AFM study of the differential inhibitory effects of the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) against Gram-positive and Gram-negative bacteria.
Food Microbiol
; 29(1): 80-7, 2012 Feb.
Article
en En
| MEDLINE
| ID: mdl-22029921
ABSTRACT
(-)-Epigallocatechin-3-gallate (EGCG), a main constituent of tea catechins, affects Gram-positive and Gram-negative bacteria differently; however, the underlying mechanisms are not clearly understood. Atomic force microscopy (AFM) was used to compare morphological alterations in Gram-positive and Gram-negative bacteria induced by EGCG and by H(2)O(2) at sub-minimum inhibitory concentrations (MICs). EGCG initially induced aggregates in the cell envelopes of Staphylococcus aureus and eventually caused cell lysis, which was not observed in cells treated with H(2)O(2). It initially induced nanoscale perforations or microscale grooves in the cell envelopes of Escherichia coli O157H7 which eventually disappeared, similar to E. coli cells treated with H(2)O(2). An E. coli O157H7 tpx mutant, with a defect in thioredoxin-dependent thiol peroxidase (Tpx), was more severely damaged by EGCG when compared with its wild type. Similar differing effects were observed in other Gram-positive and Gram-negative bacteria when exposed to EGCG; it caused aggregated in Streptococcus mutans, while it caused grooves in Pseudomonas aeruginosa. AFM results suggest that the major morphological changes of Gram-negative bacterial cell walls induced by EGCG depend on H(2)O(2) release. This is not the case for Gram-positive bacteria. Oxidative stress in Gram-negative bacteria induced by EGCG was confirmed by flow cytometry.
Texto completo:
1
Base de datos:
MEDLINE
Asunto principal:
Staphylococcus aureus
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Extractos Vegetales
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Catequina
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Microscopía de Fuerza Atómica
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Escherichia coli O157
Tipo de estudio:
Evaluation_studies
Idioma:
En
Revista:
Food Microbiol
Asunto de la revista:
CIENCIAS DA NUTRICAO
/
MICROBIOLOGIA
Año:
2012
Tipo del documento:
Article