Akiko Shiraishi

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

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 μg/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.

Antibacterial Activity of Long-Chain Fatty Alcohols against Staphylococcus aureus

The antibacterial activity against Staphylococcus aureus of long-chain fatty alcohols was investigated, with a focus on normal alcohols. The antibacterial activity varied with the length of the aliphatic carbon chain and not with the water/octanol partition coefficient. 1-Nonanol, 1-decanol and 1-undecanol had bactericidal activity and membrane-damaging activity. 1-Dodecanol and 1-tridecanol had the highest antibacterial activity among the long-chain fatty alcohols tested, but had no membrane-damaging activity. Consequently, it appears that not only the antibacterial activity but also the mode of action of long-chain fatty alcohols might be determined by the length of the aliphatic carbon chain.

Leakage of K+ ions from Staphylococcus aureus in response to tea tree oil

The leakage of K(+) ions from Staphylococcus aureus in response to tea tree oil (TTO) was investigated with an ion-selective electrode. The amount of leaked K(+) ions and the rate of leakage of K(+) ions induced by TTO were dependent on the concentration of TTO. Measurements of initial rates required less time than measurements of total amounts and provided an index of the interaction between TTO and the cell membrane. Thus, the initial rate of leakage might be a more useful measure of the antibacterial activity of TTO than the total amount.

Antibacterial Activities Against Staphylococcus aureus of Terpene Alcohols With Aliphatic Carbon Chains

Abstract The antibacterial activities against Staphylococcus aureus of terpene alcohols with aliphatic carbon chains of various lengths were investigated. Farnesol and nerolidol, which each contain two isoprene units, had the strongest antibacterial activities and damaging effects on cell membranes of all the terpene alcohols tested. Plaunotol, which is a diterpene, had antibacterial activity similar to that of sesquiterpenes. The relationship between the length of the carbon chain bonded to the hydroxyl group and activity suggests that the length of the carbon chain is an important determinant of antibacterial activity and cell membrane-damaging activity. It was concluded that the carbon chain length of C10-C12 was appropriate to show the activity.

Purification and characterization of 3,3-dihydroxyazetidine from culture medium of Bacillus mesentericus and B. subtilis

A method is described for the purification of 3,3-dihydroxyazetidine (DHA), which accelerates the growth of Bifidobacterium spp., from the culture medium of Bacillus mesentericus (BM). Purification involved adsorption to an ion-exchange resin; it required less time and gave a higher yield than a previously reported method. Monitoring the inhibition of E. coli NIHJ JC-2, we searched for other strains that produced 3,3-dihydroxyazetidine. We found that not only B. mesentericus TO-A but also B. subtilis IFO13719 produced the compound of interest.