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Juneja VK, Garcia-Dávila J, Lopez-Romero JC, Pena-Ramos EA, Camou JP, Valenzuela-Melendres M. Modeling the effects of temperature, sodium chloride, and green tea and their interactions on the thermal inactivation of Listeria monocytogenes in turkey. J Food Prot 2014; 77:1696-702. [PMID: 25285486 DOI: 10.4315/0362-028x.jfp-14-124] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The interactive effects of heating temperature (55 to 65°C), sodium chloride (NaCl; 0 to 2%), and green tea 60% polyphenol extract (GTPE; 0 to 3%) on the heat resistance of a five-strain mixture of Listeria monocytogenes in ground turkey were determined. Thermal death times were quantified in bags that were submerged in a circulating water bath set at 55, 57, 60, 63, and 65°C. The recovery medium was tryptic soy agar supplemented with 0.6% yeast extract and 1% sodium pyruvate. D-values were analyzed by second-order response surface regression for temperature, NaCl, and GTPE. The data indicated that all three factors interacted to affect the inactivation of the pathogen. The D-values for turkey with no NaCl or GTPE at 55, 57, 60, 63, and 65°C were 36.3, 20.8, 13.2, 4.1, and 2.9 min, respectively. Although NaCl exhibited a concentration-dependent protective effect against heat lethality on L. monocytogenes in turkey, addition of GTPE rendered the pathogen more sensitive to the lethal effect of heat. GTPE levels up to 1.5% interacted with NaCl and reduced the protective effect of NaCl on heat resistance of the pathogen. Food processors can use the predictive model to design an appropriate heat treatment that would inactivate L. monocytogenes in cooked turkey products without adversely affecting the quality of the product.
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Affiliation(s)
- Vijay K Juneja
- U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19308, USA.
| | - Jimena Garcia-Dávila
- Research Center for Food and Development, CIAD, A.C., Hermosillo, Sonora, 83000, Mexico
| | | | - Etna Aida Pena-Ramos
- Research Center for Food and Development, CIAD, A.C., Hermosillo, Sonora, 83000, Mexico
| | - Juan Pedro Camou
- Research Center for Food and Development, CIAD, A.C., Hermosillo, Sonora, 83000, Mexico
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Juneja VK, Altuntaş EG, Ayhan K, Hwang CA, Sheen S, Friedman M. Predictive model for the reduction of heat resistance of Listeria monocytogenes in ground beef by the combined effect of sodium chloride and apple polyphenols. Int J Food Microbiol 2013; 164:54-9. [DOI: 10.1016/j.ijfoodmicro.2013.03.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 02/13/2013] [Accepted: 03/10/2013] [Indexed: 10/27/2022]
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3
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Chung HJ, Yousef AE. Inactivation of Escherichia coli in broth and sausage by combined high pressure and Lactobacillus casei cell extract. FOOD SCI TECHNOL INT 2011; 16:381-8. [PMID: 21339156 DOI: 10.1177/1082013210366883] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The purpose of this study was to investigate the effect of combined high pressure and Lactobacillus casei cell extract (CE) on Escherichia coli O157 strains with variation in pressure resistance in broth and sausage. Pressure-resistant (O157:H7 and O157:H12) and -sensitive (O157-M1 and O157-M2) E. coli strains were used. Pressure treatment at 350 MPa for 20 min in broth caused 1.1-1.2 logs reduction in O157:H12 and O157:H7 and 4.1-5.5 logs reduction in the O157-M1 and O157-M2. When high pressure was treated in the presence of CE (32 CEAU/mL), the combination treatment caused a significant inactivation in the pressure-resistant O157:H7 strains resulting in the viability loss of 4.3-4.6 logs and the synergistic effect increased with increase in treatment time (p < 0.05). Similar result was observed in sausage. Differential scanning calorimetry thermogram showed that the presence of Lb. casei CE may cause considerable damage to cellular components of E. coli during the high pressure treatment. The synergy between high pressure processing and Lb. casei OSY-LB6A CE against pressure-resistant E. coli O157 strains suggests the feasibility of using this combination to minimize the risk of transmission of E. coli O157 by food.
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Affiliation(s)
- Hyun-Jung Chung
- Department of Food and Nutrition, Inha University, Incheon, Korea.
