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Identification of Specific In Vivo-Induced (ivi) Genes in Yersinia ruckeri and Analysis of Ruckerbactin, a Catecholate Siderophore Iron Acquisition System. L. Fernández, 2004.This work reports the utilization of an in vivo expression technology system to identify in vivo-induced (ivi) genes in Yersinia ruckeri after determination of the conditions needed for its selection in fish . Fourteen clones were selected, and the cloned DNA fragments were analyzed after partial sequencing . In addition to sequences with no significant similarity, homology with genes encoding proteins putatively involved in two-component and type IV secretion systems, adherence, specific metabolic functions, and others were found . Among these sequences, four were involved in iron acquisition through a catechol siderophore (ruckerbactin) . Thus, unlike other pathogenic yersiniae producing yersiniabactin, Y . ruckeri might be able to produce and utilize only this phenolate . The genetic organization of the ruckerbactin biosynthetic and uptake loci was similar to that of the Escherichia coli enterobactin gene cluster . Genes rucC and rupG, putative counterparts of E . coli entC and fepG, respectively, involved in the biosynthesis and transport of the iron siderophore complex, respectively, were analyzed further . Thus, regulation of expression by iron and temperature and their presence in other Y . ruckeri siderophore-producing strains were confirmed for these two loci . Moreover, 50% lethal dose values 100-fold higher than those of the wild-type strain were obtained with the rucC isogenic mutant, showing the importance of ruckerbactin in the pathogenesis caused by this microorganism . Factors Affecting Start Site Selection at the Escherichia coli fis Promoter. Kimberly A. Walker, 2002.Transcription initiation with CTP is an uncommon feature among Escherichia coli  70 promoters . The fis promoter (fis P), which is subject to growth phase-dependent regulation, is among the few that predominantly initiate transcription with CTP . Mutations in this promoter that cause a switch from utilization of CTP to either ATP or GTP as the initiation nucleotide drastically alter its growth phase regulation pattern, suggesting that the choice of the primary initiating nucleotide can significantly affect its regulation . To better understand what factors influence this choice in fis P, we made use of a series of promoter mutations that altered the nucleotide or position used for initiation . Examination of these promoters indicates that start site selection is determined by a combination of factors that include preference for a nucleotide distance from the -10 region (8 > 7 > 9 >> 6 >> 10 > 11), initiation nucleotide preference (A = G >> CTP
 UTP), the DNA sequence surrounding the initiation region, the position of the -35 region, and changes in the intracellular nucleoside triphosphate pools . We describe the effects that each of these factors has on start site selection in the fis P and discuss the interplay between position and nucleotide preference in this important process .
The Escherichia coli Cell Division Protein FtsW Is Required To Recruit Its Cognate Transpeptidase, FtsI (PBP3), to the Division Site. Keri L. N. Mercer, 2002.The bacterial cell division protein FtsW has been suggested to perform two functions: stabilize the FtsZ cytokinetic ring, and facilitate septal peptidoglycan synthesis by the transpeptidase FtsI (penicillin-binding protein 3) . We show here that depleting Escherichia coli cells of FtsW had little effect on the abundance of FtsZ rings but abrogated recruitment of FtsI to potential division sites . Analysis of FtsW localization confirmed and extended these results; septal localization of FtsW required FtsZ, FtsA, FtsQ, and FtsL but not FtsI . Thus, FtsW is a late recruit to the division site and is essential for subsequent recruitment of its cognate transpeptidase FtsI but not for stabilization of FtsZ rings . We suggest that a primary function of FtsW homologues—which are found in almost all bacteria and appear to work in conjunction with dedicated transpeptidases involved in division, elongation, or sporulation—is to recruit their cognate transpeptidases to the correct subcellular location . 2-Aminopurine Allows Interspecies Recombination by a Reversible Inactivation of the Escherichia coli Mismatch Repair System. Ivan Matic, 2003.2-Aminopurine treatment of Escherichia coli induces a reversible phenotype of DNA mismatch repair deficiency . This transient phenotype results in a 300-fold increase in the frequency of interspecies conjugational recombination with a Salmonella enterica serovar Typhimurium Hfr donor . This method can be used for the generation of biodiversity by allowing recombination between diverged genes and genomes .
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