title: Secreted pitfall-trap fluid of carnivorous Nepenthes plants is unsuitable for microbial growth.
abstract: OBJECTIVE
  Carnivorous plants of the genus Nepenthes possess modified leaves that form pitfall traps in order to capture prey, mainly arthropods, to make additional nutrients available for the plant. These pitchers contain a digestive fluid due to the presence of hydrolytic enzymes. In this study, the composition of the digestive fluid was further analysed with regard to mineral nutrients and low molecular-weight compounds. A potential contribution of microbes to the composition of pitcher fluid was investigated.
  
  
  METHODS
  Fluids from closed pitchers were harvested and analysed for mineral nutrients using analytical techniques based on ion-chromatography and inductively coupled plasma-optical emission spectroscopy. Secondary metabolites were identified by a combination of LC-MS and NMR. The presence of bacteria in the pitcher fluid was investigated by PCR of 16S-rRNA genes. Growth analyses of bacteria and yeast were performed in vitro with harvested pitcher fluid and in vivo within pitchers with injected microbes.
  
  
  RESULTS
  The pitcher fluid from closed pitchers was found to be primarily an approx. 25-mm KCl solution, which is free of bacteria and unsuitable for microbial growth probably due to the lack of essential mineral nutrients such as phosphate and inorganic nitrogen. The fluid also contained antimicrobial naphthoquinones, plumbagin and 7-methyl-juglone, and defensive proteins such as the thaumatin-like protein. Challenging with bacteria or yeast caused bactericide as well as fungistatic properties in the fluid. Our results reveal that Nepenthes pitcher fluids represent a dynamic system that is able to react to the presence of microbes.
  
  
  CONCLUSIONS
  The secreted liquid of closed and freshly opened Nepenthes pitchers is exclusively plant-derived. It is unsuitable to serve as an environment for microbial growth. Thus, Nepenthes plants can avoid and control, at least to some extent, the microbial colonization of their pitfall traps and, thereby, reduce the need to vie with microbes for the prey-derived nutrients.
authors.affiliation: Department Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straße 8, 07745 Jena, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Buch
authors.forename: Matthias
authors.initials: M
authors.lastname: Rott
authors.forename: Sandy
authors.initials: S
authors.lastname: Rottloff
authors.forename: Christian
authors.initials: C
authors.lastname: Paetz
authors.forename: Ines
authors.initials: I
authors.lastname: Hilke
authors.forename: Michael
authors.initials: M
authors.lastname: Raessler
authors.forename: Axel
authors.initials: A
authors.lastname: Mithöfer
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D000935:Antifungal Agents / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D001181:Arthropods; D002852:Chromatography, Ion Exchange; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development; D020459:Genes, rRNA; D009682:Magnetic Resonance Spectroscopy; D008826:Microbial Sensitivity Tests; D009285:Naphthoquinones / Q000032:analysis / Q000737:chemistry; D009584:Nitrogen / Q000032:analysis / Q000737:chemistry; D053147:Plant Exudates / Q000032:analysis* / Q000737:chemistry; D010940:Plant Proteins / Q000032:analysis / Q000737:chemistry; D017433:Protein Structure, Secondary; D044224:Pseudomonas syringae / Q000235:genetics / Q000254:growth & development*; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development*; D052583:Sarraceniaceae / Q000737:chemistry* / Q000382:microbiology* / Q000502:physiology; D013045:Species Specificity
chemical_list: D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D009285:Naphthoquinones; D053147:Plant Exudates; D010940:Plant Proteins; D012336:RNA, Ribosomal, 16S; D009584:Nitrogen; C014758:plumbagin