# Identifying the Drivers and Consequences ofHost-Microbiome Composition and Function

> **NIH NIH F31** · UNIVERSITY OF CALIFORNIA, SAN DIEGO · 2024 · $41,957

## Abstract

PROJECT SUMMARY
Microbiomes are crucial to the physiological functioning of host organisms. Understanding what regulates
microbiome assembly and function can therefore have critical implications for host health. The central hypothesis
of this proposal is that host phylogenetics is a key driver of microbiome assembly and function, which in turn,
has physiological implications for the host. Specifically, I aim to 1) assess how host phylogenetics and host traits
regulate microbiome assembly and function, and 2) assess the effects of host microbiomes on host cell
physiology and consumer fitness. Unicellular algae are an ideal model system to address these questions
because these microbes harbor an experimentally tractable exterior microbiome. Further, algae span an
unusually broad phylogenetic distance across two domains of life, allowing us to test for the implications of over
a billion years of host evolutionary divergence. Lastly, our prior work has shown that algal microbiomes are
species-specific, but whether this specificity corresponds with host evolutionary history or has implications for
host health is unknown. Therefore, I use this model system to test my hypothesis that microbiome composition
and function will be most similar among host species that are closely related, and more divergent among host
species that are distantly related. To test this, I submerged 31 strains of axenic algae in a diverse community of
freshwater bacteria to allow each strain to assemble a microbiome. I am using samples from my study to assess
bacterial abundance, community composition, and function of the microbiomes via amplicon and shotgun
sequencing. To test whether host specificity has implications for host health, I will carry out reciprocal transplant
experiments of whole microbiome communities among nine host strains that span phylogenetic distances from
hosts within the same species to those from different domains of life. I will pair these microbiome swaps with
measurements of host cellular stress, including profiles of nutrients and lipids. Considering that microbiomes can
facilitate host acquisition of limiting nutrients, including nitrogen and phosphorus, I hypothesize that hosts with
an assembled microbiome will have higher cellular %N and %P compared to hosts without a microbiome. Further,
under the expectation that microbiome composition will correspond with host phylogenetics, I hypothesize that
the magnitude of change between metrics of host cellular stress will correlate with phylogenetic divergence
between hosts. Further, I will test whether these varied algal microbiome treatments affect consumer fitness
using a zooplankton model system, thereby clarifying how the microbiomes of the foods we eat may affect human
health. Overall, I aim to unravel the mechanisms behind microbiome assembly and the consequential
implications of host-specific microbiome assembly on host health. Using the unparalleled phylogenetic breadth
of hosts available in an a...

## Key facts

- **NIH application ID:** 10997009
- **Project number:** 1F31GM156042-01
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN DIEGO
- **Principal Investigator:** Taryn Broe
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $41,957
- **Award type:** 1
- **Project period:** 2024-12-01 → 2027-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10997009

## Citation

> US National Institutes of Health, RePORTER application 10997009, Identifying the Drivers and Consequences ofHost-Microbiome Composition and Function (1F31GM156042-01). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/10997009. Licensed CC0.

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