Comparative imaging of Pseudomonas putida bacterial biofilms by scanning electron microscopy and both DC contact and AC non-contact atomic force microscopy

Both Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) have been used to visualize the morphology of Pseudomonas putida bacterial colonies isolated from model oil-in-water emulsions. A new method has been developed for growing flat homogeneous bacterial biofilms at planar oil-water interfaces. A marked increase in resolution has been achieved when these flat bacterial biofilms are imaged by both SEM and AFM methods. On flat bacterial biofilms AFM offers superior resolution with minimal sample preparation. High resolution DC contact mode AFM studies of the bacterial surfaces have revealed surface features comparable in size to large proteins. AC non-contact AFM methods hare been used to image bacterial flagella trapped in the biofilm.