Molecular Trade-Offs between Lattice Oxygen and Oxygen Vacancy Drive Organic Pollutant Degradation in Fungal Biomineralized Exoskeletons.

Fungal-mineral interactions can effectively alleviate cellular stress from organic pollutants, the production of which are expected to rapidly increase owing to the Earth moving into an unprecedented geological epoch, the Anthropocene. The underlying mechanisms that may enable fungi to combat organic pollution during fungal-mineral interactions remain unclear. Inspired by the natural fungal sporulation process, we demonstrate for the first time that fungal biomineralization triggers the formation of an ultrathin (hundreds of nanometers thick) exoskeleton, enriched in nanosized iron (oxyhydr)oxides and biomolecules, on the hyphae. Mapped biochemical composition of this coating at a subcellular scale via high spatial resolution (down to 50 nm) synchrotron radiation-based techniques confirmed aromatic C, C-N bonds, amide carbonyl, and iron (oxyhydr)oxides as the major components of the coatings. This nanobiohybrid system appeared to impart a strong (×2) biofunctionality for fungal degradation of bisphenol A through altering molecular-level trade-offs between lattice oxygen and oxygen vacancy. Together, fungal coatings could act as "artificial spores", which enable fungi to combat physical and chemical stresses in natural environments, providing crucial insights into fungal biomineralization and coevolution of the Earth's lithosphere and biosphere.

COH-203, a novel microtubule inhibitor, exhibits potent anti-tumor activity via p53-dependent senescence in hepatocellular carcinoma.

5-(3-Hydroxy-4-methoxyphenyl)-4-(3,4,5-trimethoxyphenyl)-3H-1,2-dithiol-3-one (COH-203) is a novel synthesized analogue of combretastatin A-4 that can be classified as a microtubule inhibitor. In this study, we evaluated the anti-hepatoma effect of COH-203 in vitro and in vivo and explored the underlying molecular mechanisms. COH-203 was shown to be more effective in inhibiting the proliferation of liver cancer cells compared with normal liver cells. COH-203 also displayed potent anti-tumor activity in a hepatocellular carcinoma xenograft model without significant toxicity. Mechanistic studies demonstrated that treatment with COH-203 induced mitotic arrest by inhibiting tubulin polymerization in BEL-7402 liver cancer cells. Long-term COH-203 treatment in BEL-7402 cells led to mitotic slippage followed by senescence via the p14(Arf)-p53-p21 and p16(INK4α)-Rb pathways. Furthermore, suppression of p53 via pifithrin-α (p53 inhibitor) and p53-siRNA attenuated COH-203-induced senescence in BEL-7402 cells, suggesting that COH-203 induced senescence p53-dependently. In conclusion, we report for the first time that COH-203, one compound in the combretastatin family, promotes anti-proliferative activity through the induction of p-53 dependent senescence. Our findings will provide a molecular rationale for the development of COH-203 as a promising anti-tumor agent.

Binding of organic ligands with Al(III) in dissolved organic matter from soil: implications for soil organic carbon storage.

The binding characteristics of organic ligands with Al(III) in soil dissolved organic matter (DOM) is essential to understand soil organic carbon (SOC) storage. In this study, two-dimensional (2D) FTIR correlation spectroscopy was developed as a novel tool to explore the binding of organic ligands with Al(III) in DOM present in soils as part of a long-term (21-year) fertilization experiment. The results showed that while it is a popular method for characterizing the binding of organic ligands and metals, fluorescence excitation-emission matrix-parallel factor analysis can only characterize the binding characteristics of fluorescent substances (i.e., protein-, humic-, and fulvic-like substances) with Al(III). However, 2D FTIR correlation spectroscopy can characterize the binding characteristics of both fluorescent and nonfluorescent (i.e., polysaccharides, lipids, and lignin) substances with Al(III). Meanwhile, 2D FTIR correlation spectroscopy demonstrated that the sequencing/ordering of organics binding with Al(III) could be modified by the use of long-term fertilization strategies. Furthermore, 2D FTIR correlation spectroscopy revealed that the high SOC content in the chemical plus manure (NPKM) treatment in the long term fertilization experiment can be attributed to the formation of noncrystalline microparticles (i.e., allophane and imogolite). In summary, 2D FTIR correlation spectroscopy is a promising approach for the characterization of metal-organic complexes.