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4
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Sergelidis D, Abrahim A. Adaptive response of Listeria monocytogenes to heat and its impact on food safety. Food Control 2009. [DOI: 10.1016/j.foodcont.2008.01.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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5
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GABRIEL ALONZOA, BARRIOS ERNIELB, AZANZA MARIAPATRICIAV. MODELING THE THERMAL DEATH OFSALMONELLATYPHIMURIUM IN CITRUS SYSTEMS. J FOOD PROCESS ENG 2008. [DOI: 10.1111/j.1745-4530.2007.00180.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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6
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Jørgensen F, Stephens P, Knøchel S. The effect of osmotic shock and subsequent adaptation on the thermotolerance and cell morphology ofListeria monocytogenes. ACTA ACUST UNITED AC 2008. [DOI: 10.1111/j.1365-2672.1995.tb03137.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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7
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Jørgensen F, Nybroe O, Knøchel S. Effects of starvation and osmotic stress on viability and heat resistance ofPseudomonas fluorescensAH9. ACTA ACUST UNITED AC 2008. [DOI: 10.1111/j.1365-2672.1994.tb03083.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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8
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Tangwatcharin P, Chanthachum S, Khopaibool P, Griffiths MW. Morphological and physiological responses of Campylobacter jejuni to stress. J Food Prot 2006; 69:2747-53. [PMID: 17133821 DOI: 10.4315/0362-028x-69.11.2747] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Under conditions of stress, cells of Campylobacter assume a coccoid shape that may be an evolutionary strategy evolved by the organism to enable survival between hosts. However, the physiology of Campylobacter as it devolves from spiral to coccoid-shaped morphology is poorly understood. In this study, conditions influencing the survival of Campylobacter jejuni ATCC 35921 in broth were determined. Cells in late log phase were resuspended in broth at 4 or 60 degrees C. The culturability of these cold- or heat-stressed cell suspensions was determined by spread plate counts and the activity of cells by the direct viable count technique and 5-cyano-2,3-ditolyltetrazolium chloride staining. C. jejuni changed form completely from culturable to viable but nonculturable cells (VBNC) within 25 days at 4 degrees C, and 15 min at 60 degrees C. Light microscopy of C. jejuni VBNC cells showed that the spiral-shaped cells became coccoid, and transmission electron microscopy of C. jejuni VBNC cells showed that the outer membrane was lost in aging cell suspensions. Furthermore, a limited proteomic study was carried out to compare C. jejuni proteins that exhibited increased or decreased synthesis on exposure to 60 degrees C.
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Affiliation(s)
- Pussadee Tangwatcharin
- Department of Food Science and Technology, Prince of Songkla University, Songkhla 90112, Thailand
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Teixidó N, Cañamás TP, Abadias M, Usall J, Solsona C, Casals C, Viñas I. Improving low water activity and desiccation tolerance of the biocontrol agent Pantoea agglomerans CPA-2 by osmotic treatments. J Appl Microbiol 2006; 101:927-37. [PMID: 16968304 DOI: 10.1111/j.1365-2672.2006.02948.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIMS To study the improvement of tolerance to low water activity (aw) and desiccation during spray drying in Pantoea agglomerans cells subjected to mild osmotic stress during growth. METHODS AND RESULTS The micro-organism was cultured in an unmodified liquid (control) or in aw-modified media, and viability of these cells was evaluated on unstressed (0.995) and 0.96 aw stressed solid media, in order to check total viability and aw stress tolerance respectively. Significant improvements in viability on unmodified medium were observed with cells grown for 24 h in NaCl 0.98 aw, glycerol 0.98 aw and 0.97 aw and for 48 h in NaCl 0.98 aw and 0.97 aw modified media. Both yield improvements and water stress tolerance were achieved with low aw media. Cells grown for 24 h in NaCl 0.98 aw or for 48 h in NaCl 0.98 aw, 0.97 aw and 0.96 aw, glucose 0.97 aw and glycerol 0.97 aw showed improved aw stress tolerance in comparison with control cells. The best results were obtained with NaCl treatments (0.98 aw and 0.97 aw) which also exhibited better survival rates than control cells during spray-drying process and maintained their efficacy against postharvest fungal pathogens in apples and oranges. CONCLUSIONS NaCl treatments are very appropriate for improving P. agglomerans low aw tolerance obtaining high production levels and maintaining biocontrol efficacy. SIGNIFICANCE AND IMPACT OF THE STUDY Improving stress tolerance of biocontrol agents could be an efficient way to obtain consistency and maintain efficacy of biological control under practical conditions.
