Food for microorganisms: Position-specific 13 C labeling and 13 C-PLFA analysis reveals preferences for sorbed or necromass C

Apostel, Carolin; Herschbach, Jennifer; Bore, Ezekiel; Spielvogel, Sandra; Kuzyakov, Yakov; Dippold, Michaela A.

doi:10.1016/j.geoderma.2017.09.042

Cited by 18 publications

(14 citation statements)

References 39 publications

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“…5d) and showed a pairing between high MAP sites and, in particular, branched chain methyl fatty acids ("GP10Me") that are typically attributed to actinobacteria 38 . This is consistent with actinobacteria assimilation of necromass identified in German agricultural Luvisols 39 .…”

Section: Resultssupporting

confidence: 90%

Environmental and microbial controls on microbial necromass recycling, an important precursor for soil carbon stabilization

Buckeridge

Mason

McNamara

et al. 2020

Commun Earth Environ

133

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There is an emerging consensus that microbial necromass carbon is the primary constituent of stable soil carbon, yet the controls on the stabilization process are unknown. Prior to stabilization, microbial necromass may be recycled by the microbial community. We propose that the efficiency of this recycling is a critical determinant of soil carbon stabilization rates. Here we explore the controls on necromass recycling efficiency in 27 UK grassland soils using stable isotope tracing and indicator species analysis. We found that recycling efficiency was unaffected by land management. Instead, recycling efficiency increased with microbial growth rate on necromass, and was highest in soils with low historical precipitation. We identified bacterial and fungal indicators of necromass recycling efficiency, which could be used to clarify soil carbon stabilization mechanisms. We conclude that environmental and microbial controls have a strong influence on necromass recycling, and suggest that this, in turn, influences soil carbon stabilization.

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Section: Resultssupporting

confidence: 90%

Environmental and microbial controls on microbial necromass recycling, an important precursor for soil carbon stabilization

Buckeridge

Mason

McNamara

et al. 2020

Commun Earth Environ

133

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“…This is complimentary to the notion that microbial necromass comprise nearly 50% of SOC with proportionally higher microbialderived compounds below the topsoil (e.g., Miltner et al, 2009Miltner et al, , 2012Liang et al, 2011;Rumpel and Kögel-Knabner, 2011;Khan et al, 2016). The low abundance of actinobacteria, described as microbial necromass decomposers (Apostel et al, 2018) might have favored the significant accumulation of the cell wall residues in the RootTower soils. This shows that even if the absolute contribution of rhizodeposited C to deeper soil layers might be low, this C source will become stabilized, thus contributing to C storage over potentially long time scales.…”

Section: Stabilization Of Rhizodeposited Cmentioning

confidence: 64%

Decreased rhizodeposition, but increased microbial carbon stabilization with soil depth down to 3.6 m

Peixoto

Elsgaard

Rasmussen

et al. 2020

Soil Biology and Biochemistry

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Despite the importance of subsoil carbon (C) deposition by deep-rooted crops in mitigating climate change and maintaining soil health, the quantification of root C input and its microbial utilization and stabilization below 1 m depth remains unexplored. We studied C input by three perennial deep-rooted plants (lucerne, kernza, and rosinweed) grown in a unique 4-m deep RootTower facility. 13 C multiple pulse labeling was applied to trace C flows in roots, rhizodeposition, and soil as well as 13 C incorporation into microbial groups by phospholipid fatty acids and the long-term stabilization of microbial residues by amino sugars. The ratio of rhizodeposited 13 C in the PLFA and amino sugar pools was used to compare the relative microbial stability of rhizodeposited C across depths and plant species. Belowground C allocation between roots, rhizodeposits, and living and dead microorganisms indicated depth dependent plant investment. Rhizodeposition as a fraction of the total belowground C input declined from the topsoil (0-25 cm) to the deepest layer (360 cm), i.e., from 35%, 45%, and 36%-8.0%, 2.5%, and 2.7% for lucerne, kernza, and rosinweed, respectively, where lucerne had greater C input than the other species between 340 and 360 cm. The relative microbial stabilization of rhizodeposits in the subsoil across all species showed a dominance of recently assimilated C in microbial necromass, thus indicating a higher microbial stabilization of rhizodeposited C with depth. In conclusion, we traced photosynthates down to 3.6 m soil depth and showed that even relatively small C amounts allocated to deep soil layers will become microbially stabilized. Thus, deep-rooted crops, in particular lucerne are important for stabilization and storage of C over long time scales in deep soil.

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“…Accordingly, a direct incorporation of labelled fatty acids from PLFA into Actinobacteria has been observed (Apostel et al, 2018). The observed higher priming effects after the addition of a single amino acid to soils compared to glucose and inorganic N (Mason-Jones et al, 2018) also support the "microbial resource mining" hypothesis, because amino acids and peptides provided as building blocks stimulate growth and additional mining.…”

Section: Microbial Resource Miningmentioning

confidence: 94%

Microbial Necromass in Soils—Linking Microbes to Soil Processes and Carbon Turnover

Kästner

Miltner

Thiele‐Bruhn

et al. 2021

Front. Environ. Sci.

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The organic matter of living plants is the precursor material of the organic matter stored in terrestrial soil ecosystems. Although a great deal of knowledge exists on the carbon turnover processes of plant material, some of the processes of soil organic matter (SOM) formation, in particular from microbial necromass, are still not fully understood. Recent research showed that a larger part of the original plant matter is converted into microbial biomass, while the remaining part in the soil is modified by extracellular enzymes of microbes. At the end of its life, microbial biomass contributes to the microbial molecular imprint of SOM as necromass with specific properties. Next to appropriate environmental conditions, heterotrophic microorganisms require energy-containing substrates with C, H, O, N, S, P, and many other elements for growth, which are provided by the plant material and the nutrients contained in SOM. As easily degradable substrates are often scarce resources in soil, we can hypothesize that microbes optimize their carbon and energy use. Presumably, microorganisms are able to mobilize biomass building blocks (mono and oligomers of fatty acids, amino acids, amino sugars, nucleotides) with the appropriate stoichiometry from microbial necromass in SOM. This is in contrast to mobilizing only nutrients and consuming energy for new synthesis from primary metabolites of the tricarboxylic acid cycle after complete degradation of the substrates. Microbial necromass is thus an important resource in SOM, and microbial mining of building blocks could be a life strategy contributing to priming effects and providing the resources for new microbial growth cycles. Due to the energy needs of microorganisms, we can conclude that the formation of SOM through microbial biomass depends on energy flux. However, specific details and the variability of microbial growth, carbon use and decay cycles in the soil are not yet fully understood and linked to other fields of soil science. Here, we summarize the current knowledge on microbial energy gain, carbon use, growth, decay, and necromass formation for relevant soil processes, e. g. the microbial carbon pump, C storage, and stabilization. We highlight the factors controlling microbial necromass contribution to SOM and the implications for soil carbon use efficiency (CUE) and we identify research needs for process-based SOM turnover modelling and for understanding the variability of these processes in various soil types under different climates.

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Food for microorganisms: Position-specific 13 C labeling and 13 C-PLFA analysis reveals preferences for sorbed or necromass C

Cited by 18 publications

References 39 publications

Environmental and microbial controls on microbial necromass recycling, an important precursor for soil carbon stabilization

Environmental and microbial controls on microbial necromass recycling, an important precursor for soil carbon stabilization

Decreased rhizodeposition, but increased microbial carbon stabilization with soil depth down to 3.6 m

Microbial Necromass in Soils—Linking Microbes to Soil Processes and Carbon Turnover

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