(a) Analysis of the non-infected and infected with V. cholerae O139 zebrafish larvae’s microbiota. As a control, four-day post-fertilization zebrafish larvae were exposed to water containing 106 of β3914 bacteria carrying pN ctrl or pFW plasmid for 24 h at 27 °C, and then microbiota from five larvae were plated in MH media. Blue bacteria on MH X-gal correspond to V. cholerae O139 as attested by their yellow color on TCBS Vibrio specific media. (b) Transconjugants selected from five larvae of zebrafish larvae after pN ctrl or pFW conjugation treatment on MH media with Sp and X-gal. Blue colonies were only detected upon conjugation of pN ctrl plasmid but not after pFW conjugation due to the specific killing of V. cholerae by this plasmid. Pictures are representative from the experiment with only V. cholerae O139 shown in Fig. 4a. (c) Transconjugants selected from the infection with pFW of 1:1 mixed population of V. cholerae O1 and O139, on MH media with Sp and X-gal and then replicated on TCBS plates to follow yellow development specific of Vibrio growth. Pictures are representative of the experiments using mix of Vibrio in Fig. 4a. Pictures from (a) and (c) are representative from two independent experiments (10 zebrafish larvaes) and from (b) are representative from three independent experiments (15 zebrafish larvaes).