# The role of microbial second messenger synthesis in intestinal homeostasis

> **NIH NIH F32** · UNIVERSITY OF OREGON · 2020 · $64,926

## Abstract

Project Summary
Enteric microbiota interact with STING and Myd88 pathways to reinforce healthy mucus secretion and innate
immune activation in the intestine. Mucus dysregulation precipitates microbe-induced inflammation, a driver of
GI pathologies, but the mechanisms underpinning this process are poorly understood. If we better understood
the relationship between host mucus and bacterial physiology at the molecular level, we could design therapies
to alleviate inflammation that arises from mucus dysregulation. The bacterial second messenger c-di-GMP (cdG),
which promotes bacterial aggregation in response to environmental cues, stimulates vertebrate innate immune
STING signaling. The larval zebrafish, Danio rerio, is a powerful model for exploring aspects of host-microbe
interactions conserved in humans. My recent studies indicate a zebrafish mutualist Aeromonas veronii
ZOR0001(A01), which secretes beneficial factors conserved in human-associated microbiota, increases cdG
levels in response to mucus, leading to upregulation of a mucus-binding adhesin, and A01 aggregation in the
mucus-rich mid gut of the larval zebrafish intestine. Various bacteria increase cdG when exposed to mucus,
indicating this concept is a conserved adaptive strategy in bacteria. We hypothesize that mucus-mediated A01
aggregation promotes healthy mucus secretion, setting a proper inflammatory tone to prevent excess
inflammation. Consistent with this hypothesis I observe highly motile A01 in a zebrafish genetic background with
decreased mucus-secreting cells. Furthermore, I found that treating a zebrafish mutant prone to spontaneous
intestinal inflammation with a A01 hyper-aggregating mutant that produces high levels of cdG can alleviate
intestinal neutrophil influx. Therefore, we propose to characterize the molecular basis of A01 cdG signaling in
the host and determine if normal cdG-STING signaling contributes to intestinal homeostasis. Specific Aims: (1)
determine the genetic basis by which host mucus prompts A01 cdG synthesis, and (2) investigate how STING
sensing of A01-produced cdG modulates host inflammation and intestinal mucus homeostasis in vivo. Research
Design: Using my A01 cdG reporter strain, I will first screen for A01 genes involved in mucus-mediated cdG
synthesis in vitro and compare intestinal cdG signaling and distribution patterns of these mutants to wild type
A01 in the zebrafish intestine. To understand the role of cdG regulation in mutualism and host intestinal health,
A01 mutants deficient in mucus-sensing will be monoassociated into transgenic larval zebrafish that allow
quantification of intestinal mucus-secreting cells and inflammation responses. I will also generate sting deficient
zebrafish incapable of sensing cdG and compare, through phenotypic characterization and single cell RNAseq,
how they respond to A01 and bacterial products such as cdG and LPS relative to wild type and myd88 zebrafish.
This research will improve our understanding of biologi...

## Key facts

- **NIH application ID:** 9993055
- **Project number:** 1F32DK124033-01A1
- **Recipient organization:** UNIVERSITY OF OREGON
- **Principal Investigator:** Timothy Jarrod Smith
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $64,926
- **Award type:** 1
- **Project period:** 2020-03-01 → 2023-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9993055

## Citation

> US National Institutes of Health, RePORTER application 9993055, The role of microbial second messenger synthesis in intestinal homeostasis (1F32DK124033-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9993055. Licensed CC0.

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