Centipede and inchworm models to explain Mycoplasma gliding

The twelve Mycoplasma species known to glide on solid surfaces all lack surface flagella or pili, and no genes homologous to known motility systems have been found in the five genomes sequenced to date. Recent studies on the fastest of these species, M. mobile, examined novel proteins involved in the gliding mechanism, binding targets on the solid surfaces, energy sources and mechanical characteristics of the movements. Accordingly, I propose a working model for the gliding mechanism, called the centipede (power stroke) model, in which the ‘leg’ proteins repeat a cycle of binding to and release from the solid surface, using energy from ATP. Another ‘inchworm model’ suggested from the structural studies of a human pathogen, M. pneumoniae, is also discussed.