Paenibacillus encodes a membrane-localized Spo0B.

Sporulation is a strategy employed by many bacteria to survive harsh environmental conditions. The genus Paenibacillus includes spore-forming species notorious for spoiling pasteurized dairy products and for causing American foulbrood in honeybee larvae, leading to colony collapse. Human pathogens within Paenibacillus are also a growing threat, causing fatal opportunistic infections. Here, we present a comprehensive survey of sporulation genes across 1,460 high-quality Paenibacillus genomes. We find that all members of the sporulation-initiating phosphorelay are well conserved, but that the Spo0B phosphotransferase contains a predicted transmembrane domain. We confirm that this domain localizes Spo0B to the cell membrane and therefore refer to this Spo0B variant as Spo0B-TM. Spo0B-TM is present in 92% of surveyed Paenibacillus genomes. Consistent with its high level of conservation, we find that the transmembrane domain is important for detecting its interaction with its phosphorelay partners Spo0A and Spo0F. Moreover, we find that Spo0B exhibits low sequence identity across Bacillota when compared with other members of the phosphorelay. Altogether, this work highlights the potential for diversity even within the highly conserved phosphorelay that initiates sporulation in Bacillota.IMPORTANCEThe spore is the most durable life form, and the sporulation process serves as a paradigm of cellular development and differentiation. Sporulation is well characterized in the model organism Bacillus subtilis, but we lack information about non-model spore formers. The genus Paenibacillus includes spore formers that negatively impact farming and food industries and public health. Here, we present the largest comprehensive search for sporulation genes in Paenibacillus and show that a unique membrane-localized variant of Spo0B is widespread throughout Paenibacillaceae and is present in other closely related families of Bacilli.