The relationship between the adsorption behavior of an anionic surfactant, sodium 1-octanesulfonate, onto a synthetic lipid membrane and its bactericidal activity against Escherichia coli ATCC 25922 in the presence of various cations was studied. The amounts of the sulfonate/cation mixtures adsorbed were estimated by observing frequency changes of a membrane-coated quartz-crystal microbalance. Among all cations tested, trivalent cations most effectively promoted the adsorption of the surfactant onto the membrane. Divalent cations were also effective, but substantially less so than trivalent cations. The adsorption behavior of the surfactant/cation mixtures onto the membrane was closely related to the bactericidal activity of their mixtures against E. coli.

View full abstract

Counts of coliform bacteria in sewage sludge cakes which ranged from 1×10⁵ to2×10⁵ CFU per g were diminished rapidly with radiation treatments, and completely inactivated at 4 kGy of irradiation. The number of salmonellae in sewage sludge cakes and dried sludge or hospital were determined to be from 13 to 1.4×10⁴MPN (most probable number) per 100 g, and 44 serotypes were identified. D₁₀ values of these isolates in phosphate buffer were determined to be 0.10 to 0.23 kGy, and the necessary dose for inactivation of salmonellae in sewage sludge cakes was estimated to be 4 kGy. As antagonistic bacteria, Bacillus subtilis, B. polymyxa and other Bacillus species isolated from soils or compost seeding were effective in suppressing the growth of phytopathogenic fungi. Among these bacteria, B. subtilis had the strongest suppressive effect on phytopathogenic fungi. The growth of B. subtilis occurred rapidly during 24h cultivation in radiation-disinfected sludge. When the cultivation processwas observed in terms of CO₂, evolution, the peak value was obtained after 23h incubation and fermentation was completed in a short period.

View full abstract

The bactericidal activities of different types of quaternary ammonium compounds (QAC) were measured in distilled water at 0, 20 or 25°C for concentrations between 0.001% (w/v) and 25% (w/v). Four different gram-negative bacteria were used as test organisms. In a qualitative suspension test, the existence of a concentration for maximum activity was demonstrated, depending on the temperature, and the type of QAC used and the organism tested. In a quantitative test, Pseudomonas aeruginosa and Alcaligenes xylosoxidans 9 isolated from a benzalkonium chloride concentrate, were used as test organisms with different resistances to QACs. Thebactericidal activities of QACs showed a parabolic curve when plotted against concentration. In the case of dodecyl-, tetradecyl- and hexadecyltrimethylammoniumbromide, the optimal concentration for the bactericidal activity of the homologous salts shifted toward lower concentrations as the vicinity of critical micelleconcentration.

View full abstract

In a flowing medium, more than 80% of the hyphae of filamentous fungi tended to grow against the flow. We call this phenomenon upstream-directed growth. Five strains of Aspergillus spp. showed this upstream-directed growth, but Rhizopus stolonifer and two strains of Penicillium spp. did not. In the flow rate range of 1-11ml/h (200-2200μm/s), no appreciable difference was observed in the manner of growth. In response to an alteration in the direction of flow, the growth direction of the hyphae altered accordingly, which suggested that fungi were sensing the flow direction all the time. It was also suggested that such a phenomenon was controlled by physical rather than by a chemical factors.

View full abstract

Differences in the thermal inactivation kinetics of a microbial enzyme in vitro and that in vivo were studied. Escherichia coli &-galactosidase was chosen as amodel. Inactivation patterns of the enzyme in vitro prepared in cell lysate at various constant temperatures were curvilinear with upward concaves in a semilogarithmic plot of the residual activity vs. time, deviating from first-order kinetics. These patterns in vitro were similar to the pattern of a purified enzyme in phosphate buffer. In contrast, thermal inactivation patterns of the enzyme in vivo at various constant temperatures were thoroughly straight lines, showing that the inactivation followed first-order kinetics. The enzyme in vivo was more thermostable than the one in vitro. Thermodynamic analysis revealed that the thermal inactivation of the enzyme in vivo was more sensitive to the temperatures thanthat of the cell.

