The review, authored by Mohammad Nazrul Islam Bhuiyan and Maliha Momtaj, introduces what the authors call post-microbial therapeutics. The term does not describe a new drug class, and the authors are careful about that. Instead, it proposes an operational framework that links a therapeutic intervention to a defined microbial function, then to a measurable biochemical consequence, and finally to a validated host outcome. The sequence is explicit: clinical abnormality, candidate microbial function, candidate microbial module, experimental validation, intervention, perturbation, functional measurement, host-response validation, and clinical outcome. Anything less, the authors contend, is association rather than mechanism.

At the heart of the framework sits the concept of the microbial module: a functionally bounded unit of microorganisms that demonstrably contributes to a specified biological process and produces a measurable output. The authors draw a sharp line between computationally inferred candidate modules, identified through co-abundance, network connectivity, or predicted metabolic complementarity, and experimentally validated modules, which require perturbation, reconstruction, add-back experiments, isotope tracing, pathway-specific flux analysis, or metabolite rescue. Co-occurrence, they stress, is hypothesis-generating at best. A cluster of taxa that rise and fall together is not a therapeutic target until someone shows that its members actually perform the function in question and that disrupting them changes the output reproducibly.

Bacteriophages serve as the model perturbation throughout the review, and for good reason. Phage therapy predates the antibiotic era, faded in Western medicine after penicillin, and has roared back into prominence as the antimicrobial resistance crisis deepens. Contemporary phage therapy bears little resemblance to its early empirical use. Genome sequencing, receptor characterization, quantitative pharmacology, synthetic biology, and improved manufacturing now allow systematic assessment of phage identity, host range, safety, and suitability. Clinical studies and compassionate-use experience have reported encouraging safety and case-specific benefit against multidrug-resistant organisms, particularly in difficult-to-treat infections, although the evidence remains heterogeneous across species, patient populations, preparations, and endpoints.

The review is candid about why phage therapy remains incompletely standardized. Phage specificity, often celebrated as an ecological advantage, does not equal ecological predictability. Host range depends on receptor availability, bacterial physiological state, environmental conditions, and phage adaptation, and can vary dramatically among strains of the same species. Bacterial antiviral defenses, including CRISPR-Cas systems, restriction-modification mechanisms, receptor masking, and abortive infection, can block productive infection entirely. Phage pharmacology is unlike any conventional drug: therapeutic phages replicate in the presence of susceptible bacteria, making exposure and pharmacodynamic effect dynamically interdependent, while immune clearance, tissue barriers, and bacterial density complicate dosing. The authors propose the concept of an ecological dose, the magnitude and duration of perturbation needed to shift a defined microbial function, but they frame it strictly as a research hypothesis, not a validated clinical metric.

The distinction between phage modalities receives particular attention. Whole virulent phages are replicating biological agents whose activity depends on finding and lysing susceptible hosts. Lysins are nonreplicating enzymes that cleave peptidoglycan. Depolymerases degrade capsular or extracellular polysaccharides, potentially opening biofilm matrices. Engineered phages, including CRISPR-based programmable systems, add genomic and payload variables. These differences cascade into distinct pharmacology, manufacturing requirements, safety profiles, and regulatory pathways, and the authors argue that evidence for one modality cannot be generalized to another. Temperate phages, which can establish lysogeny and alter bacterial phenotype, fitness, and gene exchange, require especially cautious genomic screening for lysogeny-associated genes, virulence determinants, and resistance elements.

Across disease contexts, the review maps a graded evidence landscape. The strongest case remains targeted control of resistant pathogens. In biofilm-associated infections such as chronic osteomyelitis, diabetic wounds, and device-related disease, phage-based interventions may act at three levels: structural disruption, bacterial population control, and restoration of local function, but a reduction in biofilm biomass alone does not establish ecosystem restoration. In oncology and immunocompromised patients, where chemotherapy and antimicrobials can devastate colonization resistance, phages offer a potentially selective alternative, though altered immunity, mucosal injury, and neutropenia introduce additional uncertainty. In gastrointestinal and cardiometabolic disease, the most provocative findings emerge: selective phage targeting of high-alcohol-producing Klebsiella pneumoniae has been associated with improvement in nonalcoholic fatty liver disease-related phenotypes, and phage-antibiotic combinations have shown metabolically reorganized killing of multidrug-resistant K. pneumoniae. Yet the authors repeatedly caution that such associations do not prove that a defined module or metabolite mediates the clinical benefit.

