from waste for the betterment of sustainable agriculture by analyzing changes in myxobacterial community structure.

A Membrane-Supported Bifunctional Poly(amidoxime-ethyleneimine) Network for Enhanced Uranium Extraction from Seawater and Wastewater.

Uranium extraction from natural seawater and wastewater are quintessential requirements to supply uninterrupted carbon-free nuclear energy and to prevent potential radiochemical and toxicological effects, respectively. Owing to the complexity and low-concentration uranium of these water samples, the design and synthesis of sorbent materials for uranium extraction with meaningful efficiencies remains a grand challenge. Herein, we reported a novel three-dimensional bifunctional network of hyperbranched poly(amidoxime-ethyleneimine) (PAO-h-PEI) using PEI as the skeleton material via cyanoethylation, crosslinking and then amidoximation. As a result of the synergistic supramolecular strategy, the PAO-h-PEI membrane achieved a remarkable adsorption capacity of 985.7 mg/g for aqueous uranium solution, which was 2.5 folds that of the monofunctional h-PEI membrane (387.6 mg/g). The PAO-h-PEI membrane also exhibited good selectivity towards uranium in the presence of various metal ions, high-content salt, and natural organic matter as well as common anions. According to the XPS and FTIR results, the utilization of amines as the second ligand enhanced uranyl binding by providing additional coordination sites or by interacting with oxime to force N-OH dissociation. The good reusability (adsorption rate of 93% after six adsorption-desorption cycles) and satisfactory adsorption performance in extracting low-concentration uranium in real seawater demonstrate its practicability.

Host age increased conjugal plasmid transfer in gut microbiota of the soil invertebrate Caenorhabditis elegans.

Plasmid conjugation contributes greatly to the spread of antibiotic resistance genes (ARGs) in soils. However, the spread potential in the gut of soil fauna remains poorly studied, and little was known about the impact of host age on ARGs dissemination in the gut microbiota of soil animals. Here, the typical nematode-Caenorhabditis elegans was employed as the model soil animal, aiming to investigate transfer of broad-host-range IncP-1ɛ from Escherichia coli MG1655 to gut microbiota within 6 days under varied temperature gradients (15, 20 and 25 °C) using qPCR combined with plate screening. Results showed that conjugation rates increased with incubation time and rising temperature in the gut of C. elegans, sharing a similar trend with abundances of plasmid conjugation relevant genes such as trbBp (mating pair formation) and trfAp (plasmid replication). Incubation time and temperature significantly shaped the gut microbial community of C. elegans. Core microbiota in the gut of C. elegans, including Enterobacteriaceae, Lactobacillaceae and Leuconostocaceae, constituted a large part of transconjugal pool for plasmid IncP-1ɛ. Our results highlight an important sink of gut microbiota for ARGs dissemination and upregulation of ARGs transfer in the gut microbiota with host age, further potentially stimulating evolution of ARGs in terrestrial environments.

Effects of Herbaspirillum sp. p5-19 assisted with alien soil improvement on the phytoremediation of copper tailings by Vetiveria zizanioides L.

Microbial assisted phytoremediation and reclamation are both potential contaminated soil remediation technologies, but little is known about the combined application of the two technologies on real contaminated soils. This study investigated the potential of Herbaspirillum sp. p5-19 (p5-19) assisted with alien soil improvement on improving stress tolerance and enhancing the accumulation of Mn, Cu, Zn, and Cd by Vetiveria zizanioides L. in copper tailings. Phytoremediation potential was evaluated by plant biomass and the ability of plants to absorb and transfer heavy metals. Results showed that the biomass was increased by 19.64-173.81% in p5-19 inoculation treatments with and without alien soil improvement compared with control. Meanwhile, photosynthetic pigment contents were enhanced in co-inoculation treatment (p5-19 with alien soil improvement). In addition, the malondialdehyde (MDA) content was decreased, and the activities of antioxidant enzymes such as ascorbate peroxidase (APX), superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were increased in p5-19 treatment, thereby alleviating the oxidative stress. Moreover, co-inoculation significantly (p < 0.05) increased the concentrations of Mn, Cu, Zn, and Cd in the roots and shoots of V. zizanioides. In particular, the highest concentrations of Mn, Zn, and Cd in the shoots (roots) were obtained in covering 10 cm combined with p5-19 inoculation treatment, which were 4.44- (2.71-), 4.73- (3.87-), and 5.93- (4.35-) fold as that of the controls, respectively. These results provided basis for the change of phytoremediation ability of V. zizanioides after inoculation. We concluded that p5-19 assisted with alien soil improvement was a potential strategy for enhancing phytoremediation ability in tailings.

