Phenotypic memory in Bacillus subtilis links dormancy entry and exit by a spore quantity-quality tradeoff

Area of Science:

• Microbiology
• Molecular Biology
• Systems Biology

Background:

• Bacteria like Bacillus subtilis form dormant spores to survive starvation.
• Spore formation and revival are critical for bacterial survival in fluctuating environments.
• The precise relationship between bacterial sporulation and spore revival has remained largely unclear.

Purpose of the Study:

• To investigate the link between Bacillus subtilis sporulation and spore revival.
• To elucidate the mechanism of phenotypic memory in bacterial spores.
• To understand how sporulation timing influences nutrient-induced spore revival.

Main Methods:

• Utilized fluorescent reporters to image the life histories of individual Bacillus subtilis cells.
• Performed theoretical analysis to model the observed phenomena.
• Conducted experiments with bacterial signaling mutants exhibiting altered sporulation timing.

Main Results:

• Demonstrated a link between sporulation and spore revival through a molecular "memory" mechanism.
• Showed that sporulation timing dictates nutrient-induced spore revival in Bacillus subtilis.
• Identified alanine dehydrogenase as a key molecule contributing to spore memory and outgrowth control.

Conclusions:

• Bacterial spore revival capacity is coupled to the gene expression and growth history of progenitor cells via molecular memory.
• This intrinsic memory generates a trade-off between spore quantity and spore quality.
• The findings may explain the evolution of complex microbial traits.