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Affiliation(s)
- N Teixidó
- Postharvest Unit, CeRTA, Centre UdL-IRTA, Lleida, Catalonia, Spain.
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10
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Abstract
In this paper I relate the loss of CFU following a life-threatening treatment to the inactivation of critical components. Equations are used to calculate the loss of CFU following isothermal and temperature-scanning treatments, and the results are discussed in relation to differential scanning calorimetry of bacteria.
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Affiliation(s)
- Christopher A Miles
- University of Bristol, Collagen Research Group, School of Veterinary Science, Langford, Bristol, UK.
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11
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Nguyen HTT, Corry JEL, Miles CA. Heat resistance and mechanism of heat inactivation in thermophilic campylobacters. Appl Environ Microbiol 2006; 72:908-13. [PMID: 16391133 PMCID: PMC1352264 DOI: 10.1128/aem.72.1.908-913.2006] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2005] [Accepted: 09/19/2005] [Indexed: 11/20/2022] Open
Abstract
The heat resistance of Campylobacter jejuni strains AR6 and L51 and the heat resistance of Campylobacter coli strains DR4 and L6 were measured over the temperature range from 50 to 60 degrees C by two methods. Isothermal measurements yielded D55 values in the range from 4.6 to 6.6 min and z values in the range from 5.5 to 6.3 degrees C. Dynamic measurements using differential scanning calorimetry (DSC) during heating at a rate of 10 degrees C/min yielded D55 values of 2.5 min and 3.4 min and z values of 6.3 degrees C and 6.5 degrees C for AR6 and DR4, respectively. Both dynamic and isothermal methods yielded mean D55 values that were substantially greater than those reported previously (0.75 to 0.95 min). DSC analysis of each strain during heating at a rate of 10 degrees C/min yielded a complex series of overlapping endothermic peaks, which were assigned to cell wall lipids, ribosomes, and DNA. Measurement of the decline in the numbers of CFU in calorimetric samples as they were heated showed that the maximum rate of cell death occurred at 56 to 57 degrees C, which is close to the value predicted mathematically from the isothermal measurements of D and z (61 degrees C). Both estimates were very close to the peak m1 values, 60 to 62 degrees C, which were tentatively identified with unfolding of the 30S ribosome subunit, showing that cell death in C. jejuni and C. coli coincided with unfolding of the most thermally labile regions of the ribosome. Other measurements indicated that several essential proteins, including the alpha and beta subunits of RNA polymerase, might also unfold at the same time and contribute to cell death.
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Affiliation(s)
- Hong T T Nguyen
- Department of Clinical Veterinary Science, University of Bristol, Langford, Bristol BS40 5DU, United Kingdom.
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12
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Abstract
The role of the bacterial ribosome in the cellular response to environmental stress has been widely considered over last decade. Certain ribosome-associated proteins have been shown to induce conformational changes that lead to the formation of inactive forms of ribosomes that are presumed to be more stable during stationary phase. This was found to aid the survival of bacteria in this phase. Such proteins include ribosome modulation factor (RMF), YfiA and YhbH. Examining the influence of RMF on the survival of E. coli under heat, acid and osmotic stress showed that it was important for bacterial viability under these environmental pressures. However, the mechanism by which this protein exerts its effect has not been fully elucidated. The present work reviews the involvement of ribosomes in determining cell behaviour during stress. It focuses on the action of the ribosome-associated proteins and their role in inactivating ribosomes for preserving their integrity and aiding cell survival under stress.
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Affiliation(s)
- Walid M El-Sharoud
- Dairy Department, Faculty of Agriculture, Mansoura University, Mansoura, Egypt.
