News highlights
June 2025
Honeker wins best for division poster in 2025 Postdoc Poster Symposium at LLNL
Soil SFA postdoctoral scholar Dr. Linnea Honeker was judged best presentation for her division during LLNL’s 2025 Postdoc Poster Symposium with her work titled “Reduced Legacy Moisture Decreases Microbial Community Growth and Efficiency and Alters Soil Organic Carbon in a California Grassland.”
May 2025
Georgiou accepts EGU Early Career Scientist Award
Soil SFA Staff Scientist Dr. Katerina Georgiou received the 2025 Division Outstanding Early Career Scientist Award from the European Geosciences Union (EGU) for “significant contributions to the understanding of the fundamental mechanisms of carbon cycling at the range of scales; from soil particle to field scale, to global predictions.”
April 2025
Pett-Ridge recognized as 2024 AAAS Fellow
The Soil SFA’s lead scientist, Dr. Jennifer Pett-Ridge, was recognized as a fellow of the American Association for the Advancement of Science (AAAS). AAS is the world’s largest general scientific society and fellows are elected for their career’s scientific achievements. See the press release for more information regarding Pett-Ridge, her career, and the AAAS award.
Soil SFA at the GenSci 2025
Members of the Soil SFA (Pett-Ridge, Blazewicz, Trubl, Chuckran, and Estera-Molina) traveled to Washington D.C., to represent the Microbes Persist Soil SFA at the DOE’s BER BSSD Genomic Sciences Annual PI Meeting. During this event, Trubl, Chuckran, and Estera-Molina presented 3 posters summarizing the various projects from the Soil SFA to other DOE BER project awardees and DOE funding managers.
January 2025
Soil SFA Annual Meeting at HREC
The Soil SFA’s in-person annual meeting occurred at the Hopland Research and Extension Center (HREC) in Hopland, CA from January 6–7, 2025. During this meeting, all active researchers on the project shared research updates and goals for 2025, participated in breakout sessions, and went on two field site visits within HREC.
Soil SFA Publication in PNAS
Dr. Peter Chuckran of U.C. Berkeley published his Soil SFA supported paper, “Condon bias, nucleotide selection, and genome size predict in situ bacterial growth rate and transcription in rewetted soil,” through PNAS on January 13, 2025. This paper found that genomic traits such as codon usage, genome size, and nucleotide frequency could be used as predictors of microbial activity.
September 2024
SFA all-hands meeting
The Soil SFA team gathered for their 2024 all-hands meeting in January. The meeting started with a visit to one of their field sites at the Hopland Research and Extension Center (HREC) in Hopland, California. The meeting was later split between the Livermore and Berkeley campuses.
November 2023
Welcome new Soil SFA postdocs: Linnea Honeker and Ikaia Leleiwi
LLNL welcomed two new bioinformatics postdocs to the Soil SFA team: Linnea Honeker and Ikaia (Kai) Leleiwi.
Linnea is joining the Microbes Persist project to apply her expertise in microbiome science and bioinformatics to answer questions such as: What soil microbes are active? How are they driving biological processes, and in particular, carbon cycling and persistence?
Kai will be working with the Microbes Persist team to understand how changes in oxygen availability affect carbon cycling and microbial metabolism in wet tropical soils.
Fungal Necromass study commences in Hopland
Postdoc Katie Beidler (University of Minnesota) is starting a new SFA field experiment focused on the fate of decomposing fungal necromass and links to soil carbon storage. Together with Jennifer Pett-Ridge, Steve Blazewicz, and Yuan Liu, the team identified multiple paired grassland/oak canopy sites at the Hopland Research and Extension Center. In these, they plan to deploy 13C-fungal necromass litter bags.
Welcome new LLNL Postdocs: Aidee Guzman and Yuan Liu
LLNL welcomed two new postdocs who will be collaborating with the Soil SFA team: Aidee Guzman and Yuan Liu.
Aidee is joining the Farming Carbon Strategic Initiative Laboratory Directed Research and Development project to apply her expertise in mycology and agroecology to answer emerging questions related to carbon cycling dynamics in agroecosystems.
