Understanding bacterial strategies for coping with heavy metal stress is essential for elucidating their resilience in contaminated environments.However,whether cell wall exfoliation contributes to bacterial tolerance...Understanding bacterial strategies for coping with heavy metal stress is essential for elucidating their resilience in contaminated environments.However,whether cell wall exfoliation contributes to bacterial tolerance under heavy metal stress,such as cadmium(Cd)exposure,remains unclear and requires further investigation.In this study,we reveal a novel self-protective mechanism in Stenotrophomonas sp.H225 isolated from a Cd-contaminated farmland soil,which underwent controlled cell wall exfoliation and regeneration in response to Cd stress up to 200 mg L^(-1).Transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses revealed that the exfoliated cell wall fragments served as extracellular Cd sinks,thereby reducing intracellular Cd accumulation.Fourier-transform infrared spectroscopy and enzyme-linked immunosorbent assay indicated progressive peptidoglycan(PG)degradation,with exfoliated PG concentration in solution increasing from 148 ng mL^(-1) at 0 mg L^(-1) Cd to 240 ng mL^(-1) at 200 mg L^(-1) Cd.This degradation was counteracted by the compensatory upregulation of PG biosynthesis genes,with the enrichment ratio reaching up to 0.83,facilitating cell wall reconstruction.Transcriptomic analysis and gene knockout experiments identified mtgA(encoding a monofunctional transglycosylase)as a key determinant in cell wall repair and Cd resistance.To our knowledge,this is the first mechanistic evidence that bacteria can mitigate heavy metal toxicity through dynamic cell wall remodeling involving exfoliation and regeneration.This finding enhances our understanding of microbial survival strategies under environmental stress and highlights potential targets for engineering metal-tolerant strains for bioremediation applications.展开更多
Elevated arsenic(As)mobilization and increased nitrous oxide(N_(2)O)emission are two primary environmental concerns existing in flooded paddy soils.In this study,dissolved As(Ⅲ),N isotope-labeled Na^(15)NO_(3),and/or...Elevated arsenic(As)mobilization and increased nitrous oxide(N_(2)O)emission are two primary environmental concerns existing in flooded paddy soils.In this study,dissolved As(Ⅲ),N isotope-labeled Na^(15)NO_(3),and/or^(14)NH_(4)Cl were incorporated into a microcosm incubation to determine the effects of N fertilization regimes on As mobilization and N_(2)O emission in a flooded paddy soil.Because nitrate had a higher redox potential and comprised a higher proportion of N substrate,As(Ⅴ)was preferentially formed due to enhanced nitrate-dependent microbial As(Ⅲ)oxidation.Thus,As availability was correspondingly attenuated due to the improved production of less mobile and toxic As(Ⅴ).After 2-d incubation,more than 90%and 98%of soluble As(Ⅲ)were immobilized in the As+NH_(4)^(+)-N+NO_(3)^(-)-N and As+NO_(3)^(-)-N treatments,respectively.Following nitrate depletion(after 2 d),microbial As(Ⅴ)and Fe(Ⅲ)reductions were gradually enhanced,which was attributed to stimulation of anaerobic ammonium oxidation(anammox)coupled to Fe(Ⅲ)reduction,known as Feammox,by the abundance of NH_(4)^(+).By the end of the incubation period(10 d),the As+NO_(3)^(-)-N treatment led to higher As immobilization of originally added As(Ⅲ)(ca.61%)than the As+NH_(4)^(+)-N+NO_(3)^(-)-N treatment(42%).The As+NH_(4)^(+)-N+NO_(3)^(-)-N treatment prominently mitigated N_(2)O emission compared to the As+NO_(3)^(-)-N treatment,which was ascribed to anammox,inducing accumulation of byproducts from incomplete denitrification.High-throughput sequencing indicated that the relative abundances of denitrifiers(e.g.,Azoarcus,Ochrobactrum,and Thiobacillus denitrificans)increased in the As+NO_(3)^(-)treatment,whereas quantitative polymerase chain reaction results indicated higher 16S rRNA gene copy numbers for anammox and Feammox(Acidimicrobiaceae bacterium A6)bacteria in the As+NH_(4)^(+)+NO_(3)^(-)treatment.Collectively,the experimental results demonstrated that N fertilization can be a feasible As remediation strategy while providing an effective strategy for mitigating N_(2)O emission from paddy soils at the same time.展开更多
