Effects of Lake Sediment on Soil Properties, Crop Growth, and the phoD-Harboring Microbial Community

Removal of lake sediment has been shown to be an effective method for lake restoration. High phosphorus (P) content makes it possible for lake sediment to provide fertility for agricultural production. However, little research has focused on the responses of the soil-phosphorus-related microbial community to the sediment-derived fertilizer enriched in phosphorus content. The phoD-harboring gene, important to the global phosphorus cycle, encodes alkaline phosphatase hydrolyzing organic P in soil. Accordingly, a plot experiment was performed to compare the effects of four different fertilization treatments—no-fertilizer control (CK), 50% chemical fertilization with compressed sediment (CS), 50% chemical fertilization with original lake sediment (S), and conventional chemical fertilization treatment (CT)—on the phoD gene community using QPCR and high-throughput sequencing analysis. Relationships among soil physicochemical properties, phoD-harboring microbial community abundance and composition were also evaluated. Results showed that compared to CT, CS significantly increased soil organic matter (SOM) content by 20.29%, and S enhanced the humus content by 20.75% (p p < 0.05). Pearson analysis showed that phoD gene abundance (copy number) had significant and negative relationships with SOM, total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), available phosphorus (AP), and the Chao1 index. Redundancy analysis showed that shifts in the phoD community structure were related to soil physicochemical properties (SOM, TN, TP, AN, AP, and humus) rather than soil pH. In conclusion, the compressed sediment can be used in farmland since it optimizes the phoD-harboring microbial community abundance, composition, and structure, and thus significantly increases the Chinese cabbage yield

&gamma;-Polyglutamic Acid Production, Biocontrol, and Stress Tolerance: Multifunction of Bacillus subtilis A-5 and the Complete Genome Analysis

Bacillus subtilis A-5 has the capabilities of high-molecular-weight &gamma;-PGA production, antagonism to plant pathogenic fungi, and salt/alkaline tolerance. This multifunctional bacterium has great potential for enhancing soil fertility and plant security in agricultural ecosystem. The genome size of B. subtilis A-5 was 4,190,775 bp, containing 1 Chr and 2 plasmids (pA and pB) with 43.37% guanine-cytosine content and 4605 coding sequences. The &gamma;-PGA synthase gene cluster was predicted to consist of pgsBCA and factor (pgsE). The &gamma;-PGA-degrading enzymes were mainly pgdS, GGT, and cwlO. Nine gene clusters producing secondary metabolite substances, namely, four unknown function gene clusters and five antibiotic synthesis gene clusters (surfactin, fengycin, bacillibactin, subtilosin_A, and bacilysin), were predicted in the genome of B. subtilis A-5 using antiSMASH. In addition, B. subtilis A-5 contained genes related to carbohydrate and protein decomposition, proline synthesis, pyruvate kinase, and stress-resistant proteins. This affords significant insights into the survival and application of B. subtilis A-5 in adverse agricultural environmental conditions