The use of cells frozen at -196o for the bioassay of preservatives

Abstract

By growing Pseudomonas cepacia in a chemically-defined medium, stationary phase cells depleted of different nutrients could be prepared. Cells depleted of various nutrients showed marked variation insensitivity to benzalkonium chloride (BKC) and to damage associated with freezing and thawing. In both cases, cells depleted of magnesium were the most resistant. These observations may be due to alterations in the envelope, of P. cepacia in response to changes in the growth environment. Mg2+ -depleted cells had lower concentrations of cyclopropane fatty acids than the more sensitive glucose-depleted cells, particularly in the cytoplasmic membrane...