The genus Geobacillus is comprised of a diverse group of spore-forming Gram-positive
thermophilic bacterial species and is well known for both its ecological diversity and
as a source of novel thermostable enzymes. Although the mechanisms underlying
the thermophilicity of the organism and the thermostability of its macromolecules are
reasonably well understood, relatively little is known of the evolutionary mechanisms,
which underlie the structural and functional properties of members of this genus.
In this study, we have compared 29 Geobacillus genomes, with a specific focus
on the elements, which comprise the conserved core and flexible genomes. Based
on comparisons of conserved core and flexible genomes, we present evidence of
habitat delineation with specific Geobacillus genomes linked to specific niches. Our
analysis revealed that Geobacillus and Anoxybacillus share a high proportion of genes.
Moreover, the results strongly suggest that horizontal gene transfer is a major factor
deriving the evolution of Geobacillus from Bacillus, with genetic contributions from other
phylogenetically distant taxa.