More than 37 genes are involved in the A-motility system, which comprises multiple motor elements that are arrayed along the entire cell body. Each motor element appears to be localized to the periplasmic space and is bound to the peptidoglycan layer. The motors are hypothesized to move on helical cytoskeletal filaments. Gliding force generated by these motors is coupled to adhesion sites that move freely in the outer membrane, and which provide a specific contact with the substratum, possibly aided by extracellular polysaccharide slime.