# Single-cell factors of tuberculosis drug tolerance during adaptation to environmental stressors

> **NIH NIH R01** · TUFTS UNIVERSITY BOSTON · 2022 · $708,159

## Abstract

Project Summary
Tuberculosis (TB) is caused by infection with Mycobacterium tuberculosis (Mtb). TB requires a lengthy multidrug
treatment and remains difficult to treat because there is considerable drug tolerance among Mtb in the host. To
rationally design drug regimens for tuberculosis, we need to understand how Mtb creates and maintains a
population structure that generates individuals with diverse drug sensitivities. Mycobacteria exhibit cell-to-cell
heterogeneity in fundamental features of their cell physiologies, arising from a deterministic, asymmetric growth
and division pattern. This unique growth pattern creates variation in cell size, growth rate, and partitioning of
cellular components. Mycobacterial cell size provides critical insight into cell physiology because cell size is
tightly connected to antibiotic sensitivity. Mtb alter their cell size distributions under different environmental
stressors that are encountered in the host. Despite the key role of stresses during the interactions of pathogenic
Mtb and the host, studies of single-cell growth, cell cycle progression, cell size control, and drug susceptibility
have been conducted in non-pathogenic, non-Mtb mycobacteria under nutrient-replete growth conditions. A lack
of understanding of the details involved in environment-specific control of Mtb cell size and cell population
structure is a critical experimental gap that must be bridged to enter into a new phase of designing TB therapies
that target drug tolerant subpopulations. To bridge this gap, we seek to understand how Mtb cell growth and
replication processes are mediated in various environmental conditions encountered in host tissues and how
these characteristics determine antibiotic susceptibility. A systematic, quantitative approach is key to
understanding how mycobacteria tolerate antibiotic stress and will allow us to rationally design more effective
TB regimens. In this project, we will investigate the process by which Mtb adapt cell size control to different
growth environments encountered during host infection and quantitatively characterize in detail the distinct
subpopulations of drug-tolerant Mtb. We will use a combination of live-cell microscopy, fluorescent markers, and
image analysis. We will integrate these quantitative analyses into mathematical models to rigorously test cellular
strategies of cell growth and division. Our multidisciplinary approach will quantify the relationships between cell
size and cell cycle progression with drug susceptibility in distinct elemental stress conditions of the host
environment. To connect Mtb growth features and variation to treatment outcome in humans, our experiments
will focus on clinical isolates from patients that were cured or relapsed. We anticipate that these models will form
the basis from which to create optimized treatment regimens that target emerging drug-tolerant subpopulations
using different combinations of existing antibiotics.

## Key facts

- **NIH application ID:** 10376226
- **Project number:** 5R01AI143611-03
- **Recipient organization:** TUFTS UNIVERSITY BOSTON
- **Principal Investigator:** Bree Beardsley Aldridge
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $708,159
- **Award type:** 5
- **Project period:** 2020-04-01 → 2024-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10376226

## Citation

> US National Institutes of Health, RePORTER application 10376226, Single-cell factors of tuberculosis drug tolerance during adaptation to environmental stressors (5R01AI143611-03). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10376226. Licensed CC0.

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