Lorea Manterola, Ignacio Moriyón, Edgardo Moreno, Alberto Sola-Landa, David S. Weiss, Michel H. J. Koch, Jörg Howe, Klaus Brandenburg and Ignacio López-Goñi J. Bacteriol. 2005, 187(16):5631. DOI: 10.1128/JB.187.16.5631-5639.2005. Downloaded fromhttp://jb.asm.org/ on November 16, 2011 by guest
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JOURNAL OF BACTERIOLOGY, Aug. 2005, p. 5631–5639 0021-9193/05/$08.00 0 doi:10.1128/JB.187.16.5631–5639.2005 Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Vol. 187, No. 16
TheLipopolysaccharide of Brucella abortus BvrS/BvrR Mutants Contains Lipid A Modiﬁcations and Has Higher Afﬁnity for Bactericidal Cationic Peptides
Lorea Manterola,1 Ignacio Moriyon,1 Edgardo Moreno,2 Alberto Sola-Landa,1† ´ David S. Weiss,3 Michel H. J. Koch,4 Jorg Howe,5 Klaus Brandenburg,5 ¨ and Ignacio Lopez-Goni1* ´ ˜
Departamento de Microbiologı y Parasitologı Universidad de Navarra, Pamplona, Spain1;Programa de ´a ´a, Investigacion en Enfermedades Tropicales, Escuela de Medicina Veterinaria, Universidad ´ Nacional de Heredia, Heredia, Costa Rica2; Department of Microbiology and Immunology, Stanford University Medical Center, Stanford, California3; European Molecular Biology Laboratory-Hamburg, Hamburg, Germany4; and Forschungszentrum Borstel, Borstel, Germany5
Received 12 April 2005/Accepted30 May 2005
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The two-component BvrS/BvrR system is essential for Brucella abortus virulence. It was shown previously that its dysfunction abrogates expression of some major outer membrane proteins and increases bactericidal peptide sensitivity. Here, we report that BvrS/BvrR mutants have increased surface hydrophobicity andsusceptibility to killing by nonimmune serum. The bvrS and bvrR mutant lipopolysaccharides (LPSs) bound more polymyxin B, chimeras constructed with bvrS mutant cells and parental LPS showed augmented polymyxin B resistance, and, conversely, parental cells and bvrS mutant LPS chimeras were more sensitive and displayed polymyxin B-characteristic outer membrane lesions, implicating LPS as beingresponsible for the phenotype of the BvrS/BvrR mutants. No qualitative or quantitative changes were detected in other envelope and outer membrane components examined: periplasmic (1-2) glucans, native hapten polysaccharide, and phospholipids. The LPS of the mutants was similar to parental LPS in O-polysaccharide polymerization and ﬁne structure but showed both increased underacylated lipid A species andhigher acyl-chain ﬂuidity that correlated with polymyxin B binding. These lipid A changes did not alter LPS cytokine induction, showing that in contrast to other gram-negative pathogens, recognition by innate immune receptors is not decreased by these changes in LPS structure. Transcription of Brucella genes required for incorporating long acyl chains into lipid A (acpXL and lpxXL) or implicated inlipid A acylation control (bacA) was not affected. We propose that in Brucella the outer membrane homeostasis depends on the functioning of BvrS/BvrR. Accordingly, disruption of BvrS/BvrR damages the outer membrane, thus contributing to the severe attenuation manifested by bvrS and bvrR mutants.
Bacteria are able to survive in different environments by modulating the expression of their...