biology · environment · manufacturing · agriculture · family: making one is easy. making a million is the problem
microbial communities thatrefuse to be engineered
Synthetic microbial communities cannot be rationally designed or controlled
Problem statement
Despite extensive study of microbial systems, we cannot yet rationally design synthetic microbial communities with predictable, novel capabilities. Microbial communities play important roles in ecosystems around the planet and matter for the health of plants and animals alike, and researchers have harnessed their physiological and biochemical diversity for applications including the production of food, feed, fiber, high-value chemicals and therapeutics, wastewater management and bio-remediation. What resists us is the mapping: the functional properties of a community's constituents cannot be fully mapped onto the collective phenotype they deliver. Researchers have turned to synthetic communities (less complex, better-defined than natural systems) to address this knowledge gap, but the field lacks a comprehensive biological knowledge base for rationally engineering these communities for applications in climate resiliency, sustainability, biotechnology, and biomanufacturing.
Why this matters
The potential applications are broad: the two agencies name the biodegradation of recalcitrant or "forever chemicals," the development of biorenewable resources that could mitigate our impact on the environment and climate, and the production of novel biochemical cycles that would let the bioeconomy use resources more circularly, alongside climate resiliency, sustainability, biotechnology and bio-manufacturing. NSF places this work inside its priority areas of building a resilient planet and enhancing the bio-economy, and points to the CHIPS Act of 2022 and the Executive Order on Advancing Biotechnology and Bio-manufacturing Innovation for a Sustainable, Safe and Secure American Bio-economy as the broader context — documents that frame these areas as matters of national security and prosperity. But the knowledge base that would let researchers design such communities rationally is the thing the solicitation is trying to build, not something it can assume.
What’s been tried and why it hasn’t worked
The study of natural microbiomes can be hampered by their inherent complexity and an inability to fully map how the functional properties of their constituents combine to deliver a collective phenotype — many if not most microbes live in heterogeneous communities containing numerous species. Reproducibility presents a unique challenge because biological research of this kind is prone to context-dependent biological variation: investigators must follow or advance best practices in sample collection and preparation, experimental design, data analysis, model generation, and/or the validation of mathematical and computational methods to produce scientifically defensible results. Scalable production is treated as an open question rather than a solved one: NSF asks proposals to describe reproducible co-culturing methods and the potential for scalable production if that is the ultimate goal, and, where scalability applies, asks reviewers whether the proposal addresses it. The Lead Agency letter puts the same thing as a research question — how to design and control increasing complexity in microbial composition, behaviors, and the genetic, metabolic, signaling and physical interactions that occur, and how those properties may change in differently structured spatial environments or as processes are scaled to practical application. Advances in synthetic biology and allied fields now let researchers assemble communities from the bottom up, but the rules that govern their construction, maintenance and evolution — cooperative and competitive interactions, and the emergent properties of these systems — are exactly what the agencies are still asking researchers to establish.
What would unlock progress
Robust frameworks for co-culturing taxonomically different microbial species under well-defined, reproducible conditions. Predictive computational models for how individual microbial functions combine into collective community phenotypes — the microbial equivalent of genotype-to-phenotype prediction. Scalable production systems that maintain community stability and function through industrial-scale perturbations. Methods for defining the functions of individual species within a synthetic community and their relationship to the properties of the community as a whole. Understanding of the formation, maintenance, and functionality principles that govern natural communities, applied to synthetic design.
Entry points for student teams
A student team could design and characterize a minimal synthetic community (3–5 species) for a specific function — e.g., cellulose degradation or plastic film breakdown — measuring how community function changes as species are added or removed, and comparing observed function to predictions from metabolic models of the individual species. Alternatively, a team could build a continuous-flow bioreactor for a defined synthetic community and systematically test how environmental perturbations (pH shifts, temperature changes, dilution rate) affect community stability and function. A third door needs no laboratory at all: a team can do the prediction side on a laptop, taking published genome-scale metabolic models of a handful of candidate species, using open-source flux-balance software to predict which pairs and trios should cross-feed or compete, and writing up the co-culture protocol the prediction implies — composition, justification for a synthetic over a natural community, reproducible co-culturing conditions, the potential for scalable production if that is the ultimate goal, and the social, ethical and bio-safety considerations — against the four things NSF 25-501 says a competitive proposal should include. That write-up is a deliverable on its own, and it is also the design document for either wet-lab door if a sponsoring lab picks it up. Relevant skills: microbiology, metabolic modeling, bioreactor engineering, genomics, data science.
