The characteristic of an ideal bacteria-detection method should have high sensitivity and specificity, be easy to operate, and not have a time-consuming culture process. In this study, we report a new bacteria-detection strategy that can recognize bacteria quickly and directly by surface-enhanced Raman scattering (SERS) with the formation of well-defined bacteria-aptamer@AgNPs. SERS signals generated by bacteria-aptamer@AgNPs exhibited a linear dependence on bacteria (R = 0.9671) concentration ranging from 10 to 10 cfu/mL. The detection limit is sensitive down to 1.5 cfu/mL. Meanwhile, the bacteria SERS signal was dramatically enhanced by its specifically recognized aptamer, and the bacteria could be identified directly and visually through the SERS spectrum. This strategy eliminates the puzzling data analysis of previous studies and offers significant advantages over existing approaches, getting a critical step toward the creation of SERS-based biochips for rapid in situ bacteria detection in mixture samples.
The GAL1 and GAL10 genes of Saccharomyces cerevisiae are transcribed divergently and transcription of both genes can be induced by galactose and repressed by glucose. This study describes the construction and characterization of 8 bidirectional expression vectors. These vectors carry both a modified inducible GAL promoter in one direction and a constitutive GPD promoter in the reverse direction. When the gene-encoded alpha-galactosidase was cloned into the modified GAL1 and GAL10 vectors, promoter activity was 85% of wild-type for the GAL1 promoter and 90% of wild-type for the GAL10 promoter, respectively. The modified GAL promoters and GPD promoter did not interfere with one another in the bidirectional vectors. Furthermore, yeast overexpressing human Bax under the control of either modified GAL1 or modified GAL10 in a bidirectional vector conferred a lethal phenotype that was rescued by coexpression of human Bcl-2 under the control of the GPD promoter in the same vector. These eight vectors can be used to express lethal genes and screen for genes that rescue the yeast from the lethal gene product.
The bioluminescent signals and CFU enhancement at sub-MIC antibiotic concentrations should be of value in the research of new antibiotic drugs and bioluminescent imaging.
The evolution and spread of methicillin-resistant Staphylococcus aureus (MRSA) poses a significant hidden risk to human public health. The majority of antibiotics used clinically have become mostly ineffective, and so the development of novel anti-infection strategies is urgently required. Since Staphylococcus aureus (S. aureus) cysteine transpeptidase sortase A (SrtA) mediates the surface-anchoring of proteins to its surface, compounds that inhibit SrtA are considered potential antivirulence treatments. Herein, we report on the efficacy of the potent SrtA inhibitor taxifolin (Tax), a flavonoid compound isolated from Chinese herbs. It was able to reversibly block the activity of SrtA with an IC50 of 24.53 ± 0.42 μM. Tax did not display toxicity toward mammalian cells or S. aureus at a concentration of 200 μM. In addition, Tax attenuated the virulence-related phenotype of SrtA in vitro by decreasing the adherence of S. aureus, reducing the formation of a biofilm, and anchoring of S. aureus protein A on its cell wall. The mechanism of the SrtA-Tax interaction was determined using a localized surface plasmon resonance assay. Subsequent mechanistic studies confirmed that Asp-170 and Gln-172 were the principal sites on SrtA with which it binds to Tax. Importantly, in vivo experiments demonstrated that Tax protects mice against pneumonia induced by lethal doses of MRSA, significantly improving their survival rate and reducing the number of viable S. aureus in the lung tissue. The present study indicates that Tax is a useful pioneer compound for the development of novel agents against S. aureus infections.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.