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Biofilm Treatment with Polymers

Cindy MORRIS Cindy.Morris at avignon.inra.fr
Wed Jul 7 13:38:23 EST 1999

Dear Biofilm group:
Concerning the message from Mary Pitruzzello and the discussion that 
followed, I have 2 comments. The first concerns the use of crystal violet 
to quantify biofilms. The second remark concerns my rebuttal of the 
definition of some terms proposed by David B. Hedrick (a technical writer).
Concerning use of crystal violet to quantify biofilms: For the past year my 
lab has been trying to adapt a crystal violet-based staining method to the 
quantification of bacteria adhering to a surface. This method is based on 
the technique described by Sonak, S. and Bohsle, N. (1995. "A simple method 
to assess bacterial attachment to surfaces". Biofouling 9:31-38). After 
multiple trials, we have abandoned this technique because it is i) almost 
impossible to calibrate and ii) seems to have a very high threashold of 
sensitivity (ie you need about 10E5 to 10E6 bacteria per ml to detect CV 
that is not due to background residual) and iii) CV never stops diffusing 
out of the cells; the more you rinse, the more you remove; it is difficult 
to decide when to stop. For more details, you can discuss with my student, 
Tristan Boureau (boureau at avignon.inra.fr) who will be at the indicated 
address until mid Sept.
What are the alternatives?; well, it depends on how you want to go about it. 
If you can do direct measures by coupling viability stains to confocal 
microscopy, that would probably give interesting results. Also, check out 
one of my recent articles (Morris C.E., Monier J.M., Jacques M.A. 1998. A 
technique to quantify the population size and composition of the biofilm 
component in communities of bacteria in the phyllosphere. Applied and 
Environmental Microbiology 64:4789-4795.) Even if you don't use the 
technique we propose, you might find the introduction and discussion useful: 
we present many of the different approaches for quantification of biofilm 
populations that have been used so far in the literature.
In his response to Mary's question, DB Hendrick states that:
>"Plant leaves have a biofilm called the phyllosphere. Plant roots, the 
>rhizosphere (or rhizoplane, I can never remember). 
>Your skin, as well as every body orifice, has it's own microbial 
>community. "
'Phyllosphere', 'phylloplane', 'rhizosphere', 'rhizoplane', ARE NOT 
biofilms. "Phyllo" is the Greek combining form for leaf, "rhizo" for root, 
and the more familiar words "plane" for surface and "sphere" for (you 
guessed it!!) sphere. Hence, rhizoplane is the root surface. The rest of 
them you can figure out for yourselves. 
To more correctly state his proposition, DB Hendrick could have said that 
the phylloplane of numerous plants harbor large populations of 
micro-organisms (up to ca. 10E8 per leaf), of which some may be aggregated 
into biofilms. But, the vast majority of the phylloplane (about 90-98%) is 
virgin territory. The presence of biofilms in the rhizosphere is less well 
known, but the rhizosphere harbors a rich microbial population.
Furthermore, DB Hendrick also insinuates that microbial community = biofilm. 
Perhaps it is very likely that the organisms assembled in a biofilm function 
as a community; but just because that organisms function as a community 
does not imply that they are biofilms!!
Sorry to be so severe, but I think that a professional technical writer 
should be a bit more careful in use of terminology.

Cindy E. Morris
INRA - Station de Pathologie Vegetale 
B.P. 94 
84143 Montfavet, France
tel : (33) 490-31-63-84 
fax : (33) 490-31-63-35 
e-mail : morris at avignon.inra.fr

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