Grow now, pay later: When should a bacterium go into debt?

Area of Science:

• Microbial physiology and ecology
• Mathematical modeling of biological systems
• Evolutionary dynamics

Background:

• Microbes must balance rapid growth with stress resistance for survival.
• Understanding these trade-offs in fluctuating environments remains a challenge.
• Existing models often simplify microbial population dynamics.

Purpose of the Study:

• To introduce and validate a mathematical model of "growth debt" in microbes.
• To explore the conditions for microbial persistence in serial-dilution cultures.
• To investigate the impact of environmental noise on resistance dynamics.

Main Methods:

• Development of a mathematical model for microbial growth debt.
• Validation of the model using chemostat experiments with Escherichia coli.
• Derivation of phase diagrams for microbial persistence in serial-dilution systems.
• Analysis of the effects of environmental noise and trade-off mechanisms.

Main Results:

• The growth debt model accurately quantifies Escherichia coli stress resistance dynamics.
• Microbial debtors can coexist with nondebtors if "payment" reduces enzyme affinity, but not if it increases mortality.
• Weak environmental noise significantly enhances the persistence of resistance traits.

Conclusions:

• The microbial debt theory provides a framework for understanding growth-stress trade-offs in nonsteady environments.
• The findings have implications for managing antibiotic resistance.
• The theory bridges the gap between chemostat and serial-dilution culture dynamics.