Cytoplasmic acidification may occur in high-pressure carbon dioxide-treated Escherichia coli K12.
ABSTRACT 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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ABSTRACT: To study the chromosomal partitioning mechanism in cell division, we have isolated a novel type of Escherichia coli mutants which formed anucleate cells, by using newly developed techniques. One of them, named mukA1, is not lethal and produces normal-sized anucleate cells at a frequency of 0.5 to 3% of total cells in exponentially growing populations but does not produce filamentous cells. Results suggest that the mutant is defective in the chromosome positioning at regular intracellular positions and fails frequently to partition the replicated daughter chromosomes into both daughter cells, resulting in production of one anucleate daughter cell and one with two chromosomes. The mukA1 mutation causes pleiotropic effects: slow growth, hypersensitivity to sodium dodecyl sulfate, and tolerance to colicin E1 protein, in addition to anucleate cell formation. Cloning of the mukA gene indicates that the mukA1 mutation is recessive and that the mukA gene is identical to the tolC gene coding for an outer membrane protein.Journal of Bacteriology 04/1989; 171(3):1496-505. · 3.19 Impact Factor
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ABSTRACT: The three most common methods of sterilization in use today are ethylene oxide exposure, gamma-irradiation, and steam sterilization. Each of these methods has serious limitations for the sterilization of some materials used in medicine, especially thermally and hydrolytically sensitive polymers by themselves and in combination with proteins. In this work, we demonstrate a potential new method of sterilization by using supercritical fluid carbon dioxide. Using this method we achieve complete inactivation of a wide variety of bacterial organisms at moderate temperatures and in the absence of organic solvents or irradiation. Sterilization is a function of both the proximity to the fluid's critical point and the chemical nature of the fluid itself. When biodegradable polymers poly(lactic-co-glycolic) acid and polylactic acid were included in the sterilization process, there was no effect on the inactivation efficiency, yet no physical or chemical damage to these thermally and hydrolytically labile materials was observed.Proceedings of the National Academy of Sciences 09/1999; 96(18):10344-8. · 9.74 Impact Factor
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ABSTRACT: Bactericidal effects of high-pressure carbon dioxide against Escherichia coli were studied under 100, 75, 50 and 25 bar at 20 degrees C, 30 degrees C and 40 degrees C. E. coli suspended in nutrient broth (NB, pH = 6.75) was inactivated under 100, 75, 50, and 25 bar CO2 treatments for 50, 65, 100, and 140 min at 30 degrees C, respectively. Acidification of nutrient broth by dissolved CO2 alone might account for the bactericidal effect under pressure. E. coli was inactivated in NB with initial pH 5.50 and 4.5 at 100 bar for 80 and 95 min, respectively. Treatment at 100 bar CO2 pressure for 6 h caused a decrease of 6.42 and 7.24 log cycles in whole and skim milk, respectively.International Journal of Food Microbiology 05/2001; 65(1-2):131-5. · 3.43 Impact Factor