| During starvation, Bacillus subtilis adapts by a variety of alternative developmental pathways, one of which is the formation of a spore inside the bacterial cell. Spores are dormant, resistant to environmental assaults, and do not require any nutrients for survival.;In this study, I identified a novel spore component, TasA, which is incorporated into the spore and secreted during sporulation. Both events require the removal of a signal peptide from a TasA-precursor by a novel signal peptidase, SipW. tasA and sipW are part of a three-gene operon which is expressed in response to starvation even under conditions that suppress sporulation, indicating that the operon is a transition phase operon. The expression of the operon requires σH and Spo0A, and is negatively regulated by AbrB. Sequences required for transcription are located within 233 nucleotides upstream of the operon.;TasA overproduced in E. coli exhibits antimicrobial activity against a variety of bacterial plant and animal pathogens, suggesting that TasA may protect the starving cell by suppressing the growth of competitors. During the conversion from spore to vegetative cell, some spore-associated TasA is released into the medium and may also suppress competitors.;TasA is present in spores that lack the coat, suggesting that TasA is a component of an interior location in the spore. Secreted TasA and TasA provided extracellularly early during sporulation is built into the spore, and is most likely deposited into the septal space that is connected to the extracellular medium early during sporulation. At later stages of sporulation, the septal space becomes the site of cortex assembly, suggesting that TasA may be associated with this structure.;The operon also encodes another secreted protein of unknown function, YqxM, whose secretion also depends on SipW. The translation of YqxM is controlled by an unidentified post-transcriptional mechanism that limits synthesis to post-exponential growth in hypersaline media. Sequences upstream of yqxM are involved in this posttranscriptional mechanism as their removal permits YqxM synthesis in media with normal amounts of salt. The overproduction of both pre-YqxM and SipW in E. coli resulted in the reduction of the molecular mass of YqxM, consistent with the enzymatic removal of a signal peptide. |
