fur- MUTATION INCREASES THE SURVIVAL TIME OF ESCHERICHIA COLI UNDER PHOTOOXIDATIVE STRESS IN AQUATIC ENVIRONMENTS

We investigated the survival of the wild type Escherichia coli (QC771) and fur(-) mutant strain (QC1732) under photooxidative stress in different water sources. The survival of fur-mutant and wild type E. coli was seen as a significant decrease in the visible light samples in the presence of methylene blue (MB). The fur(-) E. coli strain lived longer than the wild type E. coli strain on exposure to MB and visible light, which generates singlet oxygen, in both lake water (48-h) and pure water (16-h). It is interesting to note that the survival of both wild type and the fur(-) mutant strain was more protected at 24 degrees C than at other temperatures. The Fur protein does not have any relation to the entry of E. coli into the viable but nonculturable state (VBNC) under photooxidative stress. This is the first study which shows that fur(-) mutation increases the resistance of E. coli to photooxidative stress in aquatic environments, and the Fur protein does not have any relation to the entry of E. coli into the VBNC state.