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Comparison of Genome Structures of Vibrios, Bacteria Possessing Two Chromosomes. Kenichi Tagomori, 2002.Vibrios are gram-negative  -proteobacteria which are ubiquitous in marine and estuarine environments . Recently, we demonstrated that some, if not all, Vibrio species have two circular chromosomes . The whole genome sequence of Vibrio cholerae N16961 has been reported . In this study, we constructed a physical and genetic map of the genome of Kanagawa phenomenon-positive Vibrio parahaemolyticus strain KX-V237 and compared it with those of V . parahaemolyticus AQ4673 and V . cholerae N16961 . The genome of KX-V237 comprised two circular chromosomes (3.3 and 1.9 Mb), similar to the structure of the AQ4673 genome . The relative positions of the genes on the genomes were well conserved in the two strains, but a large inversion on the large chromosomes, probably symmetric around the replication origin, was suggested . Although the sizes of the large chromosomes of KX-V237 and V . cholerae N16961 were similar, the sizes of the small chromosomes were very different . Unlike N16961, the superintegron of KX-V237 was located on the large chromosome . Comparison of the genetic maps of the chromosomes of KX-V237 and V . cholerae N16961 revealed that most of the open reading frames (ORFs) present on the large chromosome of the V . cholerae strain had homologues on the large chromosome of the V . parahaemolyticus strain and that most of the ORFs on the small chromosome of N16961 were present on the small chromosome of KX-V237 . The difference in the orders of the ORFs on the chromosomes of N16961 and KX-V237 implies that numerous and frequent genetic exchanges have occurred intrachromosomally rather than interchromosomally .
Characterization of a Bifunctional Archaeal Acyl Coenzyme A Carboxylase. Songkran Chuakrut, 2003.Acyl coenzyme A carboxylase (acyl-CoA carboxylase) was purified from Acidianus brierleyi . The purified enzyme showed a unique subunit structure (three subunits with apparent molecular masses of 62, 59, and 20 kDa) and a molecular mass of approximately 540 kDa, indicating an  4ß4 4 subunit structure . The optimum temperature for the enzyme was 60 to 70°C, and the optimum pH was around 6.4 to 6.9 . Interestingly, the purified enzyme also had propionyl-CoA carboxylase activity . The apparent Km for acetyl-CoA was 0.17 ± 0.03 mM, with a Vmax of 43.3 ± 2.8 U mg-1, and the Km for propionyl-CoA was 0.10 ± 0.008 mM, with a Vmax of 40.8 ± 1.0 U mg-1 . This result showed that A . brierleyi acyl-CoA carboxylase is a bifunctional enzyme in the modified 3-hydroxypropionate cycle . Both enzymatic activities were inhibited by malonyl-CoA, methymalonyl-CoA, succinyl-CoA, or CoA but not by palmitoyl-CoA . The gene encoding acyl-CoA carboxylase was cloned and characterized . Homology searches of the deduced amino acid sequences of the 62-, 59-, and 20-kDa subunits indicated the presence of functional domains for carboxyltransferase, biotin carboxylase, and biotin carboxyl carrier protein, respectively . Amino acid sequence alignment of acetyl-CoA carboxylases revealed that archaeal acyl-CoA carboxylases are closer to those of Bacteria than to those of Eucarya . The substrate-binding motifs of the enzymes are highly conserved among the three domains . The ATP-binding residues were found in the biotin carboxylase subunit, whereas the conserved biotin-binding site was located on the biotin carboxyl carrier protein . The acyl-CoA-binding site and the carboxybiotin-binding site were found in the carboxyltransferase subunit .
Survival and Resuscitation of Ten Strains of Campylobacter jejuni and Campylobacter coli under Acid Conditions. P. Chaveerach, 2003.The culturability of 10 strains of Campylobacter jejuni and Campylobacter coli was studied after the bacteria were exposed to acid conditions for various periods of time . Campylobacter cells could not survive 2 h under acid conditions (formic acid at pH 4) . The 10 Campylobacter strains could not be recovered, even when enrichment media were used . Viable cells, however, could be detected by a double-staining (5-cyano-2,3-ditolyl tetrazolium chloride [CTC]-4',6'-diamidino-2-phenylindole [DAPI]) technique, demonstrating that the treated bacteria changed into a viable but nonculturable (VBNC) form; the number of VBNC forms decreased over time . Moreover, some VBNC forms of Campylobacter could be successfully resuscitated in specific-free-pathogen fertilized eggs via two routes, amniotic and yolk sac injecting . Bioaccumulation of Copper Ions by Escherichia coli Expressing Vanabin Genes from the Vanadium-Rich Ascidian Ascidia sydneiensis samea. Tatsuya Ueki, 2003.The genes encoding two vanadium-binding proteins, vanabin1 and vanabin2, from a vanadium-rich ascidian, Ascidia sydneiensis samea, were recently identified and cloned (T . Ueki, T . Adachi, S . Kawano, M . Aoshima, N . Yamaguchi, K . Kanamori, and H . Michibata, Biochim . Biophys . Acta 1626:43-50, 2003) . The vanabins were found to bind vanadium(IV), and an excess of copper(II) ions inhibited the binding of vanadium(IV) to the vanabins in vitro . In this study, we constructed Escherichia coli strains that expressed vanabin1 or vanabin2 fused to maltose-binding protein (MBP) in the periplasmic space . We found that both strains accumulated about twenty times more copper(II) ions than the control BL21 strain, while no significant accumulation of vanadium was observed . The strains expressing either MBP-vanabin1 or MBP-vanabin2 absorbed approximately 70% of the copper ions in the medium to which 10 µM copper (II) ions were initially added . The MBP-vanabin1 and MBP-vanabin2 protein expressed in the periplasm bound to copper ions at a copper:protein molar ratio of 8:1 and 5:1, respectively, but MBP did not bind to copper ions . These data showed that the metal-binding proteins vanabin1 and vanabin2 bound copper ions directly and enhanced the bioaccumulation of copper ions by E . coli .
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