# Elucidating novel mechanisms controlling cell envelope biogenesis in Streptococcus Pneumoniae

> **NIH NIH F32** · HARVARD MEDICAL SCHOOL · 2020 · $69,306

## Abstract

Project summary
Streptococcus pneumoniae is a Gram-positive respiratory pathogen responsible for life-threatening infections
in young children and older adults. Patients with pneumococcal infections are typically treated with antibiotics
that act by targeting the assembly of the cell wall. Over the last decade S. pneumoniae has become a serious
health threat with multidrug resistance increasing at alarming rates. There is therefore an urgent need to
develop new and effective therapies. Given that the cell envelope is the primary target of many of our best
treatments, studies aimed at understanding the mechanisms controlling its assembly hold promise in defining
new vulnerabilities that can be blocked for the treatment of disease. The proposed research will address three
fundamental areas of S. pneumoniae cell envelope assembly and morphogenesis. The first is the regulation of
the major autolysin LytA, an enzyme that cleaves the cell wall peptidoglycan (PG) matrix and is responsible for
cell lysis following entry into stationary phase or upon treatment with beta-lactam antibiotics. LytA activity must
be tightly regulated to prevent cell wall damage that can lead to lysis. However, the mechanism by which this
enzyme is controlled has remained mysterious. It is also unclear how this control is subverted by beta-lactam
antibiotics and other anti-cell wall drugs to elicit lysis. The second area involves the biochemical pathways that
build the major surface polymers called teichoic acids (TAs), which are critical for host colonization and
virulence. My preliminary results have revealed an exciting connection between LytA regulation and TA
biogenesis, providing an opportunity to uncover mechanistic insight into both areas. I discovered that a novel
membrane protein (RafX) appears to be involved in the biosynthesis of TAs, and in blocking LytA-dependent
autolysis. Finally, the third area relates to how the division site is specified in S. pneumoniae. Currently, the
only known factor involved in division placement in this bacterium is not essential and its inactivation results in
mild division placement defects. Other regulators are therefore predicted to exist, but remain to be identified.
This aim will be facilitated by a screen for mutants synthetically lethal with known regulator that I have carried
out. The Specific Aims of this F32 application are:
1) Define the mechanism by which RafX modulates TA assembly and how this activity controls LytA autolysis.
2) Determine the mechanism of division site placement in S. pneumoniae.

## Key facts

- **NIH application ID:** 9852422
- **Project number:** 5F32AI136431-03
- **Recipient organization:** HARVARD MEDICAL SCHOOL
- **Principal Investigator:** Josue Flores-Kim
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $69,306
- **Award type:** 5
- **Project period:** 2018-03-01 → 2021-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9852422

## Citation

> US National Institutes of Health, RePORTER application 9852422, Elucidating novel mechanisms controlling cell envelope biogenesis in Streptococcus Pneumoniae (5F32AI136431-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9852422. Licensed CC0.

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