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Summary
Enteric bacteria can grow in river water below sewage outfalls, with optimal growth at 30°C. However, survival is poor at lower temperatures, and bacteria from above the outfall do not grow.
Area of Science:
- Environmental microbiology
- Water quality assessment
- Bacterial ecology
Background:
- Sewage outfalls introduce enteric bacteria into aquatic environments.
- Understanding bacterial survival and growth is crucial for water quality monitoring.
Purpose of the Study:
- To investigate the growth potential of enteric bacteria in river water impacted by sewage.
- To determine the influence of temperature on bacterial growth and survival.
Main Methods:
- Chemostat cultivation of enteric bacteria in autoclaved river water from below a sewage outfall.
- Incubation at different temperatures (30°C, 20°C, 5°C).
- Comparison of growth rates between laboratory strains and naturally occurring river bacteria.
Main Results:
- Maximal growth rates observed at 30°C; minimal growth or death at 20°C and 5°C.
- Laboratory strains of Escherichia coli and Enterobacter aerogenes showed faster growth than Proteus, Arizona, Salmonella, and Shigella.
- Naturally occurring coliforms had slower growth (116 hr generation time); fecal coliforms did not grow.
- Bacterial growth from river water exhibited periodicity, suggesting surface colonization.
Conclusions:
- Enteric bacteria can utilize nutrients in river water below sewage outfalls for growth at optimal temperatures.
- Low temperatures significantly inhibit enteric bacterial growth and can cause death.
- Naturally occurring bacteria in river water exhibit different growth dynamics compared to introduced strains.