Bet-hedging and epigenetic inheritance in bacterial cell development.

Area of Science:

• Microbiology
• Cell Biology
• Developmental Biology

Background:

• Bacillus subtilis undergoes sporulation under nutrient limitation, a bistable process where only a fraction of cells differentiate into endospores.
• The decision-making mechanism for sporulation in individual cells remains poorly understood.
• Understanding cellular fate decisions is crucial for bacterial development and survival strategies.

Purpose of the Study:

• To investigate the factors influencing the sporulation decision in individual Bacillus subtilis cells.
• To determine the role of cell history, ancestry, and age in the differentiation process.
• To elucidate the underlying mechanisms of epigenetic inheritance in bacterial development.

Main Methods:

• Time-lapse microscopy was used to track the growth, division, and differentiation of individual Bacillus subtilis cells.
• Cellular lineage and physiological states were monitored over multiple generations.
• Genetic and molecular analyses were employed to investigate the sporulation phosphorelay network.

Main Results:

• Bacillus subtilis utilizes a bet-hedging strategy, balancing sporulation with continued growth using alternative metabolites.
• Cellular age does not influence the sporulation decision; however, the ancestor's physiological state significantly impacts differentiation.
• Epigenetic inheritance, mediated by positive feedback in the sporulation phosphorelay, creates an intergenerational memory.
• This memory mechanism influences cellular differentiation outcomes for at least two generations.

Conclusions:

• The ancestral physiological state, not cell age, dictates Bacillus subtilis sporulation fate through epigenetic inheritance.
• Positive feedback in the sporulation phosphorelay establishes a long-term intergenerational memory.
• This epigenetic memory is vital for the coordinated development of complex bacterial multicellular structures like biofilms and fruiting bodies.