Description
Filamentous fungi (ff) are a ubiquitous and diverse group of eukaryotic organisms.
However, fungal involvement in biofilms has not been demonstrated
unambiguously. They may be responsible for the production of tastes, odours and
mycotoxins in water [1] and so rapid detection is important. Detection of ff by
conventional methods is complex, indirect and time consuming: results can be
obtained only after 3-5 days because of slow growth. In order to study the
presence of ff in water biofilms two methods for direct detection were used: (a)
the FISH technique which employed the EUK516 probe, 5’-ACCAGACTTGCCCTCC-
3’ labelled with the red Cy3 dye at the 5’ terminal; (b) Calcofluor White M2R
fluorescent dye which stained the fungal cells walls blue. Penicillium
brevicompactum was used in pure culture to establish the methods and then real
water biofilm samples in PVC-C and cast iron coupons were studied.
The FISH method demonstrated the filamentous structures we assume were fungi
after approximately 5 hours. In contrast, the Calcofluor method revealed ff in less
than one hour, and so it is possible for a rapid assessment of the presence of
fungi in biofilms. When the two methods were combined additional information
was possible to extract such as combining the images of empty filaments (blue)
with intact protoplasm (red).
In conclusion, FISH and Calcofluor staining provide rapid, direct and unambiguous
information on the involvement of ff in biofilms which form in water.