Different views on the formation mechanism of VBNC cells. (1) RpoS proteins significantly hinder the formation of VBNC cells but enhance the persistence of VBNC. “+” means an accumulation of (p)ppGpp. (2) (p)ppGpp may be an inducer which can make cells more quickly into VBNC. (3) The normal cell will enter the persister state before entering VBNC state.