The myxobacteria ("slime bacteria") are a group of bacteria that predominantly live in the soil and feed on insoluble organic substances. The myxobacteria have very large genomes relative to other bacteria, e.g. 9–10 million nucleotides except for Anaeromyxobacter and Vulgatibacter. One species of myxobacteria, Minicystis rosea, has the largest known bacterial genome with over 16 million nucleotides. The second largest is another myxobacteria Sorangium cellulosum. Myxobacteria are included among the delta group of proteobacteria, a large taxon of Gram-negative forms.
Myxobacteria can move by gliding. They typically travel in swarms (also known as wolf packs), containing many cells kept together by intercellular molecular signals. Individuals benefit from aggregation as it allows accumulation of the extracellular enzymes that are used to digest food; this in turn increases feeding efficiency. Myxobacteria produce a number of biomedically and industrially useful chemicals, such as antibiotics, and export those chemicals outside the cell.
When nutrients are scarce, myxobacterial cells aggregate into fruiting bodies (not to be confused with those in fungi), a process long-thought to be mediated by chemotaxis but now considered to be a function of a form of contact-mediated signaling. These fruiting bodies can take different shapes and colors, depending on the species. Within the fruiting bodies, cells begin as rod-shaped vegetative cells, and develop into rounded myxospores with thick cell walls. These myxospores, analogous to spores in other organisms, are more likely to survive until nutrients are more plentiful. The fruiting process is thought to benefit myxobacteria by ensuring that cell growth is resumed with a group (swarm) of myxobacteria, rather than as isolated cells. Similar life cycles have developed among certain amoebae, called cellular slime molds.
Various myxobacterial species as sketched by Roland Thaxter in 1892: Chondromyces crocatus (figs. 1–11), Stigmatella aurantiaca (figs. 12–19 and 25-28), Melittangium lichenicola (figs. 20–23), Archangium gephyra (fig. 24), Myxococcus coralloides (figs. 29-33), Polyangium vitellinum (figs. 34-36), and Myxococcus fulvus (figs. 37-41). Thaxter was the first taxonomist to recognize the bacterial nature of the myxobacteria. Previously, they had been misclassified as members of the fungi imperfecti.
^Schneiker S, Perlova O, Kaiser O, Gerth K, Alici A, Altmeyer MO, et al. (November 2007). "Complete genome sequence of the myxobacterium, Sorangium cellulosum". Nat. Biotechnol. 25 (11): 1281–9. doi:10.1038/nbt1354. PMID17965706.
^Sasse F, Steinmetz H, Höfle G, Reichenbach H (January 1995). "Gephyronic acid, a novel inhibitor of eukaryotic protein synthesis from Archangium gephyra (myxobacteria). Production, isolation, physico-chemical and biological properties, and mechanism of action". J. Antibiot. 48 (1): 21–5. doi:10.7164/antibiotics.48.21. PMID7868385.