Yuan will be joining LLNL’s Center for Advanced Bioenergy and Bioproducts Innovation (CABBI) team in collaboration with the University of Illinois Urbana Champaign. He hopes to apply his expertise in soil biogeochemistry and ecosystem ecology to elucidate plant soil and microbial mechanisms contributing to soil carbon sequestration and stabilization.
November 2020
Ben Bolduc gives KBase webinar about viral KBase apps
Dr. Ben Bolduc of the Sullivan Lab at Ohio State University gave a webinar for DOE’s Systems Biology Knowledgebase (KBase) describing apps for viral analysis that he developed as part of our Microbes Persist–KBase partnership. Watch the KBase webinar recording.
Read more about our viral informatics collaboration on the KBase Soil Microbiome SFA website.
October 2020
“PROMISE” conceptual soil carbon model published in Global Change Ecology
Members of Microbes Persist participated in a unique collaboration to re-conceptualize how we think about, measure, and model soil carbon. Read more about this novel approach, which emphasizes the mechanistic controls on the flow of carbon between ecosystem pools, in LLNL’s news release, “A PROMISE to trace the path of individual carbon atoms.”
[B.G. Waring, B.N. Sulman, S. Reed, A.P. Smith, C. Averill, C.A. Creamer, D.F. Cusack, S.J. Hall, J.D. Jastrow, A. Jilling, K.M. Kemner, M. Kleber, X.‐J.A. Liu, J. Pett‐Ridge, and M. Schulz, From pools to flow: The PROMISE framework for new insights on soil carbon cycling in a changing world, Global Change Biology 26, 6631 (2020), doi: 10.1111/gcb.15365.]
Data resource: “Metagenomes and Metatranscriptomes of Glucose-Amended Agricultural Soil”
Northern Arizona University (NAU) postdoc Pete Chuckran, along with colleagues from NAU and the Joint Genome Institute, published a trove of metagenome and metatranscriptome data describing microbial ecophysiology in response to soil glucose additions.
[P.F. Chuckran, M. Huntemann, A. Clum, B. Foster, B. Foster, S. Roux, K. Palaniappan, N. Varghese, S. Mukherjee, T.B. Reddy, C. Daum, A. Copeland, N.N. Ivanova, N.C. Kyrpides, T. Glavina del Rio, E.A. Eloe-Fadrosh, E.M. Morrissey, E. Schwartz, V. Fofanov, B. Hungate, P. Dijkstra, Metagenomes and metatranscriptomes of a glucose-amended agricultural soil, Microbiology Resource Announcements 9, e00895-20 (2020), doi: 10.1128/MRA.00895-20.]
“Harvesting” soil at HREC
Digging a soil pit during a global pandemic, wildfire season, and 90°F heat is not everyone’s idea of fun, but LLNL postdoc Eric Slessarev, UC Berkeley student Christina Fossum, and Jennifer Pett-Ridge braved it all to collect soils from the “super-dry” season at the Hopland Research and Extension Center (HREC) in Hopland, California.
September 2020
Welcome Kat Georgiou, Lawrence Fellow postdoc
Katerina Georgiou was recently awarded one of the prestigious LLNL Lawrence Fellowships to pursue her postdoctoral research. She will work in coordination with the Microbes Persist SFA on her project, “From Microbes to The Earth System—Upscaling Microbial Community Dynamics to Macro-Scale Soil Carbon Models.”
March 2020
Insights into microbial population dynamics in response to rapid change in soil moisture
Steve Blazewicz (LLNL) and colleagues at the University of California, Berkeley and Northern Arizona University used quantitative stable isotope probing (qSIP) with heavy water (H218O) to quantify the growth and mortality rates of bacteria following early season wet-up of a Mediterranean grassland soil. Their article is published in the ISME Journal.