Application of Trichoderma harzianum SQR-T037 bio-organic fertiliser significantly controls Fusarium wilt and affects the microbial communities of continuously cropped soil of cucumber.

BACKGROUND: The reduction in diversity of the soil microbial community causes the disorder of continuous cropping. The aim of this study was to determine the effects of applying Trichoderma harzianum SQR-T037 bio-organic fertiliser (BIO) on the microbial community in continuously cropped cucumber soil. Four treatments were set: (1) control, where neither seedling nursery soil (N) nor transplanted soil (T) was amended with BIO; (2) N treatment, where nursery soil was amended with BIO (1% w/w) but transplanted soil was not; (3) N + T treatment, where BIO was added to both nursery soil (1% w/w) and transplanted soil (0.5% w/w); (4) uncropped soil, where soil was left uncropped consistently. RESULTS: A disease index of 72.2% was found for the control treatment, while the N and N + T treatments had disease indices of only 25 and 15% respectively. Analysis of the denaturing gradient gel electrophoresis (DGGE) profiles showed that the bacterial communities of the N and N + T treatments were similar to those of the uncropped soil but distinct from those of the control soil. The fungal communities of the N and N + T treatments differed from those of both the uncropped soil and the control. CONCLUSION: Addition of BIO to both the nursery soil and the transplanted soil can diversify the microbial community in continuously cropped cucumber soil and thus effectively control Fusarium wilt of cucumber plants.

[Effects of reducing chemical fertilizers combined with organic fertilizers on soil microbial community in litchi orchards]. / å‡æ–½åŒ–è‚¥é æ–½æœ‰æœºè‚¥å¯¹è”æžå›­åœŸå£¤å¾®ç”Ÿç‰©åŒºç³»çš„å½±å“.

Organic fertilizer application can replace a part of chemical fertilizer (CF) to improve the quality and efficiency of litchi production. To further explore the soil microbiological mechanism, with 19-year-old 'Feizixiao' litchi trees as the research objects, we examined the effects of two consecutive years of reduced CF applications (average 21.5% of total nutrients) combined with sheep manure (OF) and bio-organic fertilizers (BIO) on soil microbial diversity, community composition and differential microorganisms. The results showed that reducing the application of chemical fertilizers and combining it with the application of sheep manure and bio-organic fertilizer for two consecutive years could significantly improve yield and quality. The average increase of yield in the two years was 23.1% and 39.0%, respectively. Soil organic matter content and pH increased significantly in response to the combination treatments. Compared to that in the chemical fertilizer treatment, the contents of soil available phosphorus, potassium, calcium, magnesium, iron, manganese, copper, and zinc displayed an increasing trend in the combination treatments. The application of organic fertilizer increased the diversity of bacteria and fungi in rhizosphere soil, but not in non-rhizosphere soil. Both treatments significantly changed soil microbial community structure, increased eutrophic bacterial groups such as Bacteroides, Proteobacteria, and Bacillus phylum, and reduced anatrophic bacterial groups such as Acidobacteria and Chloroflexus. Compared with CF, the relative abundances of MND1 under OF and TK10, Gemmatimonas, Pseudolabrys, Trichoderma and Botryotrichum under BIO were significantly increased, which was positively correlated with yield. In conclusion, reducing CF and applying organic ferti-lizer for two consecutive years could effectively improve soil pH and nutrient availability, increase rhizosphere microbial richness and diversity, change soil microbial community structure, and shape microbial communities being more conducive to yield and quality improvement.

Root exudate chemistry affects soil carbon mobilization via microbial community reassembly.

