Conservation of sporulation genes and a transmembrane-containing Spo0B variant in Paenibacillus

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 causing fatal infections in honeybee larvae, leading to colony collapse. Here, we present a comprehensive survey of sporulation genes across 1460 high-quality Paenibacillus genomes. We find that all members of the sporulation-initiating phosphorelay are well-conserved, but that the Spo0B phosphotransferase contains a transmembrane domain that is unique to this genus. The transmembrane-domain-containing variant of Spo0B is present in 92% of surveyed Paenibacillus genomes. Consistent with this high level of conservation, we find that for Paenibacillus polymyxa Spo0B, the transmembrane domain is important for interaction with its phosphorelay partners Spo0A and Spo0F. Moreover, we find that Spo0B exhibits low sequence identity across Bacilli when compared to other members of the phosphorelay. Altogether, this work highlights the potential for diversity even within the highly conserved phosphorelay that initiates sporulation in Bacilli.