Rhizobiales
Encyclopedia
Rhizobiales is an order
of alpha proteobacteria
. They are gram-negative
.
The rhizobia
, which fix nitrogen
and are symbiotic with plant roots, appear in several different families here. The Bradyrhizobiaceae
, Hyphomicrobiaceae
, Phyllobacteriaceae
, and Rhizobiaceae
are the four families that contain at least six genera of nitrogen-fixing
, legume nodulating microsymbiotic bacteria. Examples are the genera Bradyrhizobium
and Rhizobium
. Species of Methylocystaceae are methanotroph
, they use methyl alcohol
(CH3OH) or methane
(CH4) as the sole energy and carbon source. Other important genera are Bartonella
(pathogen) and Agrobacterium
(genetic engineering
).
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of alpha 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....
. They are 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...
.
The rhizobia
Rhizobia
Rhizobia are soil bacteria that fix nitrogen after becoming established inside root nodules of legumes . Rhizobia require a plant host; they cannot independently fix nitrogen...
, which fix nitrogen
Nitrogen fixation
Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...
and are symbiotic with plant roots, appear in several different families here. The Bradyrhizobiaceae
Bradyrhizobiaceae
The Bradyrhizobiaceae are a family of bacteria, with ten genera. They include plant-associated bacteria such as Bradyrhizobium, a genus of rhizobia associated with some legumes. It also contains animal-associated bacteria such as Afipia felis, formerly thought to cause cat-scratch disease...
, Hyphomicrobiaceae
Hyphomicrobiaceae
The Hyphomicrobiaceae are a family of bacteria. Among others, they include Rhodomicrobium, a genus of purple bacteria....
, Phyllobacteriaceae
Phyllobacteriaceae
The Phyllobacteriaceae are a family of bacteria that contain nine genera. The most common of these is Mesorhizobium which contains some of the rhizobia species....
, and Rhizobiaceae
Rhizobiaceae
The Rhizobiaceae are a family of proteobacteria, including many species of rhizobia as well as plant parasites like Agrobacterium. Rhizobiaceae are, like all Proteobacteria, gram-negative. They are aerobic and the cells are usually rod-shaped. Many species of the Rhizobiaceae are diazotrophs, they...
are the four families that contain at least six genera of nitrogen-fixing
Nitrogen fixation
Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...
, legume nodulating microsymbiotic bacteria. Examples are the genera Bradyrhizobium
Bradyrhizobium
Bradyrhizobium is a genus of Gram-negative soil bacteria, many of which fix nitrogen. Nitrogen fixation is an important part of the nitrogen cycle. Plants cannot use atmospheric nitrogen they must use nitrogen compounds such as nitrates....
and Rhizobium
Rhizobium
Rhizobium is a genus of Gram-negative soil bacteria that fix nitrogen. Rhizobium forms an endosymbiotic nitrogen fixing association with roots of legumes and Parasponia....
. Species of Methylocystaceae are methanotroph
Methanotroph
Methanotrophs are bacteria that are able to metabolize methane as their only source of carbon and energy. They can grow aerobically or anaerobically and require single-carbon compounds to survive...
, they use methyl alcohol
Methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...
(CH3OH) or methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
(CH4) as the sole energy and carbon source. Other important genera are Bartonella
Bartonella
Bartonella is a genus of Gram-negative bacteria. Facultative intracellular parasites, Bartonella species can infect healthy people but are considered especially important as opportunistic pathogens. Bartonella are transmitted by insect vectors such as ticks, fleas, sand flies and mosquitoes...
(pathogen) and Agrobacterium
Agrobacterium
Agrobacterium is a genus of Gram-negative bacteria established by H. J. Conn that uses horizontal gene transfer to cause tumors in plants. Agrobacterium tumefaciens is the most commonly studied species in this genus...
(genetic engineering
Genetic engineering
Genetic engineering, also called genetic modification, is the direct human manipulation of an organism's genome using modern DNA technology. It involves the introduction of foreign DNA or synthetic genes into the organism of interest...
).