Survival Mechanisms and Stress Reactions

It is widely accepted that plate culturing techniques reveal little of the true microbial population in natural ecosystems. This phenomenon can be explained by two main factors:

- the inability to detect novel microorganisms, which might not be cultivable using known media;

- the inability to recover known microorganisms which are either stressed or enter a viable but non-cultivable (VBNC) state (Fleet 1999).

The VBNC state is induced when adverse conditions such as nutrient depletion, low temperature and stresses such as pH and heat treatments can cause healthy, cultivable cells to enter a phase in which they are still capable of metabolic activity, but do not produce colonies on media (both non-selective and selective) that normally support their growth. The VBNC state has been shown in both Gram positive and Gram negative microbial species in the natural environment, and it has also been experimentally induced in most food-borne pathogens (Roszak and Colwell 1987; Fleet 1999) and Enterococcus faecalis (del Mar Lleo, et al. 2000).

Was this article helpful?

0 0

Post a comment