title: Growth on mannitol-rich media elicits a genome-wide transcriptional response in Burkholderia multivorans that impacts on multiple virulence traits in an exopolysaccharide-independent manner.
abstract: In common with other members of the Burkholderia cepacia complex (BCC), Burkholderia multivorans is capable of producing exopolysaccharide (EPS) when grown on certain mannitol-rich media. The significance of the resulting mucoid phenotype and the genome-wide response to mannitol has never been characterized despite its clinical relevance following the approval of a dried-powder preparation of mannitol as an inhaled osmolyte therapy for cystic fibrosis (CF) patients. In the present study we defined the transcriptional response of B. multivorans ATCC 17616, a model genome-sequenced strain of environmental origin, to growth on mannitol-rich yeast extract media (MYEM). EPS-dependent and -independent impact of MYEM on virulence-associated traits was assessed in both strain ATCC 17616 and the CF isolate B. multivorans C1576. Our studies revealed a significant transcriptional response to MYEM encompassing approximately 23 % of predicted genes within the genome. Strikingly, this transcriptional response identified that EPS induction occurs in ATCC 17616 without the upregulation of the bce-I and bce-II EPS gene clusters, despite their pivotal role in EPS biosynthesis. Of approximately 20 differentially expressed putative virulence factors, 16 exhibited upregulation including flagella, ornibactin, oxidative stress proteins and phospholipases. MYEM-grown B. multivorans also exhibited enhanced motility, biofilm formation and epithelial cell invasion. In contrast to these potential virulence enhancements, MYEM-grown B. multivorans C1576 showed attenuated virulence in the Galleria mellonella infection model. All of the observed phenotypic responses occurred independently of EPS production, highlighting the profound impact that mannitol-based growth has on the physiology and virulence of B. multivorans.
authors.affiliation: Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK.
authors.forename: Carmen C
authors.initials: CC
authors.lastname: Denman
authors.affiliation: Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Robinson
authors.affiliation: Organisms & Environment Division, Cardiff School of Biosciences, Cardiff University, Cardiff, UK.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Sass
authors.affiliation: Organisms & Environment Division, Cardiff School of Biosciences, Cardiff University, Cardiff, UK.
authors.forename: Eshwar
authors.initials: E
authors.lastname: Mahenthiralingam
authors.affiliation: Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Brown
mesh_terms: D000818:Animals; D018441:Biofilms / Q000254:growth & development; D042602:Burkholderia cepacia complex / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity* / Q000502:physiology*; D002460:Cell Line; D003470:Culture Media / Q000737:chemistry; D004705:Endocytosis; D004847:Epithelial Cells / Q000382:microbiology; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D006801:Humans; D007915:Lepidoptera / Q000382:microbiology; D008124:Locomotion; D008353:Mannitol / Q000378:metabolism*; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D016019:Survival Analysis; D014158:Transcription, Genetic; D037521:Virulence Factors / Q000096:biosynthesis*
chemical_list: D003470:Culture Media; D011135:Polysaccharides, Bacterial; D037521:Virulence Factors; D008353:Mannitol