Differential Actions of Chlorhexidine on the Cell Wall of Bacillus subtilis and Escherichia coli

Chlorhexidine is a chlorinated phenolic disinfectant used commonly in mouthwash for its action against bacteria. However, a comparative study of the action of chlorhexidine on the cell morphology of Gram-positive and Gram-negative bacteria is lacking. In this study, the actions of chlorhexidine on the cell morphology were identified with the aids of electron microscopy. After exposure to chlorhexidine, numerous spots of indentation on the cell wall were found in both Bacillus subtilis and Escherichia coli. The number of indentation spots increased with time of incubation and increasing chlorhexidine concentration. Interestingly, the dented spots found in B. subtilis appeared mainly at the hemispherical caps of the cells, while in E. coli the dented spots were found all over the cells. After being exposed to chlorhexidine for a prolonged period, leakage of cellular contents and subsequent ghost cells were observed, especially from B subtilis. By using 2-D gel/MS-MS analysis, five proteins related to purine nucleoside interconversion and metabolism were preferentially induced in the cell wall of E. coli, while three proteins related to stress response and four others in amino acid biosynthesis were up-regulated in the cell wall materials of B. subtilis. The localized morphological damages together with the biochemical and protein analysis of the chlorhexidine-treated cells suggest that chlorhexidine may act on the differentially distributed lipids in the cell membranes/wall of B. subtilis and E. coli

An Improvement of Magnetic Flux Linkage in Electrical Generator using the novel Permanent Magnet Arrangement

The partitioned stator permanent magnet generator (PS-PMG) has been extensively used as electrical generator due mainly to their high flux linkage, high electromotive force EMF) and high efficiency, especially the PM arrangement of the PS-PMG is an important factor to improve the performance of the generator. Therefore, we propose the novel permanent magnet PM) arrangement of the PS-PMG by using the dual rotor with coaxial core structure in order to improve the flux linkage and the EMF of PS-PMG. The PM position of stators of the conventional PS-PMG was rearranged, then the electrical characteristic of the proposed structure was characterized through the simulations based on finite element method. It was found that the flux linkage produced by the proposed structure is 37.06% higher than that of the conventional PS-PMG existed in the literatures because the area for induced flux linkage is significantly increased. This flux linkage enhancement further causes an increment of EMF about 34.95% compared to that of the conventional PS-PMG under the same condition. Especially, the EMF produced by the proposed structure is classified in the high-value range regarding the PM generator. Then, the PS-PMG using novel permanent magnet arrangement could be another remarkable choice for the electrical generator applicatio

The potential of jackfruit starch for use as suspending agent and emulsifying agent

Due to the physicochemical properties of jackfruit (JK) seed starch, it is interesting to use jackfruit mucilage for cosmetic application. The aim of this study was to investigate the physical properties and the effectiveness of JK mucilage at the range of 1 to 5% w/v for using as suspending agent and emulsifying agent. It was found that the pH of 3% w/v JK mucilage was 4.63±0.11. At the concentrations lower than 3% w/v the mucilage exhibited newtonian flow whereas at higher concentration the mucilage showed pseudoplastic with thixotropic flow. As increased the concentration of JK mucilage, the surface tension of purified water was reduced to the range of 1.77-3.8 mN/m and the interfacial tension between water and mineral oil was reduced to the range of 9.07-12.43 mN/m. The viscosity of the mucilage was reduced dramatically in acid pH but in salt solution at the concentrations lower than 2% w/v, the viscosity was increased. In addition, the JK mucilage was able to flocculate Titanium dioxide. Even though the JK mucilage was able to thicken the external phase of emulsion, it exhibited as a poor emulsifier. The JK mucilage, therefore, has the potential for use as a suspending agent and thickening agent in cosmetic products

Aspects of the mechanisms of action of biguanides on trophozoites and cysts of Acanthamoeba castellanii

A non-radioactive method was used to investigate the uptake by Acanthamoeba castellanii of chlorhexidine diacetate (CHA) and polyhexamethylene biguanide (PHMD). Based on the Giles et al. (1974) hypothesis, the uptake of CHA by trophozoites appeared to be of the L3 pattern whereas that of cysts was C2. Unlike CHA, trophozoites took up PHMB with an L2 pattern at low concentrations followed by a C-type pattern at higher concentrations, the uptake by cysts was found to be of the C2 pattern with a plateau effect at high concentrations. A diphasic leakage effect was found in trophozoites whereas a relatively low peak of maximal leakage occurred from cysts treated with high biocide concentrations. The amount of pentose release depended on the formulation ingredients. No correlation between pentose leakage and trophozoicidal or cysticidal activity was found

Acanthamoeba castellanii: growth, encystment, excystment and biocide susceptibility.

Stages in the encystment and excystment processes of Acanthamoeba castellanii have been studied. The kinetics of encystment involved measurements of the three phases (pre-encystment, cyst initiation and cyst wall synthesis). Excystment, starting from a mature cyst, involved pre-emergence, penetration outwards of the cyst wall and free trophozoite. The sensitivity to biocides of trophozoites in the exponential growth phase, pre-encystment trophozoites, mature cysts and pre-excystment cysts has been investigated. Some differences in relative sensitivity to a bisbiguanide (chlorhexidine) and a polymeric biguanide (polyhexamethylene biguanide) were observed, but mature cysts were always the most resistant cellular form