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13
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Novak JS, Yuan JTC. Viability of Clostridium perfringens, Escherichia coli, and Listeria monocytogenes surviving mild heat or aqueous ozone treatment on beef followed by heat, alkali, or salt stress. J Food Prot 2003; 66:382-9. [PMID: 12636289 DOI: 10.4315/0362-028x-66.3.382] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The threat of pathogen survival following ozone treatment of meat necessitates careful evaluation of the microorganisms surviving under such circumstances. The objective of this study was to determine whether sublethal aqueous ozone treatment (3 ppm of O3 for 5 min) of microorganisms on beef surfaces would result in increased or decreased survival with respect to subsequent heat, alkali, or NaCl stress. A mild heat treatment (55 degrees C for 30 min) was used for comparison. Reductions in three-strain cocktails of Clostridium perfringens, Escherichia coli O157:H7, and Listeria monocytogenes on beef following the heat treatment were 0.14, 0.77, and 1.47 log10 CFU/g, respectively, whereas reductions following ozone treatment were 1.28, 0.85, and 1.09 log10 CFU/g, respectively. C. perfringens cells exhibited elevated heat resistance at 60 degrees C (D60 [time at 60 degrees C required to reduce the viable cell population by 1 log10 units or 90%] = 17.76 min) following heat treatment of beef (55 degrees C for 30 min) but exhibited reduced viability at 60 degrees C following ozone treatment (D60 = 7.64 min) compared with the viability of untreated control cells (D60 = 13.84 min). The D60-values for L. monocytogenes and E. coli O157:H7 following heat and ozone exposures were not significantly different (P > 0.05). C. perfringens cells that survived ozone treatment did not exhibit increased resistance to pH (pH 6 to 12) relative to non-ozone-treated cells when grown at 37 degrees C for 24 h. The heat treatment also resulted in decreased numbers of surviving cells above and below neutral pH values for both E. coli O157:H7 and L. monocytogenes relative to those of non-heat-treated cells grown at 37 degrees C for 24 h. There were significant differences (P < 0.05) in C. perfringens reductions with increasing NaCl concentrations. The effects of NaCl were less apparent for E. coli and L. monocytogenes survivors. It is concluded that pathogens surviving ozone treatment of beef are less likely to endanger food safety than are those surviving sublethal heat treatments.
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Affiliation(s)
- John S Novak
- U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, Microbial Food Safety Research Unit, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA.
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14
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Chapter 2 Recovery of stressed microorganisms. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s0079-6352(03)80005-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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15
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Lee J, Kaletunç G. Evaluation of the heat inactivation of Escherichia coli and Lactobacillus plantarum by differential scanning calorimetry. Appl Environ Microbiol 2002; 68:5379-86. [PMID: 12406728 PMCID: PMC129879 DOI: 10.1128/aem.68.11.5379-5386.2002] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Differential scanning calorimetry (DSC) is used to evaluate the thermal stability and reversibility after heat treatment of transitions associated with various cellular components of Escherichia coli and Lactobacillus plantarum. The reversibility and the change in the thermal stability of individual transitions are evaluated by a second temperature scan after preheating in the DSC to various temperatures between 40 and 130 degrees C. The viability of bacteria after a heat treatment between 55 and 70 degrees C in the DSC is determined by both plate count and calorimetric data. The fractional viability values based on calorimetric and plate count data show a linear relationship. Viability loss and the irreversible change in DSC thermograms of pretreated whole cells are highly correlated between 55 and 70 degrees C. Comparison of DSC scans for isolated ribosomes shows that the thermal stability of E. coli ribosomes is greater than that of L. plantarum ribosomes, consistent with the greater thermal tolerance of E. coli observed from viability loss and DSC scans of whole cells.
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Affiliation(s)
- Jaesung Lee
- Department of Food, Agricultural, and Biological Engineering, The Ohio State University, Columbus, Ohio 43210, USA
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16
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Mattick KL, Jørgensen F, Wang P, Pound J, Vandeven MH, Ward LR, Legan JD, Lappin-Scott HM, Humphrey TJ. Effect of challenge temperature and solute type on heat tolerance of Salmonella serovars at low water activity. Appl Environ Microbiol 2001; 67:4128-36. [PMID: 11526015 PMCID: PMC93139 DOI: 10.1128/aem.67.9.4128-4136.2001] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2000] [Accepted: 06/11/2001] [Indexed: 11/20/2022] Open
Abstract
Salmonella spp. are reported to have an increased heat tolerance at low water activity (a(w); measured by relative vapor pressure [rvp]), achieved either by drying or by incorporating solutes. Much of the published data, however, cover only a narrow treatment range and have been analyzed by assuming first-order death kinetics. In this study, the death of Salmonella enterica serovar Typhimurium DT104 when exposed to 54 combinations of temperature (55 to 80 degrees C) and a(w) (rvp 0.65 to 0.90, reduced using glucose-fructose) was investigated. The Weibull model (LogS = -bt(n)) was used to describe microbial inactivation, and surface response models were developed to predict death rates for serovar Typhimurium at all points within the design surface. The models were evaluated with data generated by using six different Salmonella strains in place of serovar Typhimurium DT104 strain 30, two different solutes in place of glucose-fructose to reduce a(w), or six low-a(w) foods artificially contaminated with Salmonella in place of the sugar broths. The data demonstrate that, at temperatures of > or =70 degrees C, Salmonella cells at low a(w) were more heat tolerant than those at a higher a(w) but below 65 degrees C the reverse was true. The same patterns were generated when sucrose (rvp 0.80 compared with 0.90) or NaCl (0.75 compared with 0.90) was used to reduce a(w), but the extent of the protection afforded varied with solute type. The predictions of thermal death rates in the low-a(w) foods were usually fail-safe, but the few exceptions highlight the importance of validating models with specific foods that may have additional factors affecting survival.
