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A long-term field experiment demonstrates the influence of tillage on the bacterial potential to produce soil structure-stabilizing agents such as exopolysaccharides and lipopolysaccharides


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Cania, Barbara; Vestergaard, Gisle; Krauss, Maike; Fliessbach, Andreas; Schloter, Michael and Schulz, Stefanie (2019) A long-term field experiment demonstrates the influence of tillage on the bacterial potential to produce soil structure-stabilizing agents such as exopolysaccharides and lipopolysaccharides. Environmental Microbiome, 14 (1), pp. 1-14.

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Online at: https://doi.org/10.1186/s40793-019-0341-7


Background: Stable soil aggregates are essential for optimal crop growth and preventing soil erosion. However, tillage is often used in agriculture to loosen the soil, which disrupts the integrity of these aggregates. Soil aggregation can be enhanced by bacteria through their ability to produce exopolysaccharides and lipopolysaccharides. These compounds stabilize soil aggregates by “gluing” soil particles together. However, it has yet to be shown how tillage influences the bacterial potential to produce aggregate-stabilizing agents. Therefore, we sampled conventional and reduced tillage treatments at 0–10 cm, 10–20 cm and 20–50 cm from a long-term field trial in Frick, Switzerland. We compared the stable aggregate fraction of the soil and the bacterial potential to produce exopolysaccharides (EPS) and lipopolysaccharides (LPS) under different tillage regimes by employing a shotgun metagenomic approach. We established a method which combines hidden Markov model searches with blasts against sequences derived from the Kyoto Encyclopedia of Genes and Genomes database to analyze genes specific for the biosynthesis of these compounds.
Results: Our data revealed that the stable aggregate fraction as well as the bacterial potential to produce EPS and LPS were comparable under both tillage regimes. The highest potential to produce these compounds was found in the upper soil layer, which was disturbed by tillage, but had higher content of organic carbon compared to the layer below the tillage horizon. Additionally, key players of EPS and LPS production differed at different sampling depths. Some families with high potential to produce EPS and LPS, such as Chitinophagaceae and Bradyrhizobiaceae, were more abundant in the upper soil layers, while others, e.g. Nitrospiraceae and Planctomycetaceae, preferred the lowest sampled soil depth. Each family had the potential to form a limited number of different aggregate-stabilizing agents.
Conclusions: Our results indicate that conventional tillage and reduced tillage equally promote the bacterial potential to produce EPS and LPS in the tillage horizon. However, as major bacterial groups triggering EPS and LPS formation were not the same, it is likely that gene expression pattern differ in the different treatments due to various pathways of gene induction and transcription in different bacterial species.

EPrint Type:Journal paper
Keywords:Tillage, Soil aggregates, Exopolysaccharides, Lipopolysaccharides, Soil microbiome, Metagenomics, wza, lptF, lptG
Agrovoc keywords:
Englishsoil aggregates -> soil structural unitshttp://aims.fao.org/aos/agrovoc/c_7195
Subjects: Soil > Soil quality
Soil > Soil quality > Soil biology
Environmental aspects > Biodiversity and ecosystem services
Research affiliation: European Union > CORE Organic Plus > FertilCrop
Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil Sciences
Deposited By: Fließbach, Dr. Andreas
ID Code:35214
Deposited On:01 Apr 2019 14:54
Last Modified:01 Apr 2019 14:54
Document Language:English
Refereed:Peer-reviewed and accepted

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