The effect of high hydrostatic pressure on Salmonella thompson and Listeria monocytogenes examined by electron microscopy

Mackey, B.M.; Forestière, K.; Isaacs, Neil S.; Stenning, R.; Brooker, B. E.

doi:10.1111/j.1472-765x.1994.tb00973.x

Cited by 77 publications

(58 citation statements)

References 6 publications

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“…The intracellular regions of low density observed in L. lactis (Fig. 2) are similar to those observed in pressure-treated L. monocytogenes by Mackey et al (18). These authors suggest that the low-density regions are caused by transient membrane invaginations under pressure that are subsequently reversed upon pressure release, leaving the low-density regions adjacent to the cell membrane.…”

Section: Discussionsupporting

confidence: 70%

Effects of High Pressure on the Viability, Morphology, Lysis, and Cell Wall Hydrolase Activity of Lactococcus lactis subsp. cremoris

Malone

Shellhammer

Courtney

2002

Appl Environ Microbiol

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Viability, morphology, lysis, and cell wall hydrolase activity of Lactococcus lactis subsp. cremoris MG1363 and SK11 were determined after exposure to pressure. Both strains were completely inactivated at pressures of 400 to 800 MPa but unaffected at 100 and 200 MPa. At 300 MPa, the MG1363 and SK11 populations decreased by 7.3 and 2.5 log cycles, respectively. Transmission electron microscopy indicated that pressure caused intracellular and cell envelope damage. Pressure-treated MG1363 cell suspensions lysed more rapidly over time than did non-pressuretreated controls. Twenty-four hours after pressure treatment, the percent lysis ranged from 13.0 (0.1 MPa) to 43.3 (300 MPa). Analysis of the MG1363 supernatants by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) confirmed pressure-induced lysis. Pressure did not induce lysis or membrane permeability of SK11. Renaturing SDS-PAGE (zymogram analysis) revealed two hydrolytic bands from MG1363 cell extracts treated at all pressures (0.1 to 800 MPa). Measuring the reducing sugars released during enzymatic cell wall breakdown provided a quantitative, nondenaturing assay of cell wall hydrolase activity. Cells treated at 100 MPa released significantly more reducing sugar than other samples, including the non-pressure-treated control, indicating that pressure can activate cell wall hydrolase activity or increase cell wall accessibility to the enzyme. The cell suspensions treated at 200 and 300 MPa did not differ significantly from the control, whereas cells treated at pressures greater than 400 MPa displayed reduced cell wall hydrolase activity. These data suggest that high pressure can cause inactivation, physical damage, and lysis in L. lactis. Pressure-induced lysis is strain dependent and not solely dependent upon cell wall hydrolase activity.

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Section: Discussionsupporting

confidence: 70%

Effects of High Pressure on the Viability, Morphology, Lysis, and Cell Wall Hydrolase Activity of Lactococcus lactis subsp. cremoris

Malone

Shellhammer

Courtney

2002

Appl Environ Microbiol

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“…The condensed nucleoids of pressure-treated cells were often irregularly positioned within the cell, unlike those seen in chloramphenicol-treated cells, which are generally rather symmetrical and central to the cell axis. This asymmetric appearance has also been observed with pressure-treated cells of S. enterica serovar Thompson examined by electron microscopy (20). Condensation of the nucleoid was also observed for the gram-positive organisms Listeria monocytogenes and Lactobacillus plantarum (20,39).…”

Section: Discussionmentioning

confidence: 50%

“…However, it has also been reported that in some cases, pressure-killed stationary-phase cells retain a functional membrane (24), and this has led to the consideration of other structures inside the cell as potential key targets for inactivation. Some authors have reported similarities between cell inactivation and protein denaturation kinetics (19,36), and changes in the conformation of various structures in the bacterial cell, such as the nucleoid and ribosomes, have been reported for electron microscopy and differential scanning calorimetry studies (20,23,26). However, it is still not clear which, if any, of these changes is responsible for the inactivation of the cell.…”

mentioning

confidence: 99%

Morphological and Physiological Changes Induced by High Hydrostatic Pressure in Exponential- and Stationary-Phase Cells of Escherichia coli : Relationship with Cell Death

