Mechanistic study of a low-power bacterial maintenance state using high-throughput electrochemistry

Area of Science:

• Microbiology
• Microbial Physiology
• Bioenergetics

Background:

• Studying the lower metabolic limits of life is challenging due to a lack of suitable experimental systems.
• Understanding cellular maintenance is crucial for comprehending microbial survival in diverse environments, including disease states.

Purpose of the Study:

• To investigate the physiological mechanisms enabling cellular maintenance in the absence of growth.
• To quantify the metabolic rate of non-growing bacteria under specific conditions.
• To explore the bioenergetic strategies employed by microbes at their metabolic limits.

Main Methods:

• Utilized redox-cycling of phenazine-1-carboxamide (PCN) by *Pseudomonas aeruginosa*.
• Employed a high-throughput electrochemical culturing device for precise control and measurement.
• Assessed antibiotic susceptibility and characterized energy conservation pathways.

Main Results:

• Demonstrated that *Pseudomonas aeruginosa* can maintain cellular functions without growth, exhibiting a low mass-specific metabolic rate (8.7 × 10^-4 W (g C)^-1 at 25°C).
• Non-growing cells cycling PCN showed tolerance to conventional antibiotics but susceptibility to membrane-targeting agents.
• Identified a noncanonical, facilitated fermentation dependent on acetate kinase and NADH dehydrogenases for energy conservation.
• Observed a constant cell-specific metabolic rate across varying PCN concentrations, suggesting operation near the bioenergetic limit.

Conclusions:

• The PCN-cycling system provides a tractable model for studying microbial maintenance and low metabolic rates.
• This research elucidates the bioenergetic strategies and antibiotic susceptibility profiles of non-growing bacterial cells.
• The developed quantitative platform facilitates further mechanistic investigations into microbial survival under resource-limited conditions.