Distribution of Bacterial Communities in Petroleum-Contaminated Soils from the Dagang Oilfield, China

Diversity in bacterial communities was investigated along a petroleum hydrocarbon content gradient(0-0.4043 g/g)in surface(5-10 cm)and subsurface(35-40 cm)petroleum-contaminated soil samples from the Dagang Oilfield,China.Using 16S rRNA Illumina high-throughput sequencing technology and several statistical methods,the bacterial diversity of the soil was studied.Subsequently,the environmental parameters were measured to analyze its relationship with the community variation.Nonmetric multidimensional scaling and analysis of similarities indicated a significant difference in the structure of the bacterial community between the nonpetroleum-contaminated surface and subsurface soils,but no differences were observed in different depths of petroleum-contaminated soil.Meanwhile,many significant correlations were obtained between diversity in soil bacterial community and physicochemical properties.Total petroleum hydrocarbon,total organic carbon,and total nitrogen were the three important factors that had the greatest impacts on the bacterial community distribution in the long-term petroleum-contaminated soils.Our research has provided references for the bacterial community distribution along a petroleum gradient in both surface and subsurface petroleum-contaminated soils of oilfield areas.

Plant property regulates soil bacterial community structure under altered precipitation regimes in a semi-arid desert grassland, China

Variations of precipitation have great impacts on soil carbon cycle and decomposition of soil organic matter.Soil bacteria are crucial participants in regulating these ecological processes and vulnerable to altered precipitation.Studying the impacts of altered precipitation on soil bacterial community structure can provide a novel insight into the potential impacts of altered precipitation on soil carbon cycle and carbon storage of grassland.Therefore,soil bacterial community structure under a precipitation manipulation experiment was researched in a semi-arid desert grassland in Chinese Loess Plateau.Five precipitation levels,i.e.,control,reduced and increased precipitation by 40%and 20%,respectively(referred here as CK,DP40,DP20,IP40,and IP20)were set.The results showed that soil bacterial alpha diversity and rare bacteria significantly changed with altered precipitation,but the dominant bacteria and soil bacterial beta diversity did not change,which may be ascribed to the ecological strategy of soil bacteria.The linear discriminate analysis(LDA)effect size(LEfSe)method found that major response patterns of soil bacteria to altered precipitation were resource-limited and drought-tolerant populations.In addition,increasing precipitation greatly promoted inter-species competition,while decreasing precipitation highly facilitated inter-species cooperation.These changes in species interaction can promote different distribution ratios of bacterial populations under different precipitation conditions.In structural equation model(SEM)analysis,with changes in precipitation,plant growth characteristics were found to be drivers of soil bacterial community composition,while soil properties were not.In conclusion,our results indicated that in desert grassland ecosystem,the sensitive of soil rare bacteria to altered precipitation was stronger than that of dominant taxa,which may be related to the ecological strategy of bacteria,species interaction,and precipitation-induced variations of plant growth characteristics.

Wheat, maize and sunflower cropping systems selectively influence bacteria community structure and diversity in their and succeeding crop's rhizosphere

supported by the Special Fund for Agro-scientific Research in the Public Interest in China （201103001）

Lignocellulosic fraction-induced niche differentiation within dissimilatory iron reducing bacterial groups in a paddy soil

Responses of soil DIRB to lignocellulosic fractions during a 6-week microcosm incubation were investigated.Anaeromyxobacter,Bacillus,and Clostridium maintained their domi-nance throughout the incubation.Distinct DIRB groups proliferated under specific lignocellulosic fraction amendments.Limits of insufficient ferric iron on the proliferation varied by DIRB group.Dissimilatory iron reducing bacteria(DIRB)are phylogenetically and physi-ologically diverse in paddy soils,where iron reduction closely couples with the oxidation of rice straw-derived carbon in the straw returning scenarios.However,few studies have addressed the niche differentiation within DIRB groups during the degradation of lignocellulosic fractions of rice straw.This study conducted a 6-week microcosm incubation experiment to reveal the distinct responses of DIRB groups under specific lignocellulosic fraction amendments with and without ferrihydrite(Fh)addition in a flooded paddy Ultisol.Results showed that the total absolute abundance of the 19 detected DIRB groups did not vary significantly during the incubation.Anaeromyxobacter,Bacillus,and Clostridium were the dominant DIRB groups for all lignocellulosic treatments whereas Thermincola was dominant but only under xylan amendment with Fh addition.DIRB-nodes in the co-occurrence networks of bacterial community mainly belonged to Anaeromyxobacter and Bacillus.Clostridium and Thermincola,Alkaliphilus and Anaeromyxobacter,and Alicyclobacillus,Desulfobulbus,and Desulfosporosinus were specifically proliferated under xylan,cellulose,and lignin amendments,respectively.Whether the proliferation was limited by insufficient ferric iron varied by bacterial group.These findings suggested the lignocellulosic fraction-induced niche differentiation within DIRB groups,which advanced our understanding of the ecology of DIRB in paddy soils under straw returning.