Genes
Structural cousins: stuck the same way, in other fields
Sources
"Building Synthetic Microbial Communities for Biology, Mitigating Climate Change, Sustainability and Biotechnology (Synthetic Communities)," Program Solicitation NSF 25-501, U.S. National Science Foundation, Directorate for Biological Sciences, posted October 4, 2024. (accessed 2026-02-15). Also "UKRI/BBSRC- NSF/BIO Lead Agency Opportunity in Biological Informatics, Systems Understanding of Host-Microbe Interactions, Synthetic Cells and Cellular Systems, and Synthetic Microbial Communities," Dear Colleague Letter NSF 24-112. (accessed 2026-09-30). go to source 1 ↗ go to source 2 ↗
Working notes
Notes made while writing and checking this brief, shown as written. They use working shorthand.
- NSF 25-501 is a dedicated program for synthetic microbial communities, indicating NSF views this as a distinct research area rather than a subset of microbiome research.
- The UKRI/BBSRC-NSF/BIO Lead Agency mechanism funds transatlantic collaborations on this topic, reflecting international recognition of the gap.
- Cross-domain connection: shares structure with `manufacturing-biomanufacturing-scaleup-prediction` (both involve scaling biological processes from lab to production) and `bio-genotype-phenotype-prediction-gap` (community phenotype prediction is a multi-organism extension of genotype-to-phenotype prediction).
- The `failure:lab-to-field-gap` tag applies because the agencies treat behaviour at production scale as unsettled: the Lead Agency letter asks how community properties may change in differently structured spatial environments or as processes are scaled to practical application, and NSF 25-501 has reviewers ask, where it applies, whether a proposal addresses scalability.
- The `temporal:newly-tractable` tag applies because, in the agencies’ own account, advances in synthetic biology and allied fields are what now enable researchers to assemble and engineer synthetic microbial communities from the bottom up, and it is only in recent years that researchers have turned to synthetic communities in this way.
Reconciliation 2026-09-30: Fact repair after reading the whole write-up against both documents it names, then a second reader went over every repair the same day. Both documents were read in full on 2026-09-30: NSF 25-501 from https://www.nsf.gov/funding/opportunities/synthetic-communities-building-synthetic-microbial-communities-biology-mitigating/506088/nsf25-501/solicitation (the page now carries an “Archived funding opportunity” banner, but the solicitation text is intact there) and from NSF’s own PDF of it (https://nsf-gov-resources.nsf.gov/files/nsf25501.pdf), and NSF 24-112 from https://www.nsf.gov/funding/opportunities/dcl-ukribbsrc-nsfbio-lead-agency-opportunity-biological/nsf24-112 (the old nsf.gov/pubs address redirects there; it too is flagged as archived). Apart from the award budget of $8,000,000 to $10,000,000, neither document contains a dollar figure, a market projection, a species count, or the name of a specific chemical, so several of the brief’s most specific sentences had nothing behind them. (1) “The global microbiome market is projected to exceed $1.7 billion by 2027” and “the ~$200 billion global fertilizer market” are in neither document, and neither is the agriculture sentence they sat in (soil microbiomes engineered to reduce fertilizer dependence, enhance drought tolerance or suppress plant pathogens). All of it was removed rather than sourced elsewhere. In its place the section gives the applications the two documents do name — biodegradation of recalcitrant or ‘forever chemicals’, biorenewable resources that could mitigate our impact on the environment and climate, and novel biochemical cycles for more circular use of resources in the bioeconomy — and NSF’s own framing of why it matters: the priority areas of building a resilient planet and enhancing the bio-economy, with the CHIPS Act of 2022 and the Executive Order on Advancing Biotechnology and Bio-manufacturing Innovation for a Sustainable, Safe and Secure American Bio-economy named as the broader context. (2) “PFAS” was the brief’s own gloss on the Lead Agency letter’s phrase ‘forever chemicals’; the letter does not name PFAS, so the gloss was dropped and the letter’s phrase kept. Those two quoted words are in the letter. (3) “Communities of 100+ species” is in neither document. NSF 25-501 says only that many if not most microbes live in heterogenous communities containing numerous species; the sentence now says that. (4) “Bottom-up assembly from individual isolates works for 2–5 species but collapses for communities of >10 species, where emergent interactions (cross-feeding, competition, phage dynamics) dominate”: no such thresholds appear anywhere, and cross-feeding and phage dynamics are not mentioned. The passage now reports what the Lead Agency letter does say — that advances in synthetic biology and allied fields now let researchers assemble communities from the bottom