Maize functional requirements drive the selection of rhizobacteria under long-term fertilization practices.

Rhizosphere microbiomes are pivotal for crop fitness, but the principles underlying microbial assembly during root-soil interactions across soils with different nutrient statuses remain elusive. We examined the microbiomes in the rhizosphere and bulk soils of maize plants grown under six long-term (≥ 29 yr) fertilization experiments in three soil types across middle temperate to subtropical zones. The assembly of rhizosphere microbial communities was primarily driven by deterministic processes. Plant selection interacted with soil types and fertilization regimes to shape the structure and function of rhizosphere microbiomes. Predictive functional profiling showed that, to adapt to nutrient-deficient conditions, maize recruited more rhizobacteria involved in nutrient availability from bulk soil, although these functions were performed by different species. Metagenomic analyses confirmed that the number of significantly enriched Kyoto Encyclopedia of Genes and Genomes Orthology functional categories in the rhizosphere microbial community was significantly higher without fertilization than with fertilization. Notably, some key genes involved in carbon, nitrogen, and phosphorus cycling and purine metabolism were dominantly enriched in the rhizosphere soil without fertilizer input. In conclusion, our results show that maize selects microbes at the root-soil interface based on microbial functional traits beneficial to its own performance, rather than selecting particular species.

Mycotoxin contamination in organic and conventional cereal grain and products: A systematic literature review and meta-analysis.

There is still considerable controversy about the relative risk of mycotoxin exposure associated with the consumption of organic and conventional cereals. Using validated protocols, we carried out a systematic literature review and meta-analyses of data on the incidence and concentrations of mycotoxins produced by Fusarium, Claviceps, Penicillium, and Aspergillus species in organic and conventional cereal grains/products. The standard weighted meta-analysis of concentration data detected a significant effect of production system (organic vs. conventional) only for the Fusarium mycotoxins deoxynivalenol, with concentrations ∼50% higher in conventional than organic cereal grains/products (p < 0.0001). Weighted meta-analyses of incidence data and unweighted meta-analyses of concentration data also detected small, but significant effects of production system on the incidence and/or concentrations of T-2/HT-2 toxins, zearalenone, enniatin, beauvericin, ochratoxin A (OTA), and aflatoxins. Multilevel meta-analyses identified climatic conditions, cereal species, study type, and analytical methods used as important confounding factors for the effects of production system. Overall, results from this study suggest that (i) Fusarium mycotoxin contamination decreased between the 1990s and 2020, (ii) contamination levels are similar in organic and conventional cereals used for human consumption, and (iii) maintaining OTA concentrations below the maximum contamination levels (3.0 µg/kg) set by the EU remains a major challenge.

Humic acid complex formation with urea alters its structure and enhances biomass production in hydroponic maize.

BACKGROUND: Humic acid (HA)-enhanced urea (HAU) is the top-selling efficiency-enhanced urea in China. Comprehensive investigation into the structure and efficacy of HA complex formation with urea (HACU) - the main reaction product during HAU's production - is required to clarify the reaction mechanism between HA and urea, and to provide guidance for the development of high-efficiency HAU. RESULTS: HACU showed discrepant structural and compositional features from raw HA. Nitrogen (N) content in HACU was 7.3 times greater than that of HA. Several high-resolution analytical methods showed a sharp increase of ammonia in the gaseous product during HACU pyrolysis, suggesting that urea contributed N to HACU. HACU was characterized with significantly fewer carboxyl groups than in raw HA, implying that the carboxyl group was the main group in HA to participate in the reaction between HA and urea. The presence of amide-N in HACU verified the structure of the reaction product. Furthermore, both HACU and HA could enhance the biomass in hydroponically grown maize seedlings, but the highest stimulation for HACU came about when its carbon concentrations were 50-100 mg L-1 , higher than the optimal carbon concentration for HA (25 mg L-1 ), attributed to the lower carboxyl group content for HACU to some extent. CONCLUSION: During HAU's production, reaction with N derived from urea to form amide-N decreased the carboxyl groups in HA, leading to higher concentrations for HACU required to achieve the similar bioefficacy of HA. © 2021 Society of Chemical Industry.

