# Mycobacterium tuberculosis environmental signal integration: single cell in vivo understanding of its influence on infection heterogeneity and treatment efficacy

> **NIH NIH R01** · TUFTS UNIVERSITY BOSTON · 2021 · $608,397

## Abstract

PROJECT SUMMARY/ABSTRACT
The ionic milieu is an important source of signals for Mycobacterium tuberculosis (Mtb), key to its ability to
adapt to the local environment. It further represents a facet whose inherent non-uniformity can serve to drive
the marked heterogeneity in Mtb response and lesion outcome observed during infection, which is a critical
impediment to efficient therapy. Indeed, novel fluorescent reporter Mtb strains have uncovered marked
heterogeneity in the ionic environment (pH and chloride) and replication status of Mtb in vivo. However, how
Mtb integrates information from multiple environmental cues is poorly understood, and there is a gap in
knowledge of how drug treatment both affects, and is impacted by, the local environment experienced by
individual Mtb in vivo. To address this critical gap in knowledge, Aim 1 of this project will define the
mechanisms by which Mtb integrates response to disparate ionic signals. This will encompass (i)
transcriptional studies of a recently identified master Mtb ionic signal regulator that affects bacterial response
to pH, chloride, and potassium, and (ii) a screen for new master regulators, using a novel inducible
transcription factor over-expression library in the background of a chloride and pH-responsive fluorescent
reporter Mtb strain. Aim 2 will delineate how an integrated Mtb response to ionic cues affects infection
heterogeneity and outcome, using deletion and inducible over-expression Mtb strains of critical master ionic
signal regulators and a murine Mtb infection model that recapitulates lesion types observed in human infection.
These studies are made possible through exploitation of unique fluorescent environmental and replication
reporter Mtb strains, and an innovative imaging approach that enables single cell in vivo visualization and
signal quantification. Finally, Aim 3 seeks to understand the relationship between local ionic environment and
therapeutic modulation on Mtb replication and lesion properties in vivo. This will focus on two current drugs that
are affected by, or influence, the ionic environment (pyrazinamide and clofazimine), as well as recently
identified novel compounds that modulate Mtb response to chloride. This project is conceptually innovative in
its focus on understanding mechanisms by which Mtb integrates information from multiple signals, particularly
in the context of under-studied ionic cues. There is also innovation in the use of a novel integrated imaging
approach to reveal Mtb response to environmental cues and drug treatment with single bacterium level
resolution in vivo, while retaining spatial information from intact lesion and tissue architecture. These studies
will illuminate critical environmental response integration nodes that represent novel therapeutic targets.
Discoveries made will further build a model that drives the field beyond aggregate readouts of Mtb
environmental adaptation and infection/treatment outcome, vital for achieving the ...

## Key facts

- **NIH application ID:** 10225474
- **Project number:** 5R01AI143768-03
- **Recipient organization:** TUFTS UNIVERSITY BOSTON
- **Principal Investigator:** Shumin Tan
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $608,397
- **Award type:** 5
- **Project period:** 2019-09-18 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10225474

## Citation

> US National Institutes of Health, RePORTER application 10225474, Mycobacterium tuberculosis environmental signal integration: single cell in vivo understanding of its influence on infection heterogeneity and treatment efficacy (5R01AI143768-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10225474. Licensed CC0.

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