Plant roots are one of the major mediators that allocate carbon captured from the atmosphere to soils as rhizodeposits, including root exudates. Although rhizodeposition regulates both microbial activity and the biogeochemical cycling of nutrients, the effects of particular exudate species on soil carbon fluxes and key rhizosphere microorganisms remain unclear. By combining high-throughput sequencing, q-PCR, and NanoSIMS analyses, we characterized the bacterial community structure, quantified total bacteria depending on root exudate chemistry, and analyzed the consequences on the mobility of mineral-protected carbon. Using well-controlled incubation experiments, we showed that the three most abundant groups of root exudates (amino acids, carboxylic acids, and sugars) have contrasting effects on the release of dissolved organic carbon (DOC) and bioavailable Fe in an Ultisol through the disruption of organo-mineral associations and the alteration of bacterial communities, thus priming organic matter decomposition in the rhizosphere. High resolution (down to 50 nm) NanoSIMS images of mineral particles indicated that iron and silicon co-localized significantly more organic carbon following amino acid inputs than treatments without exudates or with carboxylic acids. The application of sugar strongly reduced microbial diversity without impacting soil carbon mobilization. Carboxylic acids increased the prevalence of Actinobacteria and facilitated carbon mobilization, whereas amino acid addition increased the abundances of Proteobacteria that prevented DOC release. In summary, root exudate functions are defined by their chemical composition that regulates bacterial community composition and, consequently, the biogeochemical cycling of carbon in the rhizosphere.

Multiple fluorescence labeling and two dimensional FTIR-13C NMR heterospectral correlation spectroscopy to characterize extracellular polymeric substances in biofilms produced during composting.

Knowledge on the structure and function of extracellular polymeric substances (EPS) in biofilms is essential for understanding biodegradation processes. Herein, a novel method based on multiple fluorescence labeling and two-dimensional (2D) FTIR-(13)C NMR heterospectral correlation spectroscopy was developed to gain insight on the composition, architecture, and function of EPS in biofilms during composting. Compared to other environmental biofilms, biofilms in the thermophilic (>55 °C) and cooling (mature) stage of composting have distinct characteristics. The results of multiple fluorescence labeling demonstrated that biofilms were distributed in clusters during the thermophilic stage (day 14), and dead cells were detected. In the mature stage (day 26), the biofilm formed a continuous layer with a thickness of approximately 20-100 µm around the compost, and recolonization of cells at the surface of the compost was easily observed. Through 2D FTIR-(13)C NMR correlation heterospectral spectroscopy, the following trend in the ease of the degradation of organic compounds was observed: heteropolysaccharides > cellulose > amide I in proteins. And proteins and cellulose showed significantly more degradation than heteropolysaccharides. In summary, the combination of multiple fluorescence labeling and 2D correlation spectroscopy is a promising approach for the characterization of EPS in biofilms.

Identification of chitinases Is-chiA and Is-chiB from Isoptericola jiangsuensis CLG and their characterization.

A 274-bp conserved fragment of chiA (chiA-CF) was amplified from the genomic DNA of Isoptericola jiangsuensis CLG (DSM 21863, CCTCC AB208287) using the specific PCR primers. Based on chiA-CF sequences, a 5233-bp DNA fragment was obtained by self-formed adaptor PCR. DNA sequencing analysis revealed there were two contiguous open reading frames coding for the precursors of Is-chiA [871 amino acids (aa)] and Is-chiB (561 aa) in the 5233-bp DNA fragment. The Is-chiA and Is-chiB exhibited 58% and 62% identity with ArChiA and ArChiB chitinase from Arthrobacter sp. TAD20, respectively. The Is-chiA and Is-chiB genes were cloned into expression vector pET28a (+) and expressed in Escherichia coli BL21 (DE3) with isopropyl-ß-D-thiogalactopyranoside induction. Is-chiA and Is-chiB were 92 kDa and 60 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and showed chitobiosidase and endochitinase activity, respectively. Is-chiA and Is-chiB were purified by Ni-nitrilotriacetic acid affinity chromatography and the characteristics of both Is-chiA and Is-chiB were studied.

Characterization of a cryptic plasmid pPZZ84 from Bacillus pumilus.

The complete nucleotide sequence of a cryptic plasmid pPZZ84 from Bacillus pumilus strain ZZ84 was determined. Plasmid pPZZ84 is 6817bp long with GC content of 36.7%. Seven putative open reading frames were identified. ORF7 shows 91% and 90% amino acid identity with rep proteins of pSH1452 and pPL1, respectively, members of rolling-circle replication (RCR) pC194-family. A typical pC194-family double strand origin (dso), a single-stranded origin (sso) and rap (regulator aspartate phosphatase) proteins were also identified in the plasmid. These results imply that pPZZ84 belongs to the Bacillus subtilis species group of small rolling circle (BsSRC) replicating plasmids. The plasmid copy number of pPZZ84 in B. pumilus ZZ84 was estimated to be 46 per cell, more than that of other BsSRC plasmids in their hosts.

