Hexadecane assimilation by Marinobacter hydrocarbonoclasticus SP17 occurs through the formation of a biofilm at the alkane-water interface. In this study we focused oil the interactions of cells with the alkane-water interface occurring during initiation of biofilm development. The behavior of cells at the interface was apprehended by investigating alterations of the mechanical properties of the interface during cell adsorption, using dynamic drop tensiometry measurements. It was found that after having reached the hexadecane-water interface, by a purely thermal diffusion process, cells released surface-active compounds (SACs) resulting in the formation of an interfacial viscoelastic film. Release of SACs was all active process requiring protein synthesis. This initial interaction occurred on metabolizable as well as non-metabolizable alkanes, indicating that at this stage cells are not affected by the nature of the alkane forming the interface. In contrast, at a later, stage, the nature of the interface turned Out to exert control over the behavior of the cells. The availability of a metabolizable alkane at the interface influenced cell activity, as revealed by cell cluster formation and differences in the interfacial elasticity. Biotechnol. Bioeng. 2010;105: 461-468. (C) 2009 Wiley Periodicals, Inc.