Campuses:

Modeling of bacterial swarming on different surfaces

Monday, September 13, 2010 - 11:30am - 12:15pm
Lind 305
Mark Alber (University of Notre Dame)
Most infections are the result of a surface-attached community
of
bacteria that displays many unique characteristics. Our
understanding
is still limited, however, with respect to how pathogens are
colonizing surfaces to begin infection. It is known that the
arrival
of bacteria to host tissues is often aided by self-generated
motility
of the organism.
Pathogens such as Salmonella enterica, Vibrio cholerae, Proteus
mirabilis, and Pseudomonas aeruginosa are able to spread
rapidly over
surfaces by the process of swarming. Many bacteria generate
flat,
spreading colonies, called swarms because they resemble swarms
of
insects. In the beginning of the talk, swarms of the
myxobacterium,
Myxococcus xanthus will be described in detail. Individual M.
xanthus
cells are
elongated; they always move in the direction of their long
axis; and
they are in
constant motion, repeatedly touching each other. Remarkably,
they
regularly reverse their gliding directions. We have constructed
a
detailed cell- and behavior-based
computational model of M. xanthus swarming that allows the
organization of cells to be
simulated [1]. By using the model, it will be shown that
reversals
of gliding direction are essential for swarming and that
specific
reversal frequencies result in optimal swarming rate of the
whole
population [2]. This suggests that the circuit regulating
reversals
evolved to its current sensitivity under selection for growth
achieved by swarming. Also, an orientation correlation function
will
be used to show that microscopic social interactions help to
form
the ordered collective motion observed in swarms. In the second
part of the talk we will discuss a model of the swarming of the
Pseudomonas aeruginosa.

1. Wu, Y., Jiang, Y., Kaiser, D., and M. Alber [2007], Social
Interactions in Myxobacterial Swarming, PLoS Computational
Biology 3
12, e253.

2. Wu, Y., Jiang, Y., Kaiser, D., and M. Alber [2009], Periodic
reversal of direction allows Myxobacteria to swarm, Proc. Natl.
Acad. Sci. USA 106 4 1222-1227 (featured in the Nature News,
January
20th, 2009, doi:10.1038/news.2009.43).
MSC Code: 
92B05
Keywords: