School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemDistinct kin strategies of the legume soybean and the non-legume balsam by accomplishing different nitrogen acquisition and rhizosphere microbiome composition(WILEY, 2022-04)SUMMARY Kin selection has been proposed vvto be an important mechanism for plant relatives growing together. To reveal kin recognition, we used 15N labeling to assess the short‐term nitrogen (N) acquisition (uptake of nitrate and ammonium), long‐term N utilization (recovery of added urea), N‐use efficiency (NUE) and rhizosphere microbiome in leguminous Glycine max and non‐leguminous Impatiens balsamina. Individuals of each species were planted pairwise with either a sibling or a stranger. Enzyme activity and soil microbial composition were compared between kinship groups. Compared with strangers, G. max siblings increased aboveground biomass, NUE, and nitrogenase activity, whereas I. balsamina siblings decreased root biomass and increased uptake rate of nitrate and potential nitrification rate. Plant kinship affected soil bacterial communities by enriching specific groups possessing explicit eco‐functions (Rhizobiales for G. max and Nitrospira for I. balsamina). Kinship‐sensitive operational taxonomic units formed independent modules in the bacterial co‐occurrence network and were positively correlated with plant growth performance, N acquisition and enzymatic activity. Plant kin recognition may depend on the growth strategies of the plant species. Kin selection was dominant in G. max by enhancing biological N fixation through the enrichment of symbiotic rhizobia (demonstrated by aboveground growth and NUE superiority among siblings). Kin selection and niche partitioning occurred simultaneously in I. balsamina, expressed through reduced root allocation but increased nitrate uptake, and enhanced soil N nitrification, by enriching functional microbial groups. Kin recognition responses are the consequence of complex interactions among the host plant, the microbiome, and soil nutrient cycling and utilization processes.
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ItemNo Preview AvailableCross-biome antibiotic resistance decays after millions of years of soil development(SPRINGERNATURE, 2022-07)Soils harbor the most diverse naturally evolved antibiotic resistance genes (ARGs) on Earth, with implications for human health and ecosystem functioning. How ARGs evolve as soils develop over centuries, to millennia (i.e., pedogenesis), remains poorly understood, which introduces uncertainty in predictions of the dynamics of ARGs under changing environmental conditions. Here we investigated changes in the soil resistome by analyzing 16 globally distributed soil chronosequences, from centuries to millennia, spanning a wide range of ecosystem types and substrate age ranges. We show that ARG abundance and diversity decline only after millions of years of soil development as observed in very old chronosequences. Moreover, our data show increases in soil organic carbon content and microbial biomass as soil develops that were negatively correlated with the abundance and diversity of soil ARGs. This work reveals natural dynamics of soil ARGs during pedogenesis and suggests that such ecological patterns are predictable, which together advances our understanding of the environmental drivers of ARGs in terrestrial environments.
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ItemNo Preview AvailableCalling for comprehensive explorations between soil invertebrates and arbuscular mycorrhizas(CELL PRESS, 2022-08)Arbuscular mycorrhizal (AM) fungi and soil invertebrates represent a large proportion of total soil biomass and biodiversity and are vital for plant performance, soil structure, and biogeochemical cycling. However, the role of soil invertebrates in AM fungi development remains elusive. In this opinion article, we summarize the ecological importance of AM fungi and soil invertebrates in the plant-soil continuum and highlight the effects of soil invertebrates on AM fungal hyphae development and functioning. In a context of global change, we envision that better mechanistic understanding of the complex feedback via chemical signaling pathways across the interactions between soil invertebrates and AM fungi is critical to predict their ecological consequences and will open new avenues for promoting ecosystem resilience and sustainability.