Characteristic component profiling and identification of different Uncaria species based on high-performance liquid chromatography-photodiode array detection tandem ion trap and time of flight mass spectrometry coupled with rDNA ITS sequence.

Uncaria is a multi-source herb and its species identification has become a bottleneck in quality control. To study the identification method of different Uncaria species herbs through HPLC-MS coupled with rDNA Internal Transcribed Spacer (rDNA ITS) sequence, both plant morphological traits and molecular identification were used to determine the species of every collected Uncaria herb. The genetic analysis of different Uncaria species was performed using their rDNA ITS sequence as a molecular marker. Meanwhile, the phylogenetic relationships of 22 samples from six Uncaria species were divided and classified clearly. By optimizing the chromatographic conditions, a practical HPLC method to differentiate various varieties of Uncaria herbs was set up based on a set of characteristic components across each species. A high-performance liquid chromatography-photodiode array detector tandem ion trap and time of flight mass spectrometry technique combined with reference substances was utilized to derive 21 characteristic compounds containing six groups of six Uncaria species in China. Thus, this study provides a feasible method to solve the current problem of confusion in Uncaria species, and makes a significant step forward in the appropriate clinical use, in-depth research and further utilization of different Uncaria species.

Brevibacillus halotolerans sp. nov., isolated from saline soil of a paddy field.

Two novel aerobic bacteria, designated strains LAM0312T and LAM0313, were isolated from saline soil samples collected from a paddy field in Dezhou city, Shandong Province, China. Cells of these strains were Gram-stain-positive, sporogenous, rod-shaped and motile with peritrichous flagella. The optimal growth temperature and pH were 30 °C and pH 7.0-8.0. Strain LAM0312T was able to grow in the presence of 12 % (w/v) NaCl. The major fatty acids were anteiso-C15 : 0 and iso-C15 : 0. The dominant polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, glycolipids, five unidentitied lipids and phosphatidylmonomethylethanolamine. The cell-wall peptidoglycan was found to contain meso-diaminopimelic acid. The predominant menaquinone was identified as menaquinone-7. The G+C content of the genomic DNA of strains LAM0312T and LAM0313 was 45.0 and 46.0 mol%, respectively, as determined by the Tm method. 16S rRNA gene sequence similarity analysis indicated that the strains were closely related to Brevibacillus laterosporus DSM 25T and Brevibacillus fluminis JCM 15716T with 98.5 and 96.4 % sequence similarity, respectively. The DNA-DNA hybridization value between strain LAM0312T and LAM0313 was 92±0.6 % (reciprocal 90±0.2 %) and the value between strain LAM0312T and Brevibacillus laterosporus DSM 25T was 48±0.5 % (reciprocal 40±0.4 %). On the basis of the phenotypic, phylogenetic and chemotaxonomic characteristics, the two strains are proposed to represent a novel species of the genus Brevibacillus, for which the name Brevibacillus halotolerans sp. nov. is proposed. The type strain is LAM0312T (=ACCC 06527T=JCM 30849T).

Bacillus vini sp. nov. isolated from alcohol fermentation pit mud.

