Bacillus subtilis in defense mode: Switch-like adaptations to protistan predation

Area of Science:

• Microbiology
• Evolutionary Biology
• Ecology

Background:

• Soil microorganisms face predation, influencing bacterial evolution.
• Previous studies often overlooked predation, biasing understanding of bacterial adaptation.
• Amoebal predation by Dictyostelium discoideum is a significant factor in soil bacterial mortality.

Purpose of the Study:

• Investigate the impact of Dictyostelium discoideum predation on Bacillus subtilis growth and survival.
• Identify genetic and phenotypic mechanisms of predation resistance in B. subtilis.
• Understand how predation shapes bacterial adaptation and heterogeneity.

Main Methods:

• Genome-scale mutant screen of B. subtilis.
• De novo evolution experiments to study resistance development.
• Analysis of B. subtilis growth, survival, and phenotypic switching under predation pressure.

Main Results:

• Predation resistance genes enable filament or aggregate formation, hindering amoebal ingestion.
• Predation resistance incurs a growth cost, creating a survival-growth trade-off.
• Bacillus subtilis exhibits switch-like adaptations between resistant (slow-growing) and susceptible (fast-growing) states.
• The Spo0A phosphorylation cascade plays a key role in regulating these adaptive behaviors.

Conclusions:

• Predation is a crucial ecological driver of phenotypic heterogeneity in soil bacteria.
• Bacillus subtilis employs dynamic genotypic and phenotypic switching to navigate predation challenges.
• The findings suggest ancestral roles for regulatory pathways in predator evasion.