Impacts of maize hybrids with different nitrogen use efficiency on root-associated microbiota based on distinct rhizosphere soil metabolites.

Plant genotypes shape root-associated microbiota that affect plant nutrient acquisition and productivity. It is unclear how maize hybrids modify root-associated microbiota and their functions and relationship with nitrogen use efficiency (NUE) by regulating rhizosphere soil metabolites. Here, two N-efficient (NE) (ZD958, DMY3) and two N-inefficient (NIE) maize hybrids (YD9953, LY99) were used to investigate this issue under low N (60 kg N ha-1 , LN) and high N (180 kg N ha-1 , HN) field conditions. NE hybrids had higher yield than NIE hybrids under LN but not HN. NE and NIE hybrids recruited only distinct root-associated bacterial microbiota in LN. The bacterial network stability was stronger in NE than NIE hybrids. Compared with NIE hybrids, NE hybrids recruited more bacterial taxa that have been described as plant growth-promoting rhizobacteria (PGPR), and less related to denitrification and N competition; this resulted in low N2 O emission and high rhizosphere NO3 - -N accumulation. NE and NIE hybrids had distinct rhizosphere soil metabolite patterns, and their specific metabolites were closely related to microbiota and specific genera under LN. Our findings reveal the relationships among plant NUE, rhizosphere soil metabolites, root-associated microbiota, and soil nutrient cycling, and this information is informative for breeding NE crops.

Comparative analysis of the effects of conventional and biodegradable plastic mulching films on soil-peanut ecology and soil pollution.

In agricultural production, biodegradable plastic mulching film (Bio-PMF) has the potential to replace conventional plastic mulching film (CPMF) due to its degradability, but their impacts on soil-crop ecology are controversial. In this study, from 2019 to 2021, effects of CPMF and Bio-PMF on the soil-crop ecology and soil pollution were evaluated on a peanut farm. Compared to the Bio-PMF, an overall improvement in the soil-peanut ecology under the CPMF was observed, including an increase of 10.77 ± 4.8% in peanut yield, an amelioration of four soil physicochemical properties (total P and available P in the flowering stage, total P and temperature in the mature stage), an increase of rhizobacterial relative abundances in class level (Bacteroidia, Blastocatellia, Thermoleophilia and Vicinamibacteria in the flowering stage, Nitrospira and Bacilli in the mature stage) and genus level (RB41 and Bacillus in the flowering stage, Bacillus and Dongia in the mature stage), and an enhancement of soil nitrogen metabolism abilities (ureolysis, nitrification and aerobic ammonia in the flowering stage, nitrate reduction and nitrite ammonification in the mature stage). These preserved soil nutrients and temperature, reshaped rhizobacterial communities, and enhanced soil nitrogen metabolism abilities in the mature stage were obviously correlated with peanut yield under CPMF. However, such remarkable relations were not existed under Bio-PMF. In addition, compared with Bio-PMF, CPMF significantly increased the contents of dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) and microplastics (MPs) in soil by 79.93, 44.55, 138.72 and 14.1%, respectively. Thus, CPMF improved soil-peanut ecology and caused serious soil pollution, while Bio-PMF introduced little pollutants into the soil and had little impact on soil-peanut ecology. Based on these, the degradation ability of CPMF or the ecological improvement capacity of Bio-PMF should be improved to obtain the environmentally and soil-crop ecology friendly plastic film in the future.

Rhizobium petrolearium sp. nov., isolated from oil-contaminated soil.

