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, 49 (5), 1770-4

Biphasic Effects of Geranylgeraniol, Teprenone, and Phytol on the Growth of Staphylococcus Aureus

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Biphasic Effects of Geranylgeraniol, Teprenone, and Phytol on the Growth of Staphylococcus Aureus

Yoshihiro Inoue et al. Antimicrob Agents Chemother.

Abstract

We examined the antibacterial activities against Staphylococcus aureus of three diterpenes, namely, geranylgeraniol, teprenone, and phytol, by using a broth dilution with shaking method to identify the effects of diterpenes with long aliphatic carbon chains. We also performed time-kill assays and measured the leakage of K(+) ions from bacterial cells in response to these diterpenes. The diterpenes used inhibited the growth of S. aureus at concentrations of 0.15 microg/ml, as determined by damage to the cell membranes, and had clear bactericidal activity. However, the inhibitory effects of the diterpenes decreased when the concentration of each was raised above a certain level. The diterpenes tested in this study appeared to have both growth-inhibitory and growth-accelerating effects, and the net effect of each depended on its concentration.

Figures

FIG. 1.
FIG. 1.
Structures of diterpenes used in the present study: geranylgeraniol (a), teprenone (b), and phytol (c).
FIG. 2.
FIG. 2.
Inhibitory effects of geranylgeraniol on the growth of S. aureus FDA209P. S. aureus FDA209P was inoculated into BHI broth medium that contained no geranylgeraniol (○) or into broth that contained geranylgeraniol at 0.15 (•), 0.3 (▴), 0.6 (▪), or 1.25 (♦) μg/ml (a) or 1.25 (♦), 2.5 (▵), 5.0 (□), 10 (⋄), 20 (•), 40 (▴), 80 (▪), or 160 (▾) μg/ml (b), and then cell growth was monitored in terms of the OD660.
FIG. 3.
FIG. 3.
Effects of diterpenes on the growth of S. aureus FDA209P. Each delay in proliferation was calculated from the growth curve of a control culture and that of a culture that contained the indicated diterpene at the indicated concentration. Symbols: •, geranylgeraniol; ▴, teprenone; and ▪, phytol.
FIG. 4.
FIG. 4.
Changes in the viable cell count of S. aureus FDA209P in medium that contained the diterpenes geranylgeraniol (a), teprenone (b), and phytol (c). S. aureus FDA209P was inoculated into BHI medium that contained no terpene (○) or that contained a diterpene at 2.5 (□), 5 (▵), 10 (♦), 20 (▪), 40 (▴), or 80 (•) μg/ml.
FIG. 5.
FIG. 5.
Time-kill assays of the effect of geranylgeraniol (a), teprenone (b), and phytol (c) on S. aureus FDA209P. S. aureus FDA209P was suspended in PBS that contained no terpenes (○) or in PBS that contained a diterpene at 10 (♦), 20 (▪), 40 (▴), or 80 (•) μg/ml.
FIG. 6.
FIG. 6.
Changes in the concentration of K+ ions in suspensions of S. aureus FDA209P in response to 80 μg/ml concentrations of geranylgeraniol (a), teprenone (b), and phytol (c).
FIG. 7.
FIG. 7.
Leakage of K+ ions from S. aureus FDA209P in response to geranylgeraniol, teprenone, and phytol. Panel a shows the initial rates of leakage of K+ ions, and panel b shows the total amounts of K+ ions leaked from bacteria. Symbols: •, geranylgeraniol; ▴, teprenone; and ▪, phytol.

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