Concluding remarks
The efficiency of bacterial adaptation depends on the regulatory
pathways that enable the cell to sense and respond to the external
environment, that encompasses both abiotic and biotic factors. Biotic
factors include the bacterial population itself and its density.Bacilli evolved to integrate population density using the Rap-Phr
quorum sensing pathways that eventually diverged to modulate distinct,
but partly overlapping, regulatory systems in the bacteria. Systemic
dissection of the Rap-Phr systems (i.e. single- and multiple-deletions
of the casettes) in different Bacillus species under diverse
conditions, including their natural environments, will reveal their
impact on the ecology of this group of microorganisms.