Microbial community structure and functional metabolic diversity are associated with organic carbon availability in an agricultural soil

Exploration of soil environmental characteristics governing soil microbial community structure and activity may improve our understanding of biogeochemical processes and soil quality. The impact of soil environmental characteristics especially organic carbon availability after 15-yr different organic and inorganic fertilizer inputs on soil bacterial community structure and functional metabolic diversity of soil microbial communities were evaluated in a 15-yr fertilizer experiment in Changping County, Beijing, China. The experiment was a wheat-maize rotation system which was established in 1991 including four different fertilizer treatments. These treatments included： a non-amended control（CK）, a commonly used application rate of inorganic fertilizer treatment（NPK）; a commonly used application rate of inorganic fertilizer with swine manure incorporated treatment（NPKM）, and a commonly used application rate of inorganic fertilizer with maize straw incorporated treatment（NPKS）. Denaturing gradient gel electrophoresis（DGGE） of the 16 S r RNA gene was used to determine the bacterial community structure and single carbon source utilization profiles were determined to characterize the microbial community functional metabolic diversity of different fertilizer treatments using Biolog Eco plates. The results indicated that long-term fertilized treatments significantly increased soil bacterial community structure compared to CK. The use of inorganic fertilizer with organic amendments incorporated for long term（NPKM, NPKS） significantly promoted soil bacterial structure than the application of inorganic fertilizer only（NPK）, and NPKM treatment was the most important driver for increases in the soil microbial community richness（S） and structural diversity（H）. Overall utilization of carbon sources by soil microbial communities（average well color development, AWCD） and microbial substrate utilization diversity and evenness indices（H＇ and E） indicated that long-term inorganic fertilizer with organic amendments incorporated（NPKM, NPKS） could significantly stimulate soil microbial metabolic activity and functional diversity relative to CK, while no differences of them were found between NPKS and NPK treatments. Principal component analysis（PCA） based on carbon source utilization profiles also showed significant separation of soil microbial community under long-term fertilization regimes and NPKM treatment was significantly separated from the other three treatments primarily according to the higher microbial utilization of carbohydrates, carboxylic acids, polymers, phenolic compounds, and amino acid, while higher utilization of amines/amides differed soil microbial community in NPKS treatment from those in the other three treatments. Redundancy analysis（RDA） indicated that soil organic carbon（SOC） availability, especially soil microbial biomass carbon（Cmic） and Cmic/SOC ratio are the key factors of soil environmental characteristics contributing to the increase of both soil microbial community structure and functional metabolic diversity in the long-term fertilization trial. Our results showed that long-term inorganic fertilizer and swine manure application could significantly improve soil bacterial community structure and soil microbial metabolic activity through the increases in SOC availability, which could provide insights into the sustainable management of China＇s soil resource.

The Microbial Metabolic Characteristics in the Course of Sulfate-Reduction

Acid-producing phase reactor of two-phase anaerobic treatment process has remarkable advantages treating sulfate-laden wastewater. In order to investigate SRB population's capability of utilizing substrate and the microbial acidification type formed during the course of sulfate reduction, continuous-flow and batch tests were conducted in a continuous stirred tank bio-film reactor supplied with sodium sulfate as electron acceptor. The experimental results demonstrated that the acidification type formed b...

Isolation and Identification of Pseudomonas solanacearum and Its Drug Sensitivity Test

Ten pathogenic strains were isolated fi-om gingers infected by blast, and were identified by substrate utilization test and biochemical test. The identifica- tion results showed that these ten strains accorded with the basic characteristics of Pseudomonas solanacearum. Drug sensitivity test of ten strains was carried out, and prevention agents were screened to provide an experimental basis for the control of ginger blast.

Deep soil microbial carbon metabolic function is important but often neglected:a study on the Songnen Plain reed wetland,Northeast China

Soil microbial carbon metabolism is critical in wetland soil carbon cycling,and is also a research hotspot at present.However,most studies focus on the surface soil layer in the wetlands and the microorganisms associated with this layer.In this study,0-75 cm soil profiles were collected from five widely separated reed wetlands in the Songnen Plain,which has a large number of middle-high latitude inland saline-sodic wetlands.The Biolog-ECO method was used to determine the carbon metabolic activity and functional diversity of soil microorganisms.The results showed that soil carbon metabolic activity decreased with increasing soil depth.The carbon metabolic activity of soil microorganisms in the 60-75 cm layer was approximately 57.41%-74.60%of that in the 0-15 cm layer.The soil microbial Shannon index and utilization rate of amines decreased with an increase in soil depth,while the Evenness index and utilization rate of polymers tended to increase with soil depth.Dissolved organic carbon(DOC)is the most important factor affecting microbial carbon source utilization preference,because microorganisms mainly obtain the carbon source from DOC.The result of the correlation analysis showed that the soil microbial carbon metabolic activity,Shannon index,and Evenness index significantly correlated with soil total carbon(TC),microbial biomass carbon(MBC),DOC,total nitrogen(TN),ammonium nitrogen(NH_(4)^(+)-N),nitrate nitrogen(NO_(3)_(−)-N)contents,and electrical conductivity(EC).This study emphasized the important role of microbial carbon metabolic function in deep soil.

Short-Term Responses of Nitrogen Mineralization and Microbial Community to Moisture Regimes in Greenhouse Vegetable Soils

Soil drying and wetting impose significant influences on soil nitrogen (N) dynamics and microbial communities. However, effects of drying-wetting cycles, while common in vegetable soils, especially under greenhouse conditions, have not been well studied. In this study, two greenhouse vegetable soils, which were collected from Xinji (XJ) and Hangzhou (HZ), China, were maintained at 30% and 75% water-holding capacity (WHC), or five cycles of 75% WHC followed by a 7-day dry-down to 30% WHC (DW). Soil inorganic N content increased during incubation. Net N mineralization (Nmin), microbial activity, and microbial biomass were significantly higher in the DW treatment than in the 30% and 75% WHC treatments. The higher water content (75% WHC) treatment had higher Nmin, microbial activity, and microbial biomass than the lower water content treatment (30% WHC). Multivariate analyses of community-level physiological profile (CLPP) and phospholipid fatty acid (PLFA) data indicated that soil moisture regime had a significant effect on soil microbial community substrate utilization pattern and microbial community composition. The significant positive correlation between Nmin and microbial substrate utilization or PLFAs suggested that soil N mineralization had a close relationship with microbial community.