Two Gram-negative, aerobic, rod-shaped bacteria, designated strains SL-1(T) and F11, which had the ability to decompose polycyclic aromatic hydrocarbons (PAHs), were isolated from soil samples contaminated by oil. The cells were motile by polar or lateral flagella. According to comparison of 16S rRNA gene sequences, strains SL-1(T) and F11 were identical and showed the greatest degree of similarity (96.8%) to both Rhizobium oryzae Alt505(T) and Rhizobium mesosinicum CCBAU 25010(T); however, only Rhizobium oryzae with SL-1(T) and F11 formed a separate clade. There were low similarities (<90%) between the atpD and recA sequences of the two strains and those of the genus of Rhizobium. The bacteria grew at temperatures of 10-40 °C with an optimum of 30 °C. The pH range for growth was 6.0-10.0 and optimum pH was 7.0-8.0. Growth occurred at NaCl concentrations up to 3.0% (w/v). They were catalase- and oxidase-positive. The main cellular fatty acids were summed feature 8 (18:1ω7c and/or 18:1ω6c) and 16:0. The DNA G+C content was 62.2 mol%. Strain SL-1(T) showed 29 and 0% DNA-DNA relatedness, respectively, with the most related strains R. oryzae Alt505(T) and R. mesosinicum CCBAU 25010(T) according to phylogenic analysis of the 16S rRNA gene. According to physiological and biochemical characteristics and genotypic data obtained in this work, the bacteria represent a novel species of the genus Rhizobium, and the name Rhizobium petrolearium is proposed. The type strain is SL-1(T) ( = ACCC 11238(T) = KCTC 23288(T)) and it could nodulate Medicago sativa in nodulation tests.

Paenibacillus beijingensis sp. nov., a novel nitrogen-fixing species isolated from jujube garden soil.

A novel Gram-positive, rod-shaped, motile, spore-forming, nitrogen-fixing bacterium, designated strain 7188(T), was isolated from jujube rhizosphere soil in Beijing, China. The strain grew at 4-40 °C and pH 6-12, with an optimum of 30 °C and pH 7.0, respectively. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain 7188(T) is a member of the genus Paenibacillus. Levels of 16S rRNA gene sequence similarities between strain 7188(T) and the type strains of all recognized members of the genus Paenibacillus were below 96 %. The major cellular fatty acids were anteiso-C(15:0), anteiso-C(17:0) and C(16:0). The predominant menaquinone was MK-7. The DNA G+C content of strain 7188(T) was 60.3 mol%. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and unknown aminophospholipids. The diamino acid in the cell wall peptidoglycan is meso-diaminopimelic acid. On the basis of these results, strain 7188(T) is considered to represent a novel species of the genus Paenibacillus, for which the name Paenibacillus beijingensis sp. nov. is proposed. The type strain is 7188(T) (=ACCC 03082(T) = DSM 24997(T)).

Synergistic interactions between Glomus mosseae and Bradyrhizobium japonicum in enhancing proton release from nodules and hyphae.

Soybean (Glycine max L. Merr.) seedlings were inoculated with Glomus mosseae (GM) and Bradyrhizobium japonicum (BJ) together or separately to study the effect of interactions on net H(+) effluxes of nodules or extraradical hyphae by in vivo vibrating electrode techniques. GM promoted three-fold the H(+) effluxes of nodules on mycorrhizal lateral roots and BJ increased eight-fold the net H(+) effluxes of hyphae developing in the vicinity of nodules on lateral roots. Increments in plant P content were positively and linearly correlated with the net H(+) efflux of nodules and hyphae. It is concluded that increased H(+) effluxes of nodules resulted from enhanced nitrogenase activities induced by the presence of the AM fungus in lateral roots. The results point to additive effects of interactions between mycorrhizal fungi and rhizobia in increasing the extent of acidification of the "nodulesphere" and the hyposphere.

Effectsof growth-promoting rhizobacteria on maize growth and rhizosphere microbial community under conservation tillage in Northeast China.

Conservation tillage in conjunction with straw mulching is a sustainable agricultural approach. However, straw mulching reduces the soil temperature, inhibits early maize growth and reduces grain yield in cold regions. To address this problem, we investigated the effects of inoculation of plant growth-promoting rhizobacteria (PGPR) on maize growth and rhizosphere microbial communities under conservation tillage in Northeast China. The PGPR strains Sinorhizobium sp. A15, Bacillus sp. A28, Sphingomonas sp. A55 and Enterobacter sp. P24 were isolated from the maize rhizosphere in the same area and inoculated separately. Inoculation of these strains significantly enhanced maize growth, and the strains A15, A28 and A55 significantly increased grain yield by as much as 22%-29%. Real-time quantitative PCR and high-throughput sequencing showed that separate inoculation with the four strains increased the abundance and species richness of bacteria in the maize rhizosphere. Notably, the relative abundance of Acidobacteria_Subgroup_6, Chloroflexi_KD4-96, and Verrucomicrobiae at the class level and Mucilaginibacter at the genus level were positively correlated with maize biomass and yield. Inoculation with PGPR shows potential for improvement of maize production under conservation tillage in cold regions by regulating the rhizosphere bacterial community structure and by direct stimulation of plant growth.