Soil biogeochemical cycles and their interconnections play a critical role in regulating functions and services of environmental systems.However,the coupling of soil biogeochemical processes with their mediating micro...Soil biogeochemical cycles and their interconnections play a critical role in regulating functions and services of environmental systems.However,the coupling of soil biogeochemical processes with their mediating microbes remains poorly understood.Here,we identified key microbial taxa regulating soil biogeochemical processes by exploring biomarker genes and taxa of contigs assembled from metagenomes of forest soils collected along a latitudinal transect(18°N to 48°N)in eastern China.Among environmental and soil factors,soil pH was a sensitive indicator for functional gene composition and diversity.A function-taxon bipartite network inferred from metagenomic contigs identified the microbial taxa regulating coupled biogeochemical cycles between carbon and phosphorus,nitrogen and sulfur,and nitrogen and iron.Our results provide novel evidence for the coupling of soil biogeochemical cycles,identify key regulating microbes,and demonstrate the efficacy of a new approach to investigate the processes and microbial taxa regulating soil ecosystem functions.展开更多
Dissolved organic matter(DOM)in soils drives biogeochemical cycling and soil functions in different directions depending on its molecular signature.Notably,there is a distinct paucity of information concerning how the...Dissolved organic matter(DOM)in soils drives biogeochemical cycling and soil functions in different directions depending on its molecular signature.Notably,there is a distinct paucity of information concerning how the molecular signatures of soil DOM vary with different degrees of weathering across wide geographic scales.Herein,we resolved the DOM molecular signatures from 22 diverse Chinese reference soils and linked them with soil organic matter and weathering-related mineralogical properties.The mixed-effects models revealed that the yields of DOM were determined by soil organic carbon content,whereas the molecular signature of DOM was primarily constrained by the weathering-related dimension.The soil weathering index showed a positive effect on the lability and a negative effect on the aromaticity of DOM.Specifically,DOM in highly weathered acidic soils featured more amino sugars,carbohydrates,and aliphatics,as well as less O-rich polyphenols and condensed aromatics,thereby conferring a higher DOM biolability and lower DOM aromaticity.This study highlights the dominance of the weathering-related dimension in constraining the molecular signatures and potential functions of DOM in soils across a wide geographic scale.展开更多
基金partially supported by the National Natural Science Foundation of China (Nos. 42377004 and 41991334)the Fundamental Research Funds for the Central Universities (No. 226-2025-0004)+1 种基金the China Agriculture Research System (No. CARS-01)the opportunity granted by the China Scholarship Council (No. 202406320448)
文摘Understanding bacterial strategies for coping with heavy metal stress is essential for elucidating their resilience in contaminated environments.However,whether cell wall exfoliation contributes to bacterial tolerance under heavy metal stress,such as cadmium(Cd)exposure,remains unclear and requires further investigation.In this study,we reveal a novel self-protective mechanism in Stenotrophomonas sp.H225 isolated from a Cd-contaminated farmland soil,which underwent controlled cell wall exfoliation and regeneration in response to Cd stress up to 200 mg L^(-1).Transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses revealed that the exfoliated cell wall fragments served as extracellular Cd sinks,thereby reducing intracellular Cd accumulation.Fourier-transform infrared spectroscopy and enzyme-linked immunosorbent assay indicated progressive peptidoglycan(PG)degradation,with exfoliated PG concentration in solution increasing from 148 ng mL^(-1) at 0 mg L^(-1) Cd to 240 ng mL^(-1) at 200 mg L^(-1) Cd.This degradation was counteracted by the compensatory upregulation of PG biosynthesis genes,with the enrichment ratio reaching up to 0.83,facilitating cell wall reconstruction.Transcriptomic analysis and gene knockout experiments identified mtgA(encoding a monofunctional transglycosylase)as a key determinant in cell wall repair and Cd resistance.To our knowledge,this is the first mechanistic evidence that bacteria can mitigate heavy metal toxicity through dynamic cell wall remodeling involving exfoliation and regeneration.This finding enhances our understanding of microbial survival strategies under environmental stress and highlights potential targets for engineering metal-tolerant strains for bioremediation applications.
