The mutualistic relationship between rhizobia and legumes is an example of a relationship where infection of the plant by a bacterium is encouraged. More often, plants will launch immune responses after detecting certain features of a potential invader. One of the more well-known elicitors of the plant immune response is flg22, a 22 amino acid region of bacterial flagellin. Flagellin is the protein that composes the largest component of the bacterial motile element, the flagellum. Sinorhizobium meliloti is a rhizobium that encodes four flagellin proteins, each with its own flg22 region. However, the flg22 epitopes of S. meliloti are not immunogenic to most plants. We hypothesized that these non-immunogenic versions of flg22 are vital for S. meliloti motility and symbiosis with host plants. To test this, S. meliloti strains were constructed in which one to four of the flg22 sequences were replaced with the immunogenic flg22 sequence of the plant pathogen, Pseudomonas syringae DC3000. Results from motility assays indicate that replacement of one to three of the flg22 sequences results in reduced swimming motility, while the replacement of all four flg22 sequences results in a complete loss of swimming motility. Transmission electron imaging of the mutant strains revealed abnormalities within the mutants with the most significantly impacted motility, as well as no flagella observed at all in the mutant with all four flg22 sequences replaced. Curiously, the recombinant S. meliloti strains failed to induce increased plant immune responses in the model plant, Arabidopsis thaliana, compared to wildtype S. meliloti. These results suggest that the immunogenic flg22 epitope does not trigger plant immune responses when embedded in an otherwise wildtype S. meliloti flagellin protein. In addition, we have used a variety of molecular and computational approaches to predict the structural impacts of altering the flg22 region of the S. meliloti flagellin proteins. Overall, these results provide novel insight into the structural and functional role of flg22 in bacterial flagellin.