Food fight: Cheese bacteria fight off viral attacks

By Julie Steenhuysen

CHICAGO (Reuters) - Scientists have found a way to ensure starter cultures used to make cheese can ward off attacks from bacteria-eating viruses -- a finding that could mean the difference between a great Gouda and wasted milk.

Attacks by viruses known as phages pose a particular problem for companies like Danish food ingredient maker Danisco, whose starter cultures are used in about half of all the ice cream and cheese produced in the world.

"Phages are one of the major causes of product failure for the food industry, especially in the dairy industry," said Philippe Horvath, a scientist at Danisco's laboratory in Dange-Saint-Romain, France.

The tiny viruses that infect bacteria enter the cell and rapidly replicate until the cell ruptures, spreading the virus in a series of repeating cycles.

"It's an explosive propagation," he said in a telephone interview.

Horvath and colleagues at Danisco have discovered how to harness bacteria's own natural defense mechanisms to produce phage-resistant bacteria. They reported their results in Friday's issue of the journal Science.

The study helps explain the role of a new family of repetitive sequences in the genome of bacteria called CRISPR sequences. They resemble some of the DNA sequences in the phages.

"LET NATURE DO THE WORK"