The importance of viable but non-culturable bacteria in monitoring microbial water quality

Abstract

When bacteria are subject to environmental stresses, they are known to enter a physiological state where they maintain activity or viability, but are no longer culturable, i.e. the viable but non-culturable (VBNC) state. Since current standard methods of detection typically rely on culture based methods, the presence of these bacteria often goes undetected. Studies have shown that these bacteria can be resuscitated once the environmental stressors have been removed. In the case of pathogenic bacteria, infectivity can be revived leading to risk of infection when humans are exposed. Bacteria such as Escherichia coli and enterococci are commonly used as fecal indicators to assess the quality and safety of waters. However, studies have shown that these bacteria can also enter the VBNC state, thereby questioning the reliability of the culture based measurement. In this chapter, a review of the VBNC phenomenon is presented, with attention to the factors inducing the VBNC state and the physiological and molecular changes in cells that result. Current methods for detection are discussed and evaluated, with specific reference to enterococcus as a target indicator. The difficulties and limitations of measuring VBNC in natural water environments are still challenges that need to be overcome. Nevertheless, the significance of VBNC cells on environmental monitoring should not be overlooked and their impact on modeling directions will be addressed. © Nova Scicence Publishers, Inc.