This article presents a study on the influence of the protocol used
for immobilization of bacterial cells onto surfaces by mechanically
trapping them into a filter. In this sense, the surface and structure of
trapped cells are analyzed. Bacteria can be present solely or with
extracellular polymeric substances (EPS). To test the behavior of the EPS
layer duing the filtering process, different strains of a well-known
EPS-producer bacteria (Staphylococcus epidermidis), which produce
an extracellular matrix clearly visible in AFM images, have been used.
Results show that this immobilization method can cause severe structural
and mechanical deformation to the cell membrane. This altered mechanical
state may possibly influence the parameters derived from AFM force curves
(which are micro/nano-mechanical tests). Also, our results suggest
that the EPS layer might move during the filtering process and could
accumulate at the upper part of the cell, thus favoring distorted data of
adhesion/pull-off forces as measured by an AFM tip, especially in the
case of submicron-sized microbial cells such as bacteria.