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1.
Antimicrob Agents Chemother ; 56(4): 1821-7, 2012 Apr.
Article in English | MEDLINE | ID: mdl-22290975

ABSTRACT

Plasmids pPAB19-1, pPAB19-2, pPAB19-3, and pPAB19-4, isolated from Salmonella and Escherichia coli clinical strains from hospitals in Argentina, were completely sequenced. These plasmids include the qnrB19 gene and are 2,699, 3,082, 2,989, and 2,702 nucleotides long, respectively, and they share extensive homology among themselves and with other previously described small qnrB19-harboring plasmids. The genetic environment of qnrB19 in all four plasmids is identical to that in these other plasmids and in transposons such as Tn2012, Tn5387, and Tn5387-like. Nucleotide sequence comparisons among these and previously described plasmids showed a variable region characterized by being flanked by an oriT locus and a Xer recombination site. We propose that this arrangement could play a role in the evolution of plasmids and present a model for DNA swapping between plasmid molecules mediated by site-specific recombination events at oriT and a Xer target site.


Subject(s)
Escherichia coli/genetics , Plasmids/genetics , Salmonella/genetics , Argentina , Base Sequence , Biological Evolution , DNA, Bacterial/genetics , Escherichia coli Infections/microbiology , Humans , Molecular Sequence Data , Polymerase Chain Reaction , Recombination, Genetic , Salmonella Infections/microbiology
2.
Biochemistry ; 50(29): 6396-408, 2011 Jul 26.
Article in English | MEDLINE | ID: mdl-21707055

ABSTRACT

Burkholderia cenocepacia is an important opportunistic pathogen, and one of the most striking features of the Burkholderia genus is the collection of polar lipids present in its membrane, including phosphatidylethanolamine (PE) and ornithine-containing lipids (OLs), as well as the 2-hydroxylated derivatives of PE and OLs (2-OH-PE and 2-OH-OLs, respectively), which differ from the standard versions by virtue of the presence of a hydroxyl group at C2 (2-OH) of an esterified fatty acyl residue. Similarly, a lipid A-esterified myristoyl group from Salmonella typhimurium can have a 2-hydroxy modification that is due to the LpxO enzyme. We thus postulated that 2-hydroxylation of 2-OH-OLs might be catalyzed by a novel dioxygenase homologue of LpxO. In B. cenocepacia, we have now identified two open reading frames (BCAM1214 and BCAM2401) homologous to LpxO from S. typhimurium. The introduction of bcam2401 (designated olsD) into Sinorhizobium meliloti leads to the formation of one new lipid and in B. cenocepacia of two new lipids. Surprisingly, the lipid modifications on OLs due to OlsD occur on the amide-linked fatty acyl chain. This is the first report of a hydroxyl modification of OLs on the amide-linked fatty acyl moiety. Formation of hydroxylated OLs occurs only when the biosynthesis pathway for nonmodified standard OLs is intact. The hydroxyl modification of OLs on the amide-linked fatty acyl moiety occurs only under acid stress conditions. An assay has been developed for the OlsD dioxygenase, and an initial characterization of the enzyme is presented.


Subject(s)
Burkholderia cenocepacia/enzymology , Burkholderia cenocepacia/genetics , Dioxygenases/genetics , Fatty Acids/metabolism , Genes, Bacterial/genetics , Membrane Lipids/metabolism , Ornithine/analogs & derivatives , Acids/pharmacology , Amides/metabolism , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Burkholderia cenocepacia/drug effects , Burkholderia cenocepacia/growth & development , Cardiolipins/metabolism , Cell Membrane/drug effects , Cell Membrane/enzymology , Dioxygenases/metabolism , Esterification/drug effects , Fatty Acids/chemistry , Hydroxylation/drug effects , Lipids/chemistry , Mass Spectrometry , Membrane Lipids/chemistry , Mutation/genetics , Ornithine/chemistry , Ornithine/metabolism , Phosphatidylethanolamines/metabolism , Phosphatidylglycerols/metabolism , Salmonella typhimurium/drug effects , Salmonella typhimurium/enzymology , Sequence Homology, Amino Acid , Sinorhizobium meliloti/drug effects , Sinorhizobium meliloti/metabolism
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