"Microbiologists
have
traditionally focused on free-floating bacteria growing in laboratory
cultures;
yet they have recently come to realize that in the natural world most
bacteria
aggregate as biofilms, a form in which they behave very differently. As
a
result, biofilms are now one of the hottest topics in microbiology."
(Potera 1996)1
The
quote above accurately depicts the tentative
nature of science; in that the more study and technology devoted to a
subject,
the more information gained, and the greater chance of finding that
previous
ideas, currently held as fact, may need to be changed.
It has happened numerous times in the past
with some of the most memorable being:
- Atomic Structure –
Thompson (plum pudding), Rutherford (planetary model),
Bohr
(electron energy levels)
-
Earth’s Crust –
Early geologists (fixed continents), Wegner
(continental drift), Hess & Dietz (seafloor spreading), Current
geologists
(plate tectonics)
-
DNA – Griffith
& Avery, et al (link genes and DNA), Chargaff
(equal amounts of A & T and C & G), Wilkins & Franklin
(X-ray
diffraction of DNA), Watson & Crick (double helix structure of DNA)
The
most recent example, and the focus of this STS unit, is the discovery
of
sessile bacteria communities as a norm in nature versus the common
belief of
planktonic bacteria.
So, what exactly am I talking about?? Bacteria,
as many students are taught, are
single celled, microorganisms floating around in the world. Some of them are very important to life
on
earth as primary producers and others, well; others are not as helpful,
especially in concentrated amounts. The E.coli
bacteria in our digestive system is necessary and helpful, however in
large
doses becomes fatal.
Now,
lets look at the words planktonic and sessile. Planktonic
means free-floating – think of
plankton in the ocean, which are
microscopic plants and animals floating and moving about in the ocean. This view is what many students have of
bacteria
when they leave biology class. While
this is not incorrect it is also not a totally correct view of bacteria. Sessile means to be attached – think of a boy
and girl dating. For the most part the
boy and girl are “together forever” and will never separate. Bacteria actually congregate like this in
natural (not laboratory) conditions and for the most part when they
attach to a
surface they are “together forever.”
That statement, however, is not completely true.
A disruption or agitation of the congregated bacteria can
cause a break
up of the community and the bacteria will
float around and reattach in another
community. This disruption can be equated
to a more
attractive classmate breaking up the “together forever” boy and girl.
The descriptions
above briefly describe one of the major
misconceptions in microbiology. In the
1800’s Robert Koch made an important breakthrough in the study of
microbiology. He devised a method to
grow isolated and pure cultures of microorganisms on a solid nutrient
media.2
This method revolutionized medicine, agriculture, and industry by
allowing easy
access to any microorganism one chose to grow.
Now remembering what was stated above about planktonic and
sessile
bacteria what can you say about Koch’s discovery? As
useful and important his discovery was
(and it was very important) it did not accurately depict the way
bacteria
interact in nature.
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