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[2] and Vulgatibacter.[3] One species of myxobacteria, Minicystis rosea,[4] has the largest known bacterial genome with over 16 million nucleotides. The second largest is another myxobacteria Sorangium cellulosum.[5][6]
Myxobacteria can move by
gliding.[7] 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.[8]
Myxobacteria are used to study the polysaccharide production in gram-negative bacteria like the model Myxococcus xanthus which have four different mechanisms[9] of polysaccharide secretion and where a new Wzx/Wzy mechanism producing a new
polysaccharide was identified in 2020.[9]
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.[11][12] 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.[15]
It has been suggested that the last common ancestor of myxobacteria was an aerobe and that their anaerobic predecessors lived syntrophically with early eukaryotes.[16]
Myxobacteria are also known to produce
gephyronic acid, an inhibitor of eukaryotic protein synthesis and a potential agent for cancer chemotherapy.[18]