Influenza A virus neuraminidase can be classified into groups 1 and 2 on the basis of its primary structure. The main structural feature of group 1 neuraminidase is an extra cavity in the active site, the 150-cavity. Here we present the crystal structure of neuraminidase from the 2009 pandemic H1N1 influenza strain. In contrast to other characterized N1 neuraminidases, which are all members of group 1, 2009 H1N1 neuraminidase does not have a 150-cavity.

This report presents a highly sensitive, rhodamine B-covered gold nanoparticle (RB-AuNP) -based assay with dual readouts (colorimetric and fluorometric) for detecting organophosphorus and carbamate pesticides in complex solutions. The detection mechanism is based on the fact that these pesticides can inhibit the activity of acetylcholinesterase (AChE), thus preventing the generation of thiocholine (which turns the RB-AuNP solutions blue and unquenches the fluorescence of RB simultaneously). The color of the RB-AuNP solution remains red and the fluorescence of RB remains quenched. By use of this dual-readout assay, the lowest detectable concentrations for several kinds of pesticides including carbaryl, diazinon, malathion, and phorate were measured to be 0.1, 0.1, 0.3, and 1 μg/L, respectively, all of which are much lower than the maximum residue limits (MRL) as reported in the European Union pesticides database as well as those from the U.S. Department Agriculture (USDA). This assay allows detection of pesticides in real samples such as agricultural products and river water. The results in detecting pesticide residues collected from food samples via this method agree well with those from high-performance liquid chromatography (HPLC). This simple assay is therefore suitable for sensing pesticides in complex samples, especially in combination with other portable platforms.

Recent cases of human infection with avian influenza H5N1 and H7N9 viruses underscore an urgent need for techniques that can rapidly assess their potential threat to the humans. Determination of the receptor-binding property of influenza virus is crucial to direct viral control and prevention measures. Current methods to perform this analysis are dependent on immunoanalytical strategies that use unstable biological components and complex procedures. We have developed a facile colorimetric assay to determine the interaction of the viral hemagglutinin (HA) protein with host glycan receptors using glycan-functionalized gold nanoparticles (gGNPs). This method is based on the color and absorbance changes of gold probes when the solution is simply mixed with HAs or intact viruses. The resulting sensitivity and selectivity has enabled HA/virus binding to various glycan structures to be differentiated visually and rapidly. Using this system, we have screened, in parallel, the receptor specificity of eight representative human and avian viral HAs and three whole viruses including an emerging H7N9 strain. Our results reveal the detailed receptor-binding profiles of H7N9 virus and its HA and show that they effectively bind to human-type receptors. This gGNP-based assay represents a strategy that would be helpful for developing simple and sensitive systems to probe glycan-mediated biological processes.

Intestinal floras influence a lot of biological functions of the organism. Although animal model are strong tools for researches on the relationship between host and microbe, a physiologically relevant in vitro human gut model was still required. Here, a novel human gut-vessel microfluidic system was established to study the host-microbial interaction. Peristaltic motion of the cells on the chip was driven by a pneumatic pump. When intestinal epithelial cells (Caco2) were co-cultured with vascular endothelial cells (HUVECs) on the peristaltic microfluidic chip, Caco2 showed normal barrier and absorption functions after 5 days cultivation, which generally took 21 days in static Transwell models. Intestinal microvilli and glycocalyx layer were seen after 4 days cultivation, and Lactobacillus casei was successfully co-cultured for a week in the intestinal cavity. A model for intestinal damage and inflammatory responses caused by E. coli was set up on this chip, which were successfully suppressed by Lactobacillus casei or antibiotic. In summary, this human gut-vessel microfluidic system showed a good potential for investigating the host-microbial interaction and the effect and mechanism of microbiome on intestinal diseases in vitro.

Recent studies have shown that subinhibitory antibiotics play important roles in regulating bacterial genes including virulence factor genes. In this study, the expression of 13 secreted virulence related gene clusters of Pseudomonas aeruginosa, an important opportunistic pathogen, was examined in the presence of subinhibitory concentrations of 4 antibiotics: vancomycin, tetracycline, ampicillin and azithromycin. Activation of gene expression was observed with phzAl, rhlAB, phzA2, lasB, exoY, and exoS. Subinhibitory concentrations of vancomycin resulted in more than 10-fold increase of rhlAB and phzA2 transcription. Both rhamnolipid production and pyocyanin production were significantly elevated, correlating phenotypes with the increased transcription. P. aeruginosa swarming and swimming motility also increased. Similar results were observed with subinhibitory tetracycline, azithromycin and ampicillin. These results indicate that the antibiotics at low concentrations can up-regulate virulence factors and therefore influence bacterial pathogenesis.

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Milk oligosaccharides (MOs) are complex carbohydrates with multifunctional health benefits for the neonate. Poor reproductive performance in primiparous gilts limits their productivity. Changes in the structure and abundance of porcine MO (PMOs) through lactation with parity remains unknown and may explain superior new-born growth in litters from multiparous sows relative to gilts. We report 55 PMOs structures, of which 25 are new (17 sialylated and 8 neutral). Their incidence in gilt and sow colostrum was almost identical (53 vs. 54), but not in transitional milk (48 vs. 53) nor mature milk (41 vs. 47). These PMOs including neutral-, sialyl- and fucosyl- MOs in colostrum were more abundant in the gilt than the sow, but always decreased during lactation. Structural diversity decreased, although fucosylated MO were conserved. In conclusion, high diversity and levels of MO in porcine milk is parity dependent. Given the similarity between porcine and human MO profiles, our findings may help define key roles for MOs as potential dietary additives to improve growth of neonates from first pregnancies in both human and sows.

Pseudomonas aeruginosa is an important human pathogen which causes a variety of infections. P. aeruginosa infections are often difficult to treat due to the pathogen's resistance to many antibiotics. Previously, it has been reported that a transposon insertion mutant in gene PA2800 of P. aeruginosa PAO1 was more sensitive to tetracycline and ciprofloxacin. Further characterization of this gene, a vacJ homolog, in this study indicated that this gene plays an important role in both antibiotic susceptibility and virulence in P. aeruginosa. The role of PA2800 in antibiotic susceptibility probably signifies its involvement in maintaining outer membrane stability, similar to the role of vacJ in E. coli and Shigella flexneri. However, in contrast to vacJ in other bacteria, PA2800 also affects antibiotic susceptibility by affecting the expression of oprH in P. aeruginosa. As shown by in vivo studies using a Drosophila melanogaster infection model, significantly increased virulence was observed in the PA2800 mutant when compared to the wild type, and such a difference is likely a result of disrupted outer membrane stability and altered expression of znuA in the mutant. The role of PA2800 or vacJ in antibiotic susceptibility and pathogenicity seems to be unique in P. aeruginosa in which it affects both outer membrane stability as well as gene expression.