Importance of microbial communities at the root-soil interface for extracellular polymeric substances and soil aggregation in semiarid grasslands

Bettermann, Antje; Zethof, Jeroen; Babin, Doreen; Cammeraat, Erik; Solé-Benet, Albert; Lázaro, Roberto; Luna, Lourdes; Nesme, Joseph; Sørensen, Søren J.; Kalbitz, Karsten; Smalla, Kornelia; Vogel, Cordula

doi:10.1016/j.soilbio.2021.108301

Cited by 25 publications

(9 citation statements)

References 89 publications

(101 reference statements)

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“…This simple concept of protection was first proposed by Luo et al (2017) to model aggregate protection in a parsimonious way. In alignment with recent studies which showed that the presence of microbially-produced binding agents stabilizes aggregates (Bettermann et al, 2021;Crouzet et al, 2019), the rate of aggregate formation in SAMM is a function of microbial growth. Furthermore, SAMM allows for physicochemical aggregate formation at a constant rate (currently defined as daily microbial growth equivalent).…”

Section: A15 Mineral Associated Organic Carbon and Nitrogen Pools -Ma...supporting

confidence: 83%

SAMM version 1.0: A numerical model for microbial mediated soil aggregate formation

Laub¹,

Blagodatsky²,

Broek³

et al. 2023

Preprint

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Abstract. In light of the large role that soil organic matter (SOM) plays in maintaining healthy and productive agricultural soils, it is crucial to understand the processes of SOM protection including the role of soil aggregate protection. Yet, few numerical process models include aggregate formation and even fewer represent the important connection between microbial growth and aggregate formation. Here, we propose a model of Soil Aggregation through Microbial Mediation (SAMM), which consist of measurable pools and 5 couples soil aggregate formation to microbial growth. The model was evaluated against data from a long term bare-fallow experiment in a tropical sandy soil, subject to plant litter additions of different compositions. The SAMM model effectively represented the microbial growth response after litter addition and the following formation and later disruption of aggregates. Model parameter correlation was low (all r < 0.5; r > 0.4 for only 4 of 22 parameters) showing that SAMM is well parameterized. Differences between treatments resulting from different litter compositions could be captured by SAMM for soil organic carbon (Nash-Sutcliffe modelling efficiency (EF) of 0.68), microbial nitrogen (EF of 0.24) and litter carbon (EF of 0.80). Aggregate-related fractions, i.e., carbon inside aggregates (EF of 0.60) and also carbon in the free silt and clay fraction (EF of 0.24) were simulated very well to satisfactory. Analysis of model parameters led to further noteworthy insights. For example, model results suggested that up to 50 % of carbon in the soil is stabilized through aggregate protection, even in a sandy soil, and that both microbial activity and physical aggregate formation coexist. When aggregate formation was deactivated, the model failed to stabilize soil organic carbon (EF dropped to -3.68) and microbial nitrogen was represented less well (EF of 0.13). By re-calibrating the model version with deactivated aggregates, it was possible to partly correct for removing the aggregate formation, i.e., by reducing the decomposition rate of mineral attached carbon by about 85 % (EF of 0.68, 0.75 and 0.18 for SOC, litter carbon and microbial nitrogen, respectively). Yet, the overall slightly better evaluation statistics (e.g., Akaike information critereon of 5351 vs 5554) show the potential importance of representing aggregate dynamics within SOM models. Our results indicate that current models without aggregate formation partly compensate the missing protection effect by lowering turnover rates of other pools and thus may still be suitable options where data on aggregate associated carbon is not available.

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Section: A15 Mineral Associated Organic Carbon and Nitrogen Pools -Ma...supporting

confidence: 83%

SAMM version 1.0: A numerical model for microbial mediated soil aggregate formation

Laub¹,

Blagodatsky²,

Broek³

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…Despite no observed alteration in microbial diversity, there was a notable shift towards the prevalence of Clostridium-related bacteria, known for their role in regulating arsenic release. This change may be attributed to certain macromolecules in REs, such as mucus and polysaccharides, contributing to the formation of soil aggregates and maintaining the stability of microbial communities [ 62 ]. Moreover, REs have an attractive effect on beneficial bacteria or can provide them with a source of nutrition, making the soil more conducive to the growth of beneficial bacteria, and inducing the alfalfa rhizosphere to recruit more beneficial bacteria to resist the damage of salt stress.…”

Section: Discussionmentioning

confidence: 99%

The Multiple Promoting Effects of Suaeda glauca Root Exudates on the Growth of Alfalfa under NaCl Stress

