Response of soil bacterial communities in wheat rhizosphere to straw mulching and N fertilization.

Straw mulching and N fertilization are effective in augmenting crop yields. Since their combined effects on wheat rhizosphere bacterial communities remain largely unknown, our aim was to assess how the bacterial communities respond to these agricultural measures. We studied wheat rhizosphere microbiomes in a split-plot design experiment with maize straw mulching (0 and 8,000 kg straw ha-1) as the main-plot treatment and N fertilization (0, 120 and 180 kg N ha-1) as the sub-plot treatment. Bacterial communities in the rhizosphere were analyzed using 16S rRNA gene amplicon sequencing and quantitative PCR. Most of the differences in soil physicochemical properties and rhizosphere bacterial communities were detected between the straw mulching (SM) and no straw mulching (NSM) treatments. The contents of soil organic C (SOC), total N (TN), NH4 +-N, available N (AN), available P (AP) and available K (AK) were higher with than without mulching. Straw mulching led to greater abundance, diversity and richness of the rhizosphere bacterial communities. The differences in bacterial community composition were related to differences in soil temperature and SOC, AP and AK contents. Straw mulching altered the soil physiochemical properties, leading to greater bacterial diversity and richness of the rhizosphere bacterial communities, likely mostly due to the increase in SOC content that provided an effective C source for the bacteria. The relative abundance of Proteobacteria was high in all treatments and most of the differentially abundant OTUs were proteobacterial. Multiple OTUs assigned to Acidobacteria, Chloroflexi and Actinobacteria were enriched in the SM treatment. Putative plant growth promoters were enriched both in the SM and NSM treatments. These findings indicate potential strategies for the agricultural management of soil microbiomes.

[Effects of straw mulching and phosphorus application on forms and availability of soil phosphorus in hilly dryland of Sichuan, China]. / 秸秆覆盖与施磷对四川丘陵旱地土壤磷形态及有效性的影响.

We conducted a two-factor split-plot experiment to examine the alteration of soil inorganic phosphorus forms and phosphorus availability under straw mulching and phosphorus fertilizer rates. The main factor was straw mulching and non-mulching, while the sub-factor was phosphorus supply rates, including 0, 75, and 120 kg·hm-2. We analyzed the characteristics of phosphorus adsorption-desorption, the content of inorganic phosphorus components and their relationship with available phosphorus in hilly upland purple soil in Sichuan. Results showed that compared with the non-mulching, the maximum phosphorus adsorption capacity of straw mulching was notably decreased by 7.7% and 7.4% in the two experimental years from 2018 to 2020. The degree of phosphorus saturation and readily desorbable phosphorus of straw mulching were remarkably increased by 35.4% and 21.6% in 2019 and 18.6% and 35.2% in 2020, respectively. The maximum buffer capacity of phosphorus was not different between straw mulching and non-mulching. The maximum phosphorus adsorption capacity and maximum buffer capacity of phosphorus were significantly lower, and the degree of phosphorus saturation was notably higher in the phosphorus application treatment than that under no phosphorus treatment. The readily desorbable phosphorus increased with the increases of phosphorus rates. The contents of dicalcium phosphate (Ca2-P), octa-calcium phosphate (Ca8-P) and iron phosphorus (Fe-P) in straw mulching treatment were notably higher than those in non-mulching treatment, whereas the content of aluminum phosphorus (Al-P) significantly lower under the straw mulching. Meanwhile, the contents of occluded phosphate (O-P) and apatite (Ca10-P) tended to decrease in the straw mulching compared with that under the non-mulching. Phosphorus application increased the content of different inorganic phosphorus components. Compared with the non-mulching, soil available phosphorus content and the phosphorus activation coefficient of straw mulching remarkably increased by 23.2% and 21.3% in 2019, and 9.6% and 8.9% in 2020, respectively. Soil available phosphorus content and phosphorus activation coefficient increased with the increases of phosphorus rate. Results of regression analysis showed that the contribution of inorganic phosphorus components to the availability of available phosphorus in purple soil was Ca2-P > Fe-P > Al-P > Ca8-P > Ca10-P > O-P. Therefore, straw mulching combined with a reasonable phosphorus fertilizer rate could promote the decomposition and transformation of insoluble soil phosphorus to moderately active or easily absorbed phosphorus forms, reduce soil phosphorus adsorption, stimulate soil phosphorus desorption, and improve soil phosphorus availability. Based on the economic benefits, phosphate fertilizer application at the rate of 75 kg·hm-2 combined with straw mulching was recommended in Sichuan hilly dryland, which would be more beneficial in improving soil phosphorus availability.

Straw Mulching and Nitrogen Fertilization Affect Diazotroph Communities in Wheat Rhizosphere.

Diazotrophs that carry out the biological fixation of atmospheric dinitrogen (N2) replenish biologically available nitrogen (N) in soil and are influenced by the input of inorganic and organic substrates. To date, little is known about the effects of combined organic substrate addition and N fertilization on the diazotroph community composition and structure in purple soils. We investigated the effects of N fertilization and straw mulching on diazotroph communities by quantifying and sequencing the nifH gene in wheat rhizosphere. The abundance and richness of diazotrophs were greater the higher the fertilization level in the mulched treatments, whereas in the nonmulched treatments (NSMs), richness was lowest with the highest N fertilization level. The abundance and α-diversity of diazotrophs correlated with most of the soil properties but not with pH. At the genus level, the relative abundances of Azospirillum, Bacillus, and Geobacter were higher in the NSMs and those of Pseudacidovorax, Skermanella, Azospira, Paraburkholderia, Azotobacter, Desulfovibrio, Klebsiella, and Pelomonas in the mulched treatments. The differences in community composition between the mulched and the NSMs were associated with differences in soil temperature and soil organic carbon and available potassium contents and C:N ratio. Overall, straw mulching and N fertilization were associated with changes in diazotroph community composition and higher abundance of nifH gene in alkaline purple soils.

Straw mulching and nitrogen application altered ammonia oxidizers communities and improved soil quality in the alkaline purple soil of southwest China.

Microbe-mediated ammonia oxidation is a key process in soil nitrogen cycle. However, the effect of maize straw mulching on the ammonia oxidizers in the alkaline purple soil remains largely unknown. A three-year positioning experiment was designed as follows: straw mulching measures as the main-plot treatment and three kinds of nitrogen application as the sub-plot treatment. We found the contents of soil organic carbon (SOC), total nitrogen (TN), available potassium (AK), available nitrogen (AN), available phosphorus (AP), and NH4+-N were increased after straw mulching and nitrogen application in alkaline purple soil, so did the amoA genes abundance of ammonia-oxidizing archaeal (AOA) and bacterial (AOB). Terminal restriction fragment length polymorphism (T-RFLP) analysis revealed that Thaumarchaeote (448-bp T-RF) was dominated the AOA communities, whereas Nitrosospira sp (111-bp T-RF) dominated the AOB communities. The community compositions of both AOA and AOB were altered by straw mulching and nitrogen application in alkaline purple soil, however, the AOB communities was more responsive than AOA communities to the straw mulching and nitrogen application. Further analysis indicated that SOC and AP were the main factors affecting the abundance and community compositions of AOA and AOB in alkaline purple soil. The present study reported that straw mulching and nitrogen strategies differently shape the soil ammonia oxidizers community structure and abundance, which should be considered when evaluating agricultural management strategies regarding their sustainability and soil quality.

Distribution and evolution of T-cell receptor Vbeta repertoire on peripheral blood lymphocytes of newborn infants of human immunodeficiency virus (HIV)-infected mothers: differential display on CD4 and CD8 T cells and effect of HIV infection.

Neonatal human peripheral blood mononuclear cells from 12 human immunodeficiency virus (HIV)-infected and 84 uninfected children were assessed for their distribution of T-cell receptors (TCRs) by flow cytometry employing monoclonal antibodies to 14 Vbeta types. Vbeta 2, 5c, and 13 were the most commonly found on CD4 cells (in that order). There was a bimodal distribution of Vbeta 2, being most common in 48% of individuals but in limiting frequency (<2% of CD4) in 21%. Vbeta 2, 3, 8b, and 13 were most commonly expressed on CD8 cells at similar frequencies. There was little difference in the pattern displayed among the infected compared to that of the uninfected. The variation of the distribution over time was studied in 12 infants (7 infected). Only a single HIV-infected child had a significant difference in the interquartile range; none of the HIV-negative patients showed a significant difference. In conclusion, newborns demonstrate different distributions of TCR Vbeta types on CD4 and CD8 cells. HIV infection produces no change in neonatal TCR and little change over the course of 2 years compared to that seen in the uninfected.

The peroxynitrite decomposition catalyst FP15 improves ageing-associated cardiac and vascular dysfunction.

Overproduction of oxidants and free radicals in ageing tissues induces nitro-oxidative stress, which has recently been implicated in the pathogenesis of cardiovascular dysfunction associated with ageing. Peroxynitrite, a strong cytotoxic oxidant damages proteins and DNA and activates several pathways causing tissue injury, including the peroxynitrite-poly(ADP-ribose) polymerase (PARP) pathway. In this study, we investigated the effectiveness of the peroxynitrite decomposition catalyst FP15 on ageing-associated cardiac and vascular dysfunction. Young and ageing rats were treated with vehicle or FP15 intraperitoneally. Using a microtip Millar pressure catheter we performed left ventricular blood pressure analysis to assess systolic and diastolic function. Endothelium-dependent and -independent vasorelaxation of isolated aortic rings were investigated by using acetylcholine and sodium nitroprusside. Ageing animals showed a marked reduction of systolic and diastolic cardiac function and loss of endothelium-dependent relaxant responsiveness of aortic rings. FP15-treatment significantly improved cardiac performance and endothelial function. Immunohistochemical staining confirmed that FP15 effectively reduced nitrosative stress and prevented the activation of PARP in the aortic wall of ageing rats. Our results demonstrate the importance of endogenous peroxynitrite-overproduction in the pathogenesis of ageing-associated cardiovascular dysfunction. Pharmacological decomposition of peroxynitrite by FP15 may represent a novel therapeutic utility to improve cardiac and vascular dysfunction associated with ageing.