A novel aerobic, Gram-stain-positive, sporogenous, rod-shaped bacterium, designated LAM0415(T), was isolated from an alcohol fermentation pit mud sample collected from Sichuan Luzhou-flavour liquor enterprise in China. The isolate was found to be able to grow at NaCl concentrations of 0-10 % (w/v) (optimum: 1.0 %), 10-50 °C (optimum: 30-35 °C) and pH 3.0-10.0 (optimum: 7.0-8.0). Phylogenetic analysis of 16S rRNA gene sequences indicated that the new isolate belonged to the genus Bacillus and was closely related to Bacillus sporothermodurans DSM 10599(T) and Bacillus oleronius DSM 9356(T), with 98.4 and 97.2 % sequence similarity, respectively. The DNA-DNA hybridization values between strain LAM0415(T) and the two reference strains were 33.3 ± 1.2 and 42.8 ± 0.8 %, respectively. The genomic DNA G+C content was 35.2 mol% as determined by the T m method. The major fatty acids were determined to be iso-C15:0, anteiso-C15:0 and anteiso-C17:0. The predominant menaquinones were identified as MK7 and MK8. The major polar lipids were found to be diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, one unidentified phospholipid and four unidentified glycolipids. The diagnostic amino acid of the cell wall peptidoglycan was determined to be meso-diaminopimelic acid. On the basis of its phenotypic, phylogenetic and chemotaxonomic characteristics, strain LAM0415(T) (=ACCC 06413(T) = JCM 19841(T)) represents the type strain of a novel species of the genus Bacillus, for which the name Bacillus vini sp. nov. is proposed.

Chromobacterium rhizoryzae sp. nov., isolated from rice roots.

A novel facultatively anaerobic, rod-shaped bacterium, designated LAM1188T, was isolated from the roots of rice (Oryzasativa) in Hubei Province. Cells of LAM1188T were Gram-stain-negative and motile. The temperature and pH ranges for growth were 15-40 °C (optimum: 30 °C) and pH 5-10 (optimum: pH 7), respectively. The strain did not require NaCl for growth but tolerated up to 3.5 % NaCl (w/v). Analysis of the 16S rRNA gene sequence indicated that the isolate represented a member of the genus Chromobacterium, and was most closely related to Chromobacterium haemolyticum MDA0585T and Chromobacterium aquaticum CC-SEYA-1T with 98.7 % and 97.3 % sequence similarity, respectively. The values of DNA-DNA hybridization between LAM1188T and C. haemolyticum JCM 14163T and C. aquaticum CCUG 55175T were 54.0±2.1 % and 44.0±1.2 %, respectively. The major cellular fatty acids were C16 : 0 and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c). The main polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, four unidentified aminolipids and four unidentified lipids. The respiratory quinone was ubiquinone Q-8. The DNA G+C content was 64.1 mol% as determined by the Tm method. On the basis of its phenotypic, chemotaxonomic and phylogenetic characteristics, strain LAM1188T is suggested to represent a novel species of the genus Chromobacterium, for which the name Chromobacte riumrhizoryzae sp. nov. is proposed. The type strain is LAM1188T (=ACCC 19900T=JCM 31180T).

Frigoribacterium salinisoli sp. nov., isolated from saline soil, transfer of Frigoribacterium mesophilum to Parafrigoribacterium gen. nov. as Parafrigoribacterium mesophilum comb. nov.

A Gram-stain-positive, short-rod, aerobic bacterium, designated as strain LAM9155T, was isolated from saline soil sample collected from Lingxian County, Shandong Province, PR China. The strain grew optimally at 25-30 °C, pH 7.0 and 0.5 % (w/v) NaCl. The 16S rRNA gene sequence analysis revealed that strain LAM9155T belonged to the genus Frigoribacterium and was closely related to Frigoribacteriumendophyticum EGI 6500707T (99.4 %), Frigoribacteriumfaeni 801T (98.6 %) and Frigoribacteriummesophilum MSL-08T (96.2 %). The DNA-DNA hybridization values between strain LAM9155T and F. endophyticum JCM 30093T and between strain LAM9155T and F. faeni DSM 10309T were 40.2±2.1 and 32.8±1.6 %, respectively. The major fatty acids of LAM9155T were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0. The cell-wall analysis showed the B-type peptidoglycan containing alanine, glutamate, glycine, serine and lysine and that the cell wall contained the sugars galactose and ribose. The genomic DNA G+C content of strain LAM9155T was 68.2 mol%. The predominant menaquinone was MK-9. The main polar lipids were diphosphatidylglycerol, phosphatidylglycerol, one unknown glycolipid and four unknown lipids. Based on the DNA-DNA hybridization and phenotypic, phylogenetic and chemotaxonomic properties, strain LAM9155T could be distinguished from the recognized species of the genus Frigoribacterium and was suggested to represent a novel species, for which the name Frigoribacterium salinisoli sp. nov. is proposed. The type strain is LAM9155T (=ACCC 19902T=JCM 30848T). Moreover, the transfer of F. mesophilum Dastager et al. 2008 to Parafrigoribacterium gen. nov. as Parafrigoribacterium mesophilum comb. nov. (type strain MSL-08T=DSM 19442T=KCTC 19311T) is also proposed.

