Bacteria in natural environments are mostly in an attached state. The surface characteristics of bacterial cells greatly affect cell attachment and hence bacterial ecology. Under normal conditions, bacterial cell surfaces are negatively charged. It was revealed that slower growing strains are less negatively charged and more hydrophobic at their cell surfaces. Bacterial cells carry various polymers on their surfaces. The polymer layers on bacterial cells reduce surface electric potential, resulting in a low energy barrier between bacterial cells and substratum surface of both negatively charged. Some experimental results for cell attachment force are shown as well as the effect of interfaces on bacterial activities.