Partial substitution of manure reduces nitrous oxide emission with maintained yield in a winter wheat crop.

Conventional fertilization of agricultural soils results in increased N2O emissions. As an alternative, the partial substitution of organic fertilizer may help to regulate N2O emissions. However, studies assessing the effects of partial substitution of organic fertilizer on both N2O emissions and yield stability are currently limited. We conducted a field experiment from 2017 to 2021 with six fertilizer regimes to examine the effects of partial substitution of manure on N2O emissions and yield stability. The tested fertilizer regimes, were CK (no fertilizer), CF (chemical fertilizer alone, N 300 kg ha-1, P2O5 150 kg ha-1, K2O 90 kg ha-1), CF + M (chemical fertilizer + organic manure), CFR (chemical fertilizer reduction, N 225 kg ha-1, P2O5 135 kg ha-1, K2O 75 kg ha-1), CFR + M (chemical fertilizer reduction + organic manure), and organic manure alone (M). Our results indicate that soil N2O emissions are primarily regulated by soil mineral N content in arid and semi-arid regions. Compared with CF, N2O emissions in the CF + M, CFR, CFR + M, and M treatments decreased by 16.8%, 23.9%, 42.0%, and 39.4%, respectively. The highest winter wheat yields were observed in CF, followed by CF + M, CFR, and CFR + M. However, the CFR + M treatment exhibited lower N2O emissions while maintaining high yield, compared with CF. Four consecutive years of yield data from 2017 to 2021 illustrated that a single application of organic fertilizer resulted in poor yield stability and that partial substitution of organic fertilizer resulted in the greatest yield stability. Overall, partial substitution of manure reduced N2O emissions while maintaining yield stability compared with the synthetic fertilizer treatment during the wheat growing season. Therefore, partial substitution of manure can be recommended as an optimal N fertilization regime for alleviating N2O emissions and contributing to food security in arid and semi-arid regions.

Evaluation of carbon mineralization and its temperature sensitivity in different soil aggregates and moisture regimes: A 21-year tillage experiment.

Characterizing soil organic carbon (SOC) mineralization and its temperature sensitivity (Q10) under different soil moisture in tillage systems is crucial for determining global carbon balance under climate warming and increasing precipitation. Aggregate protection can potentially govern SOC mineralization and its Q10. However, how tillage and aggregate sizes affect SOC mineralization and its Q10, especially under varying soil moisture, remains unclear. Soil samples (0-10 cm and 10-20 cm) were collected from a 21-year field study with four tillage treatments: conventional tillage (CT), reduced tillage (RT), no-tillage (NT), and subsoiling (SS). Bulk soil and dry-sieved aggregates were incubated at 15°C and 25°C at low, medium, and high moistures (i.e., 40%, 70%, and 100% water-holding capacity, respectively). Macro-aggregates (> 0.25 mm) had lower SOC mineralization relative to micro-aggregates (< 0.25 mm) across all soil temperatures, moistures, and depths (P < 0.01), which was attributed to their lower SOC quality (i.e., higher ratio of SOC to total nitrogen and lower ratio of dissolved organic carbon to SOC). Moreover, NT and SS promoted macro-aggregation relative to CT and RT, and thereby decreased mineralization (P < 0.001). However, Q10 was higher in macro-aggregates than in micro-aggregates at low and medium moistures. The Q10 was negatively correlated with the SOC quality in macro-aggregates (P < 0.05). The macroaggregate-associated SOC quality was lower under NT and SS than under CT and RT, which resulted in a greater Q10 under NT and SS at low and medium moistures, suggesting that NT and SS may accelerate SOC losses under global warming. Furthermore, increased soil moisture could lower Q10, and no differences among tillage practices were observed at high moisture levels (P > 0.05). Overall, our findings indicated that NT and SS decreased SOC mineralization but increased Q10 because of their large amounts of macro-aggregates with low SOC quality, and the improvement of Q10 was constrained by increasing soil moisture.

Novel fluorescent cephalosporins: synthesis, antimicrobial activity and photodynamic inactivation of antibiotic resistant bacteria.

Two novel fluorescent cephalosporins, TCA and TBCA, were synthesized and characterized by (1)H NMR, (13)C NMR, UV-vis, and fluorescence spectroscopies. Biological activity assays demonstrated that TCA inactivated a Klebsiella pneumonia strain that expressed extended-spectrum ß-lactamases. Incubation of 6 µM TCA with K. pneumonia cultures resulted in cell death for 84% of the cells after 126 J/cm(2) of light irradiation. In vitro, TCA exhibited a MIC = 0.5 µg/mL with Staphylococcus aureus. Kinetic evaluation revealed that TCA and TBCA were substrates for B1 and B3 subclass metallo-ß-lactamases. TBCA exhibited stronger binding affinities to the Gram-positive bacterial strains MRSA1, MRSA2, and S. aureus with value of 2.95-6.59 µM per 10(8) cells/mL.

Synthesis and activity study of phosphonamidate dipeptides as potential inhibitors of VanX.

In an effort to develop inhibitors of VanX, the phosphonamidate analogs of D-Ala-D-Ala dipeptides, N-[(1-aminoethyl) hydroxyphosphinyl]-glycine (1a), -alanine (1b), -valine (1c), -leucine (1d) and -phenylalanine (1e) were synthesized, characterized and evaluated using recombinant VanX. The crystal structure of the intermediate 6d was obtained (Deposition number: CCDC 839134), and structural analysis revealed that it is orthorhombic with a space group P2(1)2(1)2(1), the bond length of P-N is 1.62Å and angle of C-N-P is 123.6°. Phosphonamidate 1(a-e) showed to be inhibitors of VanX with IC(50) values of 0.39, 0.70, 1.12, 2.82, and 4.13mM, respectively, which revealed that the inhibition activities of the phosphonamidates were dependent on the size of R-substituent of them, with the best inhibitor 1a having the smallest substituent. Also, 1a showed antibacterial activity against Staphylococcus aureus (ATCC 25923) with a MIC value of 0.25 µg/ml.

Novel conjugation of norvancomycin-fluorescein for photodynamic inactivation of Bacillus subtilis.

A simple and unique conjugation of norvancomycin-fluorescein (VanF) has been achieved. It was characterized by UV-vis and fluorescence spectra and confirmed by MALDI-TOF mass spectrum. The photodynamic assay indicated that VanF effectively inactivated the Gram-positive Bacillus subtilis (ATCC 6633) from clinic with inactivation rate of 30-70% within 1-7.5 µM. In vitro, VanF showed low antimicrobial activity with value of >128 µg/mL, binding affinity with value of 180 nM per 10(8) cells/mL against the bacteria strains. The fluorescence imaging showed that VanF could label the B. subtilis strain, but not the Escherichia coli (ATCC 25922), Enterococcus faecalis (ATCC 51299, VanD), and VRE strains from clinic.