Metabolites occupy the mechanistic middle ground of the framework. Short-chain fatty acids such as butyrate, tryptophan-derived indoles that activate the aryl hydrocarbon receptor, secondary bile acids, polyamines, and related compounds influence epithelial integrity, immune regulation, and systemic metabolism. Phage intervention can alter these pools through metabolic reprogramming before lysis, changed substrate competition and cross-feeding, or release of intracellular nutrients. The interactions run both ways: bacterial metabolic state and receptor expression shape phage susceptibility, while phage activity reshapes the chemical environment. The authors insist, however, that metabolites be treated as measurable functional intermediates requiring causal validation, not as assumed mediators of benefit, because diet, host metabolism, and microbial redundancy confound nearly every measurement.

The translational and governance implications are substantial. The review calls for product-specific regulation that distinguishes whole phages, engineered phages, lysins, depolymerases, and combination products, each with its own requirements for identity, potency, genomic safety, stability, and post-treatment surveillance. It urges integration of biofilm-aware susceptibility testing, bacterial antiviral-defense profiling, resistance surveillance, and standardized pharmacokinetics and pharmacodynamics into clinical workflows. Ethically, the authors warn that personalized phage matching, sequencing, and metabolomics could concentrate advanced therapy in specialized centers, widening health disparities unless standardized libraries, scalable manufacturing, and simplified workflows accompany the science. Compassionate-use successes, they note, should never be mistaken for proof of efficacy.

The review closes with a research agenda that reads as a checklist for the coming decade: causal validation linking defined phage perturbation to microbial function, metabolite change, and host outcome; systematic defense profiling; modality-specific comparisons; validated functional biomarkers; ecological pharmacology; and long-term monitoring of nontarget microbial functions. Computational tools, including machine learning and eventual digital-twin models, may support host-range prediction and module identification, but the authors insist they remain investigational and cannot replace phenotypic testing. The verdict is measured but ambitious: post-microbial therapeutics will earn their place in medicine not through the novelty of their terminology, but by whether they genuinely improve the prediction, testing, and reproducibility of microbiome-directed interventions, moving the field from describing ecosystems to engineering them with causal precision.

Subject of Research: Phage-based post-microbial therapeutics linking microbial modules, metabolites, and host outcomes

Article Title: Post‐Microbial Therapeutics for the Next Generation of Medicine

Article References: Bhuiyan, M. N. I., & Momtaj, M. (2026). Post‐Microbial Therapeutics for the Next Generation of Medicine. MicrobiologyOpen, 15(5), Article e70427. https://doi.org/10.1002/mbo3.70427

Image Credits: AI Generated

DOI: 10.1002/mbo3.70427

Keywords: bacteriophage therapy, antimicrobial resistance, microbiome, microbial metabolites, phage engineering, biofilms, microbial modules, pharmacokinetics, synthetic biology, CRISPR, ecological dose, clinical translation

Anaerobic microbes, by nature, inhabit niches where oxygen is absent or present only in trace amounts. Many of these organisms cannot tolerate oxygen exposure, which has led to substantial challenges in studying their physiology, ecology, and interactions within microbial consortia. Over the last two decades, molecular tools like next-generation sequencing (NGS) have become indispensable for profiling these communities. High-throughput sequencing enables researchers to identify microbial taxa and infer functional potential, even when cultivation is impossible. Yet, this genomic information alone is insufficient to fully unravel the complexities of microbial function, metabolic pathways, and interspecies relationships that define microbial ecosystems.

Cultivation of anaerobic microbes, therefore, remains the cornerstone for comprehensive microbiome research. Isolating strains in pure culture allows scientists to delve into the biochemical and genetic underpinnings that govern microbial behavior. These isolates serve as model organisms to experimentally validate findings generated through ‘omics’ data, making possible the discovery of novel enzymes, metabolic pathways, and mechanisms of microbe–microbe and microbe–host interactions. Furthermore, cultured anaerobic microbes are invaluable for translational applications in biotechnology and medicine, including the development of probiotics, bioremediation strategies, and the harnessing of microbes for sustainable bioenergy production.

The past decades have seen incremental advances in anaerobic cultivation methods, ranging from the use of custom-built anaerobic chambers and sophisticated media formulations to the application of co-culture techniques. Despite these innovations, many anaerobic microbes remain uncultivated, creating a formidable “microbial dark matter” that conceals vast biodiversity and unexplored functions. Pioneering new approaches in biotechnology are now being leveraged to overcome these limitations. These include automated cultivation platforms that can precisely control anaerobic conditions, microfluidics for high-throughput isolation and screening, and innovative culture media designed to mimic natural microbial habitats more closely.

A key bottleneck in cultivating anaerobic microbes is maintaining stringent anoxic conditions throughout the isolation and growth processes. Oxygen is toxic to many obligate anaerobes due to their lack of protective enzymes like catalases and superoxide dismutases, which detoxify reactive oxygen species. Advances in inert gas atmospheres, oxygen scavengers, and rapid transfer systems have improved anaerobic handling, but the development of next-generation anaerobic workstations integrating automation, real-time monitoring, and parallel cultivation capacity promises to revolutionize throughput and reproducibility in cultivation workflows.

