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Drivers of the composition of active rhizosphere bacterial communities in temperate grasslands.

ABSTRACT: The active bacterial rhizobiomes and root exudate profiles of phytometers of six plant species growing in central European temperate grassland communities were investigated in three regions located up to 700?km apart, across diverse edaphic conditions and along a strong land use gradient. The recruitment process from bulk soil communities was identified as the major direct driver of the composition of active rhizosphere bacterial communities. Unexpectedly, the effect of soil properties, particularly soil texture, water content, and soil type, strongly dominated over plant properties and the composition of polar root exudates of the primary metabolism. While plant species-specific selection of bacteria was minor, the RNA-based composition of active rhizosphere bacteria substantially differed between rhizosphere and bulk soil. Although other variables could additionally be responsible for the consistent enrichment of particular bacteria in the rhizosphere, distinct bacterial OTUs were linked to the presence of specific polar root exudates independent of individual plant species. Our study also identified numerous previously unknown taxa that are correlated with rhizosphere dynamics and hence represent suitable targets for future manipulations of the plant rhizobiome.

SUBMITTER: Vieira S

PROVIDER: S-EPMC6976627 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Drivers of the composition of active rhizosphere bacterial communities in temperate grasslands.

Vieira Selma S Sikorski Johannes J Dietz Sophie S Herz Katharina K Schrumpf Marion M Bruelheide Helge H Scheel Dierk D Friedrich Michael W MW Overmann Jörg J

The ISME journal 20191028 2

The active bacterial rhizobiomes and root exudate profiles of phytometers of six plant species growing in central European temperate grassland communities were investigated in three regions located up to 700 km apart, across diverse edaphic conditions and along a strong land use gradient. The recruitment process from bulk soil communities was identified as the major direct driver of the composition of active rhizosphere bacterial communities. Unexpectedly, the effect of soil properties, particul ...[more]

PMID: 31659233

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Project description:BackgroundTree-based intercropping (agroforestry) has been advocated to reduce adverse environmental impacts of conventional arable cropping. Modern agroforestry systems in the temperate zone are alley-cropping systems that combine rows of fast-growing trees with rows of arable crops. Soil microbial communities in these systems have been investigated intensively; however, molecular studies with high taxonomical resolution are scarce.MethodsHere, we assessed the effect of temperate agroforestry on the abundance, diversity and composition of soil bacterial communities at three paired poplar-based alley cropping and conventional monoculture cropland systems using real-time PCR and Illumina sequencing of bacterial 16S rRNA genes. Two of the three systems grew summer barley (Hordeum vulgare); one system grew maize (Zea mays) in the sampling year. To capture the spatial heterogeneity induced by the tree rows, soil samples in the agroforestry systems were collected along transects spanning from the centre of the tree rows to the centre of the agroforestry crop rows.ResultsTree rows of temperate agroforestry systems increased the abundance of soil bacteria while their alpha diversity remained largely unaffected. The composition of the bacterial communities in tree rows differed from those in arable land (crop rows of the agroforestry systems and conventional monoculture croplands). Several bacterial groups in soil showed strong association with either tree rows or arable land, revealing that the introduction of trees into arable land through agroforestry is accompanied by the introduction of a tree row-associated microbiome.ConclusionThe presence of tree row-associated bacteria in agroforestry increases the overall microbial diversity of the system. We speculate that the increase in biodiversity is accompanied by functional diversification. Differences in plant-derived nutrients (root exudates and tree litter) and management practices (fertilization and tillage) likely account for the differences between bacterial communities of tree rows and arable land in agroforestry systems.

Project description:BackgroundWhile the rootstock genotype (belowground part of a plant) can impact rhizosphere microbial communities, few studies have examined the relationships between rootstock genotype-based recruitment of active rhizosphere bacterial communities and the availability of root nutrients for plant uptake. Rootstocks are developed to provide resistance to disease or tolerance of abiotic stresses, and compost application is a common practice to also control biotic and abiotic stresses in crops. In this field study, we examined: (i) the effect of four citrus rootstocks and/or compost application on the abundance, diversity, composition, and predicted functionality of active rhizosphere bacterial communities, and (ii) the relationships between active rhizosphere bacterial communities and root nutrient concentrations, with identification of bacterial taxa significantly correlated with changes in root nutrients in the rhizosphere.ResultsThe rootstock genotype determined differences in the diversity of active rhizosphere bacterial communities and also impacted how compost altered the abundance, diversity, composition, and predicted functions of these active communities. Variations in the active bacterial rhizobiome were strongly linked to root nutrient cycling, and these interactions were root-nutrient- and rootstock-specific. Direct positive relationships between enriched taxa in treated soils and specific root nutrients were detected, and potentially important taxa for root nutrient uptake were identified. Significant differences in specific predicted functions were related to soil nutrient cycling (carbon, nitrogen, and tryptophan metabolisms) in the active bacterial rhizobiome among rootstocks, particularly in soils treated with compost.ConclusionsThis study illustrates that interactions between citrus rootstocks and compost can influence active rhizosphere bacterial communities, which impact root nutrient concentrations. In particular, the response of the rhizobiome bacterial abundance, diversity, and community composition to compost was determined by the rootstock. Specific bacterial taxa therefore appear to be driving changes in root nutrient concentrations in the active rhizobiome of different citrus rootstocks. Several potential functions of active bacterial rhizobiomes recruited by different citrus rootstocks did not appear to be redundant but rather rootstock-specific. Together, these findings have important agronomic implications as they indicate the potential for agricultural production systems to maximize benefits from rhizobiomes through the choice of selected rootstocks and the application of compost. Video Abstract.

