CytR Is a Global Positive Regulator of Competence, Type VI Secretion, and Chitinases in Vibrio cholerae
V. cholerae C6706 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 first gene of a T6SS auxiliary cluster, vca0017 (Panel A). Bioluminescence is defined as relative light production per OD600 (RLU). All strains are deleted for luxO and are therefore constitutive for HapR expression (*) when the hapR gene is present. Data shown are mean values ± standard deviation for triplicates from one representative experiment of three performed. ‡ 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 and bars 7–9 are compared to bar 6. Panel B: Chloramphenicol resistant E. coli prey were incubated with the indicated V. cholerae predator strains at a ratio of 1:10 on membrane filters to monitor contact-dependent killing. Total surviving prey cfus are represented in each case.