Bacillus stearothermophilus contains two carbamoyl-phosphate synthetases (CPS), one specific for pyrimidine biosynthesis and the other for arginine biosynthesis. The pyrimidine-specific CPS is repressed by exogenous pyrimidines, and its activity is inhibited by UMP and activated by 5-phospho-a-~-ribosyI diphosphate. The arginine-specific CPS is similarly repressed by exogenous arginine but its activity is not sensitive to these or other potential effectors. Each of the two enzymes consist of two unequal subunits, as is the case for other microbial CPS ; however, the large subunit for the arginine-specific CPS is smaller than that for the pyrimidine-specific enzyme. Comparison of the derived amino acid sequence for the cloned large subunit of the arginine-specific CPS with those for subunits from pyrimidine-sensitive CPS showed significant similarity throughout the polypeptides except at the carboxy terminus, which was identified by other laboratories to contain the binding site for the pyrimidine effector. Unlike the results previously reported for CPS from an enteric mesophile, the kinetic properties of the arginine-specific CPS were not affected by growth of B. stearothermophilus at temperatures near the minimal growth temperature. Furthermore, calorimetric studies showed that the thermal stability of cloned CPS was identical regardless of the growth temperature of B. stearothermophilus between 42°C and 63°C. The thermal stability of cloned CPS was not affected by expression at 37OC in Bacillus subtilis or Escherichia coli. In contrast, the thermal stabilities for CPS and other proteins were higher in extracts of cells grown at higher temperatures. These results indicate that cellular factors, probably chaperonins, are necessary for thermal stability of proteins at and below the optimal temperature for this thermophile.Keywords: thermal stability ; growth temperature; carbamoylphosphate synthetase; kinetics.Carbamoyl-phosphate synthetase (CPS) catalyzes the synthesis of carbamoyl phosphate from ATP, bicarbonate and either ammonia or glutamine. Bacterial CPS consist of two unequal subunits ; the large subunit alone catalyzes the synthesis of carbamoyl phosphate from MgATP, bicarbonate and ammonia; the small subunit functions as a glutamine amidotransferase (Glansdorff, 1996). In gram-negative bacteria, a single CPS catalyzes the synthesis of carbamoyl phosphate as a precursor for arginine and pyrimidines (Glansdorff, 1996). In contrast, studies with Bacillus subtilis showed that this gram-positive bacterium possesses two CPS, each specific for arginine or pyrimidine biosynthesis and each under separate control (Paulus and Switzer, 1979). The nucleotide sequences for the two CPS from B. subtilis have been determined (Quinn et al., 1991;O'Reilly and Devine, 1994) and limited studies with partially purified enzymes have been reported (Paulus and Switzer, 1979 Enzymes. Carbamoyl-phosphate synthetase (glutaniine-hydrolyzing) (EC 6.3.5.5); glyceraldehyde-3-phosphate dehydrogenase (phosphorylating) (EC 1.2.1.12).Note....

Aster yellows phytoplasma was detected for the first time in goldenrain tree (Koelreuteria paniculata) growing in Sinpyeong-myeon, Jeollabuk-do, South Korea. DNA was extracted from the infected leaf samples and part of the 16S rDNA, rp operon and tuf gene were amplified using R16F2n⁄R2 and gene-specific primers. The sequence analysis showed that the phytoplasma was closely related (99%) to members of the Aster Yellows (AY) group, and belonging to 16Sr I, subgroup B. Moreover, the 16S rDNA sequences of the isolate showed 88-96% identity with members of other 16Sr and undesignated groups. Based on the sequence identity and phylogenetic studies, it was confirmed that phytoplasma infecting goldenrain tree in South Korea belongs to the AY group.

Zero-valent iron (ZVI) has great potential to be used as a remediation material for the removal of a wide range of pollutants from groundwater. The present study assessed the potential of ZVI for arsenic remediation by investigating (i) the removal kinetics of arsenic by ZVI in a batch reactor and (ii) the longevity of ZVI to remove arsenic in a flow-through column system which mimics the permeable reactive barrier (PRB) technology. Results of the batch experiments showed an effective removal (99.5%) of arsenic compounds from the synthetic water samples. Based on our kinetic study, the arsenic removals are expected to occur in a timescale of less than a few hours in typical PRB treatment conditions using ZVI (e.g. [ZVI] > 20 g/L and [As] < 1 mg/L). The flow-through columns were continuously operated for 360 days at a flow rate of 2 mL/h. Samples were taken at regular intervals (90, 150, 230 and 360 days) and analysed for total arsenic concentration. The removal rates decreased by (45% in aerobic and 39% in anoxic) after 360 days of operation indicate that the regular replacement of the reactive material would be required for efficient removal of arsenic.

Other bioactive products U 1300 Xylarinols A and B, Two New 2-Benzoxepin Derivatives from the Fruiting Bodies of Xylaria polymorpha. -Xylarinols A (I) and B (II) exhibit no antibacterial activity but moderate ABTS radical scavenging activity. -(LEE, I.-K.; JANG, Y.-W.; KIM, Y.-S.; YU, S. H.; LEE, K. J.; PARK, S.-M.; OH, B.-T.; CHAE, J.-C.; YUN*, B.-S.; J.