The relationship between initial Rubisco activity and the ratio of leaf photosynthetic rate (<i>A</i>) to Rubisco content on Shanyou 63 (solid cycles) and Yangdao 6 (open cycles).

<p>The line represents linear regression: y = 3.51x−0.53 R² = 0.88 <i>P</i><0.01.</p

Frequency of the most abundant bacterial genera, indicated in % of all classified sequences, within each treatment of bio-organic fertilizer (BIO), cattle manure compost (CM), Chinese medicine residue compost (CMR), general operation control (GCK) and pig manure compost (PM).

<p>Only the genera frequency higher than 1% was listed in the table. Values are the means followed by standard error of the mean. Different letters indicate statistically significant differences at the 0.05 probability level according to Fisher's least significant difference test (LSD) and the Duncan test.</p

Rarefaction analysis at different 3% dissimilarity levels for treatments with bio-organic fertilizer (BIO), cattle manure compost (CM), Chinese medicine residue compost (CMR), general operation control (GCK) and pig manure compost (PM).

<p>Rarefaction analysis at different 3% dissimilarity levels for treatments with bio-organic fertilizer (BIO), cattle manure compost (CM), Chinese medicine residue compost (CMR), general operation control (GCK) and pig manure compost (PM).</p

Electron micrographs of chloroplasts in newly expanded leaves of Shanyou 63 (a, low-N supply; b, intermediate.-N supply; c, high-N supply) and Yangdao 6 (d, low-N supply; e, intermediate.-N supply; f, high-N supply).

<p>Bar = 1 µm. C, chloroplasts; M, mitochondrion; N, nucleus; SG, starch granules; CW, cell wall; arrows point to plasma membrane.</p

The relationships between the ratio of mesophyll conductance (g_m) to Rubisco content and (a) photosynthetic N-use efficiency (PNUE) and (b) the ratio of leaf photosynthetic rate (<i>A</i>) and Rubisco content on Shanyou 63 (solid cycles) and Yangdao 6 (open cycles).

<p>The lines represent the following regressions: (a) y = 32.89x+26.28 R² = 0.86 <i>P</i><0.01; (b) y = 0.096x−0.038 R² = 0.80 <i>P</i><0.05.</p

Anaerobic Arsenite Oxidation by an Autotrophic Arsenite-Oxidizing Bacterium from an Arsenic-Contaminated Paddy Soil

Microbe-mediated arsenic (As) redox reactions play an important role in the biogeochemical cycling of As. Reduction of arsenate [As­(V)] generally leads to As mobilization in paddy soils and increased As availability to rice plants, whereas oxidation of arsenite [As­(III)] results in As immobilization. A novel chemoautotrophic As­(III)-oxidizing bacterium, designated strain SY, was isolated from an As-contaminated paddy soil. The isolate was able to derive energy from the oxidation of As­(III) to As­(V) under both aerobic and anaerobic conditions using O₂ or NO₃^– as the respective electron acceptor. Inoculation of the washed SY cells into a flooded soil greatly enhanced As­(III) oxidation to As­(V) both in the solution and adsorbed phases of the soil. Strain SY is phylogenetically closely related to <i>Paracoccus niistensis</i> with a 16S rRNA gene similarity of 96.79%. The isolate contains both the denitrification and ribulose 1,5-bisphosphate carboxylase/oxygenase gene clusters, underscoring its ability to denitrify and to fix CO₂ while coupled to As­(III) oxidation. Deletion of the <i>aioA</i> gene encoding the As­(III) oxidase subunit A abolished the As­(III) oxidation ability of strain SY and led to increased sensitivity to As­(III), suggesting that As­(III) oxidation is a detoxification mechanism in this bacterium under aerobic and heterotrophic growth conditions. Analysis of the <i>aioA</i> gene clone library revealed that the majority of the As­(III)-oxidizing bacteria in the soil were closely related to the genera <i>Paracoccus</i> of α-<i>Proteobacteria</i>. Our results provide direct evidence for As­(III) oxidation by <i>Paracoccus</i> species and suggest that these species may play an important role in As­(III) oxidation in paddy soils under both aerobic and denitrifying conditions

Heat map of the bacterial communities based on abundance of phyla (a) and Jackknifed principal coordination analysis (PCoA) plots with unweighted UniFrac distance metric (b) from treatments with bio-organic fertilizer (BIO), cattle manure compost (CM), Chinese medicine residue compost (CMR), general operation control (GCK) and pig manure compost (PM).

<p>Color from pink to blue indicates increasing abundance.</p

Correlation analysis between the relative abundance of two bacteria phyla (a), three of the most classified bacteria genera (b) and banana <i>Fusarium</i> wilt disease incidence for treatments with bio-organic fertilizer (BIO), cattle manure compost (CM), Chinese medicine residue compost (CMR), general operation control (GCK) and pig manure compost (PM).

<p>Correlation analysis between the relative abundance of two bacteria phyla (a), three of the most classified bacteria genera (b) and banana <i>Fusarium</i> wilt disease incidence for treatments with bio-organic fertilizer (BIO), cattle manure compost (CM), Chinese medicine residue compost (CMR), general operation control (GCK) and pig manure compost (PM).</p

Calculations of Chao1, ACE, Shannon and Good's Coverage indices for treatments with bio-organic fertilizer (BIO), cattle manure compost (CM), Chinese medicine residue compost (CMR), general operation control (GCK) and pig manure compost (PM) at a 97% similarity threshold.

<p>Values indicate the means followed by standard error of the mean. Different letters indicate statistically significant differences at the 0.05 probability level according to Fisher's least significant difference test (LSD) and the Duncan test.</p

Redundancy analysis (RDA) of the abundant phyla and soil properties for soil samples from treatments with bio-organic fertilizer (BIO), cattle manure compost (CM), Chinese medicine residue compost (CMR), general operation control (GCK) and pig manure compost (PM).

<p>Redundancy analysis (RDA) of the abundant phyla and soil properties for soil samples from treatments with bio-organic fertilizer (BIO), cattle manure compost (CM), Chinese medicine residue compost (CMR), general operation control (GCK) and pig manure compost (PM).</p