Abstract:[Background] Bacterial diversity plays an important role in the ecological function of green space soil. However, there is no report on the soil bacterial diversity of urban parks at different age. [Objective] In order to study soil bacterial community diversity and structure characters. [Methods] Illumina Miseq sequencing was adopted to analyze soil bacterial community structures of typical old and young urban parks in Beijing. [Results] The results showed that 45 known phylum were found, among them, Acidobacteria, Proteobacteria, Chloroflexi and Actinobacteria were dominant bacterial groups in all soil samples. Alpha diversity analysis showed that there was a significant differentiation on soil bacterial diversity. The richness and diversity of soil bacterial community in old parks were higher than that of young parks. In addition, similarities analysis and principle coordinate analysis indicated that there was a significant differentiation in bacterial community structure between old and young parks. The redundancy analysis of soil microbial community structure and environmental factors showed that soil moisture, soil organic matter and total nitrogen were the key determinants influencing the soil microbial community structure, whereas none of the soil properties was found responsible for the changes in the soil bacterial community structure. [Conclusion] This study introduced the park age as an influencing factor for redundancy analysis. The results showed that park age is an important factor affecting the diversity of the bacterial communities in the urban parks.

Abstract:[Objective] The application of chemical fertilizers and straw returning are important agricultural strategies to improve the fertility of lime concretion black soil. However, there is little information about the impact of fertilization on microbial community in lime concretion black soil. The objective of this study was to investigate the effect of long-term application of chemical fertilizers and wheat straw returning on bacterial community in lime concretion black soil. [Methods] Quantitative PCR (qPCR) and 454 pyrosequencing-based analysis of the V4-V5 16S rRNA gene region were used to determine bacterial abundance, community structure and diversity in soils under different fertilization strategies. [Results] The most dominant bacterial phyla in lime concretion black soil were Actinobacteria, Proteobacteria, Acidobacteria, Chloroflexi and Bacteroidetes. Long-term application of chemical fertilizer greatly increased soil fertility, but resulted in significant bacterial community shift and diversity loss. Although wheat straw returning improved soil fertility, it could not mitigate the negative impact of chemical fertilizers on soil bacterial community. Statistical analysis revealed that changes in microbial community composition and diversity were strongly correlated with changes in pH induced by the fertilization regime. [Conclusion] Long-term application of chemical fertilizers and straw returning improved the fertility of lime concretion black soil, but soil acidification caused by fertilization had negative impact on soil bacterial community. Our results emphasized the importance of soil pH in addition to soil fertility for agricultural sustainability in lime concretion black soil region, and suggest that straw returning has little help for the stability of microbial community in lime concretion black soil, and comprehensive means must be taken to develop environmental friendly agriculture.

Abstract:[Background] Salt marshes in desert steppe are an important part of terrestrial ecosystems, and soil moisture and salinity changes are important factors affecting the soil bacterial community assembly in this ecosystem. [Objective] The soil bacterial community assembly is a continuous ecological process dominated by deterministic and stochastic processes. Revealing the assembly mechanism of soil bacterial communities in salt marshes of desert steppe helps to deepen our understanding about the importance of microorganisms as key ecosystem factors. [Methods] The physicochemical properties were measured for the soil samples collected near the Kushuihu lake (NL) and far from the Kushuihu lake (FL), a typical salt marsh area of the desert steppe in central Ningxia. High-throughput sequencing was performed to analyze the bacterial information. [Results] NL and FL sampling sites presented significant water-salt gradients. The NL soil samples had higher pH, water content, and electrical conductivity than the FL soil samples. Proteobacteria, Actinobacteriota, Firmicutes, Bacteroidota, and Myxococcota were the dominant phyla in the soil samples. As the water-salt gradient increased, the relative abundance of Proteobacteria increased, while that of Actinobacteriota and Firmicutes decreased. Most of the members belong to the phyla had obvious correlations with water-salt changes. In addition, the soil bacterial network in the FL sites had stable network relationship. From the NL to FL sampling sites, the soil bacterial community gradually became being dominated by stochastic factors and was influenced by soil pH, electrical conductivity, and environmental variables. [Conclusion] The changes in soil moisture and salinity in salt marshes of desert steppe altered the soil bacterial community structure. Soil bacterial communities improved the survival under stress by strategies such as niche occupation. The assembly of bacterial communities is a continuum consisting of stochastic and deterministic processes, which are influenced by environmental changes. The results reveal the response characteristics of bacterial community structure and interrelationship to environmental changes in salt marshes of desert steppe and clarify the assembly mechanism and influencing factors of soil bacterial community, providing a theoretical reference for related studies.