[Effects of lime and ammonium carbonate fumigation coupled with bio-organic fertilizer application on banana fusarium wilt and bacterial community.] / çŸ³ç°ç¢³é“µç†è’¸è”åˆç”Ÿç‰©æœ‰æœºè‚¥å¯¹é¦™è•‰æž¯èŽç— å’Œç»†èŒç¾¤è½çš„å½±å“.

Taking banana continuous planting soil with high banana fusarium wilt disease incidence as a test site, we examined the effect of lime and ammonium carbonate fumigation coupled with bio-organic fertilizer on the suppression of banana fusarium wilt disease and the structure and composition of bacterial community, using real-time quantitative PCR and high-throughput sequencing. The results showed that the disease incidence was reduced by 13.3% and 21.7% in the treatments of LAOF (lime and ammonium carbonate fumigation coupled with organic fertilizer) and LABF (lime and ammonium carbonate fumigation coupled with bio-organic fertilizer), respectively, compared with OF (application of organic fertilizer without fumigation), while the copy number of Fusarium was decreased by 22.4% and 33.0%, respectively. Compared with non-fumigation treatment, lime and ammonium fumigation coupled with different fertilizer applications significantly reduced bacteria richness and diversity, with different community structure, while fumigation had a decisive effect on bacterial community composition. Bacterial richness and diversity of LABF were lower than those of other treatments, while microbial community structure was clearly disparate from other treatments. Compared with non-fumigation treatment, the relative abundance of Mizugakiibacter, Brucella, and Rhodanobacter were significantly improved in the fumigation coupled with different fertilization treatments. Those three genera in LABF were higher than those in LAOF, with significant differences for the relative abundances of Mizugakiibacter and Brucella. Therefore, fumigation combined with bio-organic fertilizer application could reduce the copy number of pathogen, alter soil bacterial community structure and stimulate beneficial bacteria in the resident soil, and thus reduce the occurrence of banana fusarium wilt.

In vitro physiological responses of Fusarium oxysporum f. sp. niveum to exogenously applied syringic acid.

Plant-microbe interactions are often accompanied by allelochemicals, such as syringic acid, released from the host plant. To explore the role of phenolic acids released from crop host plants in response to pathogen invasion, we examined the allelopathic effect of an artificially applied syringic acid on Fusarium oxysporum f. sp. niveum. We demonstrated that the growth and the conidial germination rate of F. oxysporum f. sp. niveum were stimulated at lower concentrations of syringic acid, though inhibited by higher dosage compared with control. The yield of fungus mycotoxin was increased from 60.9% to 561.5%. We conclude that syringic acid can be considered as a allelochemical inducer, stimulating the relative virulence factors of invading pathogens.

Growth of in vitro Fusarium oxysporum f. sp. niveum in chemically defined media amended with gallic acid.

Gallic acid was artificially added to the media to grow Fusarium oxysporum f.sp.niveum to investigate its effect on the pathogenic fungus. Results indicate that gallic acid inhibited the growth of F. oxysporum f.sp.niveum. The colony diameter, the conidia germinating rate and the conidia yield were reduced by 5.7-22.9%%, 35.8-55.6% and 38.9-62.2% respectively. However, the virulence factors by the fungus were stimulated. The activity of pectinase, proteinase and cellulase increased by 12.3-627.8%, 11.8-41.2% and 0.5-325.0% respectively, while the activity of amylase increased slightly. The results suggest that gallic acid repressed growth but facilitated the relative pathogenicity of invading pathogens.

High-throughput absolute quantification sequencing reveals the effect of different fertilizer applications on bacterial community in a tomato cultivated coastal saline soil.

