The River Cam in Cambridge is best known as the place to find students in their punts on lazy summer days.
The River Cam was the source of the bacteria-killing viruses
But researchers have also found it may hold the secret to battling antibiotic resistant diseases, such as MRSA.
A "cocktail" of special viruses which kill bacteria were sourced from the river and shown to treat bacterial stomach infections in mice.
The study, presented at the Society for General Microbiology conference, may lead to alternatives to antibiotics.
Dr Derek Pickard and colleagues at the Wellcome Trust Sanger Institute isolated the viruses, known as bacteriophages, from the river water.
A bacteriophage attaches itself to the outside of the bacterial cell, penetrates it and uses the cell to produce lots more bacteriophage particles which then burst out of the cell killing the bacterium.
The researchers isolated a type of bacteriophage which kills a bacterium that infects the stomach of mice - similar to the E. coli bacteria that cause food poisoning in humans.
They found that using a cocktail of a few different bacteriophages produced the best results because even if the bacteria managed to evade one of them, for example by changing the receptors present on their surface, another could latch on.
Unlike broad-spectrum antibiotics, such as penicillin, bacteriophages do not kill the healthy bacteria present naturally in the body at the same time as getting rid of the infection.
Hundreds of different bacteriophages have been isolated by the team which says the next step is to work out how best to deliver them in humans and the appropriate cocktail of viruses for different bacterial infections.
In Eastern Europe, bacteriophages have been used successfully to treat diabetic ulcers and wounds.
Dr Pickard, a research associate at the Institute, said the Cam was a good source for the bacteriophages because of the abundance of wildlife and run off from farm land.
"Conventional antibiotic treatment has led to MRSA and other superbug infections becoming not only more prevalent but also more infectious and dangerous.
"Bacteriophage therapy offers an alternative that needs to be taken more seriously in Western Europe," he said.
Professor Nicholas Mann, microbiology expert at the University of Warwick, said: "It is an exciting time for a re-evaluation of phage therapy at the moment.
"It holds lots of promise but there are many potential commercial pitfalls in getting products into a medical setting."