Climate and salinity drive soil bacterial richness and diversity in sandy grasslands in China

Bacteria constitute a large proportion of the biodiversity in soils and control many important processes in terrestrial ecosystems.However,our understanding of the interactions between soil bacteria and environmental factors remains limited,especially in sensitive and fragile ecosystems.In this study,geographic patterns of bacterial diversity across four sandy grasslands along a 1,600 km north-south transect in northern China were characterized by high-throughput 16S rRNA gene sequencing.Then,we analyzed the driving factors behind the patterns in bacterial diversity.The results show that of the 21 phyla detected,the most abundant were Proteobacteria,Actinobacteria,Acidobacteria and Fir‐micutes(average relative abundance>5%).Soil bacterial operational taxonomic unit(OTU)numbers(richness)and Faith's phylogenetic diversity(diversity)were highest in the Otindag Sandy Land and lowest in the Mu Us Sandy Land.Soil electrical conductivity(EC)was the most influential factor driving bacterial richness and diversity.The bacterial communities differed significantly among the four sandy grasslands,and the bacterial community structure was signifi‐cantly affected by environmental factors and geographic distance.Of the environmental variables examined,climatic factors(mean annual temperature and precipitation)and edaphic properties(pH and EC)explained the highest propor‐tion of the variation in bacterial community structure.Biotic factors such as plant species richness and aboveground bio‐mass exhibited weak but significant associations with bacterial richness and diversity.Our findings revealed the impor‐tant role of climate and salinity factors in controlling bacterial richness and diversity;understanding these roles is critical for predicting the impacts of climate change and promoting sustainable management strategies for ecosystem services in these sandy lands.

Pyrosequencing-based assessment of bacterial community structure in mine soils affected by mining subsidence

Based on the 454 pyrosequencing approach, this research evaluated the influence of coal mining subsi- dence on soil bacterial diversity and community structure in Chinese mining area. In order to characterize the bacterial community comparatively, this study selected a field experiment site with coal-excavated subsidence soils and an adjacent site with non-disturbed agricultural soils, respectively. The dataset com- prises 24512 sequences that are affiliated to the 7 phylogenetic groups： proteobacteria, actinobacteria, bacteroidetes, gemmatimonadetes, chlorofiexi, nitrospirae and unclassified phylum. Proteobacteria is the largest bacterial phylum in all samples, with a marked shift of the proportions of alpha-, beta-, and gammaproteobacteria. The results show that undisturbed soils are relatively more diverse and rich than subsided soils, and differences in abundances of dominant taxonomic groups between the two soil groups are visible. Compared with the control, soil nutrient contents decline achieves significant level in subsided soils. Correlational analysis showed bacterial diversity indices have significantly positive corre- lation with soil organic matter, total N, total P, and available K. but in negative relation with soil salinity. Ground subsidence noticeably affects the diversity and composition of soil microbial community. Degen- eration of soil fertility and soil salinization inhibits the sole-carbon-source metabolic ability of microbial community, leading to the simplification of advantage species and uneven distribution of microbial spe- cies. This work demonstrates the great potential of pyrosequencing technique in revealing microbial diversity and presents background information of microbial communities of mine subsidence land.

Analysis of Rhizosphere Microbial Community Structure in Different Pathogenesis Stages of Watermelon Fusarium Wilt

High-throughput sequencing technique was applied to analyze the microbial community structure of rhizosphere soil at different stages of watermelon fusarium wilt to find out the difference of dominant microbial community in rhizosphere during the occurrence of watermelon fusarium wilt.Illumina-Hiseq high-throughput sequencing platform was used to sequence 16S and ITS rDNA in rhizosphere soil.The soil was named CK1 before planting,CK2 at peak stage and CK3 at stable stage.The results showed that the soil bacterial diversity was in the order of CK1>CK3>CK2,indicating no significant difference between CK1 and CK3 and a significant difference between CK2 and CK1,CK3.At the genus level,the dominant bacteria were Mizugakiibacter(21.9299%),Rhodanobacter(5.0933%),and Lactobacillus(3.1921%).The diversity of soil fungi was in the order of CK1>CK3>CK2,all showing significant differences.At the genus level,the dominant fungus was Lysurus(54.4601%),Papulaspora(12.4252%),Acrophialophora(3.1729%).The results showed that the diversity and abundance of bacteria and fungi in rhizosphere soil decreased during the peak period of watermelon fusarium wilt.With the gradual stabilization of the disease,the diversity and abundance of bacteria and fungi in rhizosphere soil recovered to a certain extent.