up, and that the rules governing their construction, maintenance and evolution, including cooperative and competitive interactions and emergent properties, are what the agencies are asking researchers to establish. (5) The scale-up sentence blamed unpredictable shifts with “reactor volume, feeding regime, and environmental fluctuations.” No cause of that kind is given. Both documents treat scale as an open question: NSF 25-501 asks a competitive proposal for reproducible co-culturing methods and the potential for scalable production if that is the ultimate goal, and asks reviewers, where it applies, whether the proposal addresses scalability; the Lead Agency letter asks how community properties may change within differently spatially structured environments or as processes are scaled to enable practical application. The sentence now says that and no more. (6) “Investigators struggle to follow best practices” reversed the source: NSF 25-501 says investigators must follow or advance best practices in sample collection and preparation, experimental design, data analysis, model generation, and/or validation of mathematical and computational methods to produce scientifically defensible results. The sentence now follows the solicitation, including the two items the brief had dropped and the solicitation’s “and/or”. (7) “Natural microbiome study is hampered” was stated more strongly than the Lead Agency letter, which says the study of natural microbiomes “can be hampered”; softened to match. (8) The opening list of what natural microbiomes do — gut, soil, ocean and industrial communities degrading pollutants, cycling nutrients, producing metabolites and resisting pathogens — is in neither document, which instead name production of food, feed, fiber, high value chemicals and therapeutics, wastewater management and bio-remediation. The list was replaced with theirs, and “Despite decades of microbiome research” became “despite extensive study of microbial systems,” which is what NSF 25-501 claims. (9) “High-throughput screening methods for community function” is in neither document; that line now gives the solicitation’s third theme, defining the functions of individual species within a synthetic community and their relationship to the properties of the community as a whole. (10) Source line: the solicitation’s title was given as “Synthetic Communities: Building Synthetic Microbial Communities,” and the Lead Agency letter’s as “UKRI/BBSRC-NSF/BIO Lead Agency.” Neither is the document’s title. Both titles, the document types and the solicitation’s posting date are now copied from the pages themselves, and the Lead Agency letter now carries the address it was read at. (11) In the notes above, the lab-to-field bullet asserted that emergent interactions appear only at scale, and the newly-tractable bullet credited CRISPR, metabolic engineering, computational modeling and high-throughput sequencing by name. None of that is in either document; both bullets now give the agencies’ own wording. (12) Entry points: the two existing doors both need a wet lab, so a third was added that needs none — predicting cross-feeding and competition from published genome-scale metabolic models with open-source flux-balance software, and writing the resulting co-culture protocol against the four things NSF 25-501 says a competitive proposal should include. Confirmed in the sources and left as written: that researchers turned to synthetic communities because they are less complex and better defined than natural systems; the definition of a synthetic microbial community as a host-associated or free-living consortium of taxonomically different microbial species that can be studied and co-cultured under well-defined and reproducible conditions; the aim of building a comprehensive biological knowledge base for rational design with applications in climate resiliency, sustainability, biotechnology and bio-manufacturing; the inability to fully map how constituents’ functional properties combine into a collective phenotype; that NSF 25-501 is a solicitation dedicated to this topic; and that the Lead Agency mechanism is for transatlantic collaboration. The second reader re-fetched both documents independently, including the solicitation PDF, could not find any of the removed figures, thresholds or named technologies in either one, and so kept all twelve repairs; four sentences that had still gone past the sources were tightened. The two places that had made scalability something reviewers must judge now say they are asked to judge it where it applies; the best-practices list now carries the solicitation’s “and/or” and its “scientifically defensible results”; and the new entry point’s scalable-production item now carries the solicitation’s condition “if scalable production is the ultimate goal.” Nothing was left unchecked: both documents were read in full, and every claim in the write-up was traceable to them or found to be absent from them. No title changed. Genome tags untouched.