6 chloroindole

V. parahaemolyticus strain ATCC 17802 and V. harveyi ATCC 14126 (American Type Culture Collection, Manassas, United States) were used in this study. Marine Luria-Bertani (mLB) broth containing 3% (w/v) NaCl was purchased from Becton Dickinson (Franklin Lakes, NJ, United States). V. parahaemolyticus was streaked from a glycerol stock −80°C onto mLB agar plates and incubated overnight at 30°C. For biofilm and other assays, a single colony from each plate was inoculated into 2 mL of an mLB broth and incubated overnight at 30°C in a shaking incubator at 250 rpm (Ashrafudoulla et al., 2020 (link)). Sixteen halogenated indole derivatives (4-bromoindole, 5-bromoindole, 6-bromoindole, 7-bromoindole, 4-chloroindole, 5-chloroindole, 6-chloroindole, 7-chloroindole, 4-fluoroindole, 5-fluoroindole, 6-fluoroindole, 7-fluoroindole, 4-iodoindole, 5-iodoindole, 6-iodoindole, 7-iodoindole, and indole) and other chemicals were purchased from Sigma-Aldrich (St. Louis, MO, United States) and Combi-Blocks, Inc. (San Diego, CA, United States). The compounds were dissolved in dimethyl sulfoxide (DMSO). Kanamycin, tetracycline, and crystal violet were obtained from Sigma-Aldrich. Dimethyl sulfoxide (DMSO) was also used as a negative control in all experiments at a concentration of 0.1% (v/v) in media; it did not affect cell growth or the biofilm formation.

L-tryptophan, indole, 5-chloroindole, 6-chloroindole, 7-chloroindole, 5-bromoindole, 6-bromoindole and 7-bromoindole were purchased from Sigma-Aldrich. 5-chloro-L-tryptophan, 5-bromo-L-tryptophan, 6-chloro-L-tryptophan, 7-chloro-L-tryptophan, and 7-bromo-L-tryptophan were purchased from Advanced Chemblocks, Inc. 6-bromo-L-tryptophan was purchased from Santa Cruz Biotechnology. D/L versions were purchased from the same vendor. M9, Minimal Salts, 5X was purchased through Sigma-Aldrich.