Journal Article

Secreted pitfall-trap fluid of carnivorous <i>Nepenthes</i> plants is unsuitable for microbial growth

Franziska Buch, Matthias Rott, Sandy Rottloff, Christian Paetz, Ines Hilke, Michael Raessler and Axel Mithöfer

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 111, issue 3, pages 375-383
Published in print March 2013 | ISSN: 0305-7364
Published online December 2012 | e-ISSN: 1095-8290 | DOI:
Secreted pitfall-trap fluid of carnivorous Nepenthes plants is unsuitable for microbial growth

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  • Plant Ecology
  • Plant Physiology


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Background and Aims

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.


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.

Key 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.


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.

Keywords: Antimicrobial activity; carnivorous plants; defensive proteins; digestive pitcher fluid; naphthoquinones; Nepenthes spp.; mineral nutrients; pitfall traps

Journal Article.  6154 words.  Illustrated.

Subjects: Plant Ecology ; Plant Physiology

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