[Effects of multifunctional plant rhizosphere promoting bacteria on maize growth in black soil areas in Northeast China]. / å¤šåŠŸèƒ½æ¤ç‰©æ ¹é™ ä¿ƒç”ŸèŒå¯¹ä¸œåŒ—é»‘åœŸåŒºçŽ‰ç±³çš„ä¿ƒç”Ÿæ•ˆæžœ.

The application of microbial fertilizer plays an important role in improving soil restoration and fertilizer utilization. The effects of microbial fertilizer are greatly affected by crop genotypes and ecological conditions. Little is known about the effects of microbial fertilizers on maize production in Northeast China. To develop microbial fertilizer specific to the black soil and the climate characteristics of Northeast China, we isolated five plant rhizosphere-promoting bacteria (PGPR), named as MZ1, MZ2, MZ3, MZ4 and MZ5, with different degrees of biological functions such as IAA synthesis, phosphate-solubilizing, potassium-solubilizing and siderophore-releasing, from the rhizosphere of maize field. The analysis of ecological adaptability showed that those five strains differed in salt resistance, drought tolerance, acid and alkali resistance, pesticide resistance. The 16S rRNA gene sequences analysis showed that the strains MZ1, MZ2, MZ3, MZ4 and MZ5 belonged to the genus of Sphingomonas, Enterobacter, Pseudomonas, Bacillus and Rhizobium, respectively. In maize field experiment with 50% nitrogen fertilizer reduction, the inoculation with MZ1, MZ3 and MZ5 increased grain yield by 19.9%-25.0%. MZ1, MZ3, and MZ5 could be used as microbial fertilizers for maize in Northeast China.

Novel associations between rhizobial populations and legume species within the genera Lathyrus and O xytropis grown in the temperate region of China.

Fifty rhizobial isolates of Lathyrus and Oxytropis collected from northern regions of China were studied in their genotypic characterization based upon analyses of ARDRA, 16S-23S IGS PCR-RFLP, TP-RAPD, MLEE, sequences of 16S rDNA gene and housekeeping genes of atpD, recA and glnII. The results demonstrated that most of the Lathyrus rhizobia belonged to Rhizobium and most of the Oxytropis rhizobia belonged to Sinorhizobium. A novel group of Rhizobium sp. I and S. meliloti were identified as the main microsymbionts respectively associated with Lathyrus and Oxytropis species in the collection area, which were new associations between rhizobia and the mentioned hosts. This study also provides new evidence for biogeography of rhizobia.

The novel alkali tolerance function of tfxG in Sinorhizobium meliloti.

TfxG, one of the tfxABCDEFG cluster genes that code for trifolitoxin (TFX) production, was initially described in Rhizobium leguminosarum bv. trifolii T24. Although several genes in the tfx family have functions related to TFX production or resistance to TFX, the function of tfxG is largely unknown. Using cDNA-amplified fragment length polymorphism (cDNA-AFLP) analysis, we found that expression of the tfxG gene dramatically increased under alkaline culture conditions in Sinorhizobium meliloti CCBAU 81024. This result was confirmed by northern blot analysis. Mutagenesis of tfxG significantly decreased the viability of Sinorhizobium meliloti CCBAU 81024 under alkali stress. Complementation of the tfxG mutant strain using the functional tfxG gene recovered its alkali tolerance to a wild-type level. Genomic analysis of the tfxG gene suggests that choline and homoserine kinase domains may contribute to its alkali tolerance function. This is the first clear evidence that tfxG plays a crucial role in the alkali tolerance of S. meliloti CCBAU 81024, and the finding provides its biological function.

Various tolerances to arsenic trioxide between human cortical neurons and leukemic cells.