Mañas

Mackey

2004

Appl Environ Microbiol

154

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The relationship between a loss of viability and several morphological and physiological changes was examined with Escherichia coli strain J1 subjected to high-pressure treatment. The pressure resistance of stationary-phase cells was much higher than that of exponential-phase cells, but in both types of cell, aggregation of cytoplasmic proteins and condensation of the nucleoid occurred after treatment at 200 MPa for 8 min. Although gross changes were detected in these cellular structures, they were not related to cell death, at least for stationary-phase cells. In addition to these events, exponential-phase cells showed changes in their cell envelopes that were not seen for stationary-phase cells, namely physical perturbations of the cell envelope structure, a loss of osmotic responsiveness, and a loss of protein and RNA to the extracellular medium. Based on these observations, we propose that exponential-phase cells are inactivated under high pressure by irreversible damage to the cell membrane. In contrast, stationary-phase cells have a cytoplasmic membrane that is robust enough to withstand pressurization up to very intense treatments. The retention of an intact membrane appears to allow the stationary-phase cell to repair gross changes in other cellular structures and to remain viable at pressures that are lethal to exponential-phase cells.

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“…In all cases, the integrity of the cytoplasmic membrane was apparently maintained. The types of physical damage observed by electron microscopy in this study were both different and less severe than those observed for other treatments, such as freezing and exposure to lysozyme or high pressure (El-Kest and Marth 1992;Mackey et al 1994). Even the presence of a preservative such as potassium sorbate appeared to have little visible effect on cells during chill-storage.…”

Section: Discussionmentioning

confidence: 70%

Physical and metabolic causes of sub-lethal damage in Listeria monocytogenes after long-term chilled storage at 4 oC

Dykes¹

1999

J Appl Microbiol

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S. 1999. Cells of Listeria monocytogenes display sub-lethal injury when subjected to long-term chill-storage in a nutrient-poor environment. The physical and metabolic causes of sub-lethal injury to two meat (L61 and L62) and two clinical (L98 and L99) L. monocytogenes strains chill-stored (4°C) for 4 weeks in phosphate-buffered saline at pH 7·0 and pH 5·5, and pH 5·5 in the presence of 0·3% potassium sorbate, were characterized. Causes of sub-lethal injury were determined by examining changes in the cell structure, leakage of nucleic acids and proteins from the cells, and cell recovery from injury in the presence of the metabolic inhibitors rifampicin, D-cycloserine, carbonyl cyanide m-chlorophenylhydrazone and chloramphenicol. Visible shrinkage of the cytoplasm and slight cell wall damage were apparent over the 4 week storage period by electron microscopy for all four strains and three storage conditions. By contrast, over the same storage period, only three of the strains (L62, L98 and L99) displayed slight leakage of cellular content in all three storage media, while one strain (L61) displayed greater leakage. The three strains also displayed similar storage mediadependent metabolic damage. For these strains, phosphate-buffered saline pH 5·5 caused the least damage and potassium sorbate, the most. Recovery experiments also indicated that at pH 5·5, the energy transduction system of these three strains remained undamaged, and that injury to the cell transcription machinery was greatest at pH 7·0. The fourth strain, L61, displayed less damage than the others but this was attributed to the death of the injured cell sub-population in this strain. In this study, damage to sub-lethally injured chill-stored L. monocytogenes was different from that caused by other agents, such as heat. Therefore, cells injured by chill-storage under starvation conditions may require novel protocols to assure their effective recovery.

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The effect of high hydrostatic pressure on Salmonella thompson and Listeria monocytogenes examined by electron microscopy

Cited by 77 publications

References 6 publications

Effects of High Pressure on the Viability, Morphology, Lysis, and Cell Wall Hydrolase Activity of Lactococcus lactis subsp. cremoris

Effects of High Pressure on the Viability, Morphology, Lysis, and Cell Wall Hydrolase Activity of Lactococcus lactis subsp. cremoris

Morphological and Physiological Changes Induced by High Hydrostatic Pressure in Exponential- and Stationary-Phase Cells of Escherichia coli : Relationship with Cell Death

Physical and metabolic causes of sub-lethal damage in Listeria monocytogenes after long-term chilled storage at 4 oC

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