Elucidation of the RamA Regulon in Klebsiella pneumoniae Reveals a Role in LPS Regulation

Shyamasree De Majumdar*, Jing Yu, Maria Fookes, Sean P. McAteer, Enrique Llobet, Sarah Finn, Shaun Spence, Avril Monahan, Adrien Kissenpfennig, Rebecca J. Ingram, José Bengoechea, David L. Gally, Séamus Fanning, Joseph S. Elborn, Thamarai Schneiders

*Corresponding author for this work

Research output: Contribution to journalArticle

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Abstract

Klebsiella pneumoniae is a significant human pathogen, in part due to high rates of multidrug resistance. RamA is an intrinsic regulator in K. pneumoniae established to be important for the bacterial response to antimicrobial challenge; however, little is known about its possible wider regulatory role in this organism during infection. In this work, we demonstrate that RamA is a global transcriptional regulator that significantly perturbs the transcriptional landscape of K. pneumoniae, resulting in altered microbe-drug or microbe-host response. This is largely due to the direct regulation of 68 genes associated with a myriad of cellular functions. Importantly, RamA directly binds and activates the lpxC, lpxL-2 and lpxO genes associated with lipid A biosynthesis, thus resulting in modifications within the lipid A moiety of the lipopolysaccharide. RamA-mediated alterations decrease susceptibility to colistin E, polymyxin B and human cationic antimicrobial peptide LL-37. Increased RamA levels reduce K. pneumoniae adhesion and uptake into macrophages, which is supported by in vivo infection studies, that demonstrate increased systemic dissemination of ramA overexpressing K. pneumoniae. These data establish that RamA-mediated regulation directly perturbs microbial surface properties, including lipid A biosynthesis, which facilitate evasion from the innate host response. This highlights RamA as a global regulator that confers pathoadaptive phenotypes with implications for our understanding of the pathogenesis of Enterobacter, Salmonella and Citrobacter spp. that express orthologous RamA proteins.

Original languageEnglish
Article numbere1004627
Number of pages22
JournalPLoS Pathogens
Volume11
Issue number1
DOIs
Publication statusPublished - Jan 2015

Keywords

  • ENTERICA SEROVAR TYPHIMURIUM
  • MULTIDRUG-RESISTANCE REGULATOR
  • AIRWAY EPITHELIAL-CELLS
  • ESCHERICHIA-COLI
  • TRANSCRIPTIONAL ACTIVATORS
  • ANTIMICROBIAL PEPTIDES
  • ANTIBIOTIC-RESISTANCE
  • VIRULENCE FACTORS
  • EFFLUX
  • MARA

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