Abstract:Both culture-dependent and culture-independent methods, denaturing gradient gel electrophoresis (DGGE) based on the sequence of 16S rDNA, were used to examine the microbial quantity, bacterial community structure and diversity in different soil types (Peat soil, Swamp soil, Meadow soil and Sandy soil) and soil detphs (0?20 cm, 20 cm?40 cm and 40 cm?60 cm) under different stages of degradation in Zoige Wetland. Experimental results showed that total microbial quantity decreased with the soil types (Peat soil>Meadow soil>Swamp soil>Sandy soil) and declined with soil depths (0?20 cm>20 cm? 40 cm>40 cm?60 cm). Bacterial community structure was affected by soil type more primarily than by soil depth. Bacterial community diversity generally declined with soil types (Peat soil>Sandy soil>Meadow soil>Swamp soil). However, no significant tendency was found for the soil depth. In addition, the total microbial quantity was strongly correlated with organic matter, total nitrogen and pH, and bacterial community diversity exhibited significant negative correlation with pH. Ten bands were excised from the DGGE gel and re-amplified for 16S rDNA sequencing. Based on the sequencing results, seven bands can be identified as related to γ-Proteobacteria, one close to α-Proteobacteria, and the other two belong to Bacteroidetes. These results provide evidence that Proteobacteria are the domain bacterial communities in the soil of Zoige Wetland.

Abstract:[Background] Heavy metal pollution of roads becomes more and more serious, and it is urgent to find efficient microbial resources for environmental remediation. [Objective] To screen heavy metal-resistant strains from the soil of road forest belt in Urumqi of China and test the heavy metal-removing ability. [Methods] Four media containing five heavy metal ions (Pb, Cd, Zn, Cu, and Ni) were used to screen the resistance strains which were then identified based on morphological characteristics and 16S rRNA gene. The removal of heavy metal ions by the strains was tested by inductively coupled plasma optical emission spectrometer (ICP-OES). [Results] Among the four media, TSA was the optimal one for the screening of strains. A total of 16 resistance strains were screened out: 4 Pb-resistant strains (tolerant concentration: 3 000 mg/L), 4 Cd-resistant strains (tolerant concentration: 800 mg/L), 4 Zn-resistant strains (tolerant concentration: 600 mg/L), 3 Cu-resistant strains (tolerant concentration: 300 mg/L), and 1 Ni-resistant strain (tolerant concentration: 400 mg/L). Among the 16 strains, the majority were Bacillus. The removal rate of 700 mg/L Pb2+ by strain Pb6 stood at 92.48%, and the removal rates by strains Pb11, 3 and 9 hit 27.70%, 40.37%, and 58.88%, separately. The removal rate of 200 mg/L Cd2+ by strain Cd4 was the highest (63.84%), and the removal rates by other Cd-resistant strains were about 30%-40%. The removal rates of 200 mg/L Zn2+ by strains Zn1 and Zn4 were 65.34% and 60.87%, respectively, while those by strains Zn5 and Zn6 registered 15.78% and 12.60%, separately. The removal rates of 300 mg/L Cu2+ by the three Cu-resistant strains were low (<3%). The removal rate of 200 mg/L Ni2+ by strain Ni2 was 4.31%. The strains (except for Cu1 and Cu3) mainly removed the heavy metals by adsorption, supplemented by absorption. After UV irradiation of strains Pb6, Cd4, and Zn1 for 30 s and continuous subculture, the removal rates of the corresponding heavy metals by three stable strains were 91.11%, 65.10%, and 66.48%, respectively. [Conclusion] Three strains with high tolerance to and removal rate of heavy metals were screened out: Bacillus sp. Pb6, Pseudomonas sp. Cd4, Bacillus sp. Zn1, which can be used as candidate strains for the remediation and treatment of soil or water polluted by heavy metals.

Abstract:[Background] The continuous cropping and poor fertilization habits in the tobacco-planting areas of Panzhihua have brought serious stress to the nutrient balance and microbial diversity in the soil, leading to declines in the yield and quality of tobacco and seriously affecting the development of the tobacco industry. [Objective] To study the effects of applying rhizobium-inoculated leguminous green manure on the microbial diversity and community composition in the soil cultivated with tobacco for years in Panzhihua and provide a theoretical basis for scientific fertilization and establishment of a reasonable planting pattern of flue-cured tobacco in Panzhihua. [Methods] We collected soil samples from the newly reclaimed tobacco field and the field planted with tobacco for years (both with the application of green manure) in Pingshan Township, Miyi County of Panzhihua. The physical and chemical properties of the soil samples were determined, and the bacterial community composition and diversity were analyzed by high-throughput sequencing. [Results] Inoculation with rhizobia increased the number of nodules and roots of pea seedlings, especially in the newly reclaimed tobacco field. The application of green manure increased the content of organic carbon and inorganic nutrients in soil and reduced soil pH and volume weight. In addition, the application of pea green manure changed the bacterial diversity and community composition in the soil. Specifically, it elevated the Simpson and Shannon indexes of bacteria in the newly reclaimed tobacco field and reduced the relevant diversity indexes in the field cultivated with tobacco for years. The predominant bacterial phyla of the soil samples planted with tobacco for different years included Proteobacteria, Chloroflexi, and Actinobacteria, while the dominant bacterial genera were Acinetobacter, Ochrobactrum, Sphingomonas, and Streptomyces. The redundant analysis showed that soil pH, available potassium (AK), and alkali-hydrolyzed nitrogen (AN) had strong correlations with the microbial community structure (P<0.05). [Conclusion] The application of green manure improves the nutrients and changes the bacterial diversity and community composition of the tobacco-growing soil.