3-Aminophenylboronic acid-mediated aggregation of gold nanoparticles for colorimetric sensing of iohexol in environmental and biological samples.

Iohexol (IHO), as one of iodinated X-ray contrast, is often used as not only a chemical marker for tracking wastewater contamination in aquatic environment, but also an ideal glomerular filtration rate marker for explorating kidney disease. To these aims, it is important to establish reliable, fast, and cheap methods to detect IHO in environmental and biological samples. This work describes for the first time the development of a selective, sensitive and reliable colorimetric sensing assay for the fast determination of IHO in environmental and biological samples based on 3-aminophenylboronic acid (3-APBA) mediated aggregation of gold nanoparticles (AuNPs). In this approach, 3-APBA can assemble on the AuNPs surface through electrostatic interaction between its amino groups with the negatively charged citrate stabilizer of AuNPs to form AuNP@3-APBA. Subsequently, the aggregation and visual color change of the assembled AuNP@3-APBA are induced by the covalent reaction between boronic acid ligands of 3-APBA and cis-diols of IHO. The developed assay presented a very simple operating procedure and a rapid analysis time of around 10 min. The developed assay also exhibited good selectivity and a low limit of detection (LOD) of 0.005 mM for detecting IHO. Moreover, the developed assay showed comparable accuracy and precision to the high-performance liquid chromatography-diode array detector (HPLC-DAD) method when used for the rapid determination of IHO in river water and human urine samples. The recoveries of IHO at three spiking levels were in the range of 91.5-106.3% with relative standard deviation (RSD) values below 6.39%.

Mechanisms and risks of joint control of nitrogen and phosphorus through sediment capping technology in a pilot-scale study.

Purpose: Nitrogen (N) and phosphorus (P) are the key elements leading to eutrophication, and it is important to jointly control N and P release from sediments into the water column. Methods: Different mixed materials including P sorbent, natural organic carbon (C), and an oxidizing agent were applied in a 1-year pilot-scale experiment. Results: The addition of iron-rich (IR) clay and Phoslock agent promoted the formation of iron bound P (Fe(OOH)~P) and calcium bound P (CaCO3~P) in sediments, respectively. IR clay offered more advantages in immobilization of phosphorus as refractory P, and the Phoslock agent more effectively reduced the risk of P release into water, which was expressed as a low equilibrium P concentration (EPC0). Mixtures of sugarcane (SU) detritus and IR clay exhibited high carbohydrate (CHO) contents, which further fuelled both denitrification and dissimilatory nitrate reduction to ammonium (DNRA). This indicated that the SU dosage should be controlled to avoid DNRA over denitrification. Attention should be given to the fact that SU introduction significantly promoted the generation of an anaerobic state, leading to the desorption and release of Fe(OOH)~P, which could be alleviated by using Oxone. Multienzyme activity analysis showed that P and N transformation shifted from P desorption to organic P hydrolysis and from ammonification to denitrification and DNRA, respectively. Conclusion: We recommend the use of P sorbent and organic C combined with oxidizing agents as effective mixed materials for sediment remediation, which could enhance P adsorption and provide electron donors for denitrification, while also avoiding the generation of anoxia.

Denitrifier abundance and community composition linked to denitrification potential in river sediments.

Denitrification in river sediments plays a very important role in removing nitrogen in aquatic ecosystem. To gain insight into the key factors driving denitrification at large spatial scales, a total of 135 sediment samples were collected from Huaihe River and its branches located in the northern of Anhui province. Bacterial community composition and denitrifying functional genes (nirS, nirK, and nosZ) were measured by high-throughput sequencing and real-time PCR approaches. Potential denitrification rate (PDR) was measured by acetylene inhibition method, which varied from 0.01 to 15.69 µg N g-1 h-1. The sequencing results based on 16S rRNA gene found that the main denitrification bacterial taxa included Bacillus, Thiobacillus, Acinetobacter, Halomonas, Denitratisoma, Pseudomonas, Rhodanobacter, and Thauera. Therein, Thiobacillus might play key roles in the denitrification. Total nitrogen and N:P ratio were the only chemical factors related with all denitrification genes. Furthermore, nirS gene abundance could be more susceptible to environmental parameters compared with nirK and nosZ genes. Canonical correspondence analysis indicated that NO3-, NO2-, NH4+ and IP had the significant impacts on the nirS-encoding bacterial community and spatial distributions. There was a significantly positive correlation between Thiobacillus and nirS gene. We considered that higher numbers of nosZ appeared in nutrient rich sediments. More strikingly, PDR was positively correlated with the abundance of three functional genes. Random forest analysis showed that NH4+ was the most powerful predictor of PDR. These findings can yield practical and important reference for the bioremediation or evaluation of wetland systems.

