Tightly regulated expression vectors for Ochrobactrum anthropi.

Genetic studies of Ochrobactrum anthropi, a bacterial species important in bioremediation and biopesticide degradation, are hindered by the lack of suitably regulated gene expression system. A tightly regulated gene-expression system was developed for O. anthropi using the lacI(q) gene and a re-engineered coliphage T5 promoter containing completely symmetrical DNA segment that binds more efficiently to the lactose repressor. The beta-galactosidase activity was increased 57-fold when the expression of the re-engineered T5 promoter was induced. The degree of induction was controllable by varying the concentration of inducer isopropyl-beta-D: -thiogalactopyranoside.

Silica-antibiotic hybrid nanoparticles for targeting intracellular pathogens.

We investigated the capability of biodegradable silica xerogel as a novel carrier of antibiotic and the efficacy of treatment compared to that with the same dose of free drug against murine salmonellosis. The drug molecules (31%) entrapped in the sol-gel matrix remained in biologically active form, and the bactericidal effect was retained upon drug release. The in vitro drug release profiles of the gentamicin from the xerogel and that from the xerogel-polyethylene glycol (PEG) were distinctly different at pH 7.4. A delayed release of gentamicin was observed from the silica xerogel network (57% in 33 h), and with the addition of 2% PEG, the release rate reached 90% in 33 h. Administration of two doses of the silica xerogel significantly reduced the Salmonella enterica serovar Typhimurium load in the spleens and livers of infected AJ 646 mice. The silica xerogel and xerogel-PEG achieved a 0.45-log and a 0.41-log reduction in the spleens, respectively, while for the free drug there was no reduction. On the other hand, silica xerogel and xerogel-PEG achieved statistically significant 1.13-log and 1.15-log reductions in the livers, respectively, while for the free drug the reduction was a nonsignificant value of 0.07 log. This new approach, which utilizes a room-temperature synthetic route for incorporating therapeutic drugs into the silica matrix, should improve the capability for targeting intracellular pathogens.

Activity of native vs. synthetic promoters in Brucella.

Brucellosis caused by Brucella species is reportedly the most common zoonotic infection worldwide. The bacterial pathogen is also classified by the Centers for Disease Control and Prevention as a category (B) pathogen that has the potential for development as a bioweapon. Although eight genomes of Brucella have been sequenced, little information is available regarding the regulation of gene expression and promoter activity in Brucella spp. We therefore constructed a set of broad-host-range vectors expressing the lacZ reporter gene from various promoters. Four groups of promoters (Brucella native, antibiotic resistant, bacteriophage and synthetic promoters) were tested in vivo and in vitro in Brucella suis. The highest level of heterologous gene expression was achieved with synthetic hybrid trc promoter carrying the adenine-rich upstream element. Furthermore, this demonstrates the usefulness of synthetic promoters for enhanced level of gene expression in Brucella spp.

Electroporation-delivered fluorescent protein biosensors for probing molecular activities in cells without genetic encoding.

Fluorescent protein biosensors are typically implemented via genetic encoding which makes the examination of scarce cell samples impractical. By directly delivering the protein form of the biosensor into cells using electroporation, we detected intracellular molecular activity with the sample size down to ∼100 cells with high spatiotemporal resolution.