The effect of osmotic shock on the expression of genes in the lux regulon of marine bacteria Vibrio fischeri was studied in cells of Escherichia coli. Bioluminescence of cells was shown to drastically increase, when cells were exposed to osmotic shock at the early logarithmic growth phase. The expression of lux genes induced by osmotic shock is determined by the two-component regulatory system RcsC-RcsB. A nucleotide sequence in the regulatory region of the luxR gene homologous to the RcsB-box consensus of E. coli is assumed to be a primary site for this system.