A specific DMPO-OH adduct signal(1:2:2:1) related to hydroxyl radical generation in a longterm stored improved iodide formulation, tentatively designated as the distilled KMT reagent which prepared from a pH 0.3 solution containing FeCl3, EDTA, KI and ethanol termed the KMT reagent, was detected by electron spin resonance(ESR)spectroscopy. Although the color intensities of N, N,N,N-tetramethyl- p-phenylenediamine(TMPD)and N,N-diethyl-p-phenylenediamine(DPD) differ, the mixture of the long-term stored distilled KMT reagent and TMPD exhibited a purple color similar to Wurster's blue, and the mixture of the long-term stored distilled KMT reagent and DPD exhibited a pink color similar to Wurster's red. There is a possibility that the long- term stored distilled KMT reagent may possess with the ability to generate a hydroxyl radical.
The genus Fusarium causes a wide range of infections in human, animals and herbs. The purpose of this research was to investigate and identify the native strains of Bacillus subtilis playing an inhibitory role against Fusarium oxysporum by producing surfactin. B. subtilis was isolated from the soil of various parks in Tehran-Iran, and identified by biochemical tests. Growth inhibition zone, minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of B. subtilis were determined. After purification of surfactin, quantitative and qualitative analysis of surfactin conducted using high performance liquid chromatography (HPLC) . Finally, two selected native strains with the highest production rate of surfactin identified using PCR for 16S rRNA and phylogenetic tree was drawn. Sixty strains of B. subtilis were isolated from soil, after identification through phenotypical and biochemical tests, the antagonistic activity of 27 different strains against F. oxysporum by Agar well diffusion assay determined and the highest inhibition zone was 13.66 mm. Six strains showing the best inhibitory effect, were isolated and their metabolite were purified by methanol. MIC and MFC values of different strains were in the range of 0.5-1.6 and 1.6-2.6 mg/mL. Using HPLC, the purified surfactin content in B. subtilis was about 56.7 - 131.9 μg/mL. Based on the curves of the chromatogram, the preferred strains with the highest production of surfactin, by molecular identification, displayed high similarity to B. subtilis. We got a maximum amount of yellow and transparent surfactin from native strains. Furthermore, the selected bacteria can be good candidates for biological control of fungal pathogens.
Bacillus cereus is an important foodborne pathogenic bacterium. Although several B. cereus strains have been isolated from the environment, the differences among these strains with respect to spore formation ability and cell morphology need clarification. In this study, a phylogenetic tree was constructed based on the 16S rRNA gene sequences of nine strains of B. cereus. Spore formation and morphology of these nine strains were compared using both phase-contrast and fluorescence microscopy to create an index of the designated sporulation stages. Additionally, to investigate the efficiency of heat-resistant spore formation. Phylogenetic analysis revealed that five strains(ATCC 14579(T), NBRC 3457, NBRC 3514, NBRC 3836, and NBRC 13597)clustered together and the remaining four(ATCC 10987, NBRC 3003, NBRC 13494, and NBRC 13690)were genetically distinct from each other. Phase-contrast microscopy revealed significant differences in the sporulation stages among the nine strains. Furthermore, the efficiency of heat-resistant spore formation also differed, even among genetically related strains. In conclusion, a variety of cell morphologies during sporulation were observed among the nine B. cereus strains. We propose a designation of sporulation stages in B. cereus ATCC 14579T, which may be used as an index for evaluating the sporulation progress of B. cereus.
Ultrafine bubbles (UFBs) are gaining attention in diverse industries as a new type of material with specific physical properties. Bactericidal activity has been reported as one of the unique properties of UFB water; however, the bactericidal activities of UFBs related to the gas type remain unclear. In particular, the bactericidal effect of hydrogen (H2) -filled UFB water has not been verified. Therefore, this study aimed to evaluate the bactericidal effects of H2- or ozone (O3) -filled UFB water using a bacterial suspension test. The results of this study clearly showed that H2- or O3-filled UFB water had strong bactericidal activity. Exposure of Escherichia coli for 6 h and Staphylococcus aureus for 3 h reduced the survival rate of those bacteria by >90%. This finding suggests that both O3 gas- and H2-filled UFBs are novel environmentally friendly disinfectants that can be employed to avoid the use of chemicals.
The remote bactericidal effect of TiO2 photocatalyst, i.e., the bactericidal effect away from the photocatalyst, was successfully achieved using a humidified airflow. The TiO2 photocatalyst used was anatase-type TiO2 nanoparticles (NPs) annealed with a low-temperature O2 plasma. For comparison, anatase-type TiO2 NPs annealed in the air were used. The bacteria, Bacillus subtilis, were placed away from the TiO2 NPs. The plasma-assisted-annealed TiO2 NPs significantly inactivated 99% of the bacterial cells in 5 h, whereas the pristine and air-annealed TiO2 NPs inactivated 88-90% of the bacterial cells. The remote bactericidal effect of plasmaassisted-annealed TiO2 NPs would be attributed to a larger amount of H2O2 molecules traveled by the airflow from the TiO2 NPs. The molecules were generated by chemically reacting more photoexcited carriers on the TiO2 surface with H2O and O2 in the airflow. These photoexcited carriers originated from more oxygen-based species adsorbed and more oxygen vacancies introduced on the TiO2 surface by the plasma-assisted-annealing.
