REGULAR ARTICLE A volatile organic compound analysis from Arthrobacter agilis identifies dimethylhexadecylamine, an amino-containing lipid modulating bacterial growth and Medicago sativa morphogenesis in vitro Crisanto Velázquez-Becerra & Lourdes Iveth Macías-Rodríguez & José López-Bucio & Josué Altamirano-Hernández & Idolina Flores-Cortez & Eduardo Valencia-Cantero Received: 8 July 2010 / Accepted: 16 September 2010 / Published online: 28 September 2010 # Springer Science+Business Media B.V. 2010 Abstract Plant growth promoting rhizobacteria (PGPR) stimulate plant growth and development by different mechanisms, including the production of different classes of signaling molecules, which may directly affect plant morphogenesis. Here, we report the effects of inoculation of Arthrobacter agilis UMCV2, a PGPR isolated from the rhizosphere of maize plants on growth and development of Medi- cago sativa seedlings. A. agilis UMCV2 inoculation promoted growth in M. sativa plants as revealed by increased stem length, root length and plant biomass. Inoculation of A. agilis using divided Petri plates decreased taproot growth and increased lateral root formation in plants grown in separate compartments suggesting a role of volatile organic compounds (VOCs) produced by this bacterium in root develop- ment. The analysis of VOCs produced by A. agilis UMCV2 identified N,N-dimethyl-hexadecanamine (dimethylhexadecylamine), an amino lipid structurally related to bacterial quorum-sensing signals, which modulated A. agilis UMCV2 growth and plant development in a dose-dependent way. Taken together, our results indicate that bacterial VOCs can be perceived by legume plants to modulate growth and morphoge- netic processes and identify a novel signaling molecule potentially involved in plant-rhizobacterial interactions. Keywords Legume plants . Arthrobacter agilis . Dimethylhexadecylamine . Root development Introduction The rhizosphere is a unique environment formed at the interface of plant roots and the soil. Myriads of micro- organisms proliferate in such region, which can affect plant growth and development. The interaction of plants with microbes can be classified as positive, negative or neutral regarding their effects on the interacting organ- isms (Campbell and Greaves 1990). Plants invest high proportions of their photosynthetically fixed carbon to produce root exudates, some of which modify the rhizosphere, increasing nutrient availability and exert- ing an attracting effect over bacterial populations (Badri and Vivanco 2009). Some of these bacteria may positively contribute to plant growth and are collectively termed Plant Growth Promoting Rhizobac- teria (PGPR) (Persello-Cartieaux et al. 2003). Plant Soil (2011) 339:329–340 DOI 10.1007/s11104-010-0583-z Responsible Editor: Jorge Vivanco. Electronic supplementary material The online version of this article (doi:10.1007/s11104-010-0583-z) contains supplementary material, which is available to authorized users. C. Velázquez-Becerra : L. I. Macías-Rodríguez : J. López-Bucio : J. Altamirano-Hernández : I. Flores-Cortez : E. Valencia-Cantero (*) Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Edificio B5, Ciudad Universitaria, C. P. 58030 Morelia, Michoacán, Mexico e-mail: vcantero@umich.mx