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Site-Specific Integrative Elements of Rhizobiophage 16-3 Can Integrate into Proline tRNA (CGG) Genes in Different Bacterial Genera. Szabolcs Semsey, 2002.The integrase protein of the Rhizobium meliloti 41 phage 16-3 has been classified as a member of the Int family of tyrosine recombinases . The site-specific recombination system of the phage belongs to the group in which the target site of integration (attB) is within a tRNA gene . Since tRNA genes are conserved, we expected that the target sequence of the site-specific recombination system of the 16-3 phage could occur in other species and integration could take place if the required putative host factors were also provided by the targeted cells . Here we report that a plasmid (pSEM167) carrying the attP element and the integrase gene (int) of the phage can integrate into the chromosomes of R . meliloti 1021 and eight other species . In all cases integration occurred at so-far-unidentified, putative proline tRNA (CGG) genes, indicating the possibility of their common origin . Multiple alignment of the sequences suggested that the location of the att core was different from that expected previously . The minimal attB was identified as a 23-bp sequence corresponding to the anticodon arm of the tRNA .
 B Modulates Virulence Determinant Expression and Stress Resistance: Characterization of a Functional rsbU Strain Derived from Staphylococcus aureus 8325-4.Malcolm J. Horsburgh, 2002.The accessory sigma factor B controls a general stress response that is thought to be important for Staphylococcus aureus survival and may contribute to virulence . The strain of choice for genetic studies, 8325-4, carries a small deletion in rsbU, which encodes a positive regulator of
B activity . Consequently, to enable the role of
B in virulence to be addressed, we constructed an rsbU+ derivative, SH1000, using a method that does not leave behind an antibiotic resistance marker . The phenotypic properties of SH1000 (8325-4 rsbU+) were characterized and compared to those of 8325-4, the rsbU mutant, parent strain . A recognition site for
B was located in the promoter region of katA, the gene encoding the sole catalase of S . aureus, by primer extension analysis . However, catalase expression and activity were similar in SH1000 (8325-4 rsbU+), suggesting that this promoter may have a minor role in catalase expression under normal conditions . Restoration of
B activity in SH1000 (8325-4 rsbU+) resulted in a marked decrease in the levels of the exoproteins SspA and Hla, and this is likely to be mediated by reduced expression of agr in this strain . By using Western blotting and a sarA-lacZ reporter assay, the levels of SarA were found to be similar in strains 8325-4 and SH1000 (8325-4 rsbU+) and sigB mutant derivatives of these strains . This finding contrasts with previous reports that suggested that SarA expression levels are altered when they are measured transcriptionally . Inactivation of sarA in each of these strains resulted in an expected decrease in agr expression; however, the relative level of agr in SH1000 (8325-4 rsbU+) remained less than the relative levels in 8325-4 and the sigB mutant derivatives . We suggest that SarA is not likely to be the effector in the overall
B-mediated effect on agr expression .
Characterization and Regulation of the Genes for a Novel Anthranilate 1,2-Dioxygenase from Burkholderia cepacia DBO1. Hung-Kuang Chang, 2003.Anthranilate (2-aminobenzoate) is an important intermediate in tryptophan metabolism . In order to investigate the degradation of tryptophan through anthranilate by Burkholderia cepacia, several plasposon mutations were constructed of strain DBO1 and one mutant with the plasposon insertion in the anthranilate dioxygenase (AntDO) genes was chosen for further study . The gene sequence obtained from flanking DNA of the plasposon insertion site revealed unexpected information . B . cepacia DBO1 AntDO (designated AntDO-3C) is a three-component Rieske-type [2Fe-2S] dioxygenase composed of a reductase (AndAa), a ferredoxin (AndAb), and a two-subunit oxygenase (AndAcAd) . This is in contrast to the two-component (an oxygenase and a reductase) AntDO enzyme from Acinetobacter sp . strain ADP1, P . aeruginosa PAO1, and P . putida P111 . AntDO from strains ADP1, PAO1, and P111 are closely related to benzoate dioxygenase, while AntDO-3C is closely related to aromatic hydrocarbon dioxygenases from Novosphingobium aromaticivorans F199 and Sphingomonas yanoikuyae B1 and 2-chlorobenzoate dioxygenase from P . aeruginosa strains 142 and JB2 . Escherichia coli cells expressing the functional AntDO-3C genes transform anthranilate and salicylate (but not 2-chlorobenzoate) to catechol . The enzyme includes a novel reductase whose absence results in less efficient transformation of anthranilate by the oxygenase and ferredoxin . AndR, a possible AraC/XylS-type transcriptional regulator, was shown to positively regulate expression of the andAcAdAbAa genes . Anthranilate was the only effector (of 12 aromatic compounds tested) that was able to induce expression of the genes . DNA Microarrays in Analysis of Quorum Sensing: Strengths and Limitations. Michael L. Vasil, 2003. Improved Anaerobic Use of Arginine by Saccharomyces cerevisiae. Olga Martin, 2003.Anaerobic arginine catabolism in Saccharomyces cerevisiae was genetically modified to allow assimilation of all four rather than just three of the nitrogen atoms in arginine . This was accomplished by bypassing normal formation of proline, an unusable nitrogen source in the absence of oxygen, and causing formation of glutamate instead . A pro3 ure2 strain expressing a PGK1 promoter-driven PUT2 allele encoding  1-pyrroline-5-carboxylate dehydrogenase lacking a mitochondrial targeting sequence produced significant cytoplasmic activity, accumulated twice as much intracellular glutamate, and produced twice as much cell mass as the parent when grown anaerobically on limiting arginine as sole nitrogen source .
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