Arsenic trioxide (As2O3) is very effective for treatment of acute promyelocytic leukaemia (APL) but little can pass through the blood-brain-barrier (BBB), which limits its use in the prevention and treatment of central nervous system leukaemia (CNSL). Before creating a non-invasive method to help As2O3 's access, the safe and effective therapeutic concentration of As2O3 in the CNS ought to be known. The changes of apoptosis biomarkers, [Ca2+]i and PKC activity of both leukaemia cells and human cortical neurons, were monitored before and after being treated with As2O3 in vitro with laser confocal microscopy and Western blot. NSE concentration, the neuron invasive biomarker, was monitored by enzyme immunoassay (NSE-EIA). This study revealed that cortical neuron was more tolerable to As2O3 compared to NB4. 1.0 micromol / L As2O3 showed little influence on cortical neuron but effectively promoted apoptosis and induced differentiation of NB4.

Effects of arsenic trioxide administration styles on leukocytosis.

OBJECTIVE: To study the effects of constantly slow intravenous arsenic trioxide (As2O3) infusion regimen on decreasing leukocytosis in vivo and in vitro. METHODS: Three kinds of leukemia cells, NB4, K562, and acute promyelocytic leukemia (APL) cells, were cultured in the media with constant concentration and varying concentrations of As2O3 respectively for 24 hours. Seventy-five patients were enrolled in two groups randomly. In trial group, 37 patients received continuously slow intravenous As2O3 infusion regimen for 24 hours with an infusion rate of 8 drips per minute and total infusion duration of about 18-21 hours daily. In control group, 38 patients received routine regimen with an infusion rate of 45-55 drips per minute and total infusion duration of about 2-3 hours daily for 24 hours. The daily As2O3 dosage was 0. 16 mg/kg. The intracellular arsenic concentration was measured by atomic fluorescence assay. The apoptosis rate of cells, CD33- CD11b+ cells, and CD33+ CD11b- cells were monitored by flow cytometry. RESULTS: The apoptosis rates of NB4, K562, and APL leukemia cells in the media with constant As2O3 concentration were 56.6% +/- 2.4%, 27.6% +/- 3.1%, and 52.2% +/- 2.8%, respectively, which were significantly higher than those with changing As2O3 concentration (23.2% +/- 2.1%, 11.0% +/- 2.5%, and 21.0% +/- 2.5%, respectively, P < 0.01). The apoptosis rates of APL, M2 type acute myeloid leukemia (AML-M2), and chronic myeloid leukemia (CML) patients in the trial group (28.5% +/- 1.9%, 9.5% +/- 0.6%, and 12.5% +/- 1.8%) were also significantly higher than those in control group (8.5% +/- 2.2%, 2. 9% +/- 0.8%, and 4.5% +/- 1.2%; P < 0.05). The ratios of CD33 CD11b- and CD33- CD11b+ cells in control group were significantly higher than those in trial group. CONCLUSION: The continuously slow intravenous As2O3 infusion regimen can obtain high efficiency of apoptosis and low differentiation proportion, relieve leukocytosis, and gain maximal therapeutic benefit.

Effects of administration styles of arsenic trioxide on intracellular arsenic concentration, cell differentiation and apoptosis.

We studied the effects of varying and steady-state concentrations of arsenic trioxide (As2O3) on apoptosis and differentiation of several cell lines in vitro. We also studied the same effects of fluctuating vs constant concentrations of As2O3 in vivo in patients treated with daily 3-hour fast infusions or daily slow, continuous infusions. Intracellular concentrations of arsenic and apoptosis rate were higher whereas differentiation was reduced in cells exposed to constant concentrations of As2O3.

[Screening of two phenanthrene-utilizing and high-effective phosphorus-accumulating bacteria and their effects on phosphorus-accumulating characteristics].

