The addition of simple substrates could affect the microbial respiration in soils. This substrate-induced respiration is widely used to estimate the soil microbial biomass, but little attention has been paid to its in...The addition of simple substrates could affect the microbial respiration in soils. This substrate-induced respiration is widely used to estimate the soil microbial biomass, but little attention has been paid to its influence on the changes of community-level physiological profiles. In this study, the process of microbial communities responding to the added substrate using sole-carbon-source utilization （BIOLOG） was investigated. BIOLOG is biased toward fast-growing bacteria; this advantage was taken to detect the prompt response of the active microbial communities to the added substrate. Four soil samples from agricultural fields adjacent to heavy metal mines were amended with L-arginine, citric acid, or D-glucose. Substrate amendments could, generally, not only increase the metabolic activity of the microbial communities, but also change the metabolic diverse patterns compared with no-substrate control. By tracking the process, it was found that the variance between substrate-induced treatment and control fluctuated greatly during the incubation course, and the influences of these three substrates were different. In addition, the application of these induced changes to discriminate soil microbial communities was tested. The distance among all samples was greatly increased, which further showed the functional variance among microbial communities in soils. This can be very useful in the discrimination of microbial communities even with high similarity.展开更多
Lead （Pb） contamination has often been recorded in Chinese field soils. In recent years, efforts have been made to inves- tigate Pb toxicity thresholds in soils with plant growth and microbial assays. However, the i...Lead （Pb） contamination has often been recorded in Chinese field soils. In recent years, efforts have been made to inves- tigate Pb toxicity thresholds in soils with plant growth and microbial assays. However, the influence of soil properties on Pb toxicity impacts on soil microbial processes is poorly understood. In this study ten soils with different properties were collected in China to investigate the relationships between thresholds of Pb toxicity to soil microbes and soil properties. The effect of soil leaching on Pb toxicity was also investigated to determine the possible influence of added anions on Pb toxicity during dose-response tests. Toxicity was inferred by measuring substrate-induced nitrification in leached and non-leached soils after Pb addition. We found that soil microbe Pb toxicity thresholds （ECx, x=10, 50） differed significantly between the soils; the 10% inhibition ratio values （ECI0） ranged from 86 to 218 mg kg-1 in non-leached soils and from 101 to 313 mg kg in leached soils. The 50% inhibition ratio values （EC50） ranged from 403 to 969 mg kg^-1 in non-leached soils and from 494 to 1 603 mg kg^-1 in leached soils. Soil leaching increased EC50 and EC50 values by an average leaching factor （LF） of 1.46 and 1.33, respectively. Stepwise multiple regression models predicting Pb toxicity to soil microbes were developed based on ECx and soil properties. Based on these models, soil pH and organic carbon are the most important soil properties af- fecting Pb toxicity thresholds （R2〉0.60）. The quantitative relationship between Pb toxicity and soil properties will be helpful for developing soil-specific guidance on Pb toxicity thresholds in Chinese field soils.展开更多
Rice cropping method is primarily decided by soil moisture regime.System of rice intensification(SRI)and direct-seeded aerobic rice are two primary modifications of traditional wetland rice.Understanding rice rhizosph...Rice cropping method is primarily decided by soil moisture regime.System of rice intensification(SRI)and direct-seeded aerobic rice are two primary modifications of traditional wetland rice.Understanding rice rhizosphere microbiome and functioning as influenced by these cropping methods is essential for sustaining rice productivity.The objective of this study was to assess the impact of three different rice cropping methods(wetland rice,SRI,and aerobic rice)on the biochemical properties and bacterial communities within the rice rhizosphere across three key rice growth stages:tillering,flowering,and maturity.Soil organic carbon(SOC),microbial biomass