CytR Is a Global Positive Regulator of Competence, Type VI Secretion, and Chitinases in Vibrio cholerae
Panel A: V. cholerae strains with indicated alleles of tfoX, cytR, hapR and qstR (+, native;-, deletion; *, constitutively expressed), were analyzed for expression of bioluminescence from a plasmid-encoded lux transcriptional reporter fusion to the promoter of the chitinase chiA1. All strains are deleted for luxO and are therefore constitutive for HapR expression (*) when the hapR gene is present. Bioluminescence is defined as relative light production per OD600 (RLU). ‡ indicates a p-value < 0.01, † indicates a p-value <0.05. N.S. denotes not significant, calculated using a two-tailed Student’s t-test. Bars 2–5 are compared to bar 1. Panel B and C: Chitin agar plate assays. V. cholerae strains with indicated alleles of tfoX, cytR, hapR, and qstR were assayed for chitinase activity which results in a zone of clearing on LB plates containing 2% colloidal chitin (panel B). Strains constitutive for TfoX (*) and isogenic strains deleted for cytR, tfoX and the CytR-dependent chitinases chiA1, chiA2, vc0769, vca0700, a chiA1 chiA2 double mutant and a strain deleted for all four chitinases were assayed for the contribution of individual chitinase genes to chitinase activity (panel C).