基金supported by the National Natural Science Foundation of China(No.41807035)the Public Welfare Technology Application Research Project of Zhejiang Province,China(No.LGF22E080002)+3 种基金the Higher Education Institution Scientific Research Project of Ningxia,China(No.NYG2024118)the Natural Science Foundation of Ningxia,China(No.2024AAC05063)the Natural Science Foundation of Xiamen,China(No.3502Z20227321)the Municipal Science and Technology Bureau of Wenzhou,China(Nos.X20210033 and X20210096)。
文摘Elevated arsenic(As)mobilization and increased nitrous oxide(N_(2)O)emission are two primary environmental concerns existing in flooded paddy soils.In this study,dissolved As(Ⅲ),N isotope-labeled Na^(15)NO_(3),and/or^(14)NH_(4)Cl were incorporated into a microcosm incubation to determine the effects of N fertilization regimes on As mobilization and N_(2)O emission in a flooded paddy soil.Because nitrate had a higher redox potential and comprised a higher proportion of N substrate,As(Ⅴ)was preferentially formed due to enhanced nitrate-dependent microbial As(Ⅲ)oxidation.Thus,As availability was correspondingly attenuated due to the improved production of less mobile and toxic As(Ⅴ).After 2-d incubation,more than 90%and 98%of soluble As(Ⅲ)were immobilized in the As+NH_(4)^(+)-N+NO_(3)^(-)-N and As+NO_(3)^(-)-N treatments,respectively.Following nitrate depletion(after 2 d),microbial As(Ⅴ)and Fe(Ⅲ)reductions were gradually enhanced,which was attributed to stimulation of anaerobic ammonium oxidation(anammox)coupled to Fe(Ⅲ)reduction,known as Feammox,by the abundance of NH_(4)^(+).By the end of the incubation period(10 d),the As+NO_(3)^(-)-N treatment led to higher As immobilization of originally added As(Ⅲ)(ca.61%)than the As+NH_(4)^(+)-N+NO_(3)^(-)-N treatment(42%).The As+NH_(4)^(+)-N+NO_(3)^(-)-N treatment prominently mitigated N_(2)O emission compared to the As+NO_(3)^(-)-N treatment,which was ascribed to anammox,inducing accumulation of byproducts from incomplete denitrification.High-throughput sequencing indicated that the relative abundances of denitrifiers(e.g.,Azoarcus,Ochrobactrum,and Thiobacillus denitrificans)increased in the As+NO_(3)^(-)treatment,whereas quantitative polymerase chain reaction results indicated higher 16S rRNA gene copy numbers for anammox and Feammox(Acidimicrobiaceae bacterium A6)bacteria in the As+NH_(4)^(+)+NO_(3)^(-)treatment.Collectively,the experimental results demonstrated that N fertilization can be a feasible As remediation strategy while providing an effective strategy for mitigating N_(2)O emission from paddy soils at the same time.
基金supported by the National Natural Science Foundation of China(41721001,41991334)111 Project(B17039)Zhejiang Natural Science Foundation(LD19D060001).
文摘Soil biogeochemical cycles and their interconnections play a critical role in regulating functions and services of environmental systems.However,the coupling of soil biogeochemical processes with their mediating microbes remains poorly understood.Here,we identified key microbial taxa regulating soil biogeochemical processes by exploring biomarker genes and taxa of contigs assembled from metagenomes of forest soils collected along a latitudinal transect(18°N to 48°N)in eastern China.Among environmental and soil factors,soil pH was a sensitive indicator for functional gene composition and diversity.A function-taxon bipartite network inferred from metagenomic contigs identified the microbial taxa regulating coupled biogeochemical cycles between carbon and phosphorus,nitrogen and sulfur,and nitrogen and iron.Our results provide novel evidence for the coupling of soil biogeochemical cycles,identify key regulating microbes,and demonstrate the efficacy of a new approach to investigate the processes and microbial taxa regulating soil ecosystem functions.
基金financially supported by the National Natural Science Foundation of China(42122054,42192513,41807360)Guangdong Basic and Applied Basic Research Foundation(2021B1515020082)+1 种基金Key Platform and Scientific Research Projects of Guangdong Provincial Education Department(2019KZDXM028,and 2020KCXTD006)Science and Technology Development Fund Project of Shenzhen(JCYJ20190809142611503 and JCYJ20190809162205531).
文摘Dissolved organic matter(DOM)in soils drives biogeochemical cycling and soil functions in different directions depending on its molecular signature.Notably,there is a distinct paucity of information concerning how the molecular signatures of soil DOM vary with different degrees of weathering across wide geographic scales.Herein,we resolved the DOM molecular signatures from 22 diverse Chinese reference soils and linked them with soil organic matter and weathering-related mineralogical properties.The mixed-effects models revealed that the yields of DOM were determined by soil organic carbon content,whereas the molecular signature of DOM was primarily constrained by the weathering-related dimension.The soil weathering index showed a positive effect on the lability and a negative effect on the aromaticity of DOM.Specifically,DOM in highly weathered acidic soils featured more amino sugars,carbohydrates,and aliphatics,as well as less O-rich polyphenols and condensed aromatics,thereby conferring a higher DOM biolability and lower DOM aromaticity.This study highlights the dominance of the weathering-related dimension in constraining the molecular signatures and potential functions of DOM in soils across a wide geographic scale.