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ItemNo Preview AvailableAridity decreases soil protistan network complexity and stability(PERGAMON-ELSEVIER SCIENCE LTD, 2022-03)
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ItemNo Preview AvailableClimate warming increases the proportions of specific antibiotic resistance genes in natural soil ecosystems(ELSEVIER, 2022-05-15)Understanding the future distribution of antibiotic resistance in natural soil ecosystems is important to forecast their impacts on ecosystem and human health under projected climate change scenarios. Therefore, it is critical and timely to decipher the links between climate warming and antibiotic resistance, two of Earth's most imminent problems. Here, we explored the role of five-year simulated climate warming (+ 4 °C) on the diversity and proportions of soil antibiotic resistance genes (ARGs) across three seasons in both plantation and natural forest ecosystems. We found that the positive effects of warming on the number and proportions of ARGs were dependent on the sampling seasons (summer, autumn and winter), and seasonality was a key factor driving the patterns of ARG compositions in forest soils. Fifteen ARGs, conferring resistance to common antibiotics including aminoglycoside, beta-lactam, macrolide-lincosamide-streptogramin B, multidrug, sulfonamide, and tetracycline, were significantly enriched in the warming treatment. We showed that changes in soil properties and community compositions of bacteria, fungi and protists can explain the changes in soil ARGs under climate warming. Taken together, these findings advance our understanding of environmental ARGs under the context of future climate change and suggest that elevated temperature may promote the abundance of specific soil ARGs, with important implications for ecosystem and human health.
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ItemNo Preview AvailableLivestock manure spiked with the antibiotic tylosin significantly altered soil protist functional groups(ELSEVIER, 2022-04-05)With the increasing global antibiotic uses in livestock husbandry, animal manures upon land application pose potential threats to the environments and soil microbiome. Nevertheless, effects of manures and antibiotic-administered manures on soil protists, an integral component of soil food web and primary regulators of bacteria, remain unknown. Here, we assessed impacts of cattle and poultry manures with or without an antibiotic tylosin on soil protists and their functional groups in a 130-day microcosm incubation. Protists were highly responsive to manure application, with a significant decline in their alpha diversity in all manure treatments. There were also significant temporal changes in the alpha diversity and composition of soil protists and their functional groups. Poultry manures had stronger negative influences on the community structure of protists compared to cattle manures, and more pronounced effects on protists were observed in tylosin-spiked manure treatments. Furthermore, many consumer, phototrophic and parasitic taxa were highly susceptible to all manure treatments at Day 50 and 130. Altogether, our findings demonstrate negative effects of animal manures and tylosin on soil protists. This study suggests that the applications of livestock manures and antibiotics may subsequently alter ecological functions of protists and their interactions with other soil microorganisms in agricultural systems.
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ItemNo Preview AvailableContrasting ecological processes shape the Eucalyptus phyllosphere bacterial and fungal community assemblies(Wiley, 2022-03-01)Abstract Introduction Phyllosphere microbiome is intrinsically linked to plant performance and ecosystem functioning. However, our knowledge about the role of ecological processes in shaping the biogeography of different phyllosphere microbial communities is scarce. Materials and Methods Here, we compared the biogeographic patterns of bacterial and fungal communities in phyllosphere samples of plants belonging to the genus of Eucalyptus of the Myrtaceae family collected from an over 4000 km transect. We investigated the relative importance of two major ecosystem processes (stochastic vs. deterministic) in shaping phyllosphere microbial community assemblies. Results Our results demonstrated that the neutral community model, which can quantify the degree of a community assembly determined by stochastic processes, explained 64.2% of the variations in bacterial community assembly, which had a normalized stochasticity ratio of 71.8%. These results suggest that the dominant role of stochastic processes in shaping bacterial community assembly. In contrast, phyllosphere fungal community assembly was mainly shaped by deterministic processes as revealed by a relatively small explanation rate of the neutral community model (48.7%) and a normalized stochasticity ratio of 25.1%. Variation partitioning analysis and random forest modelling results indicated that climatic factors, particularly mean annual precipitation and aridity index, were important in driving both bacterial and fungal biogeographic patterns in the phyllosphere. Edaphic factors, such as soil organic and mineral nitrogen content, were more closely related to fungal community assembly than to bacterial community assembly. The differential responses of bacterial and fungal communities to environmental factors could be attributed to the different traits of bacteria and fungi, that is, the higher potential dispersal rate and wider habitat niche of bacteria than fungi. Conclusion Our findings demonstrated that phyllosphere bacterial and fungal communities followed distinct community assembly processes, which is supported by the ‘size plasticity’ hypothesis that smaller organisms (bacteria) are less influenced by environmental conditions and are more homogeneous across space than larger organisms (fungi). These findings provide new insights into the microbial ecology of plant phyllosphere microbiomes.