Correlation between HIV-Specific CD8 cell production of interferon- gamma and plasma levels of HIV RNA in perinatally infected pediatric populations.

BACKGROUND: CD8 cell responses to human immunodeficiency virus (HIV) have been correlated with virus control in adults, and this study outcome has been controversial. Attempts to establish the same correlation in small numbers of children have also been made, with similar controversy resulting. METHODS: A total of 110 perinatally infected children were studied. Nine of the children (mean age, 1.9 years vs. 11.8 years for the remaining 101 children) received treatment with antiretrovirals within the first 3 months of life. CD4 cell and HIV RNA levels were measured. Production of interferon- gamma after exposure to recombinant vaccinia vectors was measured by enzyme-linked immunospot (ELISPOT) assay. RESULTS: Responses to Pol and Gag antigens exceeded those to Nef and Env antigens, with responses significantly approximated by a quadratic function for which peak responses occurred at plasma HIV RNA levels of 103-104 HIV RNA copies/mL. Children who are treated early in life with highly active antiretroviral therapy have fewer total responses of ELISPOT-forming cells to HIV antigens than do children who are treated later in life.

Effect of recombinant human granulocyte colony-stimulating factor on T-lymphocyte function and the mechanism of this effect.

Whether recombinant human granulocyte colony-stimulating factor (rhG-CSF) affects lymphocyte function directly or indirectly is controversial. In this study, we found that T-cell proliferation was decreased considerably in response to phytohemagglutinin in donors who received rhG-CSF but was partly restored after monocytes were removed. Intracellular cytokine staining revealed that the interferon gamma-interleukin 4 ratio decreased by 5.97-fold in donor CD4+ cells after rhG-CSF treatment. No effect of rhG-CSF on ex vivo T-cell function was observed. rhG-CSF indirectly induced significant quantitative and qualitative changes on lymphocytes, including a decrease in T-cell proliferation and type 2 helper T-cell polarization of the cytokine profile. Although monocytes suppressed T-cell proliferation, the suppressive activity induced by the quantitative change in monocyte numbers cannot completely account for the hyporesponsiveness of T-lymphocytes. We believe that there must be another mediating factor. In addition, the numbers and mean fluorescence intensities of CD14CD86+ cells and CD19+CD80+ cells declined significantly in the peripheral blood after rhG-CSF treatment. Suboptimal amounts of stimulatory signals provided by low expression levels of B7 molecules on antigen-presenting cells (monocytes, B-lymphocytes) may help explain the alteration in T-cell proliferation. In addition, the absolute counts of CD3+CD4-CD8 cells in the peripheral blood were markedly increased and enriched in leukapheresis products following G-CSF treatment. These suppressor cells may contribute to T-cell hyporesponsiveness.

[Study on the in vivo effect of rhG-CSF on peripheral T lymphocyte].

OBJECTIVE: To investigate the mechanisms of in vivo rhG-CSF affecting T lymphocyte. METHODS: Peripheral blood and apheresis graft were obtained from sibling donors before and after G-CSF administration. Proliferation of peripheral blood mononuclear cells (MNC) stimulated by PHA before and after removing monocyte by plastic-adherence was detected by MTT test. Absolute number of MNC, costimulating molecules expression on antigen presenting cells (monocyte and B lymphocyte) and the number of CD(14)(+) cells before and after plastic-adherence treatment were analyzed by flow cytometry. RESULTS: After rhG-CSF administration, absolute peripheral blood monocyte counts increased by 4.2 +/- 1.74 times. By removing monocytes, proliferation of T cells after rhG-CSF administration partly restored, but remained 20.58% lower than that before G-CSF treatment. CD(86) co-stimulating factor expression on monocyte declined (66.96 +/- 13.87)% and mean fluorescence intensity (MIF) decreased (31.31 +/- 12.91)% after rhG-CSF administration. Expression of CD(80) on B lymphocyte decreased (45.77 +/- 26.58)%. CONCLUSIONS: The increased number of monocytes after rhG-CSF administration suppressed T-cell proliferation, which was partly the mechanism of the T-cell hyporesponsiveness. The fact that monocyte and B lymphocyte expressed low level of B(7) co-stimulating factor suggested that antigen present cells might also mediate the alteration of T-cell proliferation.