Investigation of bacteriophage MS2 viral dynamics using model discrimination analysis and the implications for phage therapy

Lytic phages infect their bacterial hosts, use the host machinery to replicate, and finally lyse and kill their hosts, releasing progeny phages. Various mathematical models have been developed that describe these phage-host viral dynamics. The aim of this study was to determine which of these models best describes the viral dynamics of lytic RNA phage MS2 and its host Escherichia coli C-3000. Experimental data consisted of uninfected and infected bacterial cell densities, free phage density, and substrate concentration. Parameters of various models were either determined directly through other experimental techniques or estimated using regression analysis of the experimental data. The models were evaluated using a Bayesian-based model discrimination technique. Through model discrimination it was shown that phage-resistant cells inhibited the growth of phage population. It was also shown that the uninfected bacterial population was a quasispecies consisting of phage-sensitive and phage-resistant bacterial cells. When there was a phage attack the phage-sensitive cells died out and the phage-resistant cells were selected for and became the dominant strain of the bacterial population.     

High pressure application for food biopolymers

High hydrostatic pressure constitutes an efficient physical tool to modify food biopolymers, such as proteins or starches. This review presents data on the effects of high hydrostatic pressure in combination with temperature on protein stability, enzymatic activity and starch gelatinization. Attention is given to the protein thermodynamics in response to combined pressure and temperature treatments specifically on the pressure-temperature-isokineticity phase diagrams of selected enzymes, prions and starches relevant in food processing and biotechnology.     

Acetal linked oligoethylenimines for use as pH-sensitive gene carriers

Two types of acid-degradable nonviral gene carriers, OEI-MK and OEI-BAA, were synthesized by polymerizing oligoethylenimine of 800 Da (OEI800) with the pH-sensitive acetone ketal cross-linker 2,2-bis(N-maleimidoethyloxy) propane (MK) or the 4-methoxybenzaldehyde bisacrylate acetal cross-linker 1,1-bis-(2-acryloyloxy ethoxy)-[4-methoxy-phenyl]methane) (BAA). Corresponding acid-insensitive counterparts (OEI-BM and LT-OEI-HD) were synthesized as well, representing control polymers. Kinetics of hydrolysis were measured and confirmed the pH-dependent degradation profile of the acetal functions, with short half-lives of 3 min at pH 5.0, and 5 h (OEI-MK) or 3.5 h (OEI-BAA) at physiological pH 7.4 and 37 degrees C. DNA polyplexes of a luciferase expression plasmid were tested for gene transfer efficiency and biocompatibility in two cell lines (B16F10 and Neuro2A). Polyplexes with acid-labile polymers showed an improved toxicity profile compared to those made with acid-stable polymer analogues. At low cation/plasmid (c/p) w/w ratios the transfection efficiency of pH-sensitive polymers was slightly reduced, but it became similar or superior to the efficiency of acid-stable polymers at higher c/p ratios. An improved in vivo biocompatibility of the acid-degradable polymers over the stable control polymers was confirmed by liver histology after systemic administration of polymers in Balb/c mice.     

Pharmacologic modulation of RNA splicing enhances anti-tumor immunity

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Influence of nutrient supply and elicitors on glucosinolate production in <Emphasis Type="Italic">E. sativa</Emphasis> hairy root cultures

Glucosinolates (GS) are secondary plant metabolites comprising different subgroups with opposing effects on human health. Hairy root cultures (HRC) are potent biotechnological tools allowing the biosynthesis of special substances under defined conditions. HRC of Eruca sativa, a brassicaceaous plant, were used to test different strategies to enhance GS levels and to alter the profile. Additional sulphur supply in the nutrient medium increased especially aliphatic GS by 2.7-fold, but also enhanced indole GS by 1.8-fold. Ethephon as well as jasmonic acid as chemical elicitors enhanced only indole GS levels, whereby especially 4-methoxyindol-3-ylmethyl or 1-methoxyindol-3-ylmethyl GS accumulated. Jasmonic acid was used in combination with pulsed electric field treatment as physical elicitor. Already within 24 h, GS levels doubled in treated HRC compared to the control. For estimation of production potency, the GS levels of HRC were compared to contents of aerial and root parts of E. sativa sprouts. HRC showed a distinct GS profile compared to the parent plant with a higher content of indole GS when compared to sprout roots, but overall lower total GS levels. Furthermore, HRC released GS into the culture medium, which could be enhanced by jasmonic acid and pulsed electric field treatment. This could comprise an efficient strategy for a continuous GS production and mining without solvent extraction.