Biofilm Spreading by the Adhesin-Dependent Gliding Motility of Flavobacterium johnsoniae: 2. Role of Filamentous Extracellular Network and Cell-to-Cell Connections at the Biofilm Surface

Flavobacterium johnsoniae forms a thin spreading colony on nutrient-poor agar using gliding motility. As reported in the first paper, WT cells in the colony were sparsely embedded in self-produced extracellular polymeric matrix (EPM), while sprB cells were densely packed in immature biofilm with less matrix. The colony surface is critical for antibiotic resistance and cell survival. We have now developed the Grid Stamp-Peel method whereby the colony surface is attached to a TEM grid for negative-staining microscopy. The images showed that the top of the spreading convex WT colonies was covered by EPM with few interspersed cells. Cells exposed near the colony edge made head-to-tail and/or side-to-side contact and sometimes connected via thin filaments. Nonspreading sprB and gldG and gldK colonies had a more uniform upper surface covered by different EPMs including vesicles and filaments. The EPM of sprB, gldG, and WT colonies contained filaments ~2 nm and ~5 nm in diameter; gldK colonies did not include the latter. Every cell near the edge of WT colonies had one or two dark spots, while cells inside WT colonies and cells in SprB-, GldG-, or GldK-deficient colonies did not. Together, our results suggest that the colony surface structure depends on the capability to expand biofilm.     

Potential nutritive value and tannin bioassay of selected Acacia species from Kenya

Six Acacia forage species–A. brevispica, A. elatior, A. mellifera, A. nilotica, A. senegal and A. seyal—were analysed for their chemical composition, including phenolics and rumen fermentation characteristics. In vitro gas production technique was used to study the rumen fermentation characteristics and the effect of tannins present in the browse forages on in vitro fermentation by including polyethylene glycol (PEG‐6000) in the incubation. The forages had high crude protein content (145.7–270.1 g kg^?1 DM) and low to moderate content of neutral detergent fibre (220.2–442.8 g kg^?1 DM). The forages had variable content of total extractable phenolics ranging from 18.4 to 384.2 g kg^?1 DM and total extractable tannins ranging from 7.1 to 364.8 g kg^?1 DM (tannic acid equivalent). Fractionation of the condensed tannin flavonoids showed that the delphinidin/cyanidin ratio ranged from not detected:100 to 71:29. The gas production potential ranged from 28.4 to 40.8 mL gas 0.2 g^?1 DM. The rate of gas production was highest in A. elatior and lowest in A. nilotica. Addition of PEG‐6000 increased gas production significantly (P < 0.05) in all species except A. mellifera. PEG‐6000 addition did not have any significant effect on in vitro true dry matter and organic matter degradability but decreased the partitioning factor in all the species. Gas production and degradability parameters correlated positively with the CP content and negatively with the fibre and phenolics contents. Based on chemical composition, gas production and degradability, the forages have high potential nutritive value, especially as supplements to low‐quality feeds in the tropics and particularly during the dry season. However, the presence of tannins in terms of high levels and biological antinutritive activity may limit the nutritive potential of some of the forages, such as A. seyal and A. nilotica. Copyright © 2007 Society of Chemical Industry     

Thermochemical hydrogen production by a redox system of ZrO2-supported Co(II)-ferrite

The thermochemical two-step water splitting was examined on ZrO₂-supported Co(II)-ferrites below 1400 °C, for purpose of converting solar high-temperature heat to clean hydrogen energy as storage and transport of solar energy. The ferrite on the ZrO₂-support was thermally decomposed to the reduced phase of wustite at 1400 °C under an inert atmosphere. The reduced phase was reoxidized with steam on the ZrO₂-support to generate hydrogen below 1000 °C in a separate step. The ZrO₂-supporting alleviated the high-temperature sintering of iron oxide. As the results, the ZrO₂-supported ferrite realized a greater reactivity and a better repeatability of the cyclic water splitting than the conventional unsupported ferrites. The Co_xFe_3−xO₄/ZrO₂ with the x value of around 0.4–0.7 was found to be the promising working material for the two-step water splitting when thermally reduced at 1400 °C under an inert atmosphere.     

Low substrate temperature synthesis of carbon nanowalls by ultrasonic spray pyrolysis

In this paper, we report the synthesis of two-dimensional wall like carbon nanostructures (i.e. carbon nanowalls) by ultrasonic spray pyrolysis of ethanol and fullerene mixture. At higher temperature carbon nanofibers were formed on the substrate placed at the center of the reactor tube, whereas carbon nanowalls were observed on the substrate placed downstream of the tube below 100 °C. Spaces between the nanowalls changed with distance of the substrates from the furnace. Qualitative analysis of materials was performed using scanning electron microscopy, transmission electron microscopy and Raman spectroscopy.     

