SpoIVA contributes to efficient engulfment through a cytoskeletal-like mechanism during Bacillus subtilis sporulation.

SpoIVA ATPase polymerization at the Bacillus subtilis forespore surface is linked to efficient engulfment, with spoIVA loss causing engulfment defects and the K30A variant phenocopying them.

• Why it matters: Engulfment requires coordinated membrane remodeling and coat recruitment, but SpoIVA’s contribution beyond coat assembly was unclear, limiting understanding of how mechanical engulfment proceeds.
• What they did: Cytology of a spoIVA null mutant (ΔspoIVA) assessed engulfment defects, and combining it with engulfment-related mutants tested genetic interactions; an ATP hydrolysis/filament-formation–impaired K30A variant was analyzed for in vivo engulfment.
• The result: ΔspoIVA showed septal membrane bulges and asymmetric membrane migration, and these defects were exacerbated by additional engulfment mutants; K30A closely phenocopied the engulfment defects, supporting a coat-independent mechanical role for SpoIVA polymers.

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