Cytoplasmic Acidification May Occur in High-Pressure Carbon Dioxide-Treated Escherichia coli K12

Department of Food Science and Technology, College of Bioresource Sciences, Nihon University, Japan.
Bioscience Biotechnology and Biochemistry (Impact Factor: 1.06). 11/2007; 71(10):2522-6. DOI: 10.1271/bbb.70313
Source: PubMed


While studying the mechanism by which high-pressure carbon dioxide treatment (HCT) inactivates bacteria, we found that the efficiency of DNA recovery via phenol extraction was extraordinarily low from E. coli K12 cells that had been subjected to HCT. DAPI staining of the treated cells, however, revealed that nuclear DNA was present. Most DNA from the cells subjected to HCT was probably caught in the denatured protein layer during phenol extraction. The efficiency of DNA recovery from proteinase-treated crude extracts from cells subjected to HCT was high. Crude extracts of E. coli K12 cells that had not undergone HCT were intentionally acidified with acetic acid to pH 5.2 to cause acidic coagulation of cytoplasmic proteins. The efficiency of DNA recovery from the acidified extracts was low. These results suggest that in cells subjected to HCT, cytoplasmic pH is reduced to around pH 5.2, and that nuclear DNA becomes entangled in coagulated cytoplasmic proteins. Acidification of the cytoplasm might be the primary mechanism by which HCT inactivates bacteria.

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    • "Each of these hypotheses is able to explain results of one or several experiments, but none of them give a generally valid explanation for all type of microorganism. Recent studies demonstrates, that pH lowering of the bacterial cytoplasm play a major role in microbial inactivation of different Escherichia coli strains [15] [16]. "
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