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Affiliation(s)
- K L Mattick
- PHLS Food Microbiology Research Unit, Heavitree, Exeter EX2 5AD, United Kingdom.
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17
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Bayles DO, Tunick MH, Foglia TA, Miller AJ. Cold shock and its effect on ribosomes and thermal tolerance in Listeria monocytogenes. Appl Environ Microbiol 2000; 66:4351-5. [PMID: 11010881 PMCID: PMC92307 DOI: 10.1128/aem.66.10.4351-4355.2000] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Differential scanning calorimetry (DSC) and fatty acid analysis were used to determine how cold shocking reduces the thermal stability of Listeria monocytogenes. Additionally, antibiotics that can elicit production of cold or heat shock proteins were used to determine the effect of translation blockage on ribosome thermal stability. Fatty acid profiles showed no significant variations as a result of cold shock, indicating that changes in membrane fatty acids were not responsible for the cold shock-induced reduction in thermal tolerance. Following a 3-h cold shock from 37 to 0 degrees C, the maximum denaturation temperature of the 50S ribosomal subunit and 70S ribosomal particle peak was reduced from 73.4 +/- 0.1 degrees C (mean +/- standard deviation) to 72.1 +/- 0.5 degrees C (P < or = 0.05), indicating that cold shock induced instability in the associated ribosome structure. The maximum denaturation temperature of the 30S ribosomal subunit peak did not show a significant shift in temperature (from 67.5 +/- 0.4 degrees C to 66.8 +/- 0.5 degrees C) as a result of cold shock, suggesting that either 50S subunit or 70S particle sensitivity was responsible for the intact ribosome fragility. Antibiotics that elicited changes in maximum denaturation temperature in ribosomal components also elicited reductions in thermotolerance. Together, these data suggest that ribosomal changes resulting from cold shock may be responsible for the decrease in D value observed when L. monocytogenes is cold shocked.
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Affiliation(s)
- D O Bayles
- Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania 19038, USA.
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18
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Miller AJ, Bayles DO, Eblen BS. Cold shock induction of thermal sensitivity in Listeria monocytogenes. Appl Environ Microbiol 2000; 66:4345-50. [PMID: 11010880 PMCID: PMC92306 DOI: 10.1128/aem.66.10.4345-4350.2000] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2000] [Accepted: 08/01/2000] [Indexed: 11/20/2022] Open
Abstract
Cold shock at 0 to 15 degrees C for 1 to 3 h increased the thermal sensitivity of Listeria monocytogenes. In a model broth system, thermal death time at 60 degrees C was reduced by up to 45% after L. monocytogenes Scott A was cold shocked for 3 h. The duration of the cold shock affected thermal tolerance more than did the magnitude of the temperature downshift. The Z values were 8.8 degrees C for controls and 7.7 degrees C for cold-shocked cells. The D values of cold-shocked cells did not return to control levels after incubation for 3 h at 28 degrees C followed by heating at 60 degrees C. Nine L. monocytogenes strains that were cold shocked for 3 h exhibited D(60) values that were reduced by 13 to 37%. The D-value reduction was greatest in cold-shocked stationary-phase cells compared to cells from cultures in either the lag or exponential phases of growth. In addition, cold-shocked cells were more likely to be inactivated by a given heat treatment than nonshocked cells, which were more likely to experience sublethal injury. The D values of chloramphenicol-treated control cells and chloramphenicol-treated cold-shocked cells were no different from those of untreated cold-shocked cells, suggesting that cold shock suppresses synthesis of proteins responsible for heat protection. In related experiments, the D values of L. monocytogenes Scott A were decreased 25% on frankfurter skins and 15% in ultra-high temperature milk if the inoculated products were first cold shocked. Induction of increased thermal sensitivity in L. monocytogenes by thermal flux shows potential to become a practical and efficacious preventative control method.
