The Myxobacterales [(Fruiting) Myxobacterales] a

The Myxobacterales are Gram-negative rods that are characterized by two properties — one unusual and the other unique among the bacteria. The unusual feature concerns the motility of the vegetative rods, which occurs in the absence of flagella or any other visible organelle of locomotion. Gliding movement takes place when the cells are in contact with an interface, and seems similar to that of some of the Cyanophyta as well as other groups of gliding bacteria (e.g., Beggiatoa). While it seems likely that the laying down of slime tracks is in some way associated with the motility, there are no insights presently available into the process.6 The most unique visible characteristic of the myxobacteria is their ability to form fruiting bodies under the appropriate physical and nutritional conditions. The vegetative cells migrate to form aggregates of cells, which are then transformed into more or less elaborate structures called fruiting bodies. The physiology of the cells within the mature fruiting body is, in most cases, not well understood. In the genus Myxococcus, the cells in the fruiting body differ from vegetative cells in having a much lower metabolic rate42 and a greater resistance to environmental stresses.40 The life cycles of two typical fruiting myxobacteria are illustrated in Figures 1 and 2.