Abstract:[Objective] We did this research to analyze the impact on the soil bacterial population of the transgenic carnation, which laid the foundation for the safety assessment of GM carnation. [Methods] Bacterial 16S rDNA gene clone libraries of GM and non-GM carnations were constructed, and the soil bacterial populations of these carnations were compared. [Results] The results showed Alphaproteobacteria, Betaproteobacteria, Planctomycetes and Acidobacteria were shared with GM and non-GM carnation. Some differences were found in Actinobacteria, Verrucomicrobia and uncultured bacterium clone. [Conclusion] The results indicated that high bacterial diversity was found in these GM carnation soil bacterial libraries, and the cultivation of genetically modified carnation did not have a significant impact on the soil bacterial community structure.

Abstract:[Background] Mining practices has a serious impact on the eco-environment around the mine. It is of great significance to explore the characteristics of soil nutrients and bacterial community structure around the mine for vegetation restoration. [Objective] To explore the characteristics of soil nutrients and bacterial community structures in different habitats around the Pulang Copper Mine in Shangri-La, Yunnan province. [Methods] The rhizosphere soil samples of dominant herbaceous plants were collected from four habitats (subalpine meadow, valley meadow, mine woodland, and subalpine woodland) around the Pulang Copper Mine to reveal the characteristics of soil nutrients and bacterial community structures of different habitats around the mine. [Results] The soil samples from the mine woodland had the highest nutrient content, which generally reached the medium or above level. Acidobacteriota, Actinobacteriota, and Proteobacteria were the dominant phyla of soil bacteria in the four habitats around the mine, with relative abundance ranging from 11.7% to 60.4%. Bradyrhizobium, Afipia, and Arthrobacter were the dominant genera, with relative abundance ranging from 6.1% to 53.6%. Mantel test results showed that soil organic matter had significant effects on the soil bacterial community structure at the genus level. [Conclusion] The results suggested that soil bacterial abundance was higher in summer than in winter (P<0.05), while there were no significant differences in soil bacterial relative abundance and diversity between the four habitats around the Pulang Copper Mine in summer and winter (P>0.05). The findings contribute to the understanding of mine ecosystems and provide a theoretical basis for the ecological restoration and soil pollution treatment in mining areas.

Abstract:[Background] Forest soil bacterial diversity is one of important indexes to measure forest quality. The composition and change of soil bacterial community structure can reflect the structure and function of forest ecosystem. They play important roles in the circulation of nutrients in forest ecosystems. [Objective] The influence of different forestry density on soil bacterial community structure was analyzed and discussed in Liuxihe National Park, in order to provide a reference for the restoration of degraded ecosystems, rational utilization of forestry resources, conservation of soil fertility, improvement of ecosystem productivity and service functions of forests. [Methods] A manipulative field experiment was conducted to investigate the effects of three different forest types: high density forest type (HD), medium density forest type (MD), low density forest type (LD). The soil samples were collected by “S” sampling method and the total DNA of soil microbes was extracted. 16S rRNA gene sequences were sequenced by Illumina Miseq sequencing and analyzed using R language, SPSS 21.0 and other software. [Results] The soil fertility of high density forest was higher than those of medium and low-density forests. Soil bacterial diversity index and richness index differed among different density forests, and the highest was in middle-density forest. Proteobacteria and Acidobacteria are the major groups in Liuxihe National Park. [Conclusion] The soil bacterial diversity is abundant in Liuxihe National Park. Proteobacteria and Acidobacteria are the major groups. Soil bacterial diversity, richness and community structure were significantly affected by forest density. The medium density forest type (1 800?2 200 plants/ha) in Liuxihe National Park is suitable for bacterial growth. The fertility of soil was affected by the forest density and shrub weeds. Intragenomic heterogeneity of 16S rRNA genes causes overestimation of bacterial diversity.

Abstract:[Objective] To investigate the influence of complex microbial agent on the soil bacterial populations in apple replanted orchard. [Methods] After the treatment with complex microbial agent, soil specimens were sampled from new crop and replanted apple orchard then analyzed by the method of automated ribosomal intergenic spacer analysis to monitor the bacterial community. [Results] Two years after treatment with complex microbial agent, the operational taxonomic units (OTUs) and Shannon-Wiener diversity index of replanted orchard was 250 and 4.44, respectively. In comparison, corresponding values were 234 and 3.81 in new crop orchard. One-Way ANOSIM analysis further showed that the difference coefficient was 0.108 3 and 0.084 3 respectively. In addition, the new crop and replanted orchard shared 89 core OTUs, and had a moderate similarity (corresponding Jaccard community similarity coefficient was 0.47). [Conclusion] The application of complex microbial agent could improve the soil microbial diversity and benefits to the recovery of the soil microbial ecosystem in replanted orchard.