Impact of high salinity and the compatible solute glycine betaine on global gene expression of Bacillus subtilis

In order to reveal so far unknown facets of the adaptation of B. subtilis to growth under high-salinity conditions, a whole-transcriptome analysis of B. subtilis BSB (168 Trp+) was performed using strand-specific tiling arrays (tiling step of 22 nucleotides). In addition, the effects of glycine betaine (GB) were analyzed under high salinity and standard growth conditions in a chemically defined medium. Important novel findings were a sustained low-level induction of the SigB-dependent general stress response and strong repression of biofilm matrix genes under high-salinity conditions. GB influences gene expression not only under high-salinity, but also under standard growth conditions without additional salt. Cells were grown aerobically at 37 °C in Spizizen's minimal medium either supplemented with 1 mM glycine betaine, 1.2 M NaCl or 1.2 M NaCl and 1 mM glycine betaine. Cells were harvested in the exponential growth phase at an optical density of 1.0. Microarray hybridizations were performed with RNA from three biological replicates. The individual samples were labeled with Cy3.