FIG. 3.

Motile bacteria and motility apparatus. (A) B. burgdorferi strain 297 with the outer membrane sheath disrupted with detergent to visualize the subpolarly attached periplasmic flagella. (B and C) M. xanthus fruiting bodies. Following starvation, approximately 100,000 cells aggregate to form a fruiting body within which cells convert to spores. The process usually takes 2 to 3 days. The images are of M. xanthus after 3 weeks of development and show the aggregation of cells into fruiting bodies and a higher-magnification image of a collection of several fruiting bodies. The fruiting bodies are orange due to photoprotective carotenoids. (D) S. grandis mixed with S. enterica wild-type cells at zero time. Long filamentous cells are S. grandis, and smaller rod-shaped cells are S. enterica. (E) After 40 min of incubation, S. grandis cells form large aggregates with S. enterica cells trapped within. (F) External filaments isolated from S. grandis cell surfaces. (G) Phage-like particles, so-called rhapidosomes, isolated from S. grandis. (H) M. mobile gliding in the direction of the tapered end. (I to K) Tip-splitting (I), chiral (J), and vortex (K) morphotypes exhibited by Paenibacillus dendritiformis on agar plates. (L) M. xanthus aggregation center visualized by fluorescence microscopy of GFP-expressing cells. Wild-type cells constitutively expressing GFP were mixed 1 to 10 with nonfluorescent wild-type cells and subjected to starvation. The fluorescent cells are seen on a background of nonfluorescent cells. The arrow points to an asymmetric aggregation center. Cells enter the aggregation center organized in streams (arrowheads). Images were provided by J. Kreiling and N. Charon (A), Z. Yang (B), J. Kirby (C), S. Aizwa (D to G), M. Miyata (H), D. Gutnick and E. Ben-Jacob (I to K), and L. Søgaard-Andersen (L). Images in panels I, J, and K are reproduced with permission from the Annual Review of Microbiology (7).