Unlike other bacteria in mollicutes, spiroplasma is a kind of wall-less bacteria that can maintain their special spiral shape and motor function only with a unit membrane enveloping the cell and has become the model organism for researching motility.It is great significant to study their morphology and movement for knowing the basic properties of organisms.The cells morphology and movement is also related to cytoskeleton.The Fib protein encoded by fib gene is the principal component of cytoskeleton.And fib gene is a unique gene in spiroplasma.MreB gene is one of the relevant genes which encoding cytoskeletal proteins.