carbon(MBC),dehydrogenase activity,substrate-induced respiration(SIR),and metabolic quotient(MQ)were assessed along with high-throughput 16S rRNA sequencing of rice rhizosphere soils.The rice rhizosphere soil registered the highest SOC,MBC,and dehydrogenase activity in SRI followed by wetland rice and then aerobic rice.Cropping method had a minimal impact on SIR and MQ.Along with cropping method,growth stage also significantly altered these biological attributes of rice rhizosphere.The trends of the highest SOC content and dehydrogenase activity at the flowering stage and the highest MBC content and SIR at the tillering stage of rice were observed in all three rice cropping methods.The analysis of bacterial communities,based on 16S rRNA gene sequencing,revealed that both cropping method and growth stage significantly impacted the composition of rhizosphere microbiomes.However,the influence of cropping method was less pronounced compared to growth stage.Cropping method caused notable shifts in the abundances of Proteobacteria,Bacteroidetes,and Chloroflexi,while growth stage affected the abundances of Proteobacteria,Actinobacteria,Cyanobacteria,Firmicutes,Chloroflexi,and Bacteroidetes.Based on these results,the SRI method led to higher diversification to the rhizosphere bacteriobiota,as well as greater incorporation of carbon into the soil and increased dehydrogenase activity compared to wetland rice and aerobic rice.This study deepens our understanding of how different cropping methods influence plant-microbe interaction and the implications for overall rice productivity and soil health.展开更多
4-Hydroxyvaleric acid(4-HV)holds promise as a sustainable monomer for biodegradable polyesters and liquid transporta-tion fuels.This study achieved high-level 4-HV production from levulinic acid using an antibiotic-fr...4-Hydroxyvaleric acid(4-HV)holds promise as a sustainable monomer for biodegradable polyesters and liquid transporta-tion fuels.This study achieved high-level 4-HV production from levulinic acid using an antibiotic-free,substrate-inducible system in Escherichia coli.Enzymes involved in the conversion of levulinic acid to 4-HV were expressed with a bicistronic design of ribosome binding sites.The engineered strain demonstrated a 28%higher productivity compared to its counter-part,reaching a significant concentration of 107 g/L 4-HV with a production rate of 4.5 g/L/h and a molar conversion of 95%from levulinic acid in fed-batch cultivation.Recombinant cells from the initial cultivation were reused for a second round of biotransformation,demonstrating 73%efficiency of fresh cells.The study identified specific factors contributing to decreased system efficiency,including medium conditions,increased ionic strength,and high product concentration.Overall,the reported system and our findings hold significant potential for cost-effective microbial production of 4-HV at scale from levulinic acid.展开更多
基金supported by the National Natural Science Foundation of China(No.30470289,30670039).
文摘The addition of simple substrates could affect the microbial respiration in soils. This substrate-induced respiration is widely used to estimate the soil microbial biomass, but little attention has been paid to its influence on the changes of community-level physiological profiles. In this study, the process of microbial communities responding to the added substrate using sole-carbon-source utilization （BIOLOG） was investigated. BIOLOG is biased toward fast-growing bacteria; this advantage was taken to detect the prompt response of the active microbial communities to the added substrate. Four soil samples from agricultural fields adjacent to heavy metal mines were amended with L-arginine, citric acid, or D-glucose. Substrate amendments could, generally, not only increase the metabolic activity of the microbial communities, but also change the metabolic diverse patterns compared with no-substrate control. By tracking the process, it was found that the variance between substrate-induced treatment and control fluctuated greatly during the incubation course, and the influences of these three substrates were different. In addition, the application of these induced changes to discriminate soil microbial communities was tested. The distance among all samples was greatly increased, which further showed the functional variance among microbial communities in soils. This can be very useful in the discrimination of microbial communities even with high similarity.