Paenibacillus salinicaeni sp. nov., isolated from saline silt sample.

A novel facultatively anaerobic bacterium, designated strain LAM0A28(T), was isolated from a saline silt sample collected from the Chinese Sea of Death located in Suining city, Sichuan province, China. Cells of strain LAM0A28(T) were observed to be Gram-stain positive, motile, endospore-forming and straight-rod shaped. Strain LAM0A28(T) was found to be able to grow at 15-45 °C (optimum: 30-35 °C), pH 5.0-10.0 (optimum: 7.5) and 0-5 % NaCl (w/v) (optimum: 0.5 %). The 16S rRNA gene sequence similarity analysis showed that strain LAM0A28(T) is closely related to Paenibacillus jilunlii DSM 23019(T) (97.5 %) and Paenibacillus graminis DSM 15220(T) (97.2 %). The DNA-DNA hybridization values between the isolate and P. jilunlii DSM 23019(T), P. graminis DSM 15220(T) were 30.2 ± 1.6 % and 44.7 ± 2.1 %, respectively. The DNA G+C content was found to be 51.2 mol% as determined by the T m method. The major cellular fatty acids were identified as anteiso-C15:0, C16:0, iso-C16:0 and C14:0. The major isoprenoid quinone was identified as MK-7. The cell wall peptidoglycan was found to contain meso-diaminopimelic acid. The major polar lipids were found to be diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, two aminophospholipids and six unidentified lipids. Based on the phylogenetic, phenotypic and chemotaxonomic characteristics, strain LAM0A28(T) is concluded to represent a novel species within the genus Paenibacillus, for which the name Paenibacillus salinicaeni sp. nov. is proposed. The type strain is LAM0A28(T) (=ACCC 00741(T) = JCM 30850(T)).

Romboutsia sedimentorum sp. nov., isolated from an alkaline-saline lake sediment and emended description of the genus Romboutsia.

A Gram-stain-positive, spore-forming, obligately anaerobic bacterium, designated LAM201(T), was isolated from sediment samples from an alkaline-saline lake located in Daqing oilfield, Daqing City, PR China. Cells of strain LAM201(T) were non-motile and straight or spiral rod-shapes. Strain LAM201(T) was able to utilize glucose, fructose, maltose, trehalose and sorbitol as the sole carbon source. Acetic acid, ethanol, iso-butanoic acid and iso-valeric acid were the main products of glucose fermentation. The major fatty acids of LAM201(T) were C(16 : 0) (26.7%) and C(18 : 0) (11.2%). The main polar lipids were four unknown glycolipids and five unknown phospholipids. The predominant cell-wall sugars were ribose and galactose. The cell-wall peptidoglycan of strain LAM201(T) contained alanine, glycine, glutamic acid and aspartic acid. Sodium sulfite was used as the electron acceptor. The G+C content of the genomic DNA was 32±0.8 mol%, as determined by the T(m) method. Analysis of the 16S rRNA gene sequence indicated that the isolate belonged to the genus Romboutsia and was most closely related to Romboutsia lituseburensis DSM 797(T) and Romboutsia ilealis CRIB(T) with 97.3% and 97.2% similarities, respectively. The DNA-DNA hybridization values between strain LAM201(T) and the two reference strains were 37% and 31%, respectively. On the basis of its phenotypic, phylogenetic and chemotaxonomic characteristics, strain LAM201(T) is suggested to represent a novel species within the genus Romboutsia , for which the name Romboutsia sedimentorum sp. nov. is proposed. The type strain is LAM201(T) ( = ACCC 00717(T) = JCM 19607(T)).

