This implies that biofilm assays based on CV staining do not provide an
estimation of the number of culturable cells attached to a surface, since CV
may also bind to dead cells, eDNA, proteins and/or exopolysaccharides.
The finding that dead cells contribute to the L. plantarum biofilm matrix
was further supported by fluorescence microscopy which revealed that
the reduced cell counts coincided with an increase in the number of
dead cells. The presence of eDNA in the biofilm matrix of some
L. plantarum strains was further supported by DNase treatment of the mature
biofilms showing a large reduction in both CV staining and number of
culturable cells for WCFS1, and FBR 3 and FBR 5.