A sol-gel chemistry approach was used to fabricate nanoparticles of TiO(2) in its anatase form. The particle size is shown to be sensitive to the use of HClO(4) or HNO(3) as acid catalyst. The gold-capped TiO(2) nanocomposites were processed by the reduction of gold on the surface of the TiO(2) nanoparticles via a chemical reduction or a photoreduction method. Different percentages of vanadium-doped TiO(2) nanoparticles, which extended the TiO(2) absorption wavelength from the ultraviolet to the visible region, were successfully prepared. The synthesized nanocomposites have a size of about 12-18 nm and an anatase phase as characterized by XRD, TEM, AFM, and UV-vis spectroscopy. The TiO(2) nanocomposite coatings have been applied on glass slide substrates. The antibacterial activity of TiO(2) nanocomposites was investigated qualitatively and quantitatively. Two types of bacteria, Escherichia coli (DH 5alpha) and Bacillus megaterium (QM B1551), were used during the experiments. Good inhibition results were observed and demonstrated visually. The quantitative examination of bacterial activity for E. coli was estimated by the survival ratio as calculated from the number of viable cells, which form colonies on the nutrient agar plates. The antimicrobial efficiency and inhibition mechanisms are illustrated and discussed.

No abstract

Bacillus megaterium is deep-rooted in the Bacillus phylogeny, making it an evolutionarily key species and of particular importance in understanding genome evolution, dynamics, and plasticity in the bacilli. B. megaterium is a commercially available, nonpathogenic host for the biotechnological production of several substances, including vitamin B 12 , penicillin acylase, and amylases. Here, we report the analysis of the first complete genome sequences of two important B. megaterium strains, the plasmidless strain DSM319 and QM B1551, which harbors seven indigenous plasmids. The 5.1-Mbp chromosome carries approximately 5,300 genes, while QM B1551 plasmids represent a combined 417 kb and 523 genes, one of the largest plasmid arrays sequenced in a single bacterial strain. We have documented extensive gene transfer between the plasmids and the chromosome. Each strain carries roughly 300 strain-specific chromosomal genes that account for differences in their experimentally confirmed phenotypes. B. megaterium is able to synthesize vitamin B 12 through an oxygen-independent adenosylcobalamin pathway, which together with other key energetic and metabolic pathways has now been fully reconstructed. Other novel genes include a second ftsZ gene, which may be responsible for the large cell size of members of this species, as well as genes for gas vesicles, a second ␤-galactosidase gene, and most but not all of the genes needed for genetic competence. Comprehensive analyses of the global Bacillus gene pool showed that only an asymmetric region around the origin of replication was syntenic across the genus. This appears to be a characteristic feature of the Bacillus spp. genome architecture and may be key to their sporulating lifestyle.

No abstract

The sacT gene which controls the sacPA operon of BaciUlus subtilis encodes a polypeptide homologous to the B. subtilis SacY and the Escherichia coli BglG antiterminators. Expression of the sacT gene is shown to be constitutive. The DNA sequence upstream from sacP contains a palindromic sequence which functions as a transcriptional terminator. We have previously proposed that SacT acts as a transcriptional antiterminator, allowing transcription of the sacPA operon. In strains containing mutations inactivating ptsH or ptsI, the expression ofsacPA and sacB is constitutive. In this work, we show that this constitutivity is due to a fully active SacY antiterminator. In the wild-type sacT+ strain or in the sacT30 mutant, SacT requires both enzyme I and HPr of the phosphotransferase system (PTS) for antitermination. It appears that the PTS exerts different effects on the sacB gene and the sacPA operon. The general proteins of the PTS are not required for the activity of SacY while they are necessary for SacT activity.In Bacillus subtilis, the expression of both the sacPA operon and the sacB gene are induced by sucrose (21). The sacA gene codes for an endocellular sucrase (10,11,22), and sacP is the structural gene of a membrane-associated, specific component of the phosphoenolpyruvate-dependent carbohydrate phosphotransferase system (PTS) for sucrose transport (8, 9). The sacB gene encodes a second sucrosehydrolyzing enzyme called levansucrase (22, 37). Two regulatory loci, sacT and sacS, control the transcription of these genes (21,22). Transcriptional regulation of the sacB gene involves an antitermination mechanism (31, 35): between the promoter and the sacB coding sequence, a region of dyad symmetry acts as a transcriptional terminator. Deletion of this termination structure or single-base changes that modify the dyad symmetry led to constitutive synthesis of levansucrase (34). The regulatory locus sacS was identified by analysis of several constitutive mutants. It contains two genes, sacX and sacY, which seem to form an operon. The sacY gene encodes an antiterminator similar to the bglG gene product of Escherichia coli (2,30,42). The sacX gene encodes an enzyme II-like protein, similar to sacP of B. subtilis, bglF from E. coli, and scrA from E. coli, Streptococcus mutans, and Vibrio alginolyticus (3, 43). A specific component of the PTS is also involved in induction of the bgl operon of E. coli. A model of regulation of the bgl operon has been proposed: the enzyme IlBg1, which is involved in P-glucoside transport, negatively regulates the positive regulator BglG by phosphorylation, and thereby abolishing its activity (1,29).A similar model of regulation was proposed for sacB. In the absence of inducer, the sacB gene is not transcribed.