Introduction
Bacteria in natural settings are constantly exposed to changing
environmental conditions, and they must adapt to those changes in order
to survive. Developing a phenotypically heterogeneous population is a
strategy that bacteria utilize to increase their environmental fitness,
and as a survival mechanism . This is due to the benefit for the
population as a whole driven by cell-level phenotypic differences.
Phenotypic heterogeneity can allow specific cells to survive sudden
environmental changes that kill other members of the population. It can
also lead to division of labour between individuals, which can increase
the population’s growth rate and facilitate the development of new
biological functions . In the last decade, the study of phenotypic
heterogeneity among microbial populations and communities has become a
major research focus, and new techniques and models are being generated
to explore this facet of microbiology .
Bacillus subtilis is a Gram-positive non-pathogenic bacterium
that has been studied for over a century in a wide range of topics , and
has become a model organism for the study of bacterial differentiation,
including community movement on semi-solid agar surfaces, swarming and
sliding , sporulation , and biofilm formation . An interesting
characteristic of B. subtilis, both under planktonic and biofilm
conditions, is that its cells divide into discrete subpopulations, each
with a different phenotype although all still possessing the same
genotype . This phenotypic differentiation leads to division of labor or
bet hedging, providing an important ecological advantage to this
bacterium . In the following sections we address the role that the
family of Rap phosphatases and their Phr peptides play in the regulation
of B. subtilis phenotypic differentiation among Bacilli ,
their mechanism of action and structural functionality, as well as the
ecological and genetic reasons that may explain their wide distribution
in this genus.