title: PHB granules are attached to the nucleoid via PhaM in Ralstonia eutropha.
abstract: BACKGROUND
  Poly(3-hydroxybutyrate) (PHB) granules are important storage compounds of carbon and energy in many prokaryotes which allow survival of the cells in the absence of suitable carbon sources. Formation and subcellular localization of PHB granules was previously assumed to occur randomly in the cytoplasm of PHB accumulating bacteria. However, contradictionary results on subcellular localization of PHB granules in Ralstonia eutropha were published, recently.
  
  
  RESULTS
  Here, we provide evidence by transmission electron microscopy that PHB granules are localized in close contact to the nucleoid region in R. eutropha during growth on nutrient broth. Binding of PHB granules to the nucleoid is mediated by PhaM, a PHB granule associated protein with phasin-like properties that is also able to bind to DNA and to phasin PhaP5. Over-expression of PhaM resulted in formation of many small PHB granules that were always attached to the nucleoid region. In contrast, PHB granules of ∆phaM strains became very large and distribution of granules to daughter cells was impaired. Association of PHB granules to the nucleoid region was prevented by over-expression of PhaP5 and clusters of several PHB granules were mainly localized near the cell poles.
  
  
  CONCLUSIONS
  Subcellular localization of PHB granules is controlled in R. eutropha and depends on the presence and concentrations of at least two PHB granule associated proteins, PhaM and PhaP5.
authors.affiliation: Institute of Microbiology, University of Stuttgart, Allmandring 31, Stuttgart 70550, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Wahl
authors.forename: Nora
authors.initials: N
authors.lastname: Schuth
authors.forename: Daniel
authors.initials: D
authors.lastname: Pfeiffer
authors.forename: Stephan
authors.initials: S
authors.lastname: Nussberger
authors.forename: Dieter
authors.initials: D
authors.lastname: Jendrossek
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002876:Chromosomes, Bacterial / Q000378:metabolism*; D020118:Cupriavidus necator / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D006885:Hydroxybutyrates / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D011091:Polyesters / Q000378:metabolism*; D000094122:Polyhydroxybutyrates
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D006885:Hydroxybutyrates; D011091:Polyesters; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates