Objective  To study the sensitivity of the new lineage strains of Vibrio cholerae O1 serogroup to typing phages, and explore the molecular mechanism of the reduced sensitivity to VP3.

Methods  The sensitivity of the new lineage strains of V. cholerae O1 serogroup to typing phage VP1−VP5 was evaluated by phage cleavage experiment. The ability of VP3 to bind to the new lineage strains was evaluated by phage adsorption experiment. The sequence and structural changes of VP3 receptor protein TolC were analyzed by sequencing and protein structure prediction. The interaction between VP3 receptor binding protein Gp44 and TolC protein was quantitatively detected by bacterial two-hybridization experiment.

Results Compared with representative strain N16961 from the 7^th cholera pandemic, the the new lineage strains of V. cholerae O1 serogroup showed decreased sensitivity to VP1, VP3 and VP4, and decreased adsorption capacity to VP3 （P＜0.01）. The VP3 receptor protein TolC showed amino acid mutant sequences （TolC_VC6050-D283S, TolC_VC7132-D283S and TolC_VC7131-S281R）, which were different from the El Tor pandemic strains of V. cholerae O1 serogroup. Protein spatial structure prediction indicated that the spatial structure of the outer loop region of the new TolC sequence type was changed. VP3's receptor-binding protein Gp44's ability to interact with TolC's new sequenced protein was significantly reduced （P＜0.001）.

Conclusion  The change of amino acid sequence of TolC protein in the new lineage strains of V. cholerae significantly reduced the interaction between TolC protein and Gp44, the receptor binding protein of VP3, resulting in reduced sensitivity of the new lineage strains of V. cholerae to VP3. This study reveals that the new lineage strains of V. cholerae O1 serogroup exhibit a survival advantage under environmental phage pressure, which holds significant implications for understanding the genetic diversity and evolutionary characteristics of V. cholerae.