Coastal saline soil is an important reserve land resource that has high potential for agricultural utilization. The present study adopted a high-throughput absolute quantification 16S rRNA sequencing method to investigate the effect of four different fertilization regimes (namely 100% of bio-organic fertilizer, 70% of bio-organic fertilizer +30% of chemical fertilizer, 30% of bio-organic fertilizer +70% of chemical fertilizer, and 100% of chemical fertilizer) on bacterial community assembly in a tomato cultivated saline soil. The results from the field experiment showed that a combination of 70% bio-organic fertilizer plus 30% of chemical fertilizer was the optimal dose to develop tomato cultivation (for improving yield and fruit quality) in this coastal tidal zone. The pot experiment gave the similar results on tomato growth and indicated the application of 70% bio-organic fertilizer plus 30% of chemical fertilizer as the best treatment to active the soil microbiome. The input of nutrients by fertilizers increased the total abundance of bacteria (to >3 fold compared to the initial soil) and simultaneously led to a significant loss of bacterial diversity in soil. The predominant phyla including Proteobacteria, Bacteroidetes and Firmicutes were the main contributors in the microbiome shift especially shown by their remarkable enrichment in the soil that treated by 70% of bio-organic fertilizer and those by the 100% chemical fertilizer. The RDA and Pearson correlation analyses indicated that the soil nutrient availability, especially available P and K, and soil salinity were the key environmental factors that shaped the bacterial community in this ecosystem, though the organic matter content and soil pH also played important roles in microbiome assembly.

Cinnamic acid inhibits growth but stimulates production of pathogenesis factors by in vitro cultures of Fusarium oxysporum f.sp. niveum.

Long-term monoculture of watermelon leads to frequent occurrence of watermelon fusarium wilt caused by Fusarium oxysporum f.sp. niveum (FON). Some allelochemicals contained in watermelon root exudates and decaying residues are possibly responsible for promoting the wilt disease. The purpose of this study was to evaluate the allelopathic effect of artificially applied cinnamic acid on FON. Results demonstrated that hyphal growth of FON was strongly inhibited by cinnamic acid. At the highest concentration of cinnamic acid, the biomass in liquid culture was decreased by 63.3%, while colony diameter, conidial germination on plates, and conidial production in liquid culture were completely inhibited. However, mycotoxin production and activity of phytopathogenic enzymes were greatly stimulated. Mycotoxin yield, pectinase activity, proteinase activity, cellulase activity, and amylase activity were increased by 490, 590, 760, 2006, and 27.0%, respectively. It was concluded that cinnamic acid dramatically stimulated mycotoxin production and activities of hydrolytic enzymes by FON but inhibited growth and germination of FON. The findings presented here indicate that cinnamic acid is involved in promoting watermelon fusarium wilt.

Gene structure and expression of the high-affinity nitrate transport system in rice roots.

Rice has a preference for uptake of ammonium over nitrate and can use ammonium-N efficiently. Consequently, transporters mediating ammonium uptake have been extensively studied, but nitrate transporters have been largely ignored. Recently, some reports have shown that rice also has high capacity to acquire nitrate from growth medium, so understanding the nitrate transport system in rice roots is very important for improving N use efficiency in rice. The present study identified four putative NRT2 and two putative NAR2 genes that encode components of the high-affinity nitrate transport system (HATS) in the rice (Oryza sativa L. subsp. japonica cv. Nipponbare) genome. OsNRT2.1 and OsNRT2.2 share an identical coding region sequence, and their deduced proteins are closely related to those from mono-cotyledonous plants. The two NAR2 proteins are closely related to those from mono-cotyledonous plants as well. However, OsNRT2.3 and OsNRT2.4 are more closely related to Arabidopsis NRT2 proteins. Relative quantitative reverse transcription-polymerase chain reaction analysis showed that all of the six genes were rapidly upregulated and then downregulated in the roots of N-starved rice plants after they were re-supplied with 0.2 mM nitrate, but the response to nitrate differed among gene members. The results from phylogenetic tree, gene structure and expression analysis implied the divergent roles for the individual members of the rice NRT2 and NAR2 families. High-affinity nitrate influx rates associated with nitrate induction in rice roots were investigated and were found to be regulated by external pH. Compared with the nitrate influx rates at pH 6.5, alkaline pH (pH 8.0) inhibited nitrate influx, and acidic pH (pH 5.0) enhanced the nitrate influx in 1 h nitrate induced roots, but did not significantly affect that in 4 to 8 h nitrate induced roots.

