Myxobacteria
Encyclopedia
The myxobacteria are a group of bacteria
that predominantly live in the soil. The myxobacteria have very large genome
s, relative to other bacteria, e.g. 9-10 million nucleotide
s. Sorangium cellulosum
has the largest known (as of 2008) bacterial genome, at 13.0 million nucleotides. Myxobacteria are included among the delta group
of proteobacteria
, a large taxon of Gram-negative
forms.
Myxobacteria can move actively by gliding
. They typically travel in swarm
s (also known as wolf packs), containing many cell
s kept together by intercellular molecular signals
. This close concentration of cells may be necessary to provide a high concentration of extracellular enzyme
s used to digest food. Myxobacteria produce a number of biomedically and industrially useful chemicals, such as antibiotic
s, and export those chemicals outside of the cell.
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 spore
s in other organisms, are meant 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 mould
s.
At a molecular level, initiation of fruiting body development is regulated by Pxr sRNA
.
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
is a U.S. Food and Drug Administration approved chemotherapy agent for the treatment of metastatic breast cancer
.
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
that predominantly live in the soil. The myxobacteria have very large genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
s, relative to other bacteria, e.g. 9-10 million nucleotide
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...
s. Sorangium cellulosum
Sorangium cellulosum
Sorangium cellulosum is a soil-dwelling Gram-negative bacterium of the group myxobacteria. It is motile and shows gliding motility. It has an unusually-large genome of 13,033,779 base pairs, making it the largest bacterial genome sequenced to date....
has the largest known (as of 2008) bacterial genome, at 13.0 million nucleotides. Myxobacteria are included among the delta group
Deltaproteobacteria
Deltaproteobacteria is a class of Proteobacteria. All species of this group are, like all Proteobacteria, gram-negative.The Deltaproteobacteria comprise a branch of predominantly aerobic genera, the fruiting-body-forming Myxobacteria which release myxospores in unfavorable environments, and a...
of proteobacteria
Proteobacteria
The Proteobacteria are a major group of bacteria. They include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and many other notable genera....
, a large taxon of Gram-negative
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...
forms.
Myxobacteria can move actively by gliding
Bacterial gliding
Bacterial gliding is a process whereby a bacterium can move under its own power. This process does not involve the use of flagella, which is a more common means of motility in bacteria...
. They typically travel in swarm
Swarm
Swarm behaviour, or swarming, is a collective behaviour exhibited by animals of similar size which aggregate together, perhaps milling about the same spot or perhaps moving en masse or migrating in some direction. As a term, swarming is applied particularly to insects, but can also be applied to...
s (also known as wolf packs), containing many cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s kept together by intercellular molecular signals
Signal transduction
Signal transduction occurs when an extracellular signaling molecule activates a cell surface receptor. In turn, this receptor alters intracellular molecules creating a response...
. This close concentration of cells may be necessary to provide a high concentration of extracellular enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s used to digest food. Myxobacteria produce a number of biomedically and industrially useful chemicals, such as antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
s, and export those chemicals outside of the cell.
Life cycle
When nutrients are scarce, myxobacterial cells aggregate into fruiting bodies, a process long-thought to be mediated by chemotaxisChemotaxis
Chemotaxis is the phenomenon in which somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food by swimming towards the highest concentration of food molecules,...
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 spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s in other organisms, are meant to survive until nutrients are more plentiful. The fruiting process is thought to benefit myxobacteria by ensuring that cell growth
Cell growth
The term cell growth is used in the contexts of cell development and cell division . When used in the context of cell division, it refers to growth of cell populations, where one cell grows and divides to produce two "daughter cells"...
is resumed with a group (swarm) of myxobacteria, rather than as isolated cells. Similar life cycles have developed among certain amoebae, called cellular slime mould
Slime mould
Slime mold or mould is a broad term describing protists that use spores to reproduce. Slime molds were formerly classified as fungi, but are no longer considered part of this kingdom....
s.
At a molecular level, initiation of fruiting body development is regulated by Pxr sRNA
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 small number of the aggregated colony to transform into...
.
Clinical use
Metabolites secreted by Sorangium cellulosum known as epothiloneEpothilone
The epothilones are a new class of cancer drugs. Like taxanes, they prevent cancer cells from dividing by interfering with tubulin, but in early trials epithilones have better efficacy and milder adverse effects than taxanes....
s have been noted to have antineoplastic activity. This has led to the development of analogs
Analog (chemistry)
In chemistry, a structural analog , also known as chemical analog or simply analog, is a compound having a structure similar to that of another one, but differing from it in respect of a certain component. It can differ in one or more atoms, functional groups, or substructures, which are replaced...
which mimic its activity. One such analog, known as Ixabepilone
Ixabepilone
Ixabepilone is an epothilone B analog developed by Bristol-Myers Squibb as a cancer drug.It is produced by Sorangium cellulosum.-Pharmacology:It acts to stabilize microtubules....
is a U.S. Food and Drug Administration approved chemotherapy agent for the treatment of metastatic breast cancer
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
.