Biology Reference
In-Depth Information
Incidentally, this comparison of gravitation and electromagnetic forces
also helps to place a perspective on the
of forces that exist between
a bacterium and mineral surface. As attested to in chapters throughout this
book, the world of bacteria is dominated by forces less than one nanoNewton.
What does it feel like to experience a force of 1 nN? If you, the reader, place
this topic 1.5 m away from your body then there is, according to Newton's
Law of gravitation, a force of precisely 1 nN between you (70 kg) and the topic
(0.5 kg). This is the magnitude of the force that dictates whether a
microorganism will either form a bond or break a bond with another
surface.
magnitude
14.3 SOME EXAMPLES FROM THE LITERATURE
The irst papers dealing with force measurements on bacteria began to appear
in the literature about a decade ago.
All of these works utilized AFM,
which is still the instrument of choice for force measurement on cells. Since
these irst manuscripts, countless numbers of papers have been published
on forces between bacteria and minerals.
Table 14.1
provides a list of some
of these publications. This table is not meant to be an exhaustive review of
every publication on mineral-microbe forces. Rather, this table is meant to
show a range of studies related to bonds and forces between microorganisms
and minerals.
It is important to note that many of the papers listed in
Table 14.1
are not
“microbe-mineral” papers in the strictest sense. Minerals are, by deinition,
naturally occurring crystalline solids. Many papers make use of man-made
substances such as silicon or silicon nitride (i.e., the composition of the
typical AFM tip) rather than true minerals, and deal with the intermolecular
forces detected upon the approach of a cell towards a mineral, not the bonds
that form after a cell makes contact with a mineral. Nonetheless,
Table 14.1
is
a good starting point for those who are interested in these topics.
10-15
14.4 AN EXAMPLE OF MINERALMICROBE FORCE
SPECTROSCOPY
14.4.1 Interacons Between an Iron-Reducing Bacterium and
Fe(III) Minerals
In the late 1990s, we began to use AFM to measure intermolecular and
adhesion forces between
and the minerals muscovite,
goethite and graphite. This resulted in a publication by Lower
Escherichia coli
et al.
(2000).
14
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