The antifungal compound 2, 4-diacetylphloroglucinol-producing bacterium, Pseudomonas fluorescens strain LRB3W1, inhibits the growth of Fusarium oxysporum f. sp. lycopersici, and controls Fusarium wilt of tomato caused by F. oxysporum f. sp. lycopersici. On the other hand, Serratia marcescens strain B2, which produces cell wall-degrading enzyme chitinases, did not inhibit fungal growth and the suppressive effect of strain B2 against tomato Fusarium wilt was less than that of strain LRB3W1. Combined inoculation of strain LRB3W1 with strain B2 was more effective than treatment with strain LRB3W1 alone. When 2, 4-diacetylphloroglucinol and the chitinolytic enzymes were applied in combination, a synergistic inhibitory effect against the pathogen was observed. It was possible that bacteria which produce cell wall-degrading enzymes enhanced the biocontrol effect of the antibiotic-producing bacterium against tomato Fusarium wilt.
Two resveratrol trimers, gnemonol B isolated from Gnetum gnemon and gnetin E obtained from the Gnetum species, were found to exhibit strong antibacterial activities against vancomycin-resistant Enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). The MIC values of gnemonol B against five strains of VRE and nine strains of MRSA were 12.5 and 6.25 μg/ml, respectively. The MIC values of gnetin E against five strains of VRE and nine strains of MRSA ranged from 12.5 to 25 μg/ml. These compounds also showed synergistic effects when used in combination with commercially available antibiotics according to the evaluation method using FIC indices. These findings suggested that the application of the test compounds alone or in combination with antibiotics might be useful in controlling and treating VRE and MRSA infections
Particles of ZnO coated with carbon (ZnOCC) were prepared and evaluated for their antibacterial activity. ZnO powder and poly (vinyl alcohol) (PVA) (polymerization degree: 2, 000- 95, 000) were mixed at a mass ratio (ZnO/PVA) of 1, and then heated at 500-650°C for 3 h under argon gas with a flow rate of 50ml/min. Carbon deposited on the ZnOCC surfaCe was amorphous as revealed by X-ray diffraction studies. The ZnOCC particles maintained their shape in water, even under agitation. The antibacterial activity of ZnOCC powder against Staphylococcus aureus was evaluated quantitatively by measuring the change in the electrical conductivity of the growth medium caused by bacterial metabolism (conductimetric assay). The conductivity curves obtained were analyzed using the growth inhibition kinetic model proposed by Takahashi for calorimetric evaluation, allowing the estimation of the antibacterial efficacy and kinetic parameters of ZnOCC. In a previous study, when ZnO was immobilized on materials, such as activated carbon, the amount of ZnO immobilized was approximately 10-50%, and the antibacterial activity markedly decreased compared to that of the original ZnO. On the other hand, the ZnOCC particles prepared in this study contained approximately 95% ZnO and possessed antibacterial activity similar to that of pure ZnO. The carbon-coating treatment could maintain the antibacterial efficacy of the ZnO and may be useful in the development of multifunctional antimicrobial materials.
We investigated characteristics of the corrosion of stainless steel specimens by bacteria and the effects of using antimicrobial coating on the surface for inhibiting corrosion. Bacillus sp. 2-A and Staphylococcus sp. 2-I cells adhered tightly to a stainless steel SUS304 specimen, formed a microcolony or biofilm, and had highly corrosive activities. Microbially influenced corrosion (MC) was observed under or around adhering cells. However, dead cells were markedly less active than viable cells not only in corroding the specimen but also in adhering to its surface. The culture supernatant was not able to induce the corrosion of SUS304 effectively. A protamine coating on the specimen killed bacterial cells only on its surface, interfered with cell adhesion, and inhibited MC. From these results, adhesion of viable cells to the surface of a SUS304 specimen led to the outbreak of MC. Protamine was also found to be an effective substance tested for protecting the specimen from both cell adhesion and surface MC. We suggest that a protamine coating can be applied as a convenient and inexpensive corrosion prevention method.
Viable microbial cells distributed in a 130 μm thick surface layer of cotton fabrics were stained with a fluorescent glucose, 2- [N-(7-nitrobenz-2-oxa-1, 3-diazol-4-y1) amino] -2-deoxy-Dglucose (2-NBDG), and automatically mapped with an ultra-deep focusing range microscope (UDF) system. The software of the UDF system was upgraded and the number of Candida albicans cells could be counted at a higher precision than before. Bacterial cells of Pseudomonas fluorescens, Serratia marcescens, and Citrobacter freundll, which were smaller than 1-2μm, were successfully mapped for the first time. These results indicate the practical importance of the present method in the evaluation of the antibacterial properties of fabrics and the efficacy of washing.
Following the former version of the database on the thermal death of microorganisms, ThermoKill Database R9100, we constructed an expanded version, ThermoKill Database R8100. This database includes the thermal death data together with as many as 70 items of experimental conditions described in research papers which appeared in 23 academic journals published worldwide from 1981 to 2000. The novel version contains 7, 454 records as data sets, 12, 261 D values, and 2, 038 z values. Some statistical data based on the data input in the database are presented. The significance of this novel database in practical use is then discussed.