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Phosphoethanolamine modification of lipid A in colistin-resistant variants of Acinetobacter baumannii mediated by the pmrAB two-component regulatory system

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  • Colistin Resistance Is Rare In Acinetobacter Baumannii
  • And Little Is Known About Its Mechanism
  • We Investigated The Role Of Pmrcab In This Trait
  • Using (I) Resistant And Susceptible Clinical Strains
  • (Ii) Laboratory-Selected Mutants Of The Type Strain Atcc 19606 And Of The Clinical Isolate Abrim
  • And (Iii) A Susceptible/Resistant Pair Of Isogenic Clinical Isolates
  • Ab15/133 And Ab15/132
  • Isolated From The Same Patient
  • Pmrab Sequences In All The Colistin-Susceptible Isolates Were Identical To Reference Sequences
  • Whereas Resistant Clinical Isolates Harbored One Or Two Amino Acid Replacements Variously Located In
  • Single Substitutions In Pmrb Were Also Found In Resistant Mutants Of Strains Atcc 19606 And Abrim An
  • No Mutations In Pmra Or Pmrc Were Found
  • Reverse Transcriptase (Rt)-Pcr Identified Increased Expression Of Pmra (4- To 13-Fold)
  • Pmrb (2- To 7-Fold)
  • And Pmrc (1- To 3-Fold) In Resistant Versus Susceptible Organisms
  • Matrix-Assisted Laser Desorption Ionization-Time Of Flight (Maldi-Tof) Mass Spectrometry Showed The
  • Pmrb Gene Knockout Mutants Of The Colistin-Resistant Atcc 19606 Derivative Showed &Gt
  • 100-Fold Increased Susceptibility To Colistin And 5-Fold Decreased Expression Of Pmrc
  • They Also Lacked The Addition Of Phosphoethanolamine To Lipid A
  • We Conclude That The Development Of A Moderate Level Of Colistin Resistance In A
  • Baumannii Requires Distinct Genetic Events
  • Including (I) At Least One Point Mutation In Pmrb
  • (Ii) Upregulation Of Pmrab
  • And (Iii) Expression Of Pmrc
  • Which Lead To Addition Of Phosphoethanolamine To Lipid A
  • Copyright © 2011
  • American Society For Microbiology
  • All Rights Reserved
  • Biology
  • Medicine


1 Ludwig Eichinger and Francisco Rivero (eds.), Dictyostelium discoideum Protocols, Methods in Molecular Biology 983, DOI 10.1007/978-1-62703-302-2_1, © Springer Science+Business Media, LLC 2013 Chapter 1 The Amoebozoa Christina Schilde and Pauline Schaap Abstract The model organism Dictyostelium discoideum is a member of the Amoebozoa, one of the six major divisions of eukaryotes. Amoebozoa comprise a wide variety of amoeboid and fl agellate organisms with single cells measuring from 5 μ m to several meters across. They have adopted many different life styles and sexual behaviors and can live in all but the most extreme environments. This chapter provides an overview of Amoebozoan diversity and compares roads towards multicellularity within the Amoebozoa with inven- tions of multicellularity in other protist divisions. The chapter closes with a scenario for the evolution of Dictyostelid multicellularity from an Amoebozoan stress response. Key words Amoebozoa , Protista , Aggregative multicellularity , Encystation , Sporulation , Morphogenesis , Cyclic AMP signaling , Phylogeny The Dictyostelids have fascinated biologists for over 150 years with their ability to assemble up to a million amoebas into a tactile migrating organism, which, after seeking out a site for spore dis- persal, transforms into a well-balanced fruiting structure. The development of a range of molecular genetic and cell biological procedures for the species Dictyostelium discoideum over the past 30 years has established this species as an important model organ- ism for the study of fundamental cell biological and developmental processes ( 1 ) . More recently, the evolution of social behavior and the study of genes associated with human diseases and bacterial infections have been added to the repertoire of research questions that can be addressed in Dictyostelia ( 2 ) . With putative applications of research in mind,

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