ANHYDRIOBIOSIS 



17 



-80 -100 -120 -140 -160 -180 



Temperature of storage 



Fig. 1 . Storage death of frozen cells of E. coli. 1 5-h culture of E. coli in 1 % 

 peptone at pH 7.0, shell frozen in 0.1 -ml quantities. -1.5' and -5^ samples 

 frozen at -15' then transferred to storage at required temperatures. Other 

 samples frozen and stored at temperatures indicated. Storage time 3-5 h. 

 (Modified from Weiser and Osterud^"). 



flocculation. He found that a protein extracted from P. pyocyanea 

 coagulated when stored at — 2", but no such effect was observed 

 when the protein was stored at — 20°. 



According to Straka and Stokes^- freezing produces several 

 effects: it kills outright some of the cells, causes damage or 

 reversible injury to others, while some cells entirely escape 

 harm. The injury to bacteria may be detected by the ability of 

 thawed cells to grow in a rich nutrient medium, but not in a 

 minimal medium in which control, non-frozen bacteria grow 

 well. At storage temperatures near 0"" a higher percentage of cells 

 actually die than at — 30 \ when less bacteria are killed and 

 more only injured: the injured ones can be saved on thawing by 

 seeding them into a rich medium. The factor in the medium 

 which was found to be responsible for the repair of the damage 

 was trypticase (Baltimore Biological Laboratory), or rather 

 some peptide in it. Amino acids and vitamins could not replace 

 trypticase. 



Our own investigations of damage to the bacterial cell wall 



References p. 29 