Microbacterium petrolearium sp. nov., isolated from an oil-contaminated water sample.

A Gram-staining-positive, rod-shaped, aerobic bacterium, designated strain LAM0410(T), was isolated from an oil-contaminated water sample from the Dagang Oilfield, PR China. The temperature and pH ranges for growth were 4 °C to 50 °C and pH 4.4 to pH 12.0, respectively. The strain did not need NaCl for growth, but could tolerate a concentration of up to 12 % (w/v). Cell wall hydrolysates from the isolate showed that the diamino acid was ornithine. The cell wall sugars contained ribose and galactose. The glycan moiety of the cell wall contained N-glycolyl residues. The major respiratory quinones were MK-10, MK-11 and MK-12. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and nine unknown glycolipids. The major fatty acids were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0. 16S rRNA gene sequence analysis indicated that the isolate belonged to the genus Microbacterium and was closely related to Microbacterium sediminis MCCC 1A06153(T) and Microbacterium murale DSM 22178(T) with 97.5 % and 97.4 % sequence similarities, respectively; while the DNA-DNA hybridization values were 33.1±3.4 % and 21.8±1.6 %, respectively. The DNA G+C content was 67.4 mol%, as determined by the Tm method. Based on its phenotypic and genotypic properties, strain LAM0410(T) represents a novel species of the genus Microbacterium, for which the name Microbacterium petrolearium sp. nov. is proposed; the type strain is LAM0410(T) ( = ACCC 00719(T) = JCM 19612(T)).

Clostridium huakuii sp. nov., an anaerobic, acetogenic bacterium isolated from methanogenic consortia.

A Gram-staining-positive, spore-forming, obligately anaerobic, acetogenic bacterium, designated LAM1030(T), was isolated from methanogenic consortia enriched from biogas slurry collected from the large-scale anaerobic digester of Modern Farming Corporation in Hebei Province, China. Cells of strain LAM1030(T) were motile, straight or spiral-rod-shaped. Strain LAM1030(T) could utilize glucose, fructose, maltose, galactose, lactose, sucrose, cellobiose, mannitol, pyruvate, succinic acid and tryptophan as the sole carbon source. Acetic acid, isovaleric acid and butanoic acid were the main products of glucose fermentation. Sodium sulfite was used as an electron acceptor. Growth of strain LAM1030(T) was completely inhibited by the addition of ampicillin, tetracycline, gentamicin or erythromycin at a concentration of 20 µg ml(-1). The main polar lipids of strain LAM1030(T) were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, 11 unknown glycolipids and two unknown phospholipids. No respiratory quinone was detected. The major fatty acids of strain LAM1030(T) were C16 : 0 (21.1 %), C14 : 0 (10.3 %), summed feature 9 (including C16:0 10-methyl and/or iso-C17:1 ω9c) (11.3% ), summed feature 3 (including C16:1 ω7c and/or C16:1 ω6c) (10.6% ) and iso-C15 : 0 (6.6 %). Analysis of the 16S rRNA gene sequence indicated that strain LAM1030(T) belonged to the genus Clostridium and was most closely related to Clostridium subterminale DSM 6970(T), Clostridium thiosulfatireducens DSM 13105(T) and Clostridium sulfidigenes DSM 18982(T), with 97.0, 96.9 and 96.8 % similarity, respectively. The G+C content of the genomic DNA of strain LAM1030(T) was 31.2±0.3 mol%. On the basis of its phenotypic, phylogenetic and chemotaxonomic characterization, strain LAM1030(T) is suggested to represent a novel species of the genus Clostridium, for which the name Clostridium huakuii sp. nov. is proposed. The type strain is LAM1030(T) ( = ACCC 00698(T) = JCM 19186(T)).

