# Genetics and Axenic Growth of tick-borne E. chaffeensis and A. phagocytophilum

> **NIH NIH R01** · UNIVERSITY OF MISSOURI-COLUMBIA · 2024 · $536,741

## Abstract

Project Summary/Abstract
Human monocytic ehrlichiosis caused by Ehrlichia chaffeensis and human granulocytic anaplasmosis resulting
from Anaplasma phagocytophilum are responsible for significant morbidity and are also responsible for
mortalities in a subset of high-risk populations. Despite vertebrates and ticks having sophisticated systems of
defense, rickettsial pathogens have evolved strategies to evade host immunity and cause persistent infections.
Mutational studies to be performed with ease in all members of the rickettsiales, including for
Anaplasmataceae and Rickettsiaceae family pathogens, remain a major limiting factor. Similarly, the inability
to grow the organisms in the absence of host cell support (axenic media growth) is another major hurdle in
research progress on all important rickettsial pathogens. The ability to grow obligate intracellular bacteria
under axenic conditions can be a major advancement enabling new paths of investigation, such as
manipulating the pathogenic organisms with ease, allowing rapid clonal purification of bacterial mutants,
permitting detailed biochemical characterization and genetic studies. Our published research progress on
mutagenesis studies and axenic media development forms the basis for the current proposed research goals.
We propose to address these gaps through the following three focused specific aims: 1) optimize Himar1
mutagenesis supporting the development of a mutational library spanning a greater portion of E. chaffeensis
genome; 2) expand the targeted mutation capability in E. chaffeensis and A. phagocytophilum valuable in
diverse research applications, and 3) optimize axenic media conditions aiding the continued replication of E.
chaffeensis and A. phagocytophilum. Our prior research progress in creating mutations and similarly the
preliminary research advances on the axenic media development in Ehrlichia and Anaplasma species
highlights the importance of the planned research and substantiates our expertise that the proposed research
goals will be accomplished in a timely manner. At the conclusion of this research, we anticipate filling in major
research gaps that will aid in extending investigations on several important tick-borne rickettsial pathogens.

## Key facts

- **NIH application ID:** 10860348
- **Project number:** 1R01AI182519-01
- **Recipient organization:** UNIVERSITY OF MISSOURI-COLUMBIA
- **Principal Investigator:** ROMAN R. GANTA
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $536,741
- **Award type:** 1
- **Project period:** 2024-07-15 → 2029-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10860348

## Citation

> US National Institutes of Health, RePORTER application 10860348, Genetics and Axenic Growth of tick-borne E. chaffeensis and A. phagocytophilum (1R01AI182519-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10860348. Licensed CC0.

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