Project description:Different sugarcane cultivars are grown to produce renewable energy and sugar in China. However, we have a limited awareness of the interactive influence of varying sugarcane cultivars on rhizosphere bacterial structure and diversity. Assessing cultivar choice impact on soil bacterial communities is vital since bacterial taxa are frequently impacted by planting performance. Employing high-throughput Illumina sequencing, we examined bacterial communities' assemblage in the rhizosphere of six Chinese sugarcane cultivars (Regan14-62, Guitang 08-120, Haizhe 22, Guitang 08-1180, Taitang 22 and Liucheng 05-136). Our results indicated that different sugarcane cultivars have no significant influence on the Shannon index; however, their impact on richness was substantial. There was a difference in the bacterial community structure that is also associated with a change in the community composition, as determined by the DESeq2 results, suggesting that "Haizhe 22 (HZ22)" had a completely different beta diversity as compared to other five cultivars by enriching abundance of Firmicutes, Proteobacteria, Gemmatimonadetes, Saccharibacteria and Bacteroidetes and reducing the quantity of Actinobacteria, Chloroflexi, Acidobacteria, and Planctomycetes, respectively. The HZ22 rhizosphere significantly enriched six genera (e.g., Devosia, Mizugakiibacter, Mycobacterium, Nakamurella, Rhizomicrobium, and Virgibacillus) relative to other varieties, suggesting an important role in plant disease tolerance and growth development, including soil nutrient cycling and bioremediation. Analysis of similarity (ANOSIM) and correlation analysis revealed that cultivars, soil organic matter, pH and soil moisture were central factors influencing bacterial composition. These findings may help in selection of plant cultivars capable of supporting highly abundant specific beneficial microbial groups, improving plant disease resistance, growth stimulation, and soil bioremediation capabilities, further leading to improvements in breeding strategies.Supplementary informationThe online version contains supplementary material available at 10.1007/s13205-021-03091-1.

Project description:UnlabelledIt is well known that rhizosphere microbiomes differ from those of surrounding soil, and yet we know little about how these root-associated microbial communities change through the growing season and between seasons. We analyzed the response of soil bacteria to roots of the common annual grass Avena fatua over two growing seasons using high-throughput sequencing of 16S rRNA genes. Over the two periods of growth, the rhizosphere bacterial communities followed consistent successional patterns as plants grew, although the starting communities were distinct. Succession in the rhizosphere was characterized by a significant decrease in both taxonomic and phylogenetic diversity relative to background soil communities, driven by reductions in both richness and evenness of the bacterial communities. Plant roots selectively stimulated the relative abundance of Alphaproteobacteria, Betaproteobacteria, and Bacteroidetes but reduced the abundance of Acidobacteria, Actinobacteria, and Firmicutes. Taxa that increased in relative abundance in the rhizosphere soil displayed phylogenetic clustering, suggesting some conservation and an evolutionary basis for the response of complex soil bacterial communities to the presence of plant roots. The reproducibility of rhizosphere succession and the apparent phylogenetic conservation of rhizosphere competence traits suggest adaptation of the indigenous bacterial community to this common grass over the many decades of its presence.ImportanceWe document the successional patterns of rhizosphere bacterial communities associated with a "wild" annual grass, Avena fatua, which is commonly a dominant plant in Mediterranean-type annual grasslands around the world; the plant was grown in its grassland soil. Most studies documenting rhizosphere microbiomes address "domesticated" plants growing in soils to which they are introduced. Rhizosphere bacterial communities exhibited a pattern of temporal succession that was consistent and repeatable over two growing seasons. There are few studies assessing the reproducibility over multiple seasons. Through the growing season, the rhizosphere community became progressively less diverse, likely reflecting root homogenization of soil microniches. Phylogenetic clustering of the rhizosphere dynamic taxa suggests evolutionary adaptation to Avena roots. The reproducibility of rhizosphere succession and the apparent phylogenetic conservation of rhizosphere competence traits suggest adaptation of the indigenous bacterial community to this common grass over the many decades of its presence.

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Drivers of the composition of active rhizosphere bacterial communities in temperate grasslands.

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Drivers of the composition of active rhizosphere bacterial communities in temperate grasslands.

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