Alphaproteobacteria
Encyclopedia
Alphaproteobacteria is a class of Proteobacteria
. Like all Proteobacteria, they are Gram-negative
.
ic genera, but also several genera metabolising C1-compounds (e.g. Methylobacterium spp.), symbionts of plants (e.g. Rhizobium
spp.) and animals, and a group of pathogens, the Rickettsiaceae
. Moreover the precursors of the mitochondria of eukaryotic cells are thought to have originated from Rickettsia
spp. in this class (See endosymbiotic theory
.). Because of their symbiotic properties scientists often use Alphaproteobacteria of the genus Agrobacterium
to transfer foreign DNA into plant genomes and they also have many other biotechnological properties.
Aerobic anoxygenic phototrophic bacteria
are alphaproteobacteria that are a widely distributed marine plankton which may constitute over 10% of the open ocean microbial community.
There have been seven orders described.
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....
. Like all Proteobacteria, 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...
.
Characteristics
The Alphaproteobacteria comprise most phototrophPhototroph
Phototrophs are the organisms that carry out photosynthesis to acquire energy. They use the energy from sunlight to convert carbon dioxide and water into organic material to be utilized in cellular functions such as biosynthesis and respiration.Most phototrophs are autotrophs, also known as...
ic genera, but also several genera metabolising C1-compounds (e.g. Methylobacterium spp.), symbionts of plants (e.g. 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....
spp.) and animals, and a group of pathogens, the Rickettsiaceae
Rickettsiaceae
The Rickettsiaceae are a family of bacteria, including most notably the genus Rickettsia.Most human pathogens are in genus Rickettsia. They spend part of their life cycle in the bodies of arthropods such as ticks or lice, and are then transmitted to humans or other mammals by the bite of the...
. Moreover the precursors of the mitochondria of eukaryotic cells are thought to have originated from Rickettsia
Rickettsia
Rickettsia is a genus of non-motile, Gram-negative, non-sporeforming, highly pleomorphic bacteria that can present as cocci , rods or thread-like . Being obligate intracellular parasites, the Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells...
spp. in this class (See endosymbiotic theory
Endosymbiotic theory
The endosymbiotic theory concerns the mitochondria, plastids , and possibly other organelles of eukaryotic cells. According to this theory, certain organelles originated as free-living bacteria that were taken inside another cell as endosymbionts...
.). Because of their symbiotic properties scientists often use Alphaproteobacteria of the genus 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...
to transfer foreign DNA into plant genomes and they also have many other biotechnological properties.
Aerobic anoxygenic phototrophic bacteria
Aerobic anoxygenic phototrophic bacteria
Aerobic anoxygenic phototrophic bacteria are alphaproteobacteria that are obligate aerobes which capture energy from light by anoxygenic photosynthesis. They are widely distributed marine plankton which may constitute over 10% of the open ocean microbial community. They can be particularly...
are alphaproteobacteria that are a widely distributed marine plankton which may constitute over 10% of the open ocean microbial community.
Classification
Families, most of which belong to the Rhizobiales order, include:- AnaplasmataceaeAnaplasmataceaeAnaplasmataceae is a Proteobacteria family that includes genera Anaplasma, Ehrlichia, Neorickettsia and Wolbachia....
- BartonellaceaeBartonellaceaeThe Bartonellaceae are a family of Rhizobiales that contains the genus Bartonella, which has eight species of bacteria which are pathogenic to humans....
- BeijerinckiaceaeBeijerinckiaceaeThe Beijerinckiaceae are a family of Rhizobiales. They are named after the Dutch microbiologist Martinus Willem Beijerinck. The Beijerinckia are free living nitrogen fixing bacteria....
- BradyrhizobiaceaeBradyrhizobiaceaeThe 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...
- BrucellaceaeBrucellaceaeThe Brucellaceae are a family of the gram-negative Rhizobiales. They are named after Sir David Bruce, a Scottish microbiologist. They are aerobic chemoorganotrophes.. The family comprises pathogen and soil bacteria...
- CaulobacteraceaeCaulobacteraceaeCaulobacteraceae is a family of proteobacteria, given its own order within the alpha subgroup. Like all Proteobacteria, the Caulobacteraceae are gram-negative. Caulobacteraceae includes genera Brevundimonas and Caulobacter.-References:...
- HolosporaceaeHolosporaceaeThe Holosporaceae are a family of bacteria, included in the order Rickettsiales....
- HyphomicrobiaceaeHyphomicrobiaceaeThe Hyphomicrobiaceae are a family of bacteria. Among others, they include Rhodomicrobium, a genus of purple bacteria....
- Kiloniellaceae
- "Kopriimonadaceae"
- Kordiimonadaceae
- MethylobacteriaceaeMethylobacteriaceaeThe Methylobacteriaceae are a family of Rhizobiales....
- MethylocystaceaeMethylocystaceaeThe Methylocystaceae are a family of bacteria that are capable of obtaining carbon and energy from methane. Such bacteria are called methanotrophs, and in particular the Methylocystaceae comprise the type II methanotrophs, which are structurally and biochemically distinct from the Methylococcaceae...
- "Parvularculaceae"
- RhizobiaceaeRhizobiaceaeThe 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...
- RhodobacteraceaeRhodobacteraceaeThe Rhodobacteraceae are a family of proteobacteria, given their own order within the alpha subgroup. Like all proteobaceria, they are gram-negative. It contains chemoorganotrophs and photoheterotrophs bacteria. Many occur in aquatic habitats....
- RickettsiaceaeRickettsiaceaeThe Rickettsiaceae are a family of bacteria, including most notably the genus Rickettsia.Most human pathogens are in genus Rickettsia. They spend part of their life cycle in the bodies of arthropods such as ticks or lice, and are then transmitted to humans or other mammals by the bite of the...
- Sneathiellaceae
- SphingomonadaceaeSphingomonadaceaeSphingomonadaceae are a family of Alpha Proteobacteria that contain all the sphingomonads....
There have been seven orders described.