Compartmentalization during bacterial spore formation

Here, we explore the recent advancements in understanding cellular compartmentalization during bacterial spore formation, primarily focusing on the model organism Bacillus subtilis. The hallmark of sporulation, asymmetric septation, physically separates the mother cell and forespore, enabling distinct developmental fates. We highlight the role of the asymmetric septum as an organizational hub coordinating diverse compartmentalized functions - from gene regulation to metabolism and protein synthesis machinery localization. Asymmetric septation involves precise positioning of the division machinery, chromosome segregation, and septal pore formation. Recent studies have revealed detailed structure of the asymmetric septum and its role in maintaining compartment integrity, especially through interactions involving SpoIIE, SpoIIIE, peptidoglycan remodeling enzymes (like the SpoIIDMP complex), and the SpoIIIA-SpoIIQ channel. The asymmetric septum also plays a role in the spatiotemporal localization of ribosomes, with their entry into the forespore being coupled to septal peptidoglycan remodeling. This observation not only demonstrates translational compartmentalization during sporulation but also reveals the uncoupling of transcription and translation processes in B. subtilis. Moreover, the mother cell and forespore establish distinct metabolic roles, as the mother cell supplies essential metabolites to the forespore through the SpoIIIA-SpoIIQ feeding tube channel, supporting the synthesis of the spore structural components necessary for spore maturation. Advanced imaging techniques and multi-omics approaches have significantly enhanced our understanding of compartmentalization during sporulation. We conclude by discussing future research directions, including the application of machine learning approaches, expansion of research to nonmodel bacterial species, and exploration of evolutionary aspects of compartmentalization, which may reveal universal mechanisms of microbial organization.