Lysinibacillus halotolerans sp. nov., isolated from saline-alkaline soil.

A novel aerobic, halotolerant bacterium, designated strain LAM612(T), was isolated from saline-alkaline soil samples from Lingxian County, Shandong Province, China. Cells of strain LAM612(T) were Gram-reaction-positive, endospore-forming, motile and rod-shaped. The optimal temperature and pH for growth were 35 °C and pH 6.0, respectively. Strain LAM612(T) could grow in the presence of up to 10% (w/v) NaCl. The genomic DNA G+C conten was 36.4 mol% as detected by the T(m) method. Comparative analysis of 16S rRNA gene sequences revealed that LAM612(T) was closely related to Lysinibacillus sinduriensis KACC 16611(T) (98.0%), L. chungkukjangi KACC 16626(T) (97.5%), L. massiliensis KCTC 13178(T) (97.4%), L. xylanilyticus KACC 15113(T) (97.2%), L. macroides DSM 54(T) (97.0%) and L. manganicus DSM 26584(T) (96.5%). The DNA-DNA hybridization values between strain LAM612(T) and its closest relatives ranged from 20.6% to 41.9%. The major fatty acids of strain LAM612(T) were iso-C(15 : 0) (40.8%), iso-C(16 : 0) (15.2%) and anteiso-C(15 : 0) (10.8%). The cell-wall peptidoglycan content was A4α (L-Lys-D-Asp). The predominant menaquinone was MK-7 and the main polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, three unknown phospholipids, five unknown glycolipids and an unknown lipid. Based on the DNA-DNA hybridization results and phenotypic, phylogenetic and chemotaxonomic properties, strain LAM612(T) could be distinguished from the recognized species of the genus Lysinibacillus, and was suggested to represent a novel species of this genus, for which the name Lysinibacillus halotolerans sp. nov. is proposed. The type strain is LAM612(T) ( = ACCC 00718(T) = JCM 19611(T)).

Potential of vibrational spectroscopy coupled with machine learning as a non-invasive diagnostic method for COVID-19.

BACKGROUND AND OBJECTIVE: Efforts to alleviate the ongoing coronavirus disease 2019 (COVID-19) crisis showed that rapid, sensitive, and large-scale screening is critical for controlling the current infection and that of ongoing pandemics. METHODS: Here, we explored the potential of vibrational spectroscopy coupled with machine learning to screen COVID-19 patients in its initial stage. Herein presented is a hybrid classification model called grey wolf optimized support vector machine (GWO-SVM). The proposed model was tested and comprehensively compared with other machine learning models via vibrational spectroscopic fingerprinting including saliva FTIR spectra dataset and serum Raman scattering spectra dataset. RESULTS: For the unknown vibrational spectra, the presented GWO-SVM model provided an accuracy, specificity and F1_score value of 0.9825, 0.9714 and 0.9778 for saliva FTIR spectra dataset, respectively, while an overall accuracy, specificity and F1_score value of 0.9085, 0.9552 and 0.9036 for serum Raman scattering spectra dataset, respectively, which showed superiority than those of state-of-the-art models, thereby suggesting the suitability of the GWO-SVM model to be adopted in a clinical setting for initial screening of COVID-19 patients. CONCLUSIONS: Prospectively, the presented vibrational spectroscopy based GWO-SVM model can facilitate in screening of COVID-19 patients and alleviate the medical service burden. Therefore, herein proof-of-concept results showed the chance of vibrational spectroscopy coupled with GWO-SVM model to help COVID-19 diagnosis and have the potential be further used for early screening of other infectious diseases.

Breeding Bread-Making Wheat Varieties for Organic Farming Systems: The Need to Target Productivity, Robustness, Resource Use Efficiency and Grain Quality Traits.