Physiological responses and metal distributions of different organs of Phragmites australis shoots under acid mine drainage stress.

Phragmites australis, which is widely distributed throughout the world, is often used in the phytoremediation of acid mine drainage (AMD) due to its various mechanisms for survival under extremely harsh conditions. To explore the different responses of different aerial organs of P. australis to stress, soil and plant samples were collected from the AMD-polluted area of the Tongling mining area. The contents of manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), and lead (Pb) in the soil and the leaf blades, leaf sheaths, and stems of P. australis as well as the contents/activities of cysteine synthase (CSase), superoxide dismutase (SOD), peroxidase (POD), glutathione (GSH), malondialdehyde (MDA), and proline (Pro) in the organs were determined. Our results revealed that the leaf sheath had the highest potential to store metals of all the organs. The highest translocation factor (TF) for Fe was observed from the stems to the leaf sheaths. A higher bioconcentration factor (BCF) for Mn was found in the leaf blades and leaf sheaths, while higher BCFs for Cd and Zn were observed in the stems. The content/activity of enzymatic and non-enzymatic stress-resistance substances varied from organ to organ. In general, the leaf sheaths remained almost as or slightly less stress-resistant than the leaf blades. It can be concluded that different plant organs play different roles in stress resistance, and understanding the tolerance mechanism of leaf sheaths to metals is essential for the application of phytoremediation procedures.

Inoculation of Bacillus spp. Modulate the soil bacterial communities and available nutrients in the rhizosphere of vetiver plant irrigated with acid mine drainage.

Acid mine drainage (AMD) is one of an important pollution sources associated with mining activities and often inhibits plant growth. Plant growth promoting bacteria has received extensive attention for enhancing adaptability of plants growing in AMD polluted soils. The present study investigated the effect of plant growth promoting Bacillus spp. (strains UM5, UM10, UM13, UM15 and UM20) to improve vetiver (Chrysopogon zizanioides L.) adaptability in a soil irrigated with 50% AMD. Bacillus spp. exhibited P-solubilization, IAA and siderophore production. The Bacillus spp. strains UM10 and UM13 significantly increased shoot (4.2-2.5%) and root (3.4-1.9%) biomass in normal and AMD-impacted soil, respectively. Bacillus sp. strain UM20 significantly increased soil AP (379.93 mg/kg) while strain UM13 increased TN (1501.69 mg/kg) and WEON (114.44 mg/kg) than control. Proteobacteria, Chloroflexi, Acidobacteria and Bacteroidetes are the dominant phyla, of which Acidobacteria (12%) and Bacteroidetes (8.5%) were dominated in soil inoculated with Bacillus sp. strain UM20 while Proteobacteria (70%) in AMD soil only. However, the Chao1 and evenness indices were significantly increased in soil inoculated with Bacillus sp. strain UM13. Soil pH, AP and N fractions were positively correlated with the inoculation of bacterial strains UM13 and UM20. Plant growth promoting Bacillus spp. strains UM13 and UM20 were the main contributors to the variations in the rhizosphere bacterial community structure, improving soil available P, TN, WEON, NO3--N thus could be a best option to promote C. zizanioides adaptability in AMD-impacted soils.

[Effect of Applying Hydrochar for Reduction of Ammonia Volatilization and Mechanisms in Paddy Soil].

