Abnormal Freezing of Milk Caused by Ice-Nucleating Bacteria.

Cultures of ice nucleating bacteria isolated from raw producer bulk milk were gram negative rods, mostly Pseudomonas fluorescens . Milk samples from which the cultures were isolated prefroze during supercooling in the cryoscopic test of freezing point. Grown under conditions of restricted nutrition, cells transferred to normally freezing samples imparted the ice nucleating factor.