Swarming Serratia marcescens
When grown on soft agar (0.7-0.8%) and a rich medium, cells of Serratia marcescens (and other Gram-negative bacteria) elongate, produce more flagella, and move over the surface of the agar in a coordinated manner. Serrawettin, a lipopeptide, appears to be important as a wetting agent. Swarming is more vigorous than in Salmonella, and cells at the very edge of the swarm are more active.
The first video, made in phase contrast, shows spreading near the edge of a swarm. The second video shows that cells removed from a swarm swim vigorously.
Harshey, R. M. Bees aren't the only ones: swarming in Gram-negative bacteria. Mol. Microbiol. 13, 389-394 (1994).
We would like to thank for her help in creating these movies.