http://newsinfo.iu.edu/news/page/normal/3258.html
BLOOMINGTON, Ind. -- A bacterium that lives in rivers, streams and
human aqueducts uses nature's strongest glue to stay in one place,
according to new research by Indiana University Bloomington and
Brown University scientists reported in next week's (April 11)
Proceedings of the National Academy of Sciences.
The scientists found they had to apply a force of about 1
micronewton to remove a single Caulobacter crescentus from a glass
pipette. Because C. crescentus is so small, the pulling force of 1
micronewton generates a huge stress of 70 newtons per square
millimeter. That stress, which the bacterial adhesions could
sometimes withstand, is equivalent to five tons per square inch --
three or four cars balanced atop a quarter. By contrast, commercial
"super" glue breaks when a shear force of 18 to 28 newtons per
square millimeter is applied.
Hypothetically, C. crescentus's glue could be mass produced and
used to coat surfaces for medical and engineering purposes.
"There are obvious applications since this adhesive works on wet
surfaces," said IU Bloomington bacteriologist Yves Brun, who co-led
the study with Brown University physicist Jay Tang. "One
possibility would be as a biodegradable surgical adhesive."
C. crescentus affixes itself to rocks and the insides of water
pipes via a long, slender stalk. At the end of the stalk is a
holdfast dotted with polysaccharides (chains of sugar molecules).
The scientists show in the PNAS paper that these sugars are the
source of C. crescentus's tenacity. It is presumed these sugars are
attached to holdfast proteins, but this has not yet been confirmed.
One thing is certain -- the polysaccharides are sticky.
"The challenge will be to produce large quantities of this glue
without it sticking to everything that is used to produce it," Brun
said. "Using special mutants, we can isolate the glue on glass
surfaces. We tried washing the glue off. It didn't work."
The scientists allowed C. crescentus to attach itself to the side
of a thin, flexible glass pipette. They used a micromanipulator to
trap the cell portion of the bacterium and pull it directly away
from the pipette, measuring the force of strain. In 14 trials, the
scientists found they had to apply a force of 0.11 to 2.26
micronewtons per cell before the bacterium detached.
C. crescentus has evolved an ability to live in extremely
nutrient-poor conditions, which explains its existence as a common
fixture in tap water. Because it exists in tap water at low
concentrations and produces no human toxins, C. crescentus poses no
threat to human health.
