FIG 1 .

Environmental calcium specifically regulates brp expression. (A) Wild-type V. vulnificus cells bearing a P_brpA lacZ reporter were grown on LB or marine agar (MA) plates containing X-Gal. (B) Pie charts showing the typical composition of salt in seawater (left) and a breakdown of the concentration (mM) of the major sea salts (right). Data are from the National Oceanographic Data Center (https://www.nodc.noaa.gov/). (C) P_brpA gfp expression in V. vulnificus grown in LB or LB supplemented with the major sea salts to concentrations found in seawater. Shown on the right are wild-type V. vulnificus cells bearing a P_brpA lacZ reporter growing on LB agar–X-Gal plates containing 50 mM MgCl₂ (LB^Mg) or 10 mM CaCl₂ (LB^Ca). (D) Fluorescent imaging of V. vulnificus biofilms growing in LB or LB containing 5 or 10 mM CaCl₂ (LB^Ca-5 and LB^Ca-10). An axis indicator is shown in the bottom left corner of each panel. Statistically significant differences among the samples (P < 0.001 as determined by one-way ANOVA followed by pairwise comparisons with a Bonferroni adjustment) are indicated by different symbols above each bar.