[Development of a new type of biological organic fertilizer and its effect on the growth promotion of tomato]. / æ–°åž‹æœ¨éœ‰æ°¨åŸºé ¸æœ‰æœºè‚¥ç ”åˆ¶åŠå ¶å¯¹ç•ªèŒ„çš„ä¿ƒç”Ÿæ•ˆæžœ.

The objective of this study was to improve the ability of sporulation production of Trichoderma guizhouense NJAU4742 under solid state fermentation by using rice straw and amino acids as resources, and the fermentation products were used as inoculants of the organic fertilizers adding with different ratios of amino acids solution to develop a new type of biological organic fertilizer. The results indicated that the optimal condition for sporulation by T. guizhouense NJAU4742 was soaking in 30 times diluted amino acid solution for one whole night, with initial pH 3.5, 75% of moisture content and 30% of corn powder, under which the sporulation reached to 2.40×1010 CFU·g-1. The fermentation products were inoculated at 2% into the mature organic fertilizer containing 20% of amino acids solution, and the sporulation and IAA content were 6.40×109 CFU·g-1 and 38.66 mg·kg-1, which were 1142.30 and 1.42 times higher than that of CK after 7 days, respectively. Pot experiment showed that biological organic fertilizer could significantly promote the growth of tomato, and the height of the tomato increased by 98.8% and 23.8%, respectively, compared with CK. The stem diameters of AT (amino acids + mature organic fertilizer + T. guizhouense NJAU4742) and AA (amino acids + mature organic fertilizer) were increased by 58.9% and 10.3%, respectively, compared with CK. As for the chlorophyll, leaf length and leaf width, the values also increased significantly. The highest spore content was obtained by using amino acids and rice straw as substrates under solid state fermentation (SSF), which overcame the difficulties of producing new type of biological organic fertilizer during the large scale industrial production. Biological organic fertilizer and amino acids organic fertilizer could significantly promote the growth of tomato compared with the chemical fertilizer, and had a good application prospect in intensive agriculture.

[Effects of lime-ammonium bicarbonate fumigation and biofertilizer application on Fusarium wilt and biomass of continuous cropping cucumber and watermelon.] / çŸ³ç°ç¢³é“µç†è’¸ä¸Žæ–½ç”¨ç”Ÿç‰©æœ‰æœºè‚¥å¯¹è¿žä½œé»„ç“œå’Œè¥¿ç“œæž¯èŽç— åŠç”Ÿç‰©é‡çš„å½±å“.

In this study, the population size of soil microbes was determined using plate counting method after the application of lime-ammonium bicarbonate and ammonium bicarbonate fumigation. In addition, biofertilizer was applied after soil fumigation and population of Fusarium oxysporum, Fusarium wilt disease control efficiency and plant biomass were determined in the cucumber and watermelon continuous cropping soil. The results showed that the population of F. oxysporum in cucumber mono-cropped soil fumigated with lime-ammonium bicarbonate or ammonium bicarbonate was decreased by 95.4% and 71.4%, while that in watermelon mono-cropped soil was decreased by 87.3% and 61.2%, respectively compared with non-fumigated control (CK). Furthermore, the greenhouse experiment showed that biofertilizer application, soil fumigation and crop type showed significant effects on the number of soil F. oxysporum, Fusarium wilt disease incidence, disease control efficiency and plant biomass based on multivariate analysis of variance. In the lime-ammonium bicarbonate fumigated soil amended with biofertilizer (LFB), significant reductions in the numbers of F. oxysporum and Fusarium wilt disease incidence were observed in both cucumber and watermelon cropped soil compared to non-fumigated control soil applied with organic fertilizer. The disease control rate was 91.9% and 92.5% for cucumber and watermelon, respectively. Moreover, LFB also significantly increased the plant height, stem diameter, leaf SPAD, and dry biomass for cucumber and watermelon. It was indicated that biofertilizer application after lime-ammonium bicarbonate fumigation could effectively reduce the abundance of F. oxysporum in soil, control Fusarium wilt disease and improve plant biomass in cucumber and watermelon mono-cropping systems.

Changes in antibiotic concentrations and antibiotic resistome during commercial composting of animal manures.