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ItemThe global distribution and environmental drivers of the soil antibiotic resistome(BMC, 2022-12-12)BACKGROUND: Little is known about the global distribution and environmental drivers of key microbial functional traits such as antibiotic resistance genes (ARGs). Soils are one of Earth's largest reservoirs of ARGs, which are integral for soil microbial competition, and have potential implications for plant and human health. Yet, their diversity and global patterns remain poorly described. Here, we analyzed 285 ARGs in soils from 1012 sites across all continents and created the first global atlas with the distributions of topsoil ARGs. RESULTS: We show that ARGs peaked in high latitude cold and boreal forests. Climatic seasonality and mobile genetic elements, associated with the transmission of antibiotic resistance, were also key drivers of their global distribution. Dominant ARGs were mainly related to multidrug resistance genes and efflux pump machineries. We further pinpointed the global hotspots of the diversity and proportions of soil ARGs. CONCLUSIONS: Together, our work provides the foundation for a better understanding of the ecology and global distribution of the environmental soil antibiotic resistome. Video Abstract.
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ItemOrganic fertilization regimes suppress fungal plant pathogens through modulating the resident bacterial and protistan communities(Wiley, 2022-03-01)Abstract Introduction Fungal plant pathogens are an emerging threat to economically important crop production worldwide and a significant risk to global food security. However, we have limited knowledge of how agricultural management practices drive the emergence and spread of pathogens within crop microbiomes and the underlying ecological mechanisms. Materials and Methods We characterized the profiles of potential fungal plant pathogens, as well as bacterial and protistan communities, in sorghum phyllosphere, root endosphere, and rhizosphere and bulk soils collected from a long‐term experiment with multiple inorganic and organic fertilization regimes. Results We found contrasting patterns of fungal plant pathogens across the four sorghum–soil compartments and that organic fertilization regime significantly reduced the diversity and proportions of fungal plant pathogens in rhizosphere and bulk soils. We further found that the changes in fungal plant pathogens were driven more by resident bacterial and protistan communities than by soil physicochemical parameters. There was a significantly negative relationship between the diversity of fungal plant pathogens in the rhizosphere and bulk soils with sorghum yield and protein contents. Structural equation modeling revealed that long‐term organic fertilization regimes contributed to the suppression of fungal plant pathogens mainly through modulating the resident bacterial and protistan communities. Conclusion These findings advance our understanding of the responses of fungal plant pathogens in crop microbiomes to fertilization regimes, with implications for more targeted strategies to manage the impacts of fungal pathogens on plant health and economic losses.
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ItemManure applications alter the abundance, community structure and assembly process of diazotrophs in an acidic Ultisol(FRONTIERS MEDIA SA, 2022-08-12)The excessive usage of nitrogen (N) fertilizers can accelerate the tendency of global climate change. Biological N fixation by diazotrophs contributes substantially to N input and is a viable solution to sustainable agriculture via reducing inorganic N fertilization. However, how manure application influences the abundance, community structure and assembly process of diazotrophs in soil aggregates is not fully understood. Here, we investigated the effect of manure amendment on diazotrophic communities in soil aggregates of an arable soil. Manure application increased soil aggregation, crop yield and the abundance of nifH genes. The abundance of nifH genes increased with aggregate sizes, indicating that diazotrophs prefer to live in larger aggregates. The abundance of nifH genes in large macroaggregates, rather than in microaggregates and silt and clay, was positively associated with plant biomass and crop yield. Both manure application and aggregate size did not alter the Shannon diversity of diazotrophs but significantly changed the diazotrophic community structure. The variation of diazotrophic community structure explained by manure application was greater than that by aggregate size. Manure application promoted the relative abundance of Firmicutes but reduced that of α-Proteobacteria. Stochastic processes played a dominant role in the assembly of diazotrophs in the control treatment. Low-rate manure (9 Mg ha-1) application, rather than medium-rate (18 Mg ha-1) and high-rate (27 Mg ha-1) manure, significantly increased the relative importance of deterministic processes in diazotrophic community assembly. Taken together, our findings demonstrated that long-term manure application increased nifH gene abundance and altered the community structure and assembly process of diazotrophs in soil aggregates, which advanced our understanding of the ecophysiology and functionality of diazotrophs in acidic Ultisols.