Two viewpoints about the mechanism of Rpfs. (1) Rpfs are required to cleave the peptidoglycans with inhibitory properties distributed in specific area of dormant cell wall and thus promote cell division and growth again. (2) The breakdown product(s) of peptidoglycan divided by Rpfs may interact with other factors and function as “second messengers” to stimulate the resuscitation and growth of VBNC cells.