Figure 2.

Schematic of B. subtilis sporulation. The process starts with an asymmetric cell division, which results ultimately in the larger mother cell compartment engulfing the nascent forespore. Both compartments are characterized by the activity of RNA polymerase containing sequentially different sporulation-specific sigma factors, the products of which progressively assemble the spore prior to its release to the environment. Despite being metabolically dormant, spores contain significant amounts of mRNA, including a minority of σE and σK associated transcripts. Neither the source nor purpose, if any, of these mother-cell associated mRNA molecules has been established, although the SpoIIIA-IIQ channel that connects both cellular compartments at or around the engulfment stage of the process may have a contributing role in the former.