High-rate deposition of Sb-doped SnO2 films by reactive sputtering using the impedance control method

SnO₂ films doped with Sb (ATO) were deposited both on unheated glass substrates and on glass substrates that had been heated at 200 °C by reactive sputtering of an Sb-Sn alloy target with a plasma control unit (PCU) and mid-frequency (mf, 50 kHz) unipolar pulsing. The PCU feedback system monitors the oxidation states of target surface by detecting the sputtering cathode voltage (impedance control method). The mf pulse wave is approximately square-shaped; this helps to reduce arcing on the target when high power density is applied on the cathode. In case of the ATO depositions on the heated substrate at 200 °C in the “transition region” of reactive sputtering, the deposition rate was 280 nm/min, the lowest resistivity of the ATO films was 4.6 × 10^− 3 Ω cm and the optical transmittance was over 80% in the visible region of light.     

Background radiation and individual dosimetry in the costal area of Tamil Nadu, India

South coast of India is known as the high-level background radiation area (HBRA) mainly due to beach sands that contain natural radionuclides as components of the mineral monazite. The rich deposit of monazite is unevenly distributed along the coastal belt of Tamil Nadu and Kerala. An HBRA site that laid in 2×7 m along the sea was found in the beach of Chinnavillai, Tamil Nadu, where the maximum ambient dose equivalent reached as high as 162.7 mSv y(-1). From the sands collected at the HBRA spot, the high-purity germanium semi-conductor detector identified six nuclides of thorium series, four nuclides of uranium series and two nuclides belonging to actinium series. The highest radioactivity observed was 43.7 Bq g(-1) of Th-228. The individual dose of five inhabitants in Chinnavillai, as measured by the radiophotoluminescence glass dosimetry system, demonstrated the average dose of 7.17 mSv y(-1) ranging from 2.79 to 14.17 mSv y(-1).     

Synthesis of nanometer-sized ceria particles by alternating current electrolysis of aqueous solution

Ceria particles in an average size range from 8 to 70 nm were synthesized from cerium nitrate solutions by electrolysis at AC 0.1–10 Hz using platinum wire electrodes at 25–80 °C. The produced ceria particles dissolved in low pH solutions (pH 1.1–2.7) at a longer electrolysis time (>12 h), which caused the decrease of particle size. Increase of the concentration of Ce³⁺ ions and increase of the electrolysis temperature were effective to enhance the particle yield. Small growth of particles (10–20 nm) was measured when the electrolysis temperature was increased to 60–80 °C. When the applied frequency was increased, the particle size decreased. A theoretical equation of particle size as functions of Ce³⁺ ion concentration, electrolysis temperature and applied frequency was derived. The experimental results were in accordance with the prediction from the theoretical model.     

Synthesis and electrical conductivity of La0.6Sr0.4Ru1−xMgxO3−δ (x = 0–0.6) perovskite solid solution

Sr and Mg were doped at La- and Ru-sites of perovskite oxide LaRuO₃, respectively, to enhance electrical conductivity and catalytic property as a cathode material for a low temperature solid oxide fuel cell. Crystal structure and particle morphology of La_0.6Sr_0.4Ru_1?xMg_xO_3?δ powders (shorten as LSRM) and electrical conductivity of sintered LSRM were studied. LSRM powders (x = 0–0.6) were prepared by co-precipitation method using metal nitrate solutions and ammonium carbonate solution. The freeze-dried powders were heated at 1273 K in air to form LSRM solid solution of orthorhombic structure. The true densities and particle sizes of LSRM solid solution, where valence of Ru was estimated to be 3+, decreased with increasing Mg content. The electrical conductivity of LSRM at x = 0–0.3 was almost independent of temperature and was in a range of 19–360 S cm^?1 at 1073 K. Hole conduction contributed to the high electrical conductivities. LSRM at x = 0.4 and 0.5 was a mixed conductor of oxide ions and holes, and showed a conductivity of 11 S cm^?1 at 1073 K in air. This conductivity decreased at a lower oxygen pressure and reached a constant value below 10 Pa of oxygen pressure.     

Specific racemization of heavy-chain cysteine-220 in the hinge region of immunoglobulin gamma 1 as a possible cause of degradation during storage

Therapeutic antibodies often suffer from degradation due to various modifications during storage. We detected a degradation of immunoglobulin gamma 1 (IgG1) stored for 6 month at 40 °C, and identified the modification as the racemization of Cys220 in the hinge sequence S(219)CDKTHT(225) of the heavy chain by tryptic peptide mapping and tandem mass spectrometry. The rate of racemization at Cys220 was enhanced deliberately by incubating the protein at 50 °C and pH 9.0, while all the other cysteine residues were not affected. The racemization of Cys220 was confirmed by mass spectrometry in conjunction with extracted ion chromatography of the tryptic digest of IgG1 forced to degrade in D(2)O and a series of synthetic hinge fragments containing D-amino acid, as well as the detection of D-cysteine in the acid hydrolysate. To rationalize the possible relationship between the racemization of Cys220 and isopeptide formation at the neighboring residue of Asp221, we suggest a new reaction mechanism that assumes a base catalyst to initiate these reactions by activating the amide nitrogen of Lys222. Due to the highly flexible nature of the hinge region, Lys222 can participate in either the formation of a cyclic imidazoline intermediate involving the α-carbonyl carbon of Cys220 to facilitate the racemization of Cys220 or that of a succinimide structure leading to the isomerization of Asp221.