Agronomic protocols (rotation, tillage, fertilization and crop protection) commonly used in organic and conventional crop production differ significantly and there is evidence that modern varieties developed for conventional high-input farming systems do not have the combination of traits required for optimum performance in organic farming systems. Specifically, there is evidence that prohibition on the use of water-soluble, mineral N, P and K fertilizers and synthetic pesticide inputs in organic farming results in a need to revise both breeding and selection protocols. For organic production systems, the focus needs to be on the following: (i) traits prioritized by organic farmers such as high nutrient use efficiency from organic fertilizer inputs, competitiveness against weeds, and pest and disease resistance, (ii) processing quality parameters defined by millers and bakers and (iii) nutritional quality parameters demanded by organic consumers. In this article, we review evidence from variety trials and factorial field experiments that (i) studied to what extent there is a need for organic farming focused breeding programs, (ii) investigated which traits/trait combinations should be targeted in these breeding programs and/or (iii) compared the performance of modern varieties developed for the conventional sector with traditional/older varieties favored by organic farmers and/or new varieties developed in organic farming focused breeding programs. Our review focuses on wheat because there have been organic and/or low-input farming focused wheat breeding programs for more than 20 years in Europe, which has allowed the performance of varieties/genotypes from organic/low-input and conventional farming focused breeding programs to be compared.

Comparison of the structural basis for thermal stability between archaeal and bacterial proteins.

In this study, the structural basis for thermal stability in archaeal and bacterial proteins was investigated. There were many common factors that confer resistance to high temperature in both archaeal and bacterial proteins. These factors include increases in the Lys content, the bends and blanks of secondary structure, the Glu content of salt bridge; decreases in the number of main-side chain hydrogen bond and exposed surface area, and changes in the bends and blanks of amino acids. Certainly, the utilization of charged amino acids to form salt bridges is a primary factor. In both heat-resistant archaeal and bacterial proteins, most Glu and Asp participate in the formation of salt bridges. Other factors may influence either archaeal or bacterial protein thermostability, which includes the more frequent occurrence of shorter 3(10)-helices and increased hydrophobicity in heat-resistant archaeal proteins. However, there were increases in average helix length, the Glu content in salt bridges, temperature factors and decreases in the number of main-side chain hydrogen bonds, uncharged-uncharged hydrogen bonds, hydrophobicity, and buried and exposed polar surface area in heat-resistant bacterial proteins. Evidently, there are few similarities and many disparities between the heat-resistant mechanisms of archaeal and bacterial proteins.

Humic Acid Modified by Being Incorporated Into Phosphate Fertilizer Increases Its Potency in Stimulating Maize Growth and Nutrient Absorption.

Humic acid-enhanced phosphate fertilizer (HAP) is widely applied in Chinese agriculture due to its high efficiency. Although the structural composition and physicochemical properties of humic acid (HA) are significantly altered during HAP production, a clear understanding of the mechanisms underlying the biological effects of HA extracted from HAP fertilizer (PHA) on plant growth is still lacking. In the current study, we extracted PHA from HAP and assessed its effects on the dry biomass, phosphorus (P) and nitrogen (N) uptake, and P absorption rate of maize seedlings when supplied at different concentrations (2.5, 5, 10, and 25 mg C L-1) in the hydroponic culture. The root vigor, root plasma membrane H+-ATPase activity, and root nitrate reductase activity were also determined as the representative indicators of the root capacity for nutrient absorption, and used to clarify the mechanism by which PHA affects the maize growth and nutrient absorption. The results showed that the dry biomass, phosphorus uptake, nitrogen uptake, and average phosphorus absorption rates were significantly higher by 14.7-27.9%, 9.6-35.1%, 17.9-22.4%, and 22.1-31.0%, respectively, in plants treated with 2.5-5 mg C L-1 PHA compared to untreated controls. Application of 10-25 mg C L-1 raw HA resulted in similar stimulatory effects on plant growth and nutrient absorption. However, higher levels of PHA (10-25 mg C L-1) negatively impacted these indicators of plant growth. Furthermore, low PHA or high raw HA concentrations similarly improved root vigor and root plasma membrane H+-ATPase and nitrate reductase (NR) activities. These results indicate that lower concentrations of PHA can stimulate maize seedling growth and nutrient absorption to an extent that is comparable to the effect of higher concentrations of raw HA. Thus, the proportion of HA incorporated into HAP could be lower than the theoretical amount estimated through assays evaluating the biological effects of raw HA.

