Quasi-solid-state dye-sensitized solar cells were fabricated using low-molecular-weight gelators. They showed comparable photoenergy conversion efficiencies to the liquid cell at high illumination intensity up to AM 1.5 (1 sun). Conductivity measurements of the electrolyte phases revealed that the gelation does not affect the conductivity of the electrolyte and that the conductivity increased with an increase of iodine in both gel electrolytes and liquid electrolyte. The formation of polyiodide ions, such as I3 - and I5 -, caused by addition of iodine was confirmed by Raman spectroscopic measurement. The self-diffusion of iodide species in the gel electrolyte was found about a quarter of that of I- in acetonitrile. The formation of less-mobile polyiodide ions in electrolyte increased the conductivity in the mesoporous phase, which should be rationalized as due to the Grotthuss-type electron exchange mechanism caused by rather packed polyiodide species in the electrolytes. The optimized quasi-solid-state cell showed the values of 0.67 V for open-circuit voltage, 12.8 mA cm-2 for short-circuit photocurrent density, and 5.91% for photoenergy conversion efficiency under AM 1.5 irradiation with higher durability.

Database searches indicated that the genome of Bacillus subtilis contains three different genes encoding RNase H homologues. The ypdQ gene encodes an RNase HI homologue with 132 amino acid residues, whereas the rnh and ysgB genes encode RNase HII homologues with 255 and 313 amino acid residues, respectively. RNases HI and HII show no significant sequence similarity. These genes were individually expressed in Escherichia coli; the recombinant proteins were purified, and their enzymatic properties were compared with those of E. coli RNases HI and HII. We found that the ypdQ gene product showed no RNase H activity. The 2.2 kb pair genomic DNA containing this gene did not suppress the RNase H deficiency of an E. coli rnhA mutant, indicating that this gene product shows no RNase H activity in vivo as well. In contrast, the rnh (rnhB) gene product (RNase HII) showed a preference for Mn2+, as did E. coli RNase HII, whereas the ysgB (rnhC) gene product (RNase HIII) exhibited a Mg2+-dependent RNase H activity. Oligomeric substrates digested with these enzymes indicate similar recognition of these substrates by B. subtilis and E. coli RNases HII. Likewise, B. subtilis RNase HIII and E. coli RNase HI have generated similar products. These results suggest that B. subtilis RNases HII and HIII may be functionally similar to E. coli RNases HII and HI, respectively. We propose that Mn2+-dependent RNase HII is universally present in various organisms and Mg2+-dependent RNase HIII, which may have evolved from RNase HII, functions as a substitute for RNase HI.

No abstract

Arthrofactin is a potent cyclic lipopeptide-type biosurfactant produced by Pseudomonas sp. MIS38. In this work, an arthrofactin synthetase gene cluster (arf) spanning 38.7 kb was cloned and characterized. Three genes termed arfA, arfB, and arfC encode ArfA, ArfB, and ArfC, containing two, four, and five functional modules, respectively. Each module bears condensation, adenylation, and thiolation domains, like other nonribosomal peptide synthetases. However, unlike most of them, none of the 11 modules possess the epimerization domain responsible for the conversion of amino acid residues from L to D form. Possible L- and D-Leu adenylation domains specifically recognized only L-Leu. Moreover, two thioesterase domains are tandemly located at the C-terminal end of ArfC. These results suggest that ArfA, ArfB, and ArfC assemble to form a unique structure. Gene disruption of arfB impaired arthrofactin production, reduced swarming activity, and enhanced biofilm formation.

The extracellular matrix produced by Bacillus subtilis B-1, an environmental strain that forms robust floating biofilms, was purified, and determined to be composed predominantly of γ-polyglutamate (γ-PGA), with a molecular mass of over 1000 kDa. Both biofilm formation and γ-PGA production by B. subtilis B-1 increased with increasing Mn2+ or glycerol concentration. γ-PGA was produced in a growth-associated manner in standing culture, and floating biofilms were formed. However, γ-PGA was produced in a non-growth-associated manner in shaking culture conditions. When B. subtilis B-1 was grown in a microaerated culture system, floating biofilm formation and γ-PGA production were significantly retarded, suggesting that oxygen depletion is involved in the initial steps of floating biofilm formation in standing culture. Proteomic analysis of membrane proteins demonstrated that flagellin, oligopeptide permease and Vpr protease precursor were the major proteins produced by cells in a floating biofilm and a colony.

A psychrotrophic bacterium Shewanella sp. strain SIB1 was grown at 4 and 20°C, and total soluble proteins extracted from the cells were analyzed by two-dimensional polyacrylamide gel electrophoresis. Comparison of these patterns showed that the cellular content of a protein with a molecular mass of 28 kDa and an isoelectric point of four greatly increased at 4°C compared to that at 20°C. Determination of the N-terminal amino acid sequence, followed by the cloning and sequencing of the gene encoding this protein, revealed that this protein is a member of the FKBP family of proteins with an amino acid sequence identity of 56% to Escherichia coli FKBP22. This protein was overproduced in E. coli in a His-tagged form, purified, and analyzed for peptidyl-prolyl cis-trans isomerase activity.When this activity was determined by the protease coupling assay using N-succinyl-Ala-Leu-Pro-Phe-p-nitroanilide as a substrate at various temperatures, the protein exhibited the highest activity at 10°C with a k cat /K m value of 0.87 lM . When the peptidyl-prolyl cis-trans isomerase activity was determined by the RNase T 1 refolding assay at 10 and 20°C, the protein exhibited higher activity at 10°C with a k cat /K m value of 0.50 lM . These k cat /K m values are lower but comparable to those of E. coli FKBP22. We propose that a FKBP family protein is involved in cold-adaptation of psychrotrophic bacteria.

No abstract

We have analyzed the cleavage speci¢cities of various prokaryotic Type 2 ribonucleases H (RNases H) on chimeric DNA^RNA^DNA/DNA substrates containing one to four ribonucleotides. RNases HII from Bacillus subtilis and Thermococcus kodakaraensis cleaved all of these substrates to produce a DNA segment with a 5P P-monoribonucleotide. Consequently, these enzymes cleaved even the chimeric substrate containing a single ribonucleotide at the DNA^RNA junction (5P P-side of the single ribonucleotide). In contrast, Escherichia coli RNase HI and B. subtilis RNase HIII did not cleave the chimeric substrate containing a single ribonucleotide. These results suggest that bacterial and archaeal RNases HII are involved in excision of a single ribonucleotide misincorporated into DNA.