Dietrich Ewald,2 and
1MPI of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Golm, Germany; 2Johann Heinrich von Thünen-Institute, Federal Research Institute for Rural Areas, Forestry and Fisheries, Institute of Forest Genetics, Eberswalder Chaussee 3A, 15377 Waldsieversdorf, Germany; 3University of Vienna, Molecular Systems Biology, Althanstr.14, 1090 Vienna, Austria
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Accepted 28 April 2009.
Metabolic profiling via gas chromatography coupled to mass spectrometry was used to investigate the influence of endophytic bacteria on shoots of in vitro-grown poplar plants free from culturable endophytic bacteria. The results demonstrate that the occurrence of an endophytic Paenibacillus strain strongly affects the composition of the plant metabolites of in vitro-grown poplars. Eleven metabolites were significantly changed between inoculated and non-inoculated poplar plants as determined by two independent experiments. Detected shifts in the primary metabolism of the poplar plants pointed to a mutualistic interaction between bacteria able to fix nitrogen and the host plant with altered nitrogen assimilation patterns. The corresponding metabolic signature comprises increased asparagine and urea levels as well as depleted sugars and organic acids of the tricarboxylic acid cycle. These observations coincide with the fact that the Paenibacillus sp. strain P22 is able to grow without nitrogen in the medium, indicating nitrogen fixation from the air also known from other Paenibacillus spp. In combination with the detected plant-growth-promoting effects of the endophyte Paenibacillus P22, a novel mutualistic interaction is observed.
© 2009 The American Phytopathological Society