Screening Growth Substrates of E.coli by Monitoring Changes in Dissolved Organic Matter Composition in Sterilized River Water

摘要

Escherichia coli is prevalently used as an indicator of fecal pollution in environmental waters. However, it is reported that E.coli has a potential to grow in environmental waters under quite low dissolved organic matter (DOM) concentration conditions. DOM which supports E.coli growth in environmental waters remain unknown. In this study, growth substrates of E.coli were screened by monitoring the removal of DOM after E.coli growth in a sterilized river water. Sterilization methods were also assessed. The sample was taken from Tama River in April 2017, sterilized by filtration with 0.02 μm track-etched membrane and pasteurized at 75°C for 1 hour. E.coli K-12 was inoculated to the sterilized water and incubated under dark condition at 25°C for a few days. The DOM compositions right after sampling, filtration, pasteurization and incubation with and without E.coli inoculation were analyzed using a Orbitrap mass spectrometer. E.coli grew up to 1×10~6 CFU/mL in both filter-sterilized and heat-pasteurized samples and there were no significant differences. The sterilization processes partly affected the DOM compositions, but no new compounds were detected. The compounds reduced only after E.coli growth should be the candidates of the growth substrates and subjected to further confirmation.