Concentrations of NH₄-N and NO₃-N in leachate at the 180 cm soil depth under different fertilization treatments.

<p>C: NH₄-N; D: NO₃-N. The solid and long-dashed arrows indicate the date of fertilizer applications for organic treatments (B1A1, B2A1, and B3A1) and for the conventional treatment (LS), respectively. Bars represent standard deviations (<i>n</i> = 3).</p

Experimental treatments in terms of total nutrient inputs for N, P, and K (kg ha⁻¹).

<p>Experimental treatments in terms of total nutrient inputs for N, P, and K (kg ha⁻¹).</p

Concentrations of NH₄-N and NO₃-N in leachate at the 50 cm soil depth under different fertilization treatments.

<p>A: NH₄-N; B: NO₃-N. The solid and long-dashed arrows indicate the date of fertilizer applications for organic treatments (B1A1, B2A1, and B3A1) and for the conventional treatment (LS), respectively. Bars represent standard deviations (<i>n</i> = 3).</p

Schematic of standpipes for measuring percolate inorganic N concentrations in the paddy fields.

<p>Shaded area indicates the depth below the soil surface. Horizontal lines at 20-radium around the pipes.</p

Nitrogen budget for rice production.

a<p>Different letters in a column denote a significant difference between treatments at the 0.05 level.</p

Cumulative inorganic N leaching (kg N ha⁻¹) at 50 and 180 cm soil depths for control (CK), organic (B1A1, B2A1, and B3A1) and conventional (LS) treatments during a single rice growth cycle.

a<p>After subtraction of the leakage quantity measured in CK.</p>b<p>Different letters in a column denote a significant difference between treatments at the 0.05 level.</p

Nutrient contents of fertilizers used in the experiments (% dry weight).

<p>Nutrient contents of fertilizers used in the experiments (% dry weight).</p

A Novel Process for the Key Intermediate of Fluoroquinolones

A Novel Process for the Key Intermediate of Fluoroquinolone

Diameter of phosphate-solubilizing zone, pH and soluble P observed after 7 d incubation in NBRIP.

<p>Mean ± standard error values followed by different letters indicate statistically significant differences (<i>P</i><0.05).</p><p>Diameter of phosphate-solubilizing zone, pH and soluble P observed after 7 d incubation in NBRIP.</p

Disruption of Gene <i>pqq</i>A or <i>pqq</i>B Reduces Plant Growth Promotion Activity and Biocontrol of Crown Gall Disease by <i>Rahnella aquatilis</i> HX2

<div><p><i>Rahnella aquatilis</i> strain HX2 has the ability to promote maize growth and suppress sunflower crown gall disease caused by <i>Agrobacterium vitis, A. tumefaciens,</i> and <i>A. rhizogenes</i>. Pyrroloquinoline quinone (PQQ), a cofactor of aldose and alcohol dehydrogenases, is required for the synthesis of an antibacterial substance, gluconic acid, by HX2. Mutants of HX2 unable to produce PQQ were obtained by in-frame deletion of either the <i>pqq</i>A or <i>pqq</i>B gene. In this study, we report the independent functions of <i>pqq</i>A and <i>pqq</i>B genes in relation to PQQ synthesis. Interestingly, both the <i>pqq</i>A and <i>pqq</i>B mutants of <i>R. aquatilis</i> eliminated the ability of strain HX2 to produce antibacterial substance, which in turn, reduced the effectiveness of the strain for biological control of sunflower crown gall disease. The mutation also resulted in decreased mineral phosphate solubilization by HX2, which reduced the efficacy of this strain as a biological fertilizer. These functions were restored by complementation with the wild-type <i>pqq</i> gene cluster. Additionally, the phenotypes of HX2 derivatives, including colony morphology, growth dynamic, and pH change of culture medium were impacted to different extents. Our findings suggested that <i>pqq</i>A and <i>pqq</i>B genes individually play important functions in PQQ biosynthesis and are required for antibacterial activity and phosphorous solubilization. These traits are essential for <i>R. aquatilis</i> efficacy as a biological control and plant growth promoting strain. This study enhances our fundamental understanding of the biosynthesis of an environmentally significant cofactor produced by a promising biocontrol and biological fertilizer strain.</p></div