基金financially supported by the National Key Research and Development Program of China (2016YDF0800707)the National Key Technology R&D Program of China (2015BAD05B03)the National Natural Science Foundation of China (41271490)
文摘Lead （Pb） contamination has often been recorded in Chinese field soils. In recent years, efforts have been made to inves- tigate Pb toxicity thresholds in soils with plant growth and microbial assays. However, the influence of soil properties on Pb toxicity impacts on soil microbial processes is poorly understood. In this study ten soils with different properties were collected in China to investigate the relationships between thresholds of Pb toxicity to soil microbes and soil properties. The effect of soil leaching on Pb toxicity was also investigated to determine the possible influence of added anions on Pb toxicity during dose-response tests. Toxicity was inferred by measuring substrate-induced nitrification in leached and non-leached soils after Pb addition. We found that soil microbe Pb toxicity thresholds （ECx, x=10, 50） differed significantly between the soils; the 10% inhibition ratio values （ECI0） ranged from 86 to 218 mg kg-1 in non-leached soils and from 101 to 313 mg kg in leached soils. The 50% inhibition ratio values （EC50） ranged from 403 to 969 mg kg^-1 in non-leached soils and from 494 to 1 603 mg kg^-1 in leached soils. Soil leaching increased EC50 and EC50 values by an average leaching factor （LF） of 1.46 and 1.33, respectively. Stepwise multiple regression models predicting Pb toxicity to soil microbes were developed based on ECx and soil properties. Based on these models, soil pH and organic carbon are the most important soil properties af- fecting Pb toxicity thresholds （R2〉0.60）. The quantitative relationship between Pb toxicity and soil properties will be helpful for developing soil-specific guidance on Pb toxicity thresholds in Chinese field soils.
基金support from the Indian Council of Agricultural Research through the All India Network Project(AINP)on Soil Biodiversity and Biofertilizers to conduct this study is acknowledged。
文摘Rice cropping method is primarily decided by soil moisture regime.System of rice intensification(SRI)and direct-seeded aerobic rice are two primary modifications of traditional wetland rice.Understanding rice rhizosphere microbiome and functioning as influenced by these cropping methods is essential for sustaining rice productivity.The objective of this study was to assess the impact of three different rice cropping methods(wetland rice,SRI,and aerobic rice)on the biochemical properties and bacterial communities within the rice rhizosphere across three key rice growth stages:tillering,flowering,and maturity.Soil organic carbon(SOC),microbial biomass carbon(MBC),dehydrogenase activity,substrate-induced respiration(SIR),and metabolic quotient(MQ)were assessed along with high-throughput 16S rRNA sequencing of rice rhizosphere soils.The rice rhizosphere soil registered the highest SOC,MBC,and dehydrogenase activity in SRI followed by wetland rice and then aerobic rice.Cropping method had a minimal impact on SIR and MQ.Along with cropping method,growth stage also significantly altered these biological attributes of rice rhizosphere.The trends of the highest SOC content and dehydrogenase activity at the flowering stage and the highest MBC content and SIR at the tillering stage of rice were observed in all three rice cropping methods.The analysis of bacterial communities,based on 16S rRNA gene sequencing,revealed that both cropping method and growth stage significantly impacted the composition of rhizosphere microbiomes.However,the influence of cropping method was less pronounced compared to growth stage.Cropping method caused notable shifts in the abundances of Proteobacteria,Bacteroidetes,and Chloroflexi,while growth stage affected the abundances of Proteobacteria,Actinobacteria,Cyanobacteria,Firmicutes,Chloroflexi,and Bacteroidetes.Based on these results,the SRI method led to higher diversification to the rhizosphere bacteriobiota,as well as greater incorporation of carbon into the soil and increased dehydrogenase activity compared to wetland rice and aerobic rice.This study deepens our understanding of how different cropping methods influence plant-microbe interaction and the implications for overall rice productivity and soil health.
基金National Research Foundation of Korea(NRF)(Grant No.NRF RS-2023-00208026)Innovative science project in 2020 of the Circle Foundation.
文摘4-Hydroxyvaleric acid(4-HV)holds promise as a sustainable monomer for biodegradable polyesters and liquid transporta-tion fuels.This study achieved high-level 4-HV production from levulinic acid using an antibiotic-free,substrate-inducible system in Escherichia coli.Enzymes involved in the conversion of levulinic acid to 4-HV were expressed with a bicistronic design of ribosome binding sites.The engineered strain demonstrated a 28%higher productivity compared to its counter-part,reaching a significant concentration of 107 g/L 4-HV with a production rate of 4.5 g/L/h and a molar conversion of 95%from levulinic acid in fed-batch cultivation.Recombinant cells from the initial cultivation were reused for a second round of biotransformation,demonstrating 73%efficiency of fresh cells.The study identified specific factors contributing to decreased system efficiency,including medium conditions,increased ionic strength,and high product concentration.Overall,the reported system and our findings hold significant potential for cost-effective microbial production of 4-HV at scale from levulinic acid.
