Engineering Bacillus megaterium for production of functional intracellular materials

Background: Over the last 10-15 years, a technology has been developed to engineer bacterial polyhydroxybutyrate (PHB) inclusions as functionalized beads, for applications such as vaccines, diagnostics and enzyme immobilization. This has been achieved by translational fusion of foreign proteins to the PHB synthase (PhaC). The respective fusion protein mediates self-assembly of PHB inclusions displaying the desired protein function. So far, beads have mainly been produced in recombinant Escherichia coli which is problematic for some applications as the lipopolysaccharides (LPS) co-purified with such inclusions are toxic to humans and animals. Results: In this study, we have engineered the formation of functional PHB inclusions in the Gram-positive bacterium Bacillus megaterium, an LPS-free and established industrial production host. As B. megaterium is a natural PHB producer, the PHB-negative strain PHA05 was used to avoid any background PHB production. Plasmid-mediated T7 promoter-driven expression of the genes encoding β-ketothiolase (phaA), acetoacetyl-CoA-reductase (phaB) and PHB synthase (phaC) enabled/effected PHB production by B. megaterium PHA05. To produce functionalized PHB inclusions, the N- and C-terminus of PhaC was fused to four and two IgG binding Z-domains from Staphylococcus aureus, respectively. The ZZ-domain PhaC fusion protein was strongly overproduced at the surface of the PHB inclusions and the corresponding isolated ZZ-domain displaying PHB beads were found to purify IgG with a binding capacity of 40-50 mg IgG/g beads. As B. megaterium has the ability to sporulate and respective endospores could co-purify with cellular inclusions, a sporulation negative production strain was generated by disrupting the spoIIE gene in PHA05. This strain did not produce spores when tested under sporulation inducing conditions and it was still able to synthesize ZZ-domain displaying PHB beads. Conclusions: This study provides proof of concept for the successful genetic engineering of B. megaterium as a host for the production of functionalized PHB beads. Disruption of the spoIIE gene rendered B. megaterium incapable of sporulation but particularly suitable for production of functionalized PHB beads. This sporulation-negative mutant represents an improved industrial production strain for biotechnological processes otherwise impaired by the possibility of endospore formation.fals

Size and morphology control of ultrafine refractory complex oxide crystals

High-temperature complex oxides are of considerable interest as their applications cover a broad spectrum from catalytic to optical technology. Indeed, new exciting opportunities might emerge if these high-temperature complex oxides, in which structure crystallization is achieved at temperatures T > 1000 °C, could be synthesized as nonaggregated, ultrafine building blocks. In general, such refractory complex oxide particles are difficult to synthesize as ultrafine crystals because of the strong driving force available for sintering and coarsening in this high-temperature range. This paper reports a new synthetic process for the preparation of nonaggregated, ultrafine barium hexa-aluminate, BaO, 6Al2O3, (BHA), and Ba0.9Eu0.1MgAl10O17, (BAM) crystals in which structure crystallization occurs around 1300 °C. Our process is based on the Ba2+ and Al3+ ions high-temperature controlled diffusion from carbon−inorganic hybrid compounds prepared from soft chemistry routes. Control of morphology of these refractory complex aluminates displaying nanoplatelets morphology was achieved via the tailoring of high-temperature diffusion lengths of the various cations involved in the formation of these ultrafine refractory crystals

Antioxidant activity of thyme waste extract in O/W emulsions

Thymus vulgaris (thyme) is an aromatic plant and its essential oil has been applied as antimicrobial and antioxidant due to the presence of phenolic compounds. However, after steam distillation, the deodorized plant material is rejected, despite the possible presence of bioactive compounds. Ethanolic thyme waste extract revealed the presence of benzoic acid, 4-hydroxybenzoic acid, ferulic acid, caffeic acid, and sinapic acid. This waste thyme extract had the capacity for preventing the formation of primary and secondary lipid oxidation products in emulsions O/W (oil in water), constituted by diverse proportions of wheat and almond oils, without interfering with the viscosity parameters, for 10 weeks, at 37 °C. The increasing proportion of almond oil (≥50%) in the emulsion increases its resistance to oxidation, which is improved with the presence of an optimal concentration of tested thyme waste extract (0.02% and 0.04%). The waste thyme extract can, therefore, be used as an antioxidant either in food or pharmaceutical emulsions O/W, replacing the synthetic antioxidants.Agência financiadora Fundacao para a Ciencia e Tecnologia-FCT; Portugal UID/BIA/04325/2013-MEDTBIO UID/MAR/00350/2013info:eu-repo/semantics/publishedVersio

Efficient, sparse representation of manifold distance matrices for classical scaling

Geodesic distance matrices can reveal shape properties that are largely invariant to non-rigid deformations, and thus are often used to analyze and represent 3-D shapes. However, these matrices grow quadratically with the number of points. Thus for large point sets it is common to use a low-rank approximation to the distance matrix, which fits in memory and can be efficiently analyzed using methods such as multidimensional scaling (MDS). In this paper we present a novel sparse method for efficiently representing geodesic distance matrices using biharmonic interpolation. This method exploits knowledge of the data manifold to learn a sparse interpolation operator that approximates distances using a subset of points. We show that our method is 2x faster and uses 20x less memory than current leading methods for solving MDS on large point sets, with similar quality. This enables analyses of large point sets that were previously infeasible.Comment: Conference CVPR 201

Observational constraints on the co-evolution of supermassive black holes and galaxies

The star formation rate (SFR) and black hole accretion rate (BHAR) functions are measured to be proportional to each other at z < ~3. This close correspondence between SF and BHA would naturally yield a BH mass-galaxy mass correlation, whereas a BH mass-bulge mass correlation is observed. To explore this apparent contradiction we study the SF in spheroid-dominated galaxies between z=1 and the present day. We use 903 galaxies from the COMBO-17 survey with M* >2x10^10M_sun, ultraviolet and infrared-derived SFRs from Spitzer and GALEX, and morphologies from GEMS HST/ACS imaging. Using stacking techniques, we find that <25% of all SF occurs in spheroid-dominated galaxies (Sersic index n>2.5), while the BHAR that we would expect if the global scalings held is three times higher. This rules out the simplest picture of co-evolution, in which SF and BHA trace each other at all times. These results could be explained if SF and BHA occur in the same events, but offset in time, for example at different stages of a merger event. However, one would then expect to see the corresponding star formation activity in early-stage mergers, in conflict with observations. We conclude that the major episodes of SF and BHA occur in different events, with the bulk of SF happening in isolated disks and most BHA occurring in major mergers. The apparent global co-evolution results from the regulation of the BH growth by the potential well of the galactic spheroid, which includes a major contribution from disrupted disk stars.Comment: 14 pages, 5 figures, accepted for publication in Ap

Measurement of the Michel Parameter xi" in Polarized Muon Decay and Implications on Exotic Couplings of the Leptonic Weak Interaction

The Michel parameter xi" has been determined from a measurement of the longitudinal polarization of positrons emitted in the decay of polarized and depolarized muons. The result, xi" = 0.981 +- 0.045stat +- 0.003syst, is consistent with the Standard Model prediction of unity, and provides an order of magnitude improvement in the relative precision of this parameter. This value sets new constraints on exotic couplings beyond the dominant V-A description of the leptonic weak interaction.Comment: 15 pages, 16 figures, 3 tables; submitted to Phys. Rev.