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
'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
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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