# Biological mechanisms and consequences of efficient extracellular electron transfer in Pseudomonas aeruginosa

> **NIH NIH R01** · CALIFORNIA INSTITUTE OF TECHNOLOGY · 2024 · $728,326

## Abstract

PROJECT SUMMARY
Pseudomonas aeruginosa is an opportunistic pathogen found in acute infections (burns, wounds, ventilator
associated pneumonia, eye infections) and chronic infections of the foot (diabetic ulcers) and lung (cystic
fibrosis). This bacterium commonly survives in these contexts as a biofilm, the formation and high-level
antibiotic tolerance of which interferes with effective patient treatment. A defining aspect of P. aeruginosa is its
ability to make pyocyanin, a colorful redox-active pigment that contributes to biofilm development and its
fitness in the context of infection. Pyocyanin has been detected at appreciable concentrations in skin wounds
and in cystic fibrosis sputum, and pyocyanin has been shown to be a virulence factor in animal infection
models. Pyocyanin exerts a range of effects over the cells that produce it, ranging from toxic in the presence of
oxygen to beneficial in its absence; under oxygen-limited conditions, pyocyanin serves as an electron acceptor
that promotes redox-balancing and long-term survival. These toxic and beneficial roles are important at
different times in biofilm development, with early pyocyanin -promoted lysis generating extracellular DNA
(eDNA), a key component of the biofilm matrix together with exopolysaccharides. Recently, we determined that
eDNA underpins pyocyanin’s ability to promote extracellular electron transfer (EET) within biofilms, facilitating
metabolic activity in the oxygen-limited interior. We found that eDNA enables both the retention of pyocyanin
and charge transfer to pyocyanin. Critical to making these discoveries was our development of new
bioelectrochemical technologies and approaches and the application of advanced spectroscopic techniques to
directly probe EET in biofilms. We now seek to extend our interdisciplinary work to gain a mechanistic
understanding of how biofilm EET efficiency is tuned by the composition of the matrix and the consequences
this may have for antibiotic tolerance. Does the ratio of certain exopolysaccharides (Pel, Psl) to eDNA
modulate pyocyanin diffusivity in the matrix, controlling EET efficiency? Does EET efficiency correlate with the
rate of redox balancing in the biofilm interior? How do pyocyanin-mediated cellular effects, including EET,
contribute to antibiotic tolerance in biofilms, and do these mechanisms differ according to the amount of
oxygen in the microenvironment? Does the relative sensitivity of diverse pyocyanin-producing P. aeruginosa
isolates to antibiotics correlate with their matrix composition and EET efficiency? Aim1 will explore how the
matrix composition, particularly the ratio of Pel and Psl exopolysaccharides to eDNA, determines EET
efficiency. Aim 2 will test the hypothesis that pyocyanin is a versatile intrinsic tolerance factor, where PYO-EET
helps P. aeruginosa biofilms tolerate mechanistically distinct and clinically important antibiotic classes via
bioenergetic effects and/or by inducing defense mechanisms; we predic...

## Key facts

- **NIH application ID:** 10891509
- **Project number:** 5R01AI127850-07
- **Recipient organization:** CALIFORNIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** Dianne K Newman
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $728,326
- **Award type:** 5
- **Project period:** 2017-05-08 → 2028-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10891509

## Citation

> US National Institutes of Health, RePORTER application 10891509, Biological mechanisms and consequences of efficient extracellular electron transfer in Pseudomonas aeruginosa (5R01AI127850-07). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10891509. Licensed CC0.

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