A long-chain flavodoxin protects Pseudomonas aeruginosa from oxidative stress and host bacterial clearance

PLoS Genet. 2014 Feb 13;10(2):e1004163. doi: 10.1371/journal.pgen.1004163. eCollection 2014 Feb.


Long-chain flavodoxins, ubiquitous electron shuttles containing flavin mononucleotide (FMN) as prosthetic group, play an important protective role against reactive oxygen species (ROS) in various microorganisms. Pseudomonas aeruginosa is an opportunistic pathogen which frequently has to face ROS toxicity in the environment as well as within the host. We identified a single ORF, hereafter referred to as fldP (for fl avo d oxin from P . aeruginosa), displaying the highest similarity in length, sequence identity and predicted secondary structure with typical long-chain flavodoxins. The gene was cloned and expressed in Escherichia coli. The recombinant product (FldP) could bind FMN and exhibited flavodoxin activity in vitro. Expression of fldP in P. aeruginosa was induced by oxidative stress conditions through an OxyR-independent mechanism, and an fldP-null mutant accumulated higher intracellular ROS levels and exhibited decreased tolerance to H2O2 toxicity compared to wild-type siblings. The mutant phenotype could be complemented by expression of a cyanobacterial flavodoxin. Overexpression of FldP in a mutT-deficient P. aeruginosa strain decreased H2O2-induced cell death and the hypermutability caused by DNA oxidative damage. FldP contributed to the survival of P. aeruginosa within cultured mammalian macrophages and in infected Drosophila melanogaster, which led in turn to accelerated death of the flies. Interestingly, the fldP gene is present in some but not all P. aeruginosa strains, constituting a component of the P. aeruginosa accessory genome. It is located in a genomic island as part of a self-regulated polycistronic operon containing a suite of stress-associated genes. The collected results indicate that the fldP gene encodes a long-chain flavodoxin, which protects the cell from oxidative stress, thereby expanding the capabilities of P. aeruginosa to thrive in hostile environments.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cloning, Molecular
  • Flavodoxin / genetics*
  • Flavodoxin / metabolism
  • Gene Expression Regulation, Bacterial
  • Genome, Bacterial
  • Host-Parasite Interactions / genetics*
  • Oxidative Stress*
  • Pseudomonas aeruginosa / genetics*
  • Pseudomonas aeruginosa / metabolism
  • Reactive Oxygen Species / metabolism


  • Flavodoxin
  • Reactive Oxygen Species

Grants and funding

AMS was supported by the Agencia Nacional de Promoción Científica y Tecnológica (ANPCYT) Grant PICT-2012–2088 (http://www.agencia.gov.ar/), and Secretaría de Ciencia y Técnica (SECYT-UNC) Grant 05/C532 (http://www.secyt.unc.edu.ar/). NC was supported by ANPCYT Grant PICT-2011-2621. MCS was supported by Institut Pasteur and LabEx IBEID and the AXA Research Fund to JAM. JLB was supported by ANPCYT Grant PICT-2012-2284. AJM, ARK, JLB, NC and AMS are staff members of Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET, Argentina), and RAT and YSR are fellows of the same Institution. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.