I have recently purchased E. coli strain MG1655 ΔendA ΔrecA (DE3) cells to express a gene cloned in pET24a vector in a motile strain which also carries a fluorescent indicator. However, the cells are not as motile as normal MG1655 cells. Actually, after transformation and induction, they show good expression but become almost non-motile and too long and big compared to a normal MG1655. What might be the problem? What other ways do you suggest for my experiment - expression of a pET24a vector in a motile E. coli?