Bacterial diversity in natural aquatic biofilms

David B. Hedrick davidbhedrick at icx.net
Thu Feb 3 04:32:19 EST 2000

AHRickard wrote:

 > Hi,
 > I was just wondering if anyone has done (or knows of) any
 > studies into the bacterial diversity of freshwater biofilms. I
 > am aware of quite a bit of intense research by David White et
 > al. in the early 1990's but that is where the buck really ends!

         It really depends upon what method you use to examine the biofilms.
I'm from White's lab, so I know his work.  There are other methods
besides his, such as molecular biology and microscopy.  Let me know of
any information you get from them.

 > Also, suppose you obtain a number of closely related
 > species/strains from an established biofilm (eg. borehole/deep
 > terrestial), what are the chances of these strains having a
 > common evolutionary progenitor?

         Recently?  Not likely.  You are asking about strains you have
isolated.  Bacteria in deep boreholes do not have a high reproduction
rate.  The ones you cultured were just alive enough for you to culture
them.  Given different ideas of what an organism would want, different
organisms might be cultured.  If you had cultured the deep sub-surface
samples under 80% N2, 10% CO2, 10% H2, and lots of carbon, you would
have found different organisms.
         The culturable bugs anywhere are about 1% of the bugs.  Not

 > In general, multi-species biofilms are considered a norm but in
 > most of the studies I have come across the biofilms are usually
 > relatively immature.

         What do you mean by a "mature biofilm"?  You need to think about how
much energy the bacteria have available.  In a deep sub-surface
environment, carbon and energy are going to be in short supply.  In the
human mouth, hang on, here comes some more!  Very different
         Environments with high carbon and energy inputs will have a succession
of comunities and preditors, and paracites.  Environments with no carbon
or energy inputs, such as deep sub-surface communities, are dominated by
those that starve well.

 > Okay, someone will no doubtedly mention
 > human dental plaque but it is not a really mature biofilm. how
 > about ones that could be potentially hundreds of years old? If a
 > steady state is achieved with little or no change in the
 > external environment (going back to deep terrestrial here)
 > genetic exchange will no doubt occur between bacteria -
 > potentially causing genetic convergence between unrelated
 > species?

         Dental plaque is an especially poor model for deep sub-surface
bacteria.  The different bugs have different problems.

 > Just a few questions/thoughts to ponder on! Thanks for your
 > time and I hope somebody can help.

         Please, more details.


Technical writing, literature search, and data analysis at the interface
of chemistry and biology.

         davidbhedrick at icx.net

         David B. Hedrick
         P.O. Box 16082
         Knoxville, TN 37996

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