Adhesion Mechanisms of Bacterial Spores to Solid Surfaces
The initial adhesion of different Bacillus spores to solid surfaces was investigated. By changing environmental parameters and studying the subsequent adhesion, conclusions have been drawn concerning the different mechanisms responsible for adhesion.
Bacillus species are common microorganisms and in food industry they are common food spoilers. The endospores they form are very resistant to heat, drying and chemicals. In this investigation, these endospores have been found very adhesive to different solid surfaces. It is suggested that their adhesiveness contributes to problems of contamination from Bacillus species.
The surfaces of Bacillus spores were found to be highly hydrophobic. Hydrophobic interactions were shown to enhance their adhesion capacities, especially to hydrophobic surfaces. Electrostatic repulsion is another interaction of demonstrated importance. The adhesion process is, however, complex and other interactions are also involved, such as steric stabilization, solvation forces, van der Waals attraction, etc. Spores from some species have long appendages on the surface. These appendages were shown to enhance adhesion.
The spore species found to have the highest adhesion capacity was B. cereus. This finding is of practical interest since B. cereus is considered a pathogen. B. cereus spores have several surface qualities that were found to enhance adhesion. The spores are relatively hydrophobic with low negative surface potential and surfaces covered with several long appendages.