Study of the Bacillus subtilis PBP4* and RacX, YlmE racemases in relation with disassembly of biofilms

Bacillus subtilis is a PGPR (Plant Growth Promoting Rhizobacterium) Gram positive bacterium and a model for studying the in vitro formation or disruption of biofilms. At the liquid/air interface of standing cultures, B. subtilis forms thick pellicles of limited lifetimes. Some D-amino acids have been reported among the factors playing a role in the disassembly of B. subtilis biofilms and ylmE or racX mutants (in which the racemases YlmE or RacX are absent) show a delay in pellicle disruption. The racX encoding gene is part of a bicistronic operon in which the second gene (pbpE) codes for a Penicillin-Binding Protein, the PBP4* whose function is not characterized in Bacillus. Our studies aim to produce, purify and characterize the role of the PBP4* and RacX, YlmE racemases in relation with the disassembly of biofilms. Biochemical and structural data have been obtained and the role of the three proteins has been partly solved. X-ray structures will permit us to create inhibitor molecules against Bacillus subtilis biofilm formation or disassembly.