Combining humic acid with phosphate fertilizer affects humic acid structure and its stimulating efficacy on the growth and nutrient uptake of maize seedlings.

This paper analyzed the compositional and structural changes of humic acid (HA) after combined with phosphate fertilizer (PHA), and investigated its effects on the growth of maize seedlings with four humic acid concentrations. The results showed that the atomic ratios of O/C and (O + N)/N of PHA were significantly lower than those of HA, which indicated that PHA had poor hydrophilicity compared with HA. The spectra of FTIR and NMR results suggested that the relative content of carboxyl group in PHA was higher than that in HA. X-ray photoelectron spectroscopy technology showed that the relative amount of C-C in PHA was lower than that in HA, while C-H was the opposite. The above changes were attributed to the crack of HA structure during the preparation of humic acid enhanced phosphate fertilizer, which was verified by the results from the determination of gel permeation chromatography that there were more low molecular weight components in PHA than that in HA. However, compared with HA, PHA showed a worse effect in promoting growth and the uptake of nitrogen, phosphorus and potassium by maize seedlings. This worse effect might be attributed to the poor hydrophilicity and unsuitable addition amount of PHA.

Long-term fertilization alters soil properties and fungal community composition in fluvo-aquic soil of the North China Plain.

Different fertilization regimes can substantially influence soil fungal community composition, yet fewer studies try to control for the effects of nitrogen input. Here, we investigated the impact of fertilization with equal nitrogen upon soil properties and soil fungal diversity and community composition in the North China Plain in a long-term field experiment. Long-term (32 years) fertilization regimes were applied with equal amounts of nitrogen: no chemical fertilizer or organic manure; chemical fertilization only; organic manure fertilization only, and; combination of 1/2 chemical fertilizer and 1/2 organic manure. Then we investigated the influence of these four fertilization regimes to soil properties, fungal diversity and community composition. The results showed that applying organic manure significantly influenced soil properties. Illumina MiSeq sequencing and its analysis revealed that organic manure fertilization significantly changed soil fungal alpha diversity, but chemical fertilization did not. Although soil fungal community composition did not differ significantly among all the fertilization regimes at the phylum and class levels, they did show differences in the abundance of dominant fungi. Yet at the genus level, soil fungal community composition, abundance, and beta diversity was affected by all fertilization regimes. Application of organic manure also reduced the abundance of soil-born fungal pathogens such as Fusarium. Our results suggest that long-term application of organic manure could markedly improve soil properties, altering soil fungal community composition and its diversity. Moreover, organic manure fertilization could limit soil-born fungal diseases, to further contribute to soil ecosystem sustainability.

Structural characteristics of humic acids derived from Chinese weathered coal under different oxidizing conditions.

Humic acids derived from Chinese weathered coal were oxidized with hydrogen peroxide (H2O2) under various conditions, and their chemical composition and structure were examined. The raw material humic acids (HA) and oxidized humic acids (OHAs) were characterized by elemental analysis and ultraviolet visible (UV-Vis), Fourier transform infrared (FTIR), and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Our results show that aromatic functional groups accounted for more than 70% of the HA and OHAs and there were significant differences in their structures and compositions. Compared to the HA, the average H and N contents of the OHAs decreased by 5.15% and 2.52%, respectively, and the average O content of those of the OHAs increased by 5.30%. The hydrophobicity index (HI) of HA is higher than those of the OHAs. Importantly, in the hypothesis test between the properties and preparation conditions of humic acid using SPSS, the partial η2 of the temperature, hydrogen peroxide concentration, liquid-solid ratio, and time were 0.809, 0.771, 0.748 and 0.729, respectively; thus, among the preparation conditions, temperature is the most important factor affecting the humic acids properties.