We have studied the effects of L(+)-ascorbic acid (vitamin C) on the formation of ZnO crystals. We carried out a series of experiments under weak acidic to alkaline conditions. We obtained ZnO structures with various distinct morphologies by varying the concentration of vitamin C dissolved in the weak acidic and alkaline solutions. Under weak acidic conditions, if the concentration of added vitamin C exceeds 0.5 mM, mixed amorphous/crystalline vitamin C-ZnO (VitC-ZnO) nanostructures are obtained. We also found that the ZnO content of the VitC-ZnO nanostructures can be controlled by adjusting the concentration of vitamin C added to the reaction solution. On the basis of our results, we propose a mechanism for the formation of the various ZnO structures and VitC-ZnO nanostructures in the presence of vitamin C.

Cell-type-specific genes involved in disease can be effective therapeutic targets; therefore, the development of a cell-type-specific gene delivery system is essential.

No abstract

Bacteria often possess relatively flexible genome structures and adaptive genetic variants that allow survival in unfavorable growth conditions. Bacterial survival tactics in disadvantageous microenvironments include mutations that are beneficial against threats in their niche. Here, we report that the aerobic rice bacterial pathogen Burkholderia glumae BGR1 changes a specific gene for improved survival in static culture conditions. Static culture triggered formation of colony variants with deletions or point mutations in the gene bspP (BGLU_RS28885), which putatively encodes a protein that contains PDC2, PAS-9, SpoIIE, and HATPase domains. The null mutant of bspP survived longer in static culture conditions and produced a higher level of bis-(3 0-5 0)-cyclic dimeric guanosine monophosphate than the wild type. Expression of the bacterial cellulose synthase regulator (bcsB) gene was upregulated in the mutant, consistent with the observation that the mutant formed pellicles faster than the wild type. Mature pellicle formation was observed in the bspP mutant before pellicle formation in wild-type BGR1. However, the population density of the bspP null mutant decreased substantially when grown in Luria-Bertani medium with vigorous agitation due to failure of oxalate-mediated detoxification of the alkaline environment. The bspP null mutant was less virulent and exhibited less effective colonization of rice plants than the wild type. All phenotypes caused by mutations in bspP were recovered to those of the wild type by genetic complementation. Thus, although wild-type B. glumae BGR1 prolonged viability by spontaneous mutation under static culture conditions, such genetic changes negatively affected colonization in rice plants. These results suggest that adaptive gene sacrifice of B. glumae to survive unfavorable growth conditions is not always desirable as it can adversely affect adaptability in the host.