Visualization and characterization of spore morphogenesis in Paenibacillus polymyxa ATCC39564

[摘要] Paenibacillus polymyxa is a spore-formingGram-positive bacterial species. Both its sporulationprocess and the spore properties are poorly understood. Here, we investigated sporulation in P.polymyxa ATCC39564. When cultured at 37°C for24 h in sporulation medium, more than 80% of thetotal cells in the culture were spores. Time-lapseimaging revealed that cellular morphologicalchanges during sporulation of P. polymyxa werehighly similar to those of B. subtilis. We demonstrated that genetic deletion of spo0A, sigE, sigF,sigG, or sigK, which are highly conserved transcriptional regulators in spore-forming bacteria, abolished spore formation. In P. polymyxa, spo0A wasrequired for cell growth in sporulation medium, aswell as for the initiation of sporulation. The sigEand sigF mutants formed abnormal multiple asymmetric septa during the early stage of sporulation.The sigG and sigK mutants formed forespores inthe sporangium, but they did not become mature.Moreover, fluorescence reporter analysis confirmedcompartment-specific gene expression of spoIID andspoVFA in the mother cell and spoIIQ and sspF inthe forespore. Transmission electron microscopyimaging revealed that P. polymyxa produces multilayered endospores but lacking a balloon-shapedexosporium. Our results indicate that spore morphogenesis is conserved between P. polymyxa andB. subtilis. However, P. polymyxa genomes lack manyhomologues encoding spore-coat proteins that arefound in B. subtills, suggesting that there are differences in the spore coat composition and surfacestructure between P. polymyxa and B. subtilis.

[学科分类] 微生物学和免疫学

[关键词] Paenibacillus polymyxa;cellulardifferentiation;sporulation;endospore;sporulation-specific sigma factors