Beyond hardware innovations, conceptual shifts in cultivation strategies are underway. Traditional efforts often attempted to mimic broad environmental conditions, inadvertently excluding key symbiotic or syntrophic relationships required for growth. Emerging techniques emphasize co-cultivation and consortia assembly, recognizing that many anaerobes depend on close metabolic interactions with partner microbes for essential growth factors or electron donors and acceptors. By recreating these interdependencies, researchers can cultivate previously elusive species, thereby expanding the known microbial repertoire.

The promise of enhanced anaerobic cultivation extends into unraveling the biochemical mechanisms that govern microbial interactions and host associations. For example, in human health, anaerobic microbes dominate the gut and influence numerous physiological processes, including immune modulation, nutrient metabolism, and pathogen resistance. Cultivation allows detailed functional assays, genetic manipulation, and phenotypic characterization, enabling the translation of microbiome science into clinical interventions such as targeted microbial therapies and diagnostics.

In environmental contexts, cultivated anaerobic microorganisms contribute to ecosystem functions like nutrient cycling, organic matter degradation, and greenhouse gas emissions. Understanding their metabolic pathways through isolates leads to improved models of biogeochemical processes and informs strategies for mitigating climate change impacts, such as enhancing methane capture or reducing nitrous oxide emissions. Moreover, cultured anaerobic microbes have applications in industrial biotechnology for processes like anaerobic digestion, biogas production, and synthesis of bio-based chemicals, which are critical for sustainable development.

However, the path to achieving methodical, high-resolution anaerobic cultivation is fraught with technical and infrastructural challenges. Key obstacles include the need for specialized training, high operational costs, limited access to state-of-the-art anaerobic facilities, and a scarcity of standardized protocols across laboratories. Addressing these issues requires coordinated efforts to democratize anaerobic cultivation technologies through open-source designs, modular instrumentation, and collaborative networks that facilitate knowledge sharing and data integration.

Looking ahead, the integration of cultivation with multi-omics approaches and computational modeling heralds a new era in microbiome research. Cultivated isolates provide invaluable ‘ground truth’ for interpreting metagenomic, metatranscriptomic, and metabolomic datasets, while advanced bioinformatics can guide cultivation by predicting optimal growth conditions based on genomic signatures. Leveraging artificial intelligence and machine learning to analyze vast data streams will optimize strain selection and medium formulation, thereby accelerating the discovery pipeline.

Importantly, next-generation anaerobic cultivation is not an incremental step but a paradigm shift that elevates microbiome science from descriptive cataloging to functional elucidation. This shift unlocks the potential to design synthetic microbial communities with desired functionalities, engineer microbial consortia for therapeutic and environmental applications, and uncover fundamental principles of microbial ecology and evolution. As a result, we can anticipate profound impacts across health, agriculture, industry, and environmental stewardship.

Several pioneering laboratories are spearheading this frontier by developing integrated anaerobic cultivation platforms combining robotics, microfluidics, and high-throughput analytics. These technologies enable the screening of thousands of microbial isolates concurrently, identifying novel organisms and metabolic capabilities with unprecedented speed and precision. The deployment of these platforms will likely stimulate a renaissance in exploring microbial diversity and function, catalyzing discoveries that were previously unimaginable.

Furthermore, the ethical and regulatory landscape surrounding microbial cultivation and application is evolving alongside technological advancements. Responsible stewardship is essential to ensure that cultivated microbes, particularly genetically modified strains or those introduced into human or environmental settings, comply with safety and environmental standards. Transparent communication and collaborative governance will support the sustainable and equitable development of anaerobic microbiology.

In conclusion, the surge in biotechnological innovations aimed at enabling next-generation anaerobic cultivation marks a critical juncture in microbiome research. The capacity to culture and study anaerobic microbes in controlled environments unlocks a treasure trove of biological knowledge and practical applications. This transformation will deepen our understanding of microbial life’s hidden facets, inspire novel therapeutic and industrial strategies, and ultimately redefine the boundaries of microbiome science in the 21st century and beyond. The convergence of cultivation, sequencing, and computational tools promises an exciting future where the mysteries of anaerobic microbial communities are finally brought to light.

Subject of Research: Anaerobic microbial cultivation and its role in advancing functional microbiome research.

Article Title: Enabling next-generation anaerobic cultivation through biotechnology to advance functional microbiome research.

Article References:
Clavel, T., Faber, F., Groussin, M. et al. Enabling next-generation anaerobic cultivation through biotechnology to advance functional microbiome research. Nat Biotechnol (2025). https://doi.org/10.1038/s41587-025-02660-6

Image Credits: AI Generated