Speaker
Description
Recent studies have demonstrated that the catabolism of germinant amino acids, such as alanine and valine, is crucial for preventing the premature germination of spores within their mother cells or shortly after their release into spent sporulation medium (1), (2). In Bacillus subtilis, mutants lacking alanine dehydrogenase (Ald) are unable to catabolize alanine, leading to its accumulation in the medium and triggering the premature germination of newly formed spores. This observation suggests that metabolism and germinant selection may co-evolve in sporulating bacteria—specifically, only molecules that can be efficiently catabolized and cleared from the environment function effectively as germinants. To explore this hypothesis, we implemented an experimental evolution strategy to isolate suppressor mutants that prevent the premature germination phenotype of Ald⁻ strains. The resulting suppressor mutations fall into two main categories: modifications in germinant receptors and alterations in proteins involved in spore coat assembly. These findings suggest that sporulating bacteria can mitigate the uncoupling of germinant catabolism and selection by either adjusting the affinity of germinant receptors for their ligands or modulating spore coat permeability to specific germinants. Ongoing experiments and analyses aim to elucidate these mechanisms further.
