Bio cloud seeding

http://www.lauralee.com/news/remotecontrolbacteria.htm

Ubiquity of Biological Ice Nucleators in Snowfall http://www.sciencemag.org/cgi/content/abstract/319/5867/1214

http://theblanketeffect.blogspot.com/2008/03/natural-way-to-seed-clouds.html

http://physicsworld.com/cws/article/news/45982

Ice nucleation activity of bacteria isolated from snow compared with organic and inorganic substrates http://www.publish.csiro.au/paper/EN08055.htm

Airborne Bacteria Make It Rain, Researchers Find http://www.wired.com/science/planetearth/news/2008/02/bacteria_clouds