title: An Oxygen-Sensing Two-Component System in the Burkholderia cepacia Complex Regulates Biofilm, Intracellular Invasion, and Pathogenicity.
abstract: Burkholderia dolosa is a member of the Burkholderia cepacia complex (BCC), which is a group of bacteria that cause chronic lung infection in patients with cystic fibrosis (CF) and can be associated with outbreaks carrying high morbidity and mortality. While investigating the genomic diversity of B. dolosa strains collected from an outbreak among CF patients, we previously identified fixL as a gene showing signs of strong positive selection. This gene has homology to fixL of the rhizobial FixL/FixJ two-component system. The goals of this study were to determine the functions of FixLJ and their role in virulence in B. dolosa. We generated a fixLJ deletion mutant and complemented controls in B. dolosa strain AU0158. Using a fixK-lacZ reporter we found that FixLJ was activated in low oxygen in multiple BCC species. In a murine pneumonia model, the B. dolosa fixLJ deletion mutant was cleared faster from the lungs and spleen than wild-type B. dolosa strain AU0158 at 7 days post infection. Interestingly, the fixLJ deletion mutant made more biofilm, albeit with altered structure, but was less motile than strain AU0158. Using RNA-seq with in vitro grown bacteria, we found ~11% of the genome was differentially expressed in the fixLJ deletion mutant relative to strain AU0158. Multiple flagella-associated genes were down-regulated in the fixLJ deletion mutant, so we also evaluated virulence of a fliC deletion mutant, which lacks a flagellum. We saw no difference in the ability of the fliC deletion mutant to persist in the murine model relative to strain AU0158, suggesting factors other than flagella caused the phenotype of decreased persistence. We found the fixLJ deletion mutant to be less invasive in human lung epithelial and macrophage-like cells. In conclusion, B. dolosa fixLJ is a global regulator that controls biofilm formation, motility, intracellular invasion/persistence, and virulence.
authors.affiliation: Division of Critical Care Medicine, Department of Anesthesiology, Perioperative and Pain Medicine, Boston Children's Hospital, Boston, Massachusetts, United States of America.|Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Matthew M
authors.identifier: 0000-0001-7454-4180
authors.initials: MM
authors.lastname: Schaefers
authors.affiliation: Division of Critical Care Medicine, Department of Anesthesiology, Perioperative and Pain Medicine, Boston Children's Hospital, Boston, Massachusetts, United States of America.
authors.forename: Tiffany L
authors.initials: TL
authors.lastname: Liao
authors.affiliation: Division of Critical Care Medicine, Department of Anesthesiology, Perioperative and Pain Medicine, Boston Children's Hospital, Boston, Massachusetts, United States of America.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Boisvert
authors.affiliation: IAME, UMR 1137, INSERM, Université Paris Diderot, Sorbonne Paris Cité, Paris, France; Service de Réanimation médico-chirurgicale, Hôpital Louis Mourier, AP-HP, Colombes, France.
authors.forename: Damien
authors.identifier: 0000-0002-6103-6416
authors.initials: D
authors.lastname: Roux
authors.affiliation: Department of Biology, University of Louisville, Louisville, Kentucky, United States of America.
authors.forename: Deborah
authors.identifier: 0000-0001-9576-3833
authors.initials: D
authors.lastname: Yoder-Himes
authors.affiliation: Division of Critical Care Medicine, Department of Anesthesiology, Perioperative and Pain Medicine, Boston Children's Hospital, Boston, Massachusetts, United States of America.|Department of Anaesthesia, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Priebe
mesh_terms: D000693:Anaerobiosis / Q000502:physiology; D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D019121:Burkholderia Infections / Q000150:complications / Q000382:microbiology / Q000473:pathology*; D042602:Burkholderia cepacia complex / Q000235:genetics / Q000472:pathogenicity*; D002460:Cell Line; D003550:Cystic Fibrosis / Q000150:complications; D004195:Disease Models, Animal; D004196:Disease Outbreaks; D004789:Enzyme Activation; D005260:Female; D005407:Flagella / Q000235:genetics; D005408:Flagellin / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D006420:Hemeproteins / Q000235:genetics* / Q000378:metabolism; D000071677:Histidine Kinase; D006801:Humans; D007763:Lac Operon / Q000235:genetics; D008168:Lung / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D010100:Oxygen / Q000378:metabolism; D011014:Pneumonia / Q000150:complications / Q000382:microbiology / Q000473:pathology*; D011401:Promoter Regions, Genetic / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D006420:Hemeproteins; D005408:Flagellin; C066628:FixK protein, Bacteria; C069289:FixJ protein, Bacteria; C067929:FixL protein, Bacteria; D000071677:Histidine Kinase; D010100:Oxygen