B. subtilis biofilm formation is tightly regulated by elaborate signaling pathways. In contrast to domesticated lab strains of
B. subtilis,
which form smooth, essentially featureless colonies, undomesticated
strains such as NCIB3610 form architecturally complex
biofilms. NCIB3610 also encodes an 80-kb plasmid
absent from laboratory strains, and mutations in a plasmid-encoded
homolog
of a Rap protein, RapP, caused a hyper-rugose
biofilm phenotype.
Here we explored the role of
rapP-phrP in
biofilm formation. We found that RapP is a phosphatase that
dephosphorylates the intermediate response regulator Spo0F.
RapP appears to employ a catalytic glutamate to
dephosphorylate the Spo0F aspartylphosphate, and the implications of the
RapP
catalytic glutamate are discussed. In addition to
regulating
B. subtilis biofilm formation, we found that RapP
regulates sporulation and genetic competence as a result of its ability
to dephosphorylate
Spo0F. Interestingly, while
rap-phr gene cassettes routinely form regulatory pairs, i.e., the mature
phr gene product inhibits the activity of the
rap gene product, the
phrP gene product did not inhibit RapP activity in our assays. RapP activity was, however, inhibited by PhrH
in vivo but not
in vitro.
Additional genetic analysis suggests that RapP is directly inhibited by peptide binding. We speculate that PhrH could be
subject to post-translational modification
in vivo and directly inhibit RapP activity, or, more likely, PhrH upregulates the expression of a peptide that in turn directly binds
to RapP and inhibits its Spo0F phosphatase activity.
Acceso al trabajo