[S.J. Blazewicz, B.A. Hungate, B.J. Koch, E.E. Nuccio, E. Morrissey, E.L. Brodie, E. Schwartz, J. Pett-Ridge, and Firestone MK, Taxon-specific microbial growth and mortality patterns reveal distinct temporal population responses to rewetting in a California grassland soil, The ISME Journal 14, 1520 (2020), doi: 10.1038/s41396-020-0617-3.]
February 2020
LLNL bids farewell to Craig See
For the past six months, we have had the pleasure of hosting Craig See from Dr. Peter Kennedy’s laboratory at the University of Minnesota via a DOE Office of Science Graduate Student Research fellowship—and we are now sad to see him go. While at LLNL, Craig learned stable isotope probing, scanning electron microscope, and NanoSIMS, and he processed samples from a project focused on tracing carbon and nitrogen from decomposing fungal necromass in ecto-mycorrhizal versus arbuscular mycorrhizal hyphospheres.
January 2020
ISRaD paper provides global dataset of soil 14C
With a large team of international colleagues, scientists Karis McFarlane (LLNL) and Christina Schädel (Northern Arizona University) released a new open-source soil data archive, the International Soil Radiocarbon Database (ISRaD) version 1.0. The database is a compilation of individual study datasets that include carbon and radiocarbon measurements for bulk soil depth profiles, soil fractions, soil gas, and interstitial water.
[C.R. Lawrence, J. Beem-Miller, A.M. Hoyt, G. Monroe, C.A. Sierra, S. Stoner, K. Heckman, J.C. Blankinship, S.E. Crow, G. McNicol, S. Trumbore, P.A. Levine, O. Vindušková, K. Todd-Brown, C. Rasmussen, C.E. Hicks Pries, C. Schädel, K. McFarlane, S. Doetterl, C. Hatté, Y. He, C. Treat, J.W. Harden, M.S. Torn, C. Estop-Aragonés, A.A. Berhe, M. Keiluweit, A.D.R. Kuhnen, E. Marin-Spiotta, A.F. Plante, A. Thompson, Z. Shi, J.P. Schimel, L.J.S. Vaughn, S.F. von Fromm, and R. Wagai, An open source database for the synthesis of soil radiocarbon data: ISRaD version 1.0, Earth System Science Data Discussions 12, 61 (2020), doi: 10.5194/essd-12-61-2020.]
November 2019
Uncovering soil viral predators from rhizosphere metatranscriptomes
Very little is known about RNA viruses in the environment, and even less is known about their diversity and ecology in soil. Evan Starr, a UC Berkeley graduate student working with SFA principal investigators Mary Firestone and Jill Banfield has helped to show that RNA viruses are abundant and diverse in soil, where they prey upon organisms such as insects, nematodes, and fungi, and likely affect the carbon cycle. This cutting-edge study was featured in a recent article in the Economist.
[E.P. Starr, E.E. Nuccio, J. Pett-Ridge, J.F. Banfield, and M.K. Firestone, Metatranscriptomic reconstruction reveals RNA viruses with the potential to shape carbon cycling in soil, Proc. Natl. Acad. Sci. 116, 25900 (2019), doi: 10.1073/pnas.1908291116.]
October 2019
“DRIP-SIP” (Detritusphere Rhizosphere Isotope Persistence-Stable Isotope Probing) study complete
LLNL postdoc Noah Sokol has been working long hours in the greenhouse with Megan Foley (Northern Arizona University) and Alex Greenlon (University of California, Berkeley) to complete a complex 13CO2-labeling study examining how drought affects the microbial ecophysiological traits that modulate soil carbon formation. The samples are all now safely in the -80°C freezer(s).
June 2019
Sullivan Lab develops new viral sequence classifier
Classification of environmental viruses, specifically uncultivated viral genomes, is a key step to organizing the virosphere and isolating viral groups of potential interests. Our SFA partners in the Sullivan Lab at Ohio State University developed a genome-based, automatic phage and archaeal virus classifier, called vConTACT2, and described in Nature Biotechnology.
