Changes in DNA content and cellular death during a starvation-survival process of Escherichia coli in river water

Four nucleoid staining procedures were compared during the starvation-survi val process of Escherichia coli in river water. Only the method performed a s a modification of the standard acridine orange direct procedure allowed u s to visualize nucleoids during the 95 days of experimentation. Moreover, w ith this method the total number of cells and nucleoid-containing cells can be simultaneously enumerated. The decrease of the chromosomal DNA content of population and of the nucleoid-containing cells indicates that ghosts fo rm and cellular death occurs throughout the starvation-survival process. A long time (<30 days) is needed for non-nucleoid-containing cells to appear in river water; plasmid DNA is also negatively affected by environmental st ress. After 4 days of storage in river water, the need to increase the volu me of lysed cells used for the plasmid band visualization as well as the de crease in the plasmid band intensity would indicate a decrease in the plasm id DNA content during the starvation-survival process. According to our res ults, both chromosomal and plasmid DNA content decrease during the starvati on-survival process of E. coli in river water.