Survival and Detection of Viable but non-culturable Escherichia coli in lake water

Authors: Reşit ÖZKANCA

Abstract: Three different methods were used for the detection of Escherichia coli survival in filtered-autoclaved or untreated lake water at different temperatures. It was shown that E.coli could be detected from lake water environments by means of respiration activity when exposed to starvation stress, but not by using the traditional plate count method. Thu number of bacteria detected by plate counts was always lower than by direct microscopic counts. E.coli disappeared from the lake water or lost its abilitiy to form colonies under the effect of starvation stress and higher temperatures, even though the bacteria were still metabolically active. It is implied that some E.coli cells probably entered a viable but non-culturable state, i. e., dormant state. Thus it is very important to detected the actual number of coliform bacteria in aquatic environments in terms of the human health aspects involved.

Keywords: Bacterial survival, Coliform enumeration, E.coli , Starvation stress.