AFM study of the differential inhibitory effects of the green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) against Gram-positive and Gram-negative bacteria.
(-)-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 O157:H7 which eventually disappeared, similar to E. coli cells treated with H(2)O(2). An E. coli O157:H7 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.
Department of Chemistry and Nano Sciences, Ewha Womans University, Seoul, Republic of Korea.
Y
Y
Cui
Y J
YJ
Oh
J
J
Lim
M
M
Youn
I
I
Lee
H K
HK
Pak
W
W
Park
W
W
Jo
S
S
Park
D028241:Camellia sinensis / Q000737:chemistry; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D019453:Escherichia coli O157 / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D050296:Microbial Viability / Q000187:drug effects; D018625:Microscopy, Atomic Force / Q000379:methods*; D018384:Oxidative Stress / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism
D010936:Plant Extracts; D002392:Catechin; D006861:Hydrogen Peroxide; C045651:epigallocatechin gallate