Accumulation of Soil Microbial Necromass Controlled by Microbe–Mineral Interactions

Qian Zhao; Sheryl Bell; Ravi Kukkadapu; Jocelyn Richardson; John Cliff; Mark Bowden; Sarah Leichty; Kirsten S. Hofmockel

doi:10.1021/acs.est.5c01482

Accumulation of Soil Microbial Necromass Controlled by Microbe–Mineral Interactions

Qian Zhao
, Sheryl Bell
, Ravi Kukkadapu
, Jocelyn Richardson
, John Cliff
, Mark Bowden
, Sarah Leichty
, Kirsten S. Hofmockel

Applied Materials Analysis

Research output: Contribution to journal › Article › peer-review

5 Scopus citations

Abstract

Soil organic matter (SOM) is a key reservoir for global carbon (C), supporting soil fertility and influencing greenhouse gas emissions. Microbial residues, composed of dead cells and cellular fragments, are major contributors to SOM formation. Yet, mechanisms by which minerals enhance the accumulation of microbial residues remain poorly understood. Here, we used¹³C-labeled glucose in a year-long incubation to trace microbial residue in sandy and silty soils. Across both soils, approximately 89% of retained microbial¹³C was recovered in the fine (<53 μm) mineral-associated organic matter (MAOM) pool. Within this pool, the light MAOM fraction, enriched in poorly crystalline Fe minerals, held 4.3 times more¹³C than the heavy, phyllosilicate-dominated MAOM fraction, despite accounting for only 17.2% of the total MAOM mass and 12.3% of the total soil mass. Along with¹³C enrichment, the light MAOM fraction showed greater abundance of N-containing groups, e.g., (amides and amino groups), indicative of microbial-derived compounds like proteins and amino sugars. Fe oxides in light MAOM from both soils were spatially dispersed. Microbial residue accumulation was greater in finer-textured silty soil. These findings demonstrate that mineral composition and texture jointly regulate microbial necromass accrual, highlighting light MAOM as a key pool for enhancing soil C storage.

Original language	English
Pages (from-to)	17558-17570
Number of pages	13
Journal	Environmental Science and Technology
Volume	59
Issue number	33
DOIs	https://doi.org/10.1021/acs.est.5c01482
State	Published - Aug 26 2025

Funding

This research was supported by an Early Career Research Program award funded by the U.S. Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research (BER) Genomic Science program under FWP 68292 and FWP 07880, Environmental Molecular Sciences Laboratory (EMSL) Exploratory Research Project 51095, and Stanford Synchrotron Radiation Lightsource (SSRL) user proposal S-XV-ST-5898. A portion of this work was performed in EMSL, at Pacific Northwest National Laboratory (PNNL). PNNL is a multiprogram national laboratory operated by Battelle for the DOE under Contract DE-AC05-76RLO 1830. Use of the SSRL, SLAC National Accelerator Laboratory, is supported by the DOE, Office of Science, Office of Basic Energy Sciences under contract DE-AC02-76SF00515. The SSRL Structural Molecular Biology Program is supported by the DOE-BER and by the National Institutes of Health (NIH), National Institute of General Medical Sciences (NIGMS; P30GM133894). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of the NIGMS or the NIH. J.R. is supported by supplemental funding from DOE-BER to assist and expand biological and environmental relevant research and users at SSRL.

Keywords

C isotope labeling
amorphous iron oxide
bioenergy cropping system
carbon persistence
microbe–mineral interactions
microbial necromass
mineral-associated organic matter (MAOM)
soil organic matter (SOM)

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title = "Accumulation of Soil Microbial Necromass Controlled by Microbe–Mineral Interactions",

abstract = "Soil organic matter (SOM) is a key reservoir for global carbon (C), supporting soil fertility and influencing greenhouse gas emissions. Microbial residues, composed of dead cells and cellular fragments, are major contributors to SOM formation. Yet, mechanisms by which minerals enhance the accumulation of microbial residues remain poorly understood. Here, we used13C-labeled glucose in a year-long incubation to trace microbial residue in sandy and silty soils. Across both soils, approximately 89\% of retained microbial13C was recovered in the fine (<53 μm) mineral-associated organic matter (MAOM) pool. Within this pool, the light MAOM fraction, enriched in poorly crystalline Fe minerals, held 4.3 times more13C than the heavy, phyllosilicate-dominated MAOM fraction, despite accounting for only 17.2\% of the total MAOM mass and 12.3\% of the total soil mass. Along with13C enrichment, the light MAOM fraction showed greater abundance of N-containing groups, e.g., (amides and amino groups), indicative of microbial-derived compounds like proteins and amino sugars. Fe oxides in light MAOM from both soils were spatially dispersed. Microbial residue accumulation was greater in finer-textured silty soil. These findings demonstrate that mineral composition and texture jointly regulate microbial necromass accrual, highlighting light MAOM as a key pool for enhancing soil C storage.",

