A
new paper, from University of Southern California, elucidates the active role
of cilia in regulating flow for bacteria filtering and enhancing chemical
communication.
The
paper, published in the Proceedings of the National Academy of Sciences,
describes a framework for the role of fluid mechanics in letting symbiotic
bacteria in an organism and enhancing chemical communication between the
symbiont and the host organism. The results are contrary to previous research
which assumes that cilia solely play a "clearance function." They
could shed light on the role cilia -- which are the size of one hundredth of a
single human hair -- play in human respiratory system and even in the
reproductive systems and the brain. Their findings could also provide insights
on how cilia dysfunction within organs affect for example, pulmonary conditions
or infertility (how cilia help sperm reach eggs).
To
learn about how cilia might work in the human body, Kanso, in collaboration
with symbiosis expert McFall-Ngai and biofluid expert Janna Nawroth studied
bobtail squid. The researchers examined how these squids in their nascent stage
allow symbiotic bacteria Vibrio Fischeri to enter into their ciliated light
organs, which play a crucial role in camouflaging the ink sacks of the otherwise
translucent organism while they hunt for food at night. The scholars sought to
know: why does this bacterium gain access and why do all bacteria fail to
accumulate within the squid's light organ? In addition, they sought to explain
what, if any, is the role of cilia in allowing access?
Researchers
discovered that a vortical or "donut-like" flow generated by the
cilia was kicking away most particles. The role of the fluid motion in
filtering particles by size was verified using a physics-based mathematical
model. One of the core findings was that there were two distinct flows taking
place by two different types of cilia. Longer cilia move in a
"wave-like" fashion which creates a vortical flow field that filters
particles and then shorter cilia which beat randomly keep the particles in
place and gently mix the local flow. This random motion by the cilia and fluid
mixing enhance the chemical screening of bacteria. To further prove the
important role played by cilia, the researchers also found that if cilia are
"killed," particles will accumulate everywhere in the organism.
See:
Posted by Dr. Tim Sandle
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