Myxococcus xanthus

Myxococcus xanthus is a gram-negative, rod-shaped species of myxobacteria that exhibits various forms of self-organizing behavior in response to environmental cues. Under normal conditions with abundant food, it exists as a predatory, saprophytic single-species biofilm called a swarm. Under starvation conditions, it undergoes a multicellular development cycle. A swarm of M. xanthus is a distributed system, containing millions of bacteria that communicate among themselves in a non-centralized fashion. Simple patterns of cooperative behavior among the members of the colony combine to generate complex group behaviors in a process known as "stigmergy". For example, the tendency for one cell to glide only when in direct contact with another results in the colony forming swarms called "wolf-packs" that may measure up to several inches wide. This behavior is advantageous to the members of the swarm, as it increases the concentration of extracellular digestive enzymes secreted by the bacteria, thus facilitating predatory feeding. M. xanthus feeds on dead biomass of a broad range of bacteria and some fungi, discriminating live from dead cells, and causing cell death and lysis when required. During stressful conditions, the bacteria undergo a process in which about 100,000 individual cells aggregate to form a structure called the fruiting body over the course of several hours. On the interior of the fruiting body, the rod-shaped cells differentiate into spherical, thick-walled spores. They undergo changes in the synthesis of new proteins, as well as alterations in the cell wall, which parallel the morphological changes. During these aggregations, dense ridges of cells move in ripples, which wax and wane over 5 hours. An important part of M. xanthus behavior is its ability to move on a solid surface by a mechanism called "gliding". Gliding Motility is a method of locomotion that allows for movement, without the help of flagella, on a solid surface. Gliding Motility is also called A-motility (adventurous).