Metabolic Injury in Frozen Bacteria

S ummary : Aerobacter aerogenes populations, partly killed by freezing and thawing, usually showed more viable bacteria when plated on a rich medium than on a poor one. This 'metabolic injury' was not due to osmotic sensitivity or to toxic materials in the agar. Freezing and thawing was not significantly mutagenic and mutation to nutritional exigence did not account for the phenomenon. The survivors of freezing and thawing showed long lag phases in the recovery media, during which lag periods further mortality occurred.