In this study, two phenanthrene-utilizing and high-effective P-accumulating bacteria Y11 and Y4-2 were isolated from sludge samples of Taihu Lake using plate culture and blue-colored colonies methods. Strains Y11 and Y4-2 were identified as Acinetobacter sp. according to the results of morphology, physiology and the phylogenetical analyses of 16S rDNA sequences. The two strains showed high effective P-accumulating ability in plate and broth cultures. Y11 could grow well from 10 degrees C to 35 degrees C and pH from 6 to 9, Y4-2 could grow well from 10 degrees C to 35 degrees C and pH from 6 to 8. Phenanthrene could be used as sole carbon and energy sources. In our experiment, high phosphorus concentration in broth culture had no negative effect on the growth of strain Y11, however the growth of strain Y4-2 was slightly affected. Under cultivation condition of 30 degrees C, 170 r/min, 1% inoculation (D600 = 0.4), the accumulation of phosphorus was various by strains and cultivation concentration of phosphorus as well: In 2 mg/L phosphorus concentration medium, the highest phosphorus-accumulation ratio of strains Y11 and Y4-2 were 96.13% and 94.65%, the phosphorus concentration decreased from 2 mg/L to 0.08 mg/L and 0.11 mg/L, respectively. In 5 mg/L phosphorus concentration medium, the highest phosphorus-accumulation ratio of strains Y11 and Y4-2 were 95.94% and 71.19%, the phosphorus concentration decreased from 5 mg/L to 0.20 mg/L and 1.44 mg/L, respectively. In 8 mg/L phosphorus concentration medium, the highest phosphorus-accumulation ratio of strains Y11 and Y4-2 were 71.24% and 47.81%, the phosphorus concentration decreased from 8 mg/L to 2.30 mg/L and 4.18 mg/L, respectively. For the P removal of Yunnan Dianchi water sample containing 1.01 mg/L phosphorus, Y11 and Y4-2 were successful to decrease the phosphorus concentration from 1.01 mg/L to 0.06 mg/L in 6 h and 48 h, respectively. The results indicated that Acinetobacter sp.Y11 and Y4-2 possess high ability of phosphorus removal and suitability to various water environments. Y11 strain adapt to all kinds of eutrophic waterbody even polluted with phenanthrene, Y4-2 adapt to pH < or = 8.0 eutrophic waterbody with phenanthrene pollution.

[Effects of protein tyrosine kinase, protein tyrosine phosphatase and protein kinase C on the apoptosis of arsenic trioxide treated NB4 cells and human cortex neurons].

OBJECTIVE: To investigate the effects of protein tyrosine kinase (PTK), protein tyrosine phosphatase (PTP) and protein kinase C (PKC) on apoptosis and observe the changes of cytosolic calcium ([Ca(2+)]i) of arsenic trioxide (As2O3) treated human leukemia cells NB4 and cortex neurons. METHODS: [Ca(2+)]i of NB4 cells and cortex neurons was probed with Fluo-3/AM, its changes were assayed with laser confocal microscopy in real-time after As2O3 treatment at different concentrations, the effects of PTK and PTP and the activation of PKC on these changes with confocal microscopy and phosphorus radioisotope assay. DNA ladders of NB4 cells and cortex neurons after exposed to As2O3 were observed. RESULTS: As2O3 at 1 micromol/L could remarkably increase the [Ca(2+)]i of NB4 cells but had no effects on neurons. Vanadate, a kind of PTP inhibitor, could promote the increase of [Ca(2+)]i treated by 2, 5, 10 micromol/L As2O3 in a dose-dependent manner. The mean total increase rates at 240 seconds after exposed to As2O3 at different concentrations were (6.5 +/- 2.3)%, (21.7 +/- 2.1)%, (49.2 +/- 2.5)% for NB4 cells, and (6.7 +/- 2.1)%, (19.4 +/- 2.5)%, (52.3 +/- 2.7)% for cortex neurons, respectively. Genistein, a kind of PTK inhibitor, could decrease the increase of [Ca(2+)]i treated by 2, 5, 10 micromol/L As2O3 in a dose-dependent manner. The mean total inhibited rates at 240 seconds after As2O3 treatment at different concentrations were (6.7 +/- 2.9)%, (25.6 +/- 2.5)%, (52.2 +/- 3.5)% for NB4 cells, and (7.8 +/- 3.1)%, (18.1 +/- 2.8)%, (51.3 +/- 3.3)% for cortex neurons, respectively. The activation of PKC began to increase as exposed to As2O3 at 1 micromol/L for 3 h, and kept rising continuously in NB4 cells and at 24 h DNA ladders emerged. However, none of the above results was found in human cortex neurons, but when exposed to 2 micromol/L As2O3, the activation of PKC and DNA ladders did emerge in neurons. CONCLUSIONS: The phosphorylation and dephosphorylation of PTK and PTP participated in nonspecific apoptosis signal transduction pathway related to As2O3, and accompanied with PKC activation. The [Ca(2+)]i elevation was closely related to increased PKC activation. There existed difference in dose tolerances to As2O3 between NB4 cell and cortex neurons.