# Citrobacter illuminates the mechanistic underpinnings of gut biogeography

> **NIH NIH R21** · UNIVERSITY OF CALIFORNIA AT DAVIS · 2021 · $225,909

## Abstract

PROJECT SUMMARY
The microbiota influences many aspects of human health, but the mechanisms that balance it remain
incompletely understood. Our previous work has established the concept that enteric pathogens act as
ecosystem engineers by using their virulence factors to manipulate host habitat filters, thereby constructing new
nutrient-niches that support their invasion of the gut ecosystem. Thus, mucosal pathogens are valuable tools for
identifying host-derived habitat filters that structure the microbiota. Our long-range goal is to identify host-derived
habitat filters that shape the microbiota by using Citrobacter rodentium as a tool to identify environmental factors
that allow the pathogen to edge out gut-associated microbial communities. The objectives of this application are
to study how its main virulence factor, the type III secretion system (T3SS), helps C. rodentium to prevent
pathogen extinction during the initial phase of infection. Our central hypothesis is that virulence factors provide
C. rodentium with access to epithelial hydrogen peroxide, a host habitat filter that sustains pathogen growth early
after infection. We will test different aspects of our hypothesis by determining whether intimate attachment
mediated by the T3SS provides C. rodentium access to NOX1-derived hydrogen peroxide (H2O2) and
determining the role NOX1-derived H2O2 plays as a habitat filter structuring the spatial organization of the gut
microbiota. The proposed work makes innovative use of mucosal pathogens to provide fundamental insights into
microbiome research and we expect that a successful completion will offer mechanistic insights into host habitat
filters selecting for microbial traits that permit survival and growth in the host. By establishing the identity of a
novel host-derived habitat filter, our research will be of wide appeal among researchers interested in microbial
pathogenesis and the nutritional environment that shapes our host-associated microbial communities.

## Key facts

- **NIH application ID:** 10198730
- **Project number:** 5R21AI153069-02
- **Recipient organization:** UNIVERSITY OF CALIFORNIA AT DAVIS
- **Principal Investigator:** Andreas J Baumler
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $225,909
- **Award type:** 5
- **Project period:** 2020-07-01 → 2023-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10198730

## Citation

> US National Institutes of Health, RePORTER application 10198730, Citrobacter illuminates the mechanistic underpinnings of gut biogeography (5R21AI153069-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10198730. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*