| Popis: |
This chapter provides hints about how much of the sporulation process and its regulation is conserved. The recent release of the complete bacterial genome of Bacillus halodurans has provided data that are in general agreement with the conclusions of the chapter. It is noteworthy that this complex operon is fully conserved in B. anthracis, B. stearothermophilus, Clostridium acetobutylicum, and C. difficile, whereas it is absent from all other genomes sequenced so far. The current sequence data indicate that all the genes involved in the B. subtilis phosphorelay are present in B. anthracis and B. stearothermophilus, with the possible exception of spoOE. It was reasonable to expect that many genes involved in the sporulation process would be highly specific to endospore formers. The most significant variations are seen when the interface between the bacterium and its environment is involved. The various Bacillus and Clostridium species inhabit a wide range of ecological niches, and it seems logical that environmental signals would be differentially relayed to SpoOA depending on their chemical nature, that hostile signals threatening spore viability would be countered with an adequate coat shell, and that germination signals would be detected by a specialized, niche-appropriate array of receptors. The conclusions suggested in this chapter are obviously tentative and doomed to be contradicted by the endless flow of incoming genomic data. |
