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Aims:  To investigate the antimicrobial efficacy of an alkaloid, harmaline alone and in combination with chlorhexidine digluconate (CHG) against clinical isolates of Staphylococcus aureus (S. aureus) grown in planktonic and biofilm cultures. Methods:  Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined for each micro‐organism grown in suspension and in biofilm using microbroth dilution method. Chequerboard assays were used to determine synergistic, indifferent or antagonistic interactions between harmaline and CHG, and the some of results were verified by confocal laser scanning microscopy. Results:  Harmaline and CHG showed effective antimicrobial activity against suspensions and biofilm cultures of S. aureus, respectively. As determined by fractional inhibitory concentration index (FICI), synergistic antimicrobial effects between harmaline and CHG were observed in nine and 11 of the 13 S. aureus strains when in suspension and in biofilm, respectively. FICI values were from 0·375 to 1·25 when in suspension and from 0·25 to 1·25 when in biofilm. Conclusions:  Synergistic activity of harmaline and CHG against clinical isolates of S. aureus (in suspension and in biofilm) was observed in vitro. Significance and Impact of the Study:  This study might provide alternative methods to overcome the problem of drug‐resistance of S. aureus both in suspension and in biofilm.

Amorphous BC2N powders were prepared by mechanical milling with hexagonal boron nitride and graphite as starting materials. A bulk amorphous BC2N compound was produced by sintering the as-milled amorphous BC2N powders in a vacuum of 10−5 Torr at a temperature of 1470 K. The conductivity measurement for the bulk amorphous BC2N compound showed that it behaves as a semiconductor with band gap energy of 0.11 eV for temperatures ranging from room temperature to 560 K and a semimetal for temperatures between 560 and 740 K. The mechanism of the formation of the amorphous BC2N powders is discussed.

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Significance and Impact of the Study: Pullulanases have a great potential in industrial applications including the starch industry, the production of maltose syrups and high-purity glucose and fructose. In this study, a pullulanase from hyperthermophilic archaeon Thermococcus kodakarensis KOD1 was successfully expressed in Escherichia coli and the recombinant enzyme can be purified and characterized. The high activity, broad pH range and stability implicate it as a potential enzyme for industrial applications. AbstractIn this report, a glycoside hydrolase 13 family pullulanase gene (Tk0977) was cloned from a thermophilic anaerobic archaeon Thermococcus kodakarensis KOD1 (Pul-Tk). Pul-Tk encodes a protein of 765 amino acids including a putative 22-residue signal peptide. The protein has four consensus motives and a catalytic triad of glycoside hydrolase 13 family in the deduced amino acid sequence. The recombinant enzyme was expressed in Escherichia coli and purified to homogeneity. Pul-Tk can hydrolyse both pullulan and soluble starch. The purified enzyme was optimal at pH 5Á5-6Á0 and 100°C and exhibited good stability over a broad pH range (4-8). The V max and K m values were 118Á39 AE 1Á76 lmol mg À1 min À1 and 0Á37 AE 0Á02 mg ml À1 for pullulan and 53Á19 AE 11Á66 lmol mg À1 min À1 and 0Á36 AE 0Á05 mg ml À1 for starch.All these favourable enzymatic properties make it valuable in various industries.

Amorphous boron-carbon-nitrogen (BCN) powders were produced by mechanically milling a mixture of hexagonal boron nitride (h-BN) and graphite powders for 120 h in an argon atmosphere. By annealing the amorphous BCN powders isothermally under 4 GPa at temperatures above 880 K, a new B–C–N crystal with a tetragonal structure was obtained. Its lattice constants decrease with the increasing annealing temperature and are a=1.685 nm and c=0.537 nm, respectively at an annealing temperature of 1170 K. The conductivity measurement suggests the new B–C–N phase is a semiconductor with a very small band gap and the band gap changes depending on the temperature in the temperatures between room temperature and 840 K.

Fe–N alloys with crystalline structures different from those obtained at atmospheric pressure were produced by solid-state reaction between Fe and amorphous boron nitride under high pressure. Two new paramagnetic Fe–N phases were obtained at temperatures above 800 K under pressures between 2.0 and 4.0 GPa. One is of cubic structure with lattice constant of 6.114 Å, and another is of orthorhombic structure with lattice constants of a = 4 8.443, b = 4 4.749, and c 4 3.993 Å. ε–Fe3Nx with N contents of 18.1 to 21.4 at.%, which could not be obtained at atmospheric pressure, was produced at pressures of 3.0 to 4.0 GPa and temperatures of 690 to 800 K. The mechanism of formation of ε–Fe3Nx under high pressure is discussed.