Naoki Narisawa

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Antibiotic-sensitive bacteria have been found to coexist with antibiotic-producing bacteria in biofilms, but little is known about how the former develop in such an environment. Here we isolated pyocyanin-sensitive bacteria belonging to the genus Brevibacillus from a biofilm derived from soil extract and based on the preestablished biofilm of a pyocyanin(More)
Effect of high pressure gaseous carbon dioxide treatment (HGCT) at 6.5 MPa, 35 degrees C on the germination of bacterial spores was investigated. Germination of bacterial spores was estimated by the decrease of heat tolerance. Approximately, 40% of Bacillus coagulans and 70% of Bacillus licheniformis were germinated by HGCT for 120 min at 35 degrees C,(More)
The oral microbial flora consists of many beneficial species of bacteria that are associated with a healthy condition and control the progression of oral disease. Cooperative interactions between oral streptococci and the pathogens play important roles in the development of dental biofilms in the oral cavity. To determine the roles of oral streptococci in(More)
Effects of the clumping of bacterial spores on their heat resistance as a result of heat treatment were investigated. Spore suspensions of Bacillus cereus, Bacillus coagulans and Bacillus licheniformis were heated at 85 degrees C. Survivor curves of the three strains showed tailing in all treatments after 30 min. As the treatment time increased, the(More)
The formation of spore clumps of Bacillus coagulans and Bacillus licheniformis during high-pressure carbon dioxide treatment (HCT) was investigated. As the treatment time increased, the number of spore clumps increased. After 120 min, single spore decreased to 20-35% of the population. Addition of a surfactant decreased the hydrophobicity of spore surface(More)
The introduction of an exogenous cellulolytic bacterium into a microbial community that was degrading rice straw effectively was evaluated. A stable coexistence of the indigenous and exogenous cellulolytic bacteria was achieved by adjusting the cultivation conditions. The obtained community required several subcultures to reach the highest degradation(More)
We developed a method of estimating the biofilm formation of Escherichia coli K-12 strains in microtiter-plate wells by the cell number. Regression lines between the cell number and absorbance of crystal violet that stained the E. coli biofilm consisted of high and low slope lines, respectively.
Chemical disinfection of oral biofilms often leaves biofilm structures intact. This study aimed to examine whether the residual structure promotes secondary bacterial adhesion. Streptococcus mutans biofilms generated on resin-composite disks in a rotating disc reactor were disinfected completely with 70% isopropyl alcohol, and were again cultured in the(More)
The production of water-insoluble glucan (WIG) enables Streptococcus mutans to survive and persist in the oral niche. WIG is produced from sucrose by glucosyltransferase encoded tandemly by the highly homologous gtfB and gtfC genes. Conversely, a single hybrid gene from the endogenous recombination of gtfB and gtfC is easily generated using RecA, resulting(More)
High osmotic environments produced by NaCl or sucrose have been used as reliable and traditional methods of food preservation. We tested, Escherichia coli as an indicator of food-contaminating bacterium, to determine if it can form biofilm in a hyperosmotic environment. E. coli K-12 IAM1264 did not form biofilm in LB broth that contained 1 M NaCl. However,(More)