2 fun papers I read while home with a cold:

[Lindsay]

http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.107.028102
"Like cyclists, birds and fish travel more efficiently as a team.
Experiments have also shown that bacterial cells move in collective
swarms, but since viscous forces are more pronounced for these micron-
sized swimmers, it wasn’t clear if this behavior actually offered a
benefit in energy. Now, by making a quasi-3D velocity map of a liquid
droplet containing motile Escherichia coli (E. coli), a team of
scientists in Japan has concluded that bacteria swimming in a group
are able to move roughly three times faster than they would on their
own. The results are reported in Physical Review Letters."

and

http://www.sciencemag.org/content/323/5914/614.full
"Populations of certain unicellular organisms, such as suspensions of
yeast in nutrient solutions, undergo transitions to coordinated
activity with increasing cell density. The collective behavior is
believed to arise through communication by chemical signaling via the
extracellular solution. We studied large, heterogeneous populations of
discrete chemical oscillators (∼100,000) with well-defined kinetics to
characterize two different types of density-dependent transitions to
synchronized oscillatory behavior. For different chemical exchange
rates between the oscillators and the surrounding solution, increasing
oscillator density led to (i) the gradual synchronization of
oscillatory activity, or (ii) the sudden “switching on” of
synchronized oscillatory activity. We analyze the roles of oscillator
density and exchange rate of signaling species in these transitions
with a mathematical model of the interacting chemical oscillators."