The over-use of antibiotics in animal husbandry in China and the concomitant enhanced selection of antibiotic resistance genes (ARGs) in animal manures are of serious concern. Thermophilic composting is an effective way of reducing hazards in organic wastes. However, its effectiveness in antibiotic degradation and ARG reduction in commercial operations remains unclear. In the present study, we determined the concentrations of 15 common veterinary antibiotics and the abundances of 213 ARGs and 10 marker genes for mobile genetic elements (MGEs) in commercial composts made from cattle, poultry and swine manures in Eastern China. High concentrations of fluoroquinolones were found in the poultry and swine composts, suggesting insufficient removal of these antibiotics by commercial thermophilic composting. Total ARGs in the cattle and poultry manures were as high as 1.9 and 5.5 copies per bacterial cell, respectively. After thermophilic composting, the ARG abundance in the mature compost decreased to 9.6% and 31.7% of that in the cattle and poultry manure, respectively. However, some ARGs (e.g. aadA, aadA2, qacEΔ1, tetL) and MGE marker genes (e.g. cintI-1, intI-1 and tnpA-04) were persistent with high abundance in the composts. The antibiotics that were detected at high levels in the composts (e.g. norfloxacin and ofloxacin) might have posed a selection pressure on ARGs. MGE marker genes were found to correlate closely with ARGs at the levels of individual gene, resistance class and total abundance, suggesting that MGEs and ARGs are closely associated in their persistence in the composts under antibiotic selection. Our research shows potential disseminations of antibiotics and ARGs via compost utilization.

Probiotic Diversity Enhances Rhizosphere Microbiome Function and Plant Disease Suppression.

Bacterial communities associated with plant roots play an important role in the suppression of soil-borne pathogens, and multispecies probiotic consortia may enhance disease suppression efficacy. Here we introduced defined Pseudomonas species consortia into naturally complex microbial communities and measured the importance of Pseudomonas community diversity for their survival and the suppression of the bacterial plant pathogen Ralstonia solanacearum in the tomato rhizosphere microbiome. The survival of introduced Pseudomonas consortia increased with increasing diversity. Further, high Pseudomonas diversity reduced pathogen density in the rhizosphere and decreased the disease incidence due to both intensified resource competition and interference with the pathogen. These results provide novel mechanistic insights into elevated pathogen suppression by diverse probiotic consortia in naturally diverse plant rhizospheres. Ecologically based community assembly rules could thus play a key role in engineering functionally reliable microbiome applications. IMPORTANCE: The increasing demand for food supply requires more-efficient control of plant diseases. The use of probiotics, i.e., naturally occurring bacterial antagonists and competitors that suppress pathogens, has recently reemerged as a promising alternative to agrochemical use. It is, however, still unclear how many and which strains we should choose for constructing effective probiotic consortia. Here we present a general ecological framework for assembling effective probiotic communities based on in vitro characterization of community functioning. Specifically, we show that increasing the diversity of probiotic consortia enhances community survival in the naturally diverse rhizosphere microbiome, leading to increased pathogen suppression via intensified resource competition and interference with the pathogen. We propose that these ecological guidelines can be put to the test in microbiome engineering more widely in the future.

[Spectral analysis of dissolved organic matter derived from rice straw after chemical treatment].

Fourier transform infrared spectroscopy (FTIR), ultraviolet spectroscopy (UV), and nuclear magnetic resonance spectroscopy (NMR) were used to study the chemical composition of Dissolved Organic Matter (DOM) derived from rice straw in the hydrolysis process with a dilute complex acid solution. The results obtained are as follows. FTIR spectra could indicate the changes of DOM during the hydrolysis process of rice straw. With the progress of rice straw hydrolysis, methyl, methylene, aromatic compounds and carbohydrates decreased, most of aliphatic compounds were oxidized to CO2 and H2O, and others were turned into carbonates. Most of the organic silicon was hydrolyzed into inorganic silicon. The proteins, amino acids and other nitrogen were hydrolyzed to NH4+. All the recalcitrant fractions of rice straw, such as hemi-cellulose, cellulose and silicon sharply decreased during the process of chemical treatment. The results obtained in this paper proposed that the changes of DOM of rice straw in the hydrolysis could be an indication in the changes of chemical composition of rice straw during the hydrolyzation, and FTIR, UV and NMR were good methods to study the changes in the structure of organic compounds.