Influence of glycine betaine on the transcriptional profile of the Bacillus subtilis SigB regulon

To investigate whether salt-stress dependent activation of SigB is mitigated when cells are pre-loaded with the compatible solute glycine betaine, we analyzed salt induction of the SigB regulon in the presence of the precursor choline at a genome-wide level. The median expression value of SigB-regulated genes was 1.7-fold higher in cells that received choline immediately before salt stress compared to cells where choline was added 60 minutes prior to the salt stress. Cells were grown under vigorous agitation at 37 °C in Spizizen minimal medium. To induce hyperosmotic stress, osmolarity was increased by addition of NaCl to a final molarity of 0.4 M. Choline (1 mM) was added immediately, 15, 30 or 60 minutes before NaCl shock, respectively. Samples were taken 10 min after salt addition. Microarray hybridizations were performed with RNA from two biological replicates. The individual samples were labeled with Cy3.