Bacteriophage
Japanese: ファージ（バクテリオファージ）
A general term for viruses that infect bacteria. They invade host bacteria, replicate, and destroy the cells. In the fermentation industry, they can devastate starter cultures.
Bacteriophages are viruses that infect bacteria. They attach to host bacteria, inject their DNA, replicate inside, and ultimately destroy the cell to release new phages.
They are considered the most numerous biological entities on Earth, with estimates of millions to billions per milliliter of seawater.
For the fermentation industry, phages are a serious threat. When lactic acid bacteria used as starters in yogurt or cheese production are infected by phages, fermentation halts, leading to significant economic losses. Countermeasures include selecting phage-resistant strains and rotation strategies combining multiple starter strains.
Meanwhile, in recent years, 'phage therapy' has regained attention as a countermeasure against drug-resistant bacteria—the idea of turning bacteria's natural enemies into allies.