# Cellular mechanisms of endosymbiont transmission between host generations

> **NIH NIH K99** · UNIVERSITY OF CALIFORNIA SANTA CRUZ · 2020 · $86,180

## Abstract

Shelbi L Russell
Project Summary
Bacterial symbionts are ubiquitous among eukaryotes and are responsible for some of the most
radical lifestyles in the natural world. For example, microbial symbiosis enables hydrothermal
vent ecosystems to subsist on inorganic energy and carbon sources and plant-feeding insect
communities to thrive on nitrogen-deficient diets. Often living with one partner inside the other,
these associations require complex cellular mechanisms to ensure that conflict does not arise
between host and symbiont. Reliable transmission mechanisms to reach new hosts are vital to
stabilizing associations over evolutionary time. However, very little is known about the molecular
mechanisms underlying these processes because the majority of endosymbionts are
unculturable, and often the hosts are as well. Here, I propose to use ​Drosophila​ fruit flies and
their ​Wolbachia​ endosymbionts as models for understanding host-symbiont interactions and the
molecular mechanisms mediating symbiont transmission. ​Wolbachia ​is one of the most
abundant intracellular symbionts in nature by virtue of its ability to associate with the host
germline and manipulate host reproduction for vertical transmission. It is also occasionally
beneficial to its hosts by promoting pathogen resistance and performing necessary cellular
tasks. These traits make this bacterium useful for applications in disease vector control. While
Wolbachia i​ s faithfully inherited through the germline in all associations examined to date,
horizontal transmission between contemporary hosts, of the same and different species, is
common throughout their evolutionary history and can be recapitulated in the lab. During the
K99 funding period, I will use the ​D. melanogaster​-​Wolbachia ​system to characterize and
identify the genes/pathways necessary for endosymbiont transmission within and between cells.
This will be accomplished in two aims: In Aim 1, I will use ​Wolbachia​-infected ​Drosophila c​ ell
lines to explore the functional mechanisms and evolutionary outcomes of mixed strain
infections. In Aim 2, I will characterize the symbiont and host linker proteins ​Wolbachia ​uses for
KHC-dependent microtubule-based motility. I will use the results of this work during the R00
phase to explore how intracellular and cell-to-cell transfer mechanisms integrate in the whole fly
for vertical transmission through the germline and horizontal transmission between host
individuals. Thus, this work will provide mechanistic insight into the transmission strategies
employed by endosymbionts around the world.

## Key facts

- **NIH application ID:** 10055204
- **Project number:** 1K99GM135583-01A1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA SANTA CRUZ
- **Principal Investigator:** Shelbi Lianne Russell
- **Activity code:** K99 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $86,180
- **Award type:** 1
- **Project period:** 2020-07-02 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10055204

## Citation

> US National Institutes of Health, RePORTER application 10055204, Cellular mechanisms of endosymbiont transmission between host generations (1K99GM135583-01A1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10055204. Licensed CC0.

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