The FtsEX ABC transporter directs cellular differentiation in Bacillus subtilis

A fundamental challenge in developmental biology is to elucidate the regulatory events that trigger cellular differentiation. Sporulation in the Gram-positive bacterium Bacillus subtilis serves as a simple experimental model system to address this challenge. The hallmark of sporulation is the formation of an asymmetrically positioned septum that divides the cell into unequally sized progeny. Here we describe the role of an ABC transporter, comprising the FtsE and FtsX proteins, in the initiation of spore formation. We discovered that in the absence of this transporter, entry into sporulation is delayed and an atypical symmetric septum is formed instead of a polar one. We show that this phenotype can be suppressed by artificially activating the master regulator of sporulation, Spo0A, or by activating the histidine kinases that function upstream of Spo0A. Our data indicate that the FtsEX transporter is one of the top components in the hierarchy of factors required to initiate sporulation, and thus it is essential for establishing proper temporal activation of the process.