The effect of fur regulatory protein on survival of escherichia coli under photooxidative stress

In this study, the effect of fotooxidative stress on survival of Escherichia coli in different water sources, the role of Fur-regulator protein and the relation between this protein and viable but nonculturable (VBNC) were examined. The study was conducted under three different temperature.Because of reactive oxygen types that emerged from the effect of light on methylene blue that we added to water samples as fotosensitizer, it was observed that after 16 hours of incubation in pure water, the counts of E. coli QC771(wild type) decreased from 6.69 to 4.30 log. at 37 °C, to 5.35 log. at 24 °C and to 3.96 log. at 10 °C in MB+light conditions, while fur mutant E. coli QC1732 decreased from 6.65 to 5.58 log. at 37 °C, to 5.98 log. at 24 °C and to 5.13 log. at 10 °C in pure water. Similarly, E. coli incubated 48 hours in the studies conducted with lake water and it was observed that after 48 hours, counts of E. coli QC771 (wild type) decreased from 6.65 at the beginning to 4.61 log. at 37 °C, to 6.35 log. at 24 °C and to 4.19 log. at 10 °C whereas fur mutant E. coli decreased to 4.71 log. at 37 °C, to 6.41 log. at 24 °C and to 6.11 log. at 10 °C. This decrease which did not occur in control groups was caused by fotooxidative stress in MB+light condition and when Fur regulator protein was mutated, it was observed that survival of E. coli was longer than wild type in fotooxidative stress.When relation between Fur regulator protein and VBNC in fotooxidative stress is investigated, it can be concluded from CTC and Live/Dead counts that bacteria enters in VBNC situation, but Fur protein does not have any effect in VBNC molecular mechanism.Key words: Dormancy, Fur, Lake Water, Methylene Blue, Photooxidative Stres, Temparature