The myxobacteria ("slime bacteria") are a group of
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
that predominantly live in the soil and feed on insoluble organic substances. The myxobacteria have very large
genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding g ...
s relative to other bacteria, e.g. 9–10 million
nucleotide
Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecule ...
s 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
''Sorangium cellulosum'' is a soil-dwelling Gram-negative bacterium of the group myxobacteria. It is motile and shows gliding motility. Under stressful conditions this motility, as in other myxobacteria, the cells congregate to form fruiting bodi ...
''.
Myxobacteria can move by
gliding.
They typically travel in ''
swarm
Swarm behaviour, or swarming, is a collective behaviour exhibited by entities, particularly animals, of similar size which aggregate together, perhaps milling about the same spot or perhaps moving ''en masse'' or migrating in some direction. ...
s'' (also known as ''wolf packs''), containing many
cell
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Locations
* Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery ...
s kept together by intercellular molecular
signals
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...
. Individuals benefit from aggregation as it allows accumulation of the extracellular
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
s 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.
Myxobacteria are used to study the polysaccharide production in gram-negative bacteria like the model ''
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, sapro ...
'' which have four different mechanisms
of polysaccharide secretion and where a new Wzx/Wzy mechanism producing a new
polysaccharide was identified in 2020.
Myxobacteria are also good models to study the
multicellularity
A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism.
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- ...
in the
bacterial
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...
world.
Life cycle
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
An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...
, called cellular
slime mold
Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic mul ...
s.
At a molecular level, initiation of fruiting body development in ''
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, sapro ...
'' is regulated by
Pxr sRNA
Pxr sRNA is a regulatory RNA which downregulates genes responsible for the formation of fruiting bodies in ''Myxococcus xanthus''. Fruiting bodies are aggregations of myxobacteria formed when nutrients are scarce, the fruiting bodies permit a smal ...
.
Myxobacteria such as ''
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, sapro ...
'' and ''
Stigmatella aurantiaca
''Stigmatella aurantiaca'' is a member of myxobacteria, a group of gram-negative bacteria with a complex developmental life cycle.
Classification
The bacterial nature of this organism was recognized by Thaxter in 1892, who grouped it among the ...
'' are used as
model organisms
A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the working ...
for the study of development.
It has been suggested that the last common ancestor of myxobacteria was an aerobe and that their anaerobic predecessors lived syntrophically with early eukaryotes.
Clinical use
Metabolites
In biochemistry, a metabolite is an intermediate or end product of metabolism.
The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, ...
secreted by ''
Sorangium cellulosum
''Sorangium cellulosum'' is a soil-dwelling Gram-negative bacterium of the group myxobacteria. It is motile and shows gliding motility. Under stressful conditions this motility, as in other myxobacteria, the cells congregate to form fruiting bodi ...
'' known as
epothilone
Epothilones are a class of potential cancer drugs. Like taxanes, they prevent cancer cells from dividing by interfering with tubulin, but in early trials, epothilones have better efficacy and milder adverse effects than taxanes.
, epothilones A t ...
s have been noted to have
antineoplastic activity. This has led to the development of
analogs which mimic its activity. One such analog, known as
Ixabepilone
Ixabepilone ( INN; also known as azaepothilone B, codenamed BMS-247550) is a pharmaceutical drug developed by Bristol-Myers Squibb as a chemotherapeutic medication for cancer.
History
Ixabepilone is a semi-synthetic analog of epothilone B, a na ...
is a
U.S. Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...
approved chemotherapy agent for the treatment of
metastatic
Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then, ...
breast cancer
Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a r ...
.
Myxobacteria are also known to produce
gephyronic acid, an inhibitor of eukaryotic protein synthesis and a potential agent for cancer chemotherapy.
Phylogeny
The currently accepted taxonomy is based on the
List of Prokaryotic names with Standing in Nomenclature
List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the nomenclature, naming and Taxonomy (biology), taxonomy of prokaryotes, following the taxonomy requirements and rulings of the In ...
(LPSN)
and
National Center for Biotechnology Information
The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The ...
(NCBI)
See also
*
List of bacterial orders
This article lists the orders of the Bacteria. The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI)
and the phylogeny is based on 16S ...
*
List of bacteria genera This article lists the genera of the bacteria. The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI). However many taxonomic names are ...
References
External links
The Myxobacteria Web Page*
*
*
{{Taxonbar, from=Q1068698
Myxococcota