ABSTRACT
AIMS: The aim of this study was to evaluate the effect of gamma-irradiation on the fatty acids (FA) and muropeptides content of two strains of an Enterobacteriacea: Pantoea agglomerans. METHODS AND RESULTS: Pantoea agglomerans strains ATCC 49174 and RL1 isolated from irradiated carrots were used for this study. Radiation treatments (1 and 3.5 kGy) were performed to study the radiotolerance. Total lipids were obtained by multiple extractions using methanol/chloroform (2 : 1) and were quantified by GC. Muropeptides were purified by successive enzymatic digestions and analysed using a reverse phase C(18) column in high performance liquid chromatography. A significant (P Subject(s)
Cell Wall/radiation effects
, Food Irradiation/methods
, Gamma Rays
, Pantoea/radiation effects
, Peptidoglycan/radiation effects
, Cell Wall/chemistry
, Chromatography, High Pressure Liquid
, Daucus carota/microbiology
, Fatty Acids/analysis
, Fatty Acids/radiation effects
, Peptidoglycan/analysis
ABSTRACT
AIMS: The effects of gamma radiation on three heat shock proteins (Hsps) (GroEL, DnaK and GroES) synthesis in two Gram-negative (Escherichia coli and Salmonella serotype Typhimurium) and two Gram-positive (Staphylococcus aureus and Listeria monocytogenes) bacteria were investigated. METHODS AND RESULTS: The bacterial strains were treated with three radiation doses to induce cell damage, to obtain a viable but nonculturable state, and to cause cell death. Western blot analysis and quantification of Hsps in bacteria were performed immediately after irradiation treatment. In the four foodborne pathogens, GroEL was strongly induced by gamma rays in a dose-dependent manner, confirming the involvement of this protein in the cellular response to the stress generated by ionizing radiation. In addition, it was found that E. coli exposed to gamma radiation showed a significantly induction of DnaK and GroES proteins when compared with nonirradiated bacteria, whereas a GroES slight induction and a DnaK inhibition were observed in Salm. Typhimurium. CONCLUSIONS: The gamma rays influence the synthesis of Hsps in foodborne pathogen in a way that critically depends on the radiation dose. SIGNIFICANCE AND IMPACT OF THE STUDY: The study of stress response to several radiation doses was undertaken to elucidate how bacteria can survive in harsh conditions and cope with gamma radiation used to control foodborne pathogens and to characterize their adaptative response to this treatment.
Subject(s)
Escherichia coli Proteins/metabolism , Escherichia coli Proteins/radiation effects , Escherichia coli/metabolism , Escherichia coli/radiation effects , Gamma Rays , Heat-Shock Proteins/metabolism , Listeria monocytogenes/metabolism , Listeria monocytogenes/radiation effects , Salmonella typhimurium/metabolism , Salmonella typhimurium/radiation effects , Staphylococcus aureus/metabolism , Staphylococcus aureus/radiation effects , Blotting, Western , Chaperonin 10/metabolism , Chaperonin 10/radiation effects , Chaperonin 60/metabolism , Chaperonin 60/radiation effects , Electrophoresis, Polyacrylamide GelABSTRACT
AIM: The aim of this study was to evaluate the effect of gamma radiation on the carotenoid content of two strains of the Enterobacteriaceae: Pantoea agglomerans. METHODS AND RESULTS: Pantoea agglomerans strains ATCC 49174 and RL1 were used for this study. Successive radiation treatments were performed to study the radiotolerance. Total carotenoids were obtained by multiple extraction using chloroform/methanol (2 : 1), quantified by measuring the optical density at 453 nm and their antioxidant activity measured by a colorimetric method. The D(10) studies were conducted using a UC-15A irradiator loaded with 60Co. Bacterial counts from various dilutions were carried out after irradiation. Strain ATCC 49174 irradiated at 1 kGy produced 4.3 times more carotenoids than the control, whereas carotenoid synthesis increased by 2.9-fold in the strain RL1. However, there was no significant difference in the D(10) values. CONCLUSION: Carotenoid increased production is influenced by gamma radiation but does not modify the tolerance to radiations. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first study to demonstrate the effects of gamma radiation on carotenoid production levels.
