Assessing different ways of Bacillus subtilis spreading over abiotic surfaces

Surface-associate motility on biotic and abiotic environments is a key mechanism used by the model bacterium Bacillus subtilis and its closest relatives (i.e., B. amyloliquefaciens, B. thuringiensis, B. cereus, B. pumilus) for surface colonization and spreading across surfaces. The study of this mechanism in a research, industrial or clinic laboratory is essential; however, precautions should be taken for the reproducibility of the results, for example, the procedure to inoculate the bacteria on the testing plate, the humidity of the plate and the agar concentration. In this protocol, we describe, using Bacillus subtilis, how to perform these assays and, in addition, we show how by varying the agar concentration in the plate, you can make a first approximation of what type of motility has other bacterial species.