title: Transcriptional profiling of Legionella pneumophila biofilm cells and the influence of iron on biofilm formation.
abstract: In aquatic environments, biofilms constitute an ecological niche where Legionella pneumophila persists as sessile cells. However, very little information on the sessile mode of life of L. pneumophila is currently available. We report here the development of a model biofilm of L. pneumophila strain Lens and the first transcriptome analysis of L. pneumophila biofilm cells. Global gene expression analysis of sessile cells as compared to two distinct populations of planktonic cells revealed that a substantial proportion of L. pneumophila genes is differentially expressed, as 2.3 % of the 2932 predicted genes exhibited at least a twofold change in gene expression. Comparison with previous results defining the gene expression profile of replicative- and transmissive-phase Legionella suggests that sessile cells resemble bacteria in the replicative phase. Further analysis of the most strongly regulated genes in sessile cells identified two induced gene clusters. One contains genes that encode alkyl hydroperoxide reductases known to act against oxidative stress. The second encodes proteins similar to PvcA and PvcB that are involved in siderophore biosynthesis in Pseudomonas aeruginosa. Since iron has been reported to modify biofilm formation in other species, we further focused on iron control of gene expression and biofilm formation. Among the genes showing the greatest differences in expression between planktonic cells and biofilm, only pvcA and pvcB were regulated by iron concentration. A DeltapvcA L. pneumophila mutant showed no changes in biofilm formation compared to the wild-type, suggesting that the pvcA product is not mandatory for biofilm formation. However, biofilm formation by L. pneumophila wild-type and a DeltapvcA strain was clearly inhibited in iron-rich conditions.
authors.affiliation: Laboratoire de Chimie de l'Eau et de l'Environnement, UMR 6008, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers Cedex, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hindré
authors.affiliation: Unité de Génomique des Microorganismes Pathogènes and CNRS URA 2171, Institut Pasteur, 28 Rue du Dr Roux, 75724 Paris, France.
authors.forename: Holger
authors.initials: H
authors.lastname: Brüggemann
authors.affiliation: Unité de Génomique des Microorganismes Pathogènes and CNRS URA 2171, Institut Pasteur, 28 Rue du Dr Roux, 75724 Paris, France.
authors.forename: Carmen
authors.initials: C
authors.lastname: Buchrieser
authors.affiliation: Laboratoire de Chimie de l'Eau et de l'Environnement, UMR 6008, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers Cedex, France.
authors.forename: Yann
authors.initials: Y
authors.lastname: Héchard
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D053898:Biosynthetic Pathways / Q000235:genetics; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics; D007501:Iron / Q000378:metabolism*; D016952:Legionella pneumophila / Q000235:genetics / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017262:Siderophores / Q000096:biosynthesis / Q000235:genetics
chemical_list: D017262:Siderophores; D007501:Iron