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The synthesis of the compatible solute ectoine, mediated by the ectABC gene products, is the main mechanism used by the halophilic bacterium Chromohalobacter salexigens to cope with osmotic stress. Evidence was found that this process is regulated at the transcriptional level. S1 protection analyses performed with RNA extracted from cells grown in minimal medium at low (0·75 M NaCl) or high (2·5 M NaCl) osmolarity suggested the existence of four promoters upstream of ectA. Two of these (PectA1 and PectA2) might be recognized by the main vegetative sigma factor σ ⁷⁰, and one (PectA3) might be dependent on the general stress sigma factor σ ^S. The S1 protection assays suggest that PectA1 and PectA3 may be osmoregulated promoters. In addition, an internal promoter showing sequences homologous to promoters dependent on the heat-shock sigma factor σ ³² was found upstream of ectB …