Hajime Hamashima

Bactericidal activity of Ag–zeolite mediated by reactive oxygen species under aerated conditions

The bactericidal activity induced by the introduction of silver ions into zeolite was studied. Escherichia coli was used as the test microorganism. Silver ions were loaded into zeolite by the ion-exchange method. Silver-loaded zeolite was demonstrated the strong bactericidal activity. Dissolved oxygen was an essential factor for the occurrence of the bactericidal activity because the activity was observed only under aerated condition. Superoxide anions, hydrogen peroxide, hydroxyl radicals and singlet oxygen were formed. Scavengers of these each reactive oxygen species (ROS) inhibited the bactericidal activity. This means that all ROS contributed to the activity.

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.

Effects of Two Terpene Alcohols on the Antibacterial Activity and the Mode of Action of Farnesol against Staphylococcus aureus

We have studied changes in the antibacterial activity and the mode of action of farnesol against Staphylococcus aureus when two terpene alcohols with an aliphatic carbon chain were added, individually, to a bacterial suspension that contained farnesol. Geraniol increased the growth-inhibitory activity of farnesol, but suppressed its ability to damage cell membranes, which is one of the predominant features of the growth-inhibitory activity of farnesol. Geranylgeraniol decreased the growth-inhibitory activity of farnesol and also suppressed its cell-damaging activity. It is possible that the presence of a terpene alcohol can both enhance and suppress the antibacterial activity of farnesol, and even change its mode of action. Thus, it is important to study not only the antibacterial activity of each constituent of an essential oil but also the interactions between them in efforts to characterize the antibacterial activity of the essential oil.

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.

Genetic Transformation of Vibrio parahaemolyticus, Vibrio alginolyticus , and Vibrio cholerae Non O-1 with Plasmid DNA by Electroporation

An electroporation procedure for the plasmid‐mediated transformation of the genus Vibrio was performed, as part of an effort to develop recombinant DNA techniques for genetic manipulation of the genus Vibrio. Vibrio parahaemolyticus, V. alginolyticus, and V. cholerae non O‐1 (9 different strains) were transformed with 3 vector plasmids (pACYC184, pHSG398, and pBR325). The efficiency of transformation was highly dependent on three parameters: the concentration of plasmid DNA; the strength of the electric field; and the combination of plasmid DNA and recipient strain. The drug‐resistance genes on the vector plasmid were expressed in the Vibrio strains.

Effect of farnesol on mevalonate pathway of Staphylococcus aureus.

To investigate the mechanism of action by which farnesol functions as an antibacterial agent and inhibits Staphylococcus aureus growth, the growth rates of S. aureus cultured in farnesol versus S. aureus cultured in farnesol and supplemented with 3-hydroxy-3-methylglutaryl (HMG)-CoA or mevalonate were compared. The investigation was designed to observe whether farnesol affected on the mevalonate pathway by using the intermediate metabolites of the pathway. The resulting growth curves demonstrated that mevalonate reduced the antibacterial activity of farnesol, but HMG-CoA did not inhibit farnesol. These results suggest that farnesol affects the mevalonate pathway. Moreover, farnesol inhibited HMG-CoA reductase activity in an in vitro enzymatic assay.

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.

Mechanisms of Plasmid-Mediated Antibiotic Resistances in Vibrio parahaemolytcus

The mechanisms of drug resistance of clinical isolate, Vibrio (V.) parahaemolyticus ST550, resistant to chloramphenicol (CP), aminoglycoside antibiotics (AGs) and β‐lactam antibiotics were investigated. The mechanisms of resistance to CP, AGs and β‐lactam antibiotics were dependent on chloramphenicol acetyltransferase (CAT), aminoglycoside‐3″‐adenylyltransferase AAD(3″) and aminoglycosides‐3′‐phosphotransferase APH(3′) and TEM type penicillinase, respectively.

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.