# The molecular basis of ferrosome organelle biogenesis and its impact on host-microbe interactions

> **NIH NIH DP2** · YALE UNIVERSITY · 2024 · $502,500

## Abstract

SUMMARY
Clostridioides difficile, a Gram-positive, spore-forming anaerobic bacterium, is the leading cause of nosocomial
and antibiotic-associated intestinal infections in the United States. Over the past two decades, there has been a
significant rise in the incidence, severity, and economic burden of C. difficile infection (CDI). This increase can
be attributed to the limited efficacy of antibiotics, a growing recurrence rate of CDI, and the emergence of highly
virulent strains. These trends underscore the pressing need for alternative strategies in the treatment of CDI. To
colonize the gastrointestinal tract, C. difficile must compete with both the host and the gut microbiota for essential
nutrient iron. However, it is unclear how C. difficile adapts to nutrient iron stress in the gut during CDI. Thus, I set
out to interrogate the iron homeostasis systems in C. difficile and examine their physiological function. My
postdoctoral work has demonstrated that C. difficile undergoes an intracellular iron biomineralization process
and produces membrane-bound ferrosome organelles containing iron phosphate biominerals. The ferrosome
organelles serve as an iron storage mechanism, protecting cells against iron intoxication upon transient iron
overload. The ferrosome system is activated in the inflamed gut to combat host-mediated iron sequestration and
is important for bacterial colonization and persistence during CDI. A manuscript describing this work was recently
accepted for publication in Nature. However, the molecular basis of ferrosome biogenesis is largely unknown
and the implications of ferrosome formation within the context of CDI remain unclear. This project aims to
elucidate the underlying mechanisms of ferrosome formation and define its influence on host-microbe
interactions. In this application, we hypothesize that (i) the ferrosome membrane derives from the cytoplasmic
membrane but exhibits distinct lipid composition, (ii) iron is transported to the FezB transporter through the iron
importer FeoA3B3, aided by an iron chaperone, (iii) many other factors play roles in various stages of ferrosome
formation including iron oxidation, nucleation, and biomineralization, (iv) the ferrosome system facilitates C.
difficile adaptation to nutrient iron stress mediated by both the host and gut commensals, and (v) nutrient iron
exhibits profound effects on CDI outcomes, gut microbiome resilience, and host immune responses. The
experiments described in this proposal will test these hypotheses, elucidate the underlying mechanisms of
ferrosome biogenesis, determine the function of ferrosome organelles within the gut community, and define the
impact of nutrient iron on host-microbe interactions. Furthermore, the findings of this proposal will uncover novel
factors critical for C. difficile infection and create a framework for developing effective antimicrobial therapeutics
to combat this important infection.

## Key facts

- **NIH application ID:** 10947268
- **Project number:** 1DP2AI184552-01
- **Recipient organization:** YALE UNIVERSITY
- **Principal Investigator:** Hualiang Pi
- **Activity code:** DP2 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $502,500
- **Award type:** 1
- **Project period:** 2024-08-15 → 2029-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10947268

## Citation

> US National Institutes of Health, RePORTER application 10947268, The molecular basis of ferrosome organelle biogenesis and its impact on host-microbe interactions (1DP2AI184552-01). Retrieved via AI Analytics 2026-06-12 from https://api.ai-analytics.org/grant/nih/10947268. Licensed CC0.

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