Hydrochar, as a product of the hydrothermal carbonization of biomass, has good application prospects for the NH3 volatilization reduction in rice fields due to its rich pore structure and functional surface. In this study, hydrochar was applied as a soil conditioner to paddy soil. A soil column experiment was conducted to investigate the effect of hydrochar on NH3 volatilization throughout the growth period of rice. The experiment was conducted with three treatments:CKU (control without hydrochar); SHC (sawdust hydrochar); and W-SHC (water-washed sawdust hydrochar). The application rate of SHC and W-SHC was 0.5% (w/w). The study investigated the effects of different hydrochars on the pH and concentrations of NH4+-N in floodwater, the flux and accumulation of NH3 volatilization, and the yield-scale cumulative emission of NH3 volatilization. Results show that the SHC treatment significantly reduces cumulative emissions of NH3 volatilization and the yield-scale cumulative emissions of NH3 volatilization (P<0.05), which were 32.42% and 47.61% lower than CKU, respectively. The effect of W-SHC on ammonia volatilization reduction was slightly weaker, as the cumulative emissions of NH3 volatilization and the yield-scale cumulative emissions of NH3 volatilization decreased by 10.14% and 27.71%, respectively, compared with CKU. The NH3 volatilization reduction was possibly related to the disturbance of pH and the decrease in NH4+-N concentrations in the floodwater because of the application of hydrochar. Compared with CKU, both SHC and W-SHC treatments reduced the pH and NH4+-N concentration in the floodwater. The impacts were more obvious in the rice base fertilizer period (BF) and the first supplemental fertilizer period (SF1) than in the second supplemental fertilizer period (SF2). The soil urease activity was significantly inhibited by hydrochar (P<0.05), and the abundance of soil ammonia-oxidizing gene (AOA, AOB) also significantly increased after application of SHC (P<0.05). This resulted in the enhanced efficiency of ammonia-oxidizing, which had an effect on the reduction of the NH4+-N concentrations in the floodwater. This study provides theoretical and experimental data support for the application of hydrochar in agro-environments with regard to ammonia volatilization reduction in paddy fields.

Abundance of human pathogen genes in the phyllosphere of four landscape plants.

The surface of leaf, also known as phyllosphere, harbors diverse microbial communities which include both beneficial microorganisms promoting plants growth and harmful microorganisms, such as plant pathogens and human pathogens. Several studies have investigated the interaction between plants and human pathogens, while few works have focused on the quantitative analysis of pathogenic bacteria. On the basis of real-time polymerase chain reaction (qPCR), this study aimed to evaluate the abundance of following genes: the nuc and pvl of Staphylococcus aureus, the lytA and psaA of Streptococcus pneumoniae, and the ttr and invA of Salmonella enterica in the phyllosphere of four landscape plants (Nandina domestica, Rhododendron pulchrum, Photinia serrulata, and Cinnamomum camphora) growing in two habitats. Our results indicated that the relative abundance of pathogenic genes in the phyllosphere ranged from 10-9 to 10-6. The specific genes of S. aureus, S. pneumoniae and S. enterica in landscape plants were pvl, lytA and ttr, respectively. The two pathogenic genes of S. pneumoniae and the 16S rRNA gene were mainly affected by habitats, host species, and habitats-species interaction. Moreover, for the abundance of lytA and 16S rRNA, results showed that plants present in roadside with traffic pollution were relatively higher than that of campus with less pollution. The N. domestica and C. camphora were recommended for planting along the roadsides due to lower abundance of pathogenic genes. However, we have observed no significant difference in the abundance of pathogenic genes among four plants in the campus. Thereby, this study provided a valuable reference for selecting landscape plants in view of human health.

Assessment of variation in paddy microbial communities under different storage temperatures and relative humidity by Illumina sequencing analysis.

Temperature and relative humidity are important conditions in paddy storage; however, their influence on microbial communities in stored paddy remains poorly understood. In this study, paddy was stored at different temperatures and relative humidity, and severe mildew was observed in samples stored at relative humidity of 97% and different temperatures (15, 28, and 37 °C) after 50 days. High-throughput 16S rRNA and ITS genes amplicon sequencing analyses showed that Proteobacteria, Firmicutes, and Ascomycota were the dominant phyla across the paddy samples. Moreover, Staphylococcus in bacteria and Aspergillus in fungi were predominant in the composition of microbial community among mildewed paddy samples. The maximum abundance of the two types of organisms appeared in samples stored at 37 °C and relative humidity of 97% (T37H97; 85.02 ±â€¯9.77%), and 15 °C and relative humidity of 97% (T15H97; 93.60 ±â€¯0.01%), respectively. In addition, the two genera were also found in mildew from spoiled paddy by using plate isolation method, revealing their important role in paddy spoilage. Statistical analysis indicated that relative humidity was the most important factor affecting the relative abundances of microbial communities and had the 38.98% and 15.74% contributions to the variation of bacterial and fungal communities, respectively. Hence these results could be very conducive to the promotion of safe storage of paddy.