Analysis of flaA in flagellar synthesis and motility of Vibrio cholerae

Vibrio cholera has a single polar flagellum provide the motility. This organism causes cholera, an acute intestine disease characterized by severe watery diarrhea. The flagellin genes of V.cholerae are located in two chromosomal loci: flaAC and flaEDB. In this study, we removed all five flagellin genes in the chromosome of V.cholerae to study the influence of individual flagellins on V.cholerae flagellar synthesis. We constructed various flagellins and flagellin chimeras were reintroduced into the ∆flaABCDE and other mutant strains on plasmids, analyzed phenotypes by soft agar and transmission electron microscopy. We have identified that V.cholerae motility can be complemented by flaA flagellin gene and synthesis flagellum in ∆flaABCDE strain. The ∆flaEDB strain is flagellated and has similar motility with wide-type. The strain containing flaD promoter expressed entire flaA gene revealed better motility than with flaA promoter in ∆flaABCDE strain. Measurement of flaA and flaD promoter-lacZ fusions indicated that flaD promoter expressed in a higher level than flaA in ∆flaABCDE strains. We predicted that flaD promoter generated more flagellar by highly expression of flaA flagellin gene and provide motility in ∆flaABCDE strains. In addition, the amount of flaA falgellin is critical for motility when there are other flagellins present in the chromosome and the 328 amino acid residue of flaA protein affect motility interact with other flagellins.