[H.B. Jang, B. Bolduc, O. Zablocki, J. Kuhn, S. Roux, E. Adriaenssens, J. Brister, A. Kropinski, M. Krupovic, R. Lavigne, D. Turner, and M. Sullivan, Taxonomic assignment of uncultivated prokaryotic virus genomes is enabled by gene-sharing networks, Nature Biotechnology 37, 632 (2019), doi: 10.1038/s41587-019-0100-8.]
May 2019
A first-principles theory to predict moisture sensitivity of soil heterotrophic respiration
Jinyun Tang (Lawrence Berkeley National Laboratory), a Microbes Persist principal investigator, has co-developed a theory to predict microbial substrate affinity in variably saturated soils. The theory uses measured soil physical parameters and microbial parameters to explain the large variability in affinity parameters used in many existing land biogeochemistry models.
[J.-Y. Tang and W.J. Riley, A theory of effective microbial substrate affinity parameters in variably saturated soils and an example application to aerobic soil heterotrophic respiration, JGR Biogeosciences 124, 918 (2019), doi: 10.1029/2018JG004779.]
Research
Overview of the Microbes Persist SFA, illustrating our four primary objectives, which explore how microbial ecophysiology, population dynamics, and mineral-microbe interactions regulate cellular carbon persistence under changing moisture regimes.
Although soils store more carbon than the atmosphere and biosphere combined, little is known about the mechanisms that regulate soil carbon. Plant roots are the initial source of carbon in soil, allocating carbon captured from the atmosphere to the soil system. Our project’s premise is that microbial transformations of this carbon determine whether it is returned back to the atmosphere or stored as SOM. Since soil carbon and associated organic molecules are critical to agriculture, healthy ecosystems, and Earth’s climate, a predictive understanding of soil carbon’s residence time and turnover (i.e. “persistence”) in the soil is essential, especially as Earth systems evolve.
Our projects focus on soil moisture as a master controller of organic matter stabilization processes and soil microbial growth and death in soil. The current paradigm in soil organic matter is that microbial cell materials (necromass) are a primary starting material in the process of carbon stabilization. We presume that microbial ecophysiology is a key factor in controlling soil carbon dynamics as water availability changes because the intensity and timing of precipitation not only significantly affects soil microbial community composition and microbial ecological strategies, but also microbial-controlled decomposition, carbon use efficiency, and soil carbon dioxide efflux.
Through our research, we address three critical needs:
- Learn more about how microorganisms grow and die in soil and how those factors mediate SOM formation
- Predict more accurately how carbon cycling and biosequestration in ecosystems will respond as Earth systems evolve
- Examine potential means of biological sequestration of carbon
Our approaches
Our SFA’s key strength is an interdisciplinary and multi-scale approach. In both our complex “wild” soil studies and our pure culture experiments, we rely on isotope tracing and informatics tools that are unique to our team, allowing us to study individual genomes, their expression, and metabolic products within the soil habitat. These methods include:
- High-throughput stable isotope probing (SIP) metagenomics (HT-SIP), ChipSIP, and qSIP to quantitatively resolve strain-level assimilation of specific biomolecules
- 18O-SIP for taxon-specific growth and death rates
- SIP-viromics and in-house informatics tools for genomic tracking of phage–host linkages
- NanoSIMS-STXM (combined high-resolution secondary ion mass spectrometry and scanning transmission electron microscopy) to trace the molecular fate of specific cell-derived molecules
- FTICR-MS (Fourier-transform ion cyclotron resonance mass spectrometry) for high resolution characterization of soil solution molecular components
- 13C-NMR (nuclear magnetic resonance) to characterize solid and liquid phases of soil organic matter
- Compound specific 14C AMS (accelerator mass spectrometry) to measure the residence time of specific molecular classes of organic matter
- Field 14C measurements used for modelling of mineral-associated SOM stability under varying edaphic conditions
- Trait-based and DEB (dynamic energy budget) models to test the predictive power of microbial ecophysiological traits
Our objectives
To meet this objective, we are applying SIP-metagenomics to measure how changing water regimes shape the activity of individual microbial populations and the expression of ecophysiological traits that affect the fate of microbial and plant carbon.
