IUBio

Definition of a biofilm

Robert J. Palmer Jr. rjpalmer at utkux.utcc.utk.edu
Wed Jul 21 10:29:37 EST 1999


I don't think anyone is reinventing the wheel here. Bob brought up some 
points that are frequently raised WITHIN the biofilm community, and as such 
are even more pertinent to those entering a burgeoning field.
For example, does a single cell qualify as a biofilm by your definition? 
I would suggest not, but only by virtue of the wording that requires 
"accumulation". However a single cell can be immobilized and can produce 
extracellular material. Let's say it divides. Do those two cells now 
constitute a biofilm as an "accumulation"? They certainly fit all the 
other requirements of either of your definitions. The Characklis-edited 
magnum opus (to which many individuals made very important contributions) 
is still the Bible of biofilm research despite its heavy emphasis on 
engineering aspects and desptite our recognition that biofilms are NOT 
black boxes whose physical (and physiological) characteristertics can be 
modeled like a bomb blast.
I too am a bit bothered by all this worry about what constitutes a biofilm 
- it has been and always will be an operating definition subject to 
interpretation and "waffle". Discussion certainly does a minimal amount of 
damage, and open discussion in this (and other) forums helps clarify to 
which camps we all belong.
Rob Palmer 
CEB/UT
>I don't want to sound as though I am older than I am, but why do we need 
>another definition of a biofilm? Perhaps the first review of biofilm 
>engineering and biology was published 16 years ago by the late Bill 
>Characklis and I. In it we defined a biofilm in the following way : 
>....immobilized cells grow, reproduce, and produce extracellular polmer 
>substances that frequently extend from the cell, forming a tangled mass of 
>fibers lending structure to the entire assemblage which shall be termed a 
>biofilm. The term biofilm does not necessarily imply a surface accumulation 
>that is uniform in time and/or space. 
>We dveloped this into a shorter version that defines a biofilm as "the 
>accumulation of microbial cells , their products and inorganic particles at 
>a wetted surface ".[ to take into the account that natural biofilms 
>accumulate lots of silt]. 
>Let's not re-invent the wheel! 
>Keith Cooksey, Research Professor 
>As part of the final part of the review we mentioned 13 areas that we felt 
>were in need of further work. It is interesting to see how many of these 
>STILL need further work! 
>The reference is Adv in Appl. Microbiol. 29 93-137 [1983] 
> 
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