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Affiliation(s)
- A J Miller
- Microbial Food Safety Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, Pennsylvania 19038, USA.
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19
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Tolker-Nielsen T, Larsen MH, Kyed H, Molin S. Effects of stress treatments on the detection of Salmonella typhimurium by in situ hybridization. Int J Food Microbiol 1997; 35:251-8. [PMID: 9105934 DOI: 10.1016/s0168-1605(97)01242-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In order to assess the usefulness of quantitative in situ rRNA hybridization as an indicator of the physiological state of bacteria, we have used this method to measure the cellular contents of 16 S and 23 S rRNA in Salmonella typhimurium subjected to a number of different stress treatments. The contents of rRNA in S. typhimurium decreased when the bacteria were subjected to carbon starvation, heat stress, and osmotic stress prior to the hybridization, whereas no decrease in the intracellular contents of rRNA was observed when the bacteria were subjected to cold stress, acetic acid or ethanol treatment prior to the hybridization. We must conclude, that the content of 16 S rRNA and 23 S rRNA cannot be used as the sole indicator of the physiological state or viability of food borne pathogens. Viable as well as non-viable food borne bacteria will be detected when methods based on detection of rRNA are used.
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MESH Headings
- Acetic Acid/pharmacology
- Animals
- Carbon/analysis
- Cold Temperature
- Ethanol/pharmacology
- Hot Temperature
- Image Processing, Computer-Assisted
- In Situ Hybridization/methods
- Oxidative Stress
- RNA, Bacterial/analysis
- RNA, Bacterial/genetics
- RNA, Ribosomal, 16S/analysis
- RNA, Ribosomal, 16S/genetics
- RNA, Ribosomal, 23S/analysis
- RNA, Ribosomal, 23S/genetics
- RNA, Transfer/analysis
- RNA, Transfer/genetics
- Salmonella typhimurium/drug effects
- Salmonella typhimurium/genetics
- Salmonella typhimurium/isolation & purification
- Salmonella typhimurium/physiology
- Sodium Chloride/pharmacology
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Affiliation(s)
- T Tolker-Nielsen
- Department of Microbiology, Technical University of Denmark, Copenhagen, Denmark
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20
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Application of differential scanning calorimetry in food research and food quality assurance. ACTA ACUST UNITED AC 1996. [DOI: 10.1007/bf01980925] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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21
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Tolker-Nielsen T, Molin S. Role of ribosome degradation in the death of heat-stressed Salmonella typhimurium. FEMS Microbiol Lett 1996; 142:155-60. [PMID: 8810498 DOI: 10.1111/j.1574-6968.1996.tb08423.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Heat treatment of Salmonella typhimurium results in cell death, which coincides with a significant reduction of the cellular content of 16S ribosomal RNA. It is suggested that the degradation of ribosomal RNA is a direct cause of cell death. This conclusion is based on the observation of carbon-starved and magnesium-supplemented cells, which survive heat treatment much better, and which also maintain stable levels of ribosomal RNA.
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Affiliation(s)
- T Tolker-Nielsen
- Department of Microbiology, University of Denmark, Lyngby, Copenhagen, Denmark
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22
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Earnshaw RG, Appleyard J, Hurst RM. Understanding physical inactivation processes: combined preservation opportunities using heat, ultrasound and pressure. Int J Food Microbiol 1995; 28:197-219. [PMID: 8750667 DOI: 10.1016/0168-1605(95)00057-7] [Citation(s) in RCA: 245] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- R G Earnshaw
- Department of Microbiology, Campden and Chorleywood Food Research Association, Chipping Campden, Gloucestershire, UK
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Mackey BM, Cross D, Park SF. Thermostability of bacterial luciferase expressed in different microbes. THE JOURNAL OF APPLIED BACTERIOLOGY 1994; 77:149-54. [PMID: 7961187 DOI: 10.1111/j.1365-2672.1994.tb03058.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Bacterial luciferase was used to investigate the relationship between the thermostability of a cytoplasmic reporter molecule and cellular heat resistance. The luciferase activity of Vibrio fischeri was expressed in strains of Escherichia coli, Salmonella typhimurium, Listeria monocytogenes and Brochothrix thermosphacta following transformation with plasmid pSP13 carrying the luxAB genes. The thermostability of intracellular luciferase varied depending on the organism in which it was expressed, but was not related to the cellular heat resistance of the different organisms. Addition of xylitol to the heating medium protected against loss of viability and inactivation of intracellular luciferase. Glycerol also protected against loss of viability but was less effective at preventing thermal denaturation of luciferase.
