3. Other relevant issues
Bacterial cells are able to adhere to other cells and surfaces,
and through an exopolymeric matrix form a structure known as
bio lm [13]. It is estimated that nearly 99% of the micro-organisms
on Earth live in this type of microbial communities [14] where
cells are protected against environmental stresses.
When inspecting surface defects these bio lms may constitute a problem, e.g. by bio corrosion and, therefore, it could be harmful for the material surface. However, the present NDT technique