Cold temperatures inhibit the growth of most bacterial cells by reducing the rate of enzyme activity.  At temperatures below 0 oC, growth stops since liquid water is not available as a solvent.  Also, ice crystals can disrupt cell structure and kill cells.

Most bacteria, however, can withstand freezing  though their metabolic activities are slowed.  Psychrophiles are bacteria that require colder temperatures to grow.  Some pathogens such as Lysteria monocytogenes and Yersina pestis can remain active in refrigerators.