Dong,

Hua,

Gao

et al. 2024

Plants

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Under abiotic stress, plant root exudates can improve plant growth performance. However, studies on the effect of root exudates on the stress resistance of another plant are insufficient. In this study, root exudates (REs) were extracted from Suaeda glauca to explore their effect on alfalfa seedlings under salt stress. The results showed that the plant height and fresh weight of alfalfa significantly increased by 47.72% and 53.39% after 7 days of RE treatment at a 0.4% NaCl concentration. Under 1.2% salt stress, REs reduced the Malondialdehyde content in alfalfa by 30.14% and increased the activity of its antioxidant enzymes (peroxidase and catalase) and the content of its osmotic regulators (soluble sugar and proline) by 60.68%, 52%, 45.67%, and 38.67%, respectively. Soil enzyme activity and the abundance of soil-beneficial bacteria were increased by REs. Spearman analysis showed that urease and neutral phosphatase were related to the richness of beneficial bacteria. Redundancy analysis confirmed that urease affected the composition of the soil bacterial community. The partial least squares structural equation model (PLS-SEM) revealed that REs had a direct positive effect on alfalfa growth under salt stress by regulating the plant’s injury and antioxidant systems, and the soil bacterial community had an indirect positive effect on alfalfa growth through soil enzyme activity.

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“…As shown in Table 2, in non-rhizosphere soil of both lawn plants, the Chao1 index, Shannon index, and Simpson index increased overall under each bacterial treatment, indicating an improvement in the metabolic diversity of the treated samples. This might be attributed to the availability of soil nutrients and other soil environmental conditions, including higher nutrient content and enzyme activity in the soil [39]. In rhizosphere soil, under bacterial treatment for both lawn plants, there was no significant change in the Simpson index, but the Chao1 index and Shannon index decreased compared to the control treatment, indicating that the application of Bacillus cereus might reduce the richness of bacterial communities in rhizosphere soil.…”

Section: The Effect Of Bacillus Cereus Application Rate On the Microb...mentioning

confidence: 91%

Microbiological Mechanisms of Collaborative Remediation of Cadmium-Contaminated Soil with Bacillus cereus and Lawn Plants

Zhou,

Yang,

Chen

et al. 2024

Plants

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Severe cadmium contamination poses a serious threat to food security and human health. Plant–microbial combined remediation represents a potential technique for reducing heavy metals in soil. The main objective of this study is to explore the remediation mechanism of cadmium-contaminated soil using a combined approach of lawn plants and microbes. The target bacterium Bacillus cereus was selected from cadmium-contaminated soil in mining areas, and two lawn plants (Festuca arundinacea A‘rid III’ and Poa pratensis M‘idnight II’) were chosen as the target plants. We investigated the remediation effect of different concentrations of bacterial solution on cadmium-contaminated soil using two lawn plants through pot experiments, as well as the impact on the soil microbial community structure. The results demonstrate that Bacillus cereus promotes plant growth, and the combined action of lawn plants and Bacillus cereus improves soil quality, enhancing the bioavailability of cadmium in the soil. At a bacterial suspension concentration of 105 CFU/mL, the optimal remediation treatment was observed. The removal efficiency of cadmium in the soil under Festuca arundinacea and Poa pratensis treatments reached 33.69% and 33.33%, respectively. Additionally, the content of bioavailable cadmium in the rhizosphere soil increased by up to 13.43% and 26.54%, respectively. Bacillus cereus increased the bacterial diversity in the non-rhizosphere soil of both lawn plants but reduced it in the rhizosphere soil. Additionally, the relative abundance of Actinobacteriota and Firmicutes, which have potential for heavy metal remediation, increased after the application of the bacterial solution. This study demonstrates that Bacillus cereus can enhance the potential of lawn plants to remediate cadmium-contaminated soil and reshape the microbial communities in both rhizosphere and non-rhizosphere soils.

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Importance of microbial communities at the root-soil interface for extracellular polymeric substances and soil aggregation in semiarid grasslands

Cited by 25 publications

References 89 publications

SAMM version 1.0: A numerical model for microbial mediated soil aggregate formation

SAMM version 1.0: A numerical model for microbial mediated soil aggregate formation

The Multiple Promoting Effects of Suaeda glauca Root Exudates on the Growth of Alfalfa under NaCl Stress

Microbiological Mechanisms of Collaborative Remediation of Cadmium-Contaminated Soil with Bacillus cereus and Lawn Plants

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