In Mediterranean-climate grasslands, indigenous microbes must survive extreme desiccation during long hot summers and mineralize carbon minutes after “wet-up,” when fall rains begin. The characteristics that allow these groups to survive under dry conditions and persist through rapid changes in water potential are likely important traits for soil carbon dynamics.
To determine how soil moisture shapes microbial ecophysiological traits, we study the three seasonal moisture periods characteristic of Mediterranean grasslands: the wet “spring” growing season, the “summer” drought, and “fall” wet-up. Our experiments show how soil moisture-driven changes in microbial ecophysiology control the persistence of soil carbon.
To meet this objective, we are identifying and measuring mechanisms of mortality in the soil microbiome—focusing on phage lysis and water stress—and their contribution to carbon turnover and the biochemistry of microbial residues.
Soils represent an enormous reservoir of viruses, yet we know remarkably little about their diversity and activity. Our tools and experience position us to substantially expand this nascent field. In our experiments, we track viromes, phage–host links, and viral population dynamics throughout growth, drought, and wet-up periods. With the discovery and ecological characterization of new virus-encoded auxiliary metabolic genes, we can better understand, and better model, how viruses modulate ecosystem biogeochemical processes.
To meet this objective, we are measuring how the soil microbiome and its products interact with contrasting mineral assemblages to control both short- and long-term soil carbon persistence.
Changes in soil moisture can dramatically impact how the soil microbiome and its biochemical residues interface with the soil matrix. To determine the mechanisms that regulate how microbial carbon persists on soil minerals, we conduct sorption experiments using pure minerals incubated with microbes under a range of conditions. In these microcosm and field studies, we use spectroscopy and mass spectroscopy imaging to better understand the nature of mineral associations with biochemical residues produced by classes of microbial isolates. These experiments are intended to characterize features of SOM and cell surface moieties that may affect persistent SOM–mineral associations.
To meet this objective, we are synthesizing genome-scale ecophysiological trait data, SOM chemistry, and population-specific growth and mortality to build models of microbial functional guilds and SOM turnover. Our long-range goal is to predict the long-aspired connection between soil microbiomes and the fate of soil carbon.
We predict that in grassland ecosystems, shifts in microbiome structure and ecophysiological traits due to moisture regime are critical predictors of soil C turnover and composition. Over time, microbial recycling and reuse of SOM imposes a strong filter and narrows the diversity of molecular classes sorbed to minerals. This microbial filter results in the differential persistence of microbial-derived and plant-derived residues.
To test these hypotheses, synthesize our data, and inform predictive models of ecosystem function, we are using:
- Statistical analyses of microbial ecophysiological traits and carbon composition and turnover
- Mechanistic simulations of the sensitivity of carbon composition and turnover to variations in these ecophysiological traits
- Meta-analysis and modeling of carbon turnover constrained by extensive 14C data
In collaboration with DOE’s Systems Knowledgebase (KBase), we are developing a suite of new tools for automated curation of metagenomes and integrating this capability, along with our existing virus genome tools, into KBase. Our curation tool will massively increase the rate at which genome closure can be achieved—automating steps that are currently used to “hand finish” genomes, extending assembled scaffolds into larger assemblies, and correcting misassembled scaffold regions. Our goal is to develop an automated assembly curation procedure to reconstruct long, accurate sequences that can be binned more confidently than fragmented data.
We are also working to port the “iVirus” suite of applications and data resources and the LLNL-developed PhATE phage functional annotation pipeline into KBase. Together, these tools aim to identify, characterize, and ecologically contextualize viruses in large-scale sequence datasets.
These new open source tools will broadly benefit KBase users and will specifically benefit our SFA by creating a faster workflow for metagenome–genome curation and an integrated suite of KBase-hosted viral sequence analysis tools.
Team
Our multi-institutional team includes experts in soil microbiology, ecophysiology and biogeochemistry, metagenomics and viral ecology, organic matter–mineral chemistry, isotope and compound-specific mass spectrometry, and multiscale modeling.
Expand the sections below to meet more team members.
Aaron Chew
Academic Graduate Appointee
