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PLoS Pathog. 2015 Jan 29;11(1):e1004627. doi: 10.1371/journal.ppat.1004627. eCollection 2015 Jan.

Elucidation of the RamA regulon in Klebsiella pneumoniae reveals a role in LPS regulation.

Author information

1
Centre for Infection and Immunity, Belfast, United Kingdom; Division of Pathway and Infection Medicine, Edinburgh, United Kingdom.
2
Centre for Infection and Immunity, Belfast, United Kingdom.
3
Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom.
4
Division of Immunity and Infection, The Roslin Institute and R(D)SVS, The University of Edinburgh, Easter Bush, Midlothian, United Kingdom.
5
Laboratory Microbial Pathogenesis, Fundació d'Investigació Sanitària de les Illes Balears (FISIB) Recinto Hospital Joan March, Bunyola, Spain.
6
UCD Centre for Molecular Innovation and Drug Discovery, School of Public Health, Physiotherapy & Population Science, University College Dublin, Dublin, Ireland.
7
Centre for Infection and Immunity, Belfast, United Kingdom; Laboratory Microbial Pathogenesis, Fundació d'Investigació Sanitària de les Illes Balears (FISIB) Recinto Hospital Joan March, Bunyola, Spain.

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.

PMID:
25633080
PMCID:
PMC4310594
DOI:
10.1371/journal.ppat.1004627
[Indexed for MEDLINE]
Free PMC Article

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