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Affiliation(s)
- B M Mackey
- Institute of Food Research, Reading Laboratory, UK
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Hottiger T, De Virgilio C, Hall MN, Boller T, Wiemken A. The role of trehalose synthesis for the acquisition of thermotolerance in yeast. II. Physiological concentrations of trehalose increase the thermal stability of proteins in vitro. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 219:187-93. [PMID: 8306985 DOI: 10.1111/j.1432-1033.1994.tb19929.x] [Citation(s) in RCA: 199] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In baker's yeast (Saccharomyces cerevisiae), accumulation of the non-reducing disaccharide, trehalose, is triggered by stimuli that activate the heat-shock response. Previously, trehalose levels have been shown to be closely correlated with thermotolerance, suggesting a protective function of this substance. Genetic evidence in support of this view is presented in an accompanying paper [De Virgilio, C., Hottiger, T., Dominguez, J., Boller, T. & Wiemken, A. (1993) Eur. J. Biochem. 219, 179-186]. In this study, we have examined the effect of trehalose on the thermal stability of proteins, a parameter thought to be a major determinant of thermotolerance. Physiological concentrations of trehalose (up to 0.5 M) were found to efficiently protect enzymes of yeast (glucose-6P-dehydrogenase, phosphoglucose-isomerase) as well as enzymes of non-yeast origin (bovine glutamic dehydrogenase, EcoRI) against heat inactivation in vitro. Trehalose also reduced the heat-induced formation of protein aggregates. The disaccharide proved to be a compatible solute, as even at very high concentrations (up to 1 M) it did not significantly interfere with the activity of test enzymes. Trehalose was at least as good or better a protein stabilizer than any of a number of other compatible solutes (including sugars, polyalcohols and amino acids), while the structurally related trehalose-6P was devoid of any protective effect. Thermoprotection of enzymes by trehalose was evident even in solutions containing high concentrations of yeast protein or substrate. The data indicate that trehalose accumulation may increase the thermotolerance of yeast by enhancing protein stability in intact cells.
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Affiliation(s)
- T Hottiger
- Botanisches Institut, Universität Basel, Switzerland
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Piper PW. Molecular events associated with acquisition of heat tolerance by the yeast Saccharomyces cerevisiae. FEMS Microbiol Rev 1993; 11:339-55. [PMID: 8398211 DOI: 10.1111/j.1574-6976.1993.tb00005.x] [Citation(s) in RCA: 168] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The heat shock response is an inducible protective system of all living cells. It simultaneously induces both heat shock proteins and an increased capacity for the cell to withstand potentially lethal temperatures (an increased thermotolerance). This has lead to the suspicion that these two phenomena must be inexorably linked. However, analysis of heat shock protein function in Saccharomyces cerevisiae by molecular genetic techniques has revealed only a minority of the heat shock proteins of this organism having appreciable influences on thermotolerance. Instead, physiological perturbations and the accumulation of trehalose with heat stress may be more important in the development of thermotolerance during a preconditioning heat shock. Vegetative S. cerevisiae also acquires thermotolerance through osmotic dehydration, through treatment with certain chemical agents and when, due to nutrient limitation, it arrests growth in the G1 phase of the cell cycle. There is evidence for the activities of the cAMP-dependent protein kinase and plasma membrane ATPase being very important in thermotolerance determination. Also, intracellular water activity and trehalose probably exert a strong influence over thermotolerance through their effects on stabilisation of membranes and intracellular assemblies. Future investigations should address the unresolved issue of whether the different routes to thermotolerance induction cause a common change to the physical state of the intracellular environment, a change that may result in an increased stabilisation of cellular structures through more stable hydrogen bonding and hydrophobic interactions.
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Affiliation(s)
- P W Piper
- Department of Biochemistry and Molecular Biology, University College London, UK
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