keywords = "C isotope labeling, amorphous iron oxide, bioenergy cropping system, carbon persistence, microbe–mineral interactions, microbial necromass, mineral-associated organic matter (MAOM), soil organic matter (SOM)",

author = "Qian Zhao and Sheryl Bell and Ravi Kukkadapu and Jocelyn Richardson and John Cliff and Mark Bowden and Sarah Leichty and Hofmockel, \{Kirsten S.\}",

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AU - Zhao, Qian

AU - Bell, Sheryl

AU - Kukkadapu, Ravi

AU - Richardson, Jocelyn

AU - Cliff, John

AU - Bowden, Mark

AU - Leichty, Sarah

AU - Hofmockel, Kirsten S.

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N2 - Soil organic matter (SOM) is a key reservoir for global carbon (C), supporting soil fertility and influencing greenhouse gas emissions. Microbial residues, composed of dead cells and cellular fragments, are major contributors to SOM formation. Yet, mechanisms by which minerals enhance the accumulation of microbial residues remain poorly understood. Here, we used13C-labeled glucose in a year-long incubation to trace microbial residue in sandy and silty soils. Across both soils, approximately 89% of retained microbial13C was recovered in the fine (<53 μm) mineral-associated organic matter (MAOM) pool. Within this pool, the light MAOM fraction, enriched in poorly crystalline Fe minerals, held 4.3 times more13C than the heavy, phyllosilicate-dominated MAOM fraction, despite accounting for only 17.2% of the total MAOM mass and 12.3% of the total soil mass. Along with13C enrichment, the light MAOM fraction showed greater abundance of N-containing groups, e.g., (amides and amino groups), indicative of microbial-derived compounds like proteins and amino sugars. Fe oxides in light MAOM from both soils were spatially dispersed. Microbial residue accumulation was greater in finer-textured silty soil. These findings demonstrate that mineral composition and texture jointly regulate microbial necromass accrual, highlighting light MAOM as a key pool for enhancing soil C storage.

AB - Soil organic matter (SOM) is a key reservoir for global carbon (C), supporting soil fertility and influencing greenhouse gas emissions. Microbial residues, composed of dead cells and cellular fragments, are major contributors to SOM formation. Yet, mechanisms by which minerals enhance the accumulation of microbial residues remain poorly understood. Here, we used13C-labeled glucose in a year-long incubation to trace microbial residue in sandy and silty soils. Across both soils, approximately 89% of retained microbial13C was recovered in the fine (<53 μm) mineral-associated organic matter (MAOM) pool. Within this pool, the light MAOM fraction, enriched in poorly crystalline Fe minerals, held 4.3 times more13C than the heavy, phyllosilicate-dominated MAOM fraction, despite accounting for only 17.2% of the total MAOM mass and 12.3% of the total soil mass. Along with13C enrichment, the light MAOM fraction showed greater abundance of N-containing groups, e.g., (amides and amino groups), indicative of microbial-derived compounds like proteins and amino sugars. Fe oxides in light MAOM from both soils were spatially dispersed. Microbial residue accumulation was greater in finer-textured silty soil. These findings demonstrate that mineral composition and texture jointly regulate microbial necromass accrual, highlighting light MAOM as a key pool for enhancing soil C storage.

KW - C isotope labeling

KW - amorphous iron oxide

KW - bioenergy cropping system

KW - carbon persistence

KW - microbe–mineral interactions

KW - microbial necromass

KW - mineral-associated organic matter (MAOM)

KW - soil organic matter (SOM)

UR - https://www.scopus.com/pages/publications/105014129798

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SN - 0013-936X

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JO - Environmental Science and Technology

JF - Environmental Science and Technology

IS - 33

ER -

Accumulation of Soil Microbial Necromass Controlled by Microbe–Mineral Interactions

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Keywords

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