FIG 1.
T6SS2 promoter activity is strain specific and correlates with the presence of the genomic island. (A) T6SS2 genomic island (GI) located on chromosome II of V. fischeri strain ES401 (lethal). ES401 carries an ∼50-kb gene cluster containing predicted T6SS genes on chromosome II (T6SS2) that is lacking in nonlethal strains. Regulatory genes identified in this study are indicated in black. Structural T6SS genes are indicated in gray, and hatched arrows indicate conserved genes flanking the ES401 genomic island. (B) Structural model of a T6SS inhibitor cell firing into a target cell based on V. cholerae and other systems. (C) Phcp-lacZ promoter reporter activity for 8 representative V. fischeri strains with Phcp-lacZ (pAG01 reporter), a promoterless lacZ (pAKD701 empty vector), or a vector containing a synthetic promoter to constitutively drive lacZ expression (Pcon-lacZ, pJLB207 constitutive vector). Lethality indicates ability to eliminate ES114 in a coincubation, as shown previously by Speare et al. (21). The presence of the GI was determined using PCR amplification (21). Images were taken after 24 h of incubation on LBS–X-Gal. Blue indicates increased Phcp-lacZ activity, and white indicates no Phcp-lacZ reporter activity. Experiments were performed at least four times (n = 12), and a representative experiment is shown.