View full abstract

Novel HNPP/Fast Red TR in situ hybridization method was used to study the response of river water microbial communities to aniline, as a model chemical pollutant, in two biodegradation test systems: a river die-away (TOC-HANDAI) test and acultivation (HANDAI) test. Pseudomonas rRNA group I and Acinetobacter were the most abundant groups during peak biodegradation activity in both test systems in spite of the differences in test conditions and initial community structures. Burkholderia-Pseudomonas rRNA III-authentic Alcaligenes group were significant only in the cultivation test under highly polluted conditions. Vibrio-Aeromonas and Flavobacterium-Cytophaga groups were adversely affected by aniline in both test systems.

View full abstract

The microbial contamination levels of fifteen crude drugs “Glycyrrhiza”, which had been harvested in and imported from China and Russia, and their radiation sensitivities were investigated. Specified indicator microorganisms such as Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were not detected, and the number of bacteria and fungi adhering to those drugs were in the range 10 ³-10 ⁵cells/g and 10²-10⁵ spores/g, respectively. Those contamination levels were higher than values of the microbial limits of natural raw materials givenin The United States Pharmacopoeial Forum (1992). The average of D₁₀ value as radiation sensitivity of bacteria and fungi to gamma rays were 2.2 and 0.98kGy, respectively. From these values, the survival doses (SD) required to attain the definitive microbial limits (bacteria, <20 CFU/g or ml; fungi, <10 CFU/g or ml) were calculated to be 7.5 kGy and 2.7 kGy. These SD values are sufficiently lower than the dose of 10 kGy allowed for food irradiation. On the other hand, the quality of Glycyrrhiza powder irradiated up to 30 kGy passed the “Crude Drugs Test”prescribed in The Japanese Pharmacopoeia Thirteenth Edition.

View full abstract

Five bacterial strains were isolated from food samples, and were not easily distinguished from Salmonella via conventional methods. These bacterial strains wereidentified as Citrobacter spp. from their biochemical properties. Despite this, their characteristics after being cultured resembled those of Salmonella, with similar kinds of colony formation patterns on XLD, DHL and TSI agar. Since these salmonella-like strains grew at a rate and produced colonies with black centers characteristic of Salmonella, the selective detection of Salmonella in the presence of these salmonella-like strains was impossible, based on conventional methods.

View full abstract

The kinetics of the inactivation of Bacillus subtilis spores by ozone alone and ozone with UV irradiation were investigated in a circulation system of a 5.3l ofsaline suspension (10⁶ spores/ml) under various conditions of ozone concentration (3.0 and 7.0 mg/l in inlet gas) and UV intensity (3, 413 and 13, 650 μw/cm²).The spore inactivation by ozone with UV irradiation was more effective than by ozone alone in the presence of organic compounds such as tryptophan and ribose. The combination treatment of ozone and UV is considered to be a useful disinfection method for practical use.

View full abstract

In our study, we attempted to confirm a paradoxical effect of chlorhexidine digluconate (CHG). Two test procedures, the phenol coefficient (PC) method based on AOAC and its modified method were used. The cell concentration of test strains, Pseudomonas aeruginosa NCTC 7244, P. aeruginosa IFO 3445 and some clinically isolated strains were prepared at 10⁴-10⁹ cells/ml. According to the PC method based on AOAC, 1/800-1/1200 was the greatest dilution rate at which 5% (w/v) CHG was able to kill 10⁹ cells/ml of P. aeruginosa by contact in 10 min, and 1/10000-1/12000 was the greatest dilution rate in case of 10⁴ cells/ml. Increasing concentrations of CHG to kill P. aeruginosa were required as the viable counts of the organism increased. By the modified PC method, when undiluted 5% (w/v) CHG was added to the 10⁷ cells/ml bacterial suspension, the organisms were killed in 4 or 5 min, and those in the 10⁴ cells/ml suspension were killed within 30s. Therefore, we could not confirm the paradoxical effect of slime production by P. aeruginosa as a phenomenon due to the bactericidal activity of CHG.

View full abstract