The Viable but Nonculturable State
of Bacteria
Based on the information from the lab of James D. Oliver, Professor of Biology, Cone Distinguished
Professor for Teaching at the University of North Carolina, the EPA Office of Water have been playing
games with the pathogen test results. In fact, WEF scientists claims they just discovered this phenomenon
in treated biosolids.
Microbial ecologists have long recognized that large proportions of the microbial populations inhabiting natural
habitats appear to be nonculturable. Indeed, plate counts of bacteria in soil, rivers and oceans typically indicate that far
less than 1% of the total bacteria observed by direct microscopic examination can be grown on culture media. It has
also long been known that certain portions of bacterial populations in natural environments seem to disappear during
certain seasons, only to reappear at other times. We now understand that at least part of the explanation for these
observations is not due to seasonal die-off of the cells, but to their entry into what is most commonly called the “viable
but nonculturable” state.
A bacterial cell in the viable but nonculturable (VBNC) state may be defined as one which fails to grow on the routine
bacteriological media on which it would normally grow and develop into a colony, but which is in fact alive and
metabolically active. Bacteria enter into this dormant state in response to one or more environmental stresses which
might otherwise be ultimately lethal to the cell. Thus, the VBNC state should be considered a means of cell survival.
Eventually, when the inducing stress is removed, these cells are able to emerge from the VBNC state, and again
become culturable on routine media.
http://www.bioweb.uncc.edu/Faculty/Oliver/