Bacillus subtilis

Bacillus subtilis has evolved one of nature's most elegant systems for genetic adaptation: natural competence. Unlike E. coli, which primarily receives foreign DNA through conjugation (requiring cell-to-cell contact), B. subtilis actively imports naked DNA from its environment. When nutrients become scarce, a subset of the population—typically 10-20%—enters a competent state, expressing specialized machinery to bind, import, and integrate environmental DNA. This DNA often comes from dead neighboring cells, allowing survivors to inherit genetic solutions that may have helped their predecessors.

The competence decision itself demonstrates sophisticated population-level strategy. Not all cells become competent simultaneously. Some continue growing and dividing while others pause to sample environmental DNA. This division of labor hedges against uncertainty: if conditions improve, the growing cells capitalize immediately; if novel challenges require genetic solutions, the competent cells may acquire them. The decision involves a bistable genetic switch—cells commit fully to one state or the other, preventing wasteful half-measures.

B. subtilis also forms endospores when conditions become truly dire—metabolically dormant structures that can survive heat, radiation, desiccation, and centuries of time. This represents the ultimate corporate restructuring: shutting down all operations to preserve core assets until conditions improve. The bacterium's regulatory network continuously weighs current resource availability against predicted future conditions, deciding whether to grow, become competent, or sporulate. This multi-option decision architecture provides resilience across timescales from hours (competence) to centuries (sporulation).