VBNC, previously unrecognized in the life cycle of Porphyromonas gingivalis?

In this review, we define and summarize the significance of the viable but not culturable (VBNC) state of bacteria and discuss the VBNC state of oral bacteria with regard to Porphyromonas gingivalis. Bacteria are exposed to stressors in their environment, to which they respond in multiple ways. One such response mechanism is to convert to the VBNC state, which a large number of bacteria, including pathogenic species, has been reported to utilize. VBNC bacteria differ from culturable bacteria in various physiological properties, which result in phenotypic changes, including the loss of their ability to grow on routine growth medium. The ability of VBNC bacteria to return to the culturable state or resuscitate, when the stressor is removed in vivo poses a considerable threat to public health. There have been few publications that clearly describe the ability of oral pathogenic species to enter the VBNC state. Yet, the presence of VBNCs among oral pathogens, such as P. gingivalis, during human chronic infections may be an important virulence factor and have severe implications for therapy. Future studies focused on VBNC in oral bacteria would provide novel molecular insights on the virulence and persistence of oral pathogens during chronic infections.