title: Pinewood nematode-associated bacteria contribute to oxidative stress resistance of Bursaphelenchus xylophilus.
abstract: BACKGROUND
  Pine wilt disease (PWD) caused by the pinewood nematode Bursaphelenchus xylophilus is one of the most serious forest diseases in the world. The role of B. xylophilus-associated bacteria in PWD and their interaction with the nematode, have recently been under substantial investigation. Several studies report a potential contribution of the bacteria for the PWD development, either as a helper to enhance the pathogenicity of the nematode or as a pathogenic agent expressing interesting traits related to lifestyle host-adaptation.
  
  
  RESULTS
  We investigated the nematode-bacteria interaction under a severe oxidative stress (OS) condition using a pro-oxidant hydrogen peroxide and explored the adhesion ability of these bacteria to the cuticle surface of the nematodes. Our results clearly demonstrated a beneficial effect of the Serratia spp. (isolates LCN-4, LCN-16 and PWN-146) to B. xylophilus under the OS condition. Serratia spp. was found to be extremely OS-resistant, and promote survival of B. xylophilus and down-regulate two B. xylophilus catalase genes (Bxy-ctl-1 and Bxy-ctl-2). In addition, we show that the virulent isolate (Ka4) of B. xylophilus survives better than the avirulent (C14-5) isolate under the OS condition. The bacterial effect was transverse for both B. xylophilus isolates. We could not observe a strong and specific adhesion of these bacteria on the B. xylophilus cuticle surface.
  
  
  CONCLUSIONS
  We report, for the first time, that B. xylophilus associated bacteria may assist the nematode opportunistically in the disease, and that a virulent B. xylophilus isolate displayed a higher tolerance towards the OS conditions than an avirulent isolate.
authors.forename: Cláudia S L
authors.initials: CS
authors.lastname: Vicente
authors.forename: Yoriko
authors.initials: Y
authors.lastname: Ikuyo
authors.forename: Manuel
authors.initials: M
authors.lastname: Mota
authors.affiliation: Department of Environmental Biology, College of Bioscience & Biotechnology, Chubu University, 1200 Matsumoto, Kasugai, Aichi 487-8501, Japan. koichihasegawa@isc.chubu.ac.jp.
authors.forename: Koichi
authors.initials: K
authors.lastname: Hasegawa
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D002374:Catalase / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D015536:Down-Regulation; D006861:Hydrogen Peroxide / Q000633:toxicity*; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D017422:Sequence Analysis, DNA; D012705:Serratia / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D013312:Stress, Physiological; D016019:Survival Analysis; D017187:Tylenchida / Q000187:drug effects / Q000382:microbiology* / Q000502:physiology*
chemical_list: D004269:DNA, Bacterial; D006861:Hydrogen Peroxide; D002374:Catalase