Confronted with hyperosmotic stress, Bacillus subtilis accumulates compatible solutes to maintain viability. Glycine betaine is such a compatible solute. It can either be taken up from the environment by osmoregulated Opu-transporters or it can be synthesized by the GbsB and GbsA enzymes. The synthesis of glycine betaine requires the prior import of the precursor choline through the highly specific OpuB or the promiscuous OpuC transporter.
bioinformatics analysis, mutational studies and biochemical approaches, I study
the regulatory determinants of gbsAB,
opuB and opuC transcription, which highlights the involvement of two
MarR-type proteins (GbsR and OpcR) acting as repressors.