| Neorhizobium | |
|---|---|
Scientific classification  | |
| Domain: | Bacteria |
| Phylum: | Pseudomonadota |
| Class: | Alphaproteobacteria |
| Order: | Hyphomicrobiales |
| Family: | Rhizobiaceae |
| Genus: | Neorhizobium Mousavi et al. 2014 [1] |
| Type species | |
| Neorhizobium galegae Lindström 1989 | |
| Species [2] | |
| |
Neorhizobium is a genus of Gram-negative soil bacteria that fix nitrogen. It was recently segregated from the genus Rhizobium . Neorhizobium forms an endosymbiotic nitrogen-fixing association with roots of legumes.
Rhizobia are diazotrophic bacteria that fix nitrogen after becoming established inside the root nodules of legumes (Fabaceae). To express genes for nitrogen fixation, rhizobia require a plant host; they cannot independently fix nitrogen. In general, they are gram negative, motile, non-sporulating rods.
Rhizobium is a genus of Gram-negative soil bacteria that fix nitrogen. Rhizobium species form an endosymbiotic nitrogen-fixing association with roots of (primarily) legumes and other flowering plants.
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. Agrobacterium is well known for its ability to transfer DNA between itself and plants, and for this reason it has become an important tool for genetic engineering.
Ensifer meliloti are an aerobic, Gram-negative, and diazotrophic species of bacteria. S. meliloti are motile and possess a cluster of peritrichous flagella. S. meliloti fix atmospheric nitrogen into ammonia for their legume symbionts, such as alfalfa. S. meliloti forms a symbiotic relationship with legumes from the genera Medicago, Melilotus and Trigonella, including the model legume Medicago truncatula. This symbiosis promotes the development of a plant organ, termed a root nodule. Because soil often contains a limited amount of nitrogen for plant use, the symbiotic relationship between S. meliloti and their legume hosts has agricultural applications. These techniques reduce the need for inorganic nitrogenous fertilizers.
Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia. This process has evolved multiple times within the legumes, as well as in other species found within the Rosid clade. Legume crops include beans, peas, and soybeans.
The Rhizobiaceae is a family of Pseudomonadota comprising multiple subgroups that enhance and hinder plant development. Some bacteria found in the family are used for plant nutrition and collectively make up the rhizobia. Other bacteria such as Agrobacterium tumefaciens and Rhizobium rhizogenes severely alter the development of plants in their ability to induce crown galls or hairy roots, respectively. The family has been of an interest to scientists for centuries in their ability to associate with plants and modify plant development. The Rhizobiaceae are, like all Pseudomonadota, Gram-negative. They are aerobic, and the cells are usually rod-shaped. Many species of the Rhizobiaceae are diazotrophs which are able to fix nitrogen and are symbiotic with plant roots.
The Hyphomicrobiales are an order of Gram-negative Alphaproteobacteria.
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 (N2); they must use nitrogen compounds such as nitrates.
The nif genes are genes encoding enzymes involved in the fixation of atmospheric nitrogen into a form of nitrogen available to living organisms. The primary enzyme encoded by the nif genes is the nitrogenase complex which is in charge of converting atmospheric nitrogen (N2) to other nitrogen forms such as ammonia which the organism can use for various purposes. Besides the nitrogenase enzyme, the nif genes also encode a number of regulatory proteins involved in nitrogen fixation. The nif genes are found in both free-living nitrogen-fixing bacteria and in symbiotic bacteria associated with various plants. The expression of the nif genes is induced as a response to low concentrations of fixed nitrogen and oxygen concentrations (the low oxygen concentrations are actively maintained in the root environment of host plants). The first Rhizobium genes for nitrogen fixation (nif) and for nodulation (nod) were cloned in the early 1980s by Gary Ruvkun and Sharon R. Long in Frederick M. Ausubel's laboratory.
Trophic mutualism is a key type of ecological mutualism. Specifically, "trophic mutualism" refers to the transfer of energy and nutrients between two species. This is also sometimes known as resource-to-resource mutualism. Trophic mutualism often occurs between an autotroph and a heterotroph. Although there are many examples of trophic mutualisms, the heterotroph is generally a fungus or bacteria. This mutualism can be both obligate and opportunistic.
Agricultural microbiology is a branch of microbiology dealing with plant-associated microbes and plant and animal diseases. It also deals with the microbiology of soil fertility, such as microbial degradation of organic matter and soil nutrient transformations.
Bradyrhizobium japonicum is a species of legume-root nodulating, microsymbiotic nitrogen-fixing bacteria. The species is one of many Gram-negative, rod-shaped bacteria commonly referred to as rhizobia. Within that broad classification, which has three groups, taxonomy studies using DNA sequencing indicate that B. japonicum belongs within homology group II.
Neorhizobium galegae is a Gram negative root nodule bacteria. It forms nitrogen-fixing root nodules on legumes in the genus Galega.
Ensifer fredii is a nitrogen fixing bacteria of the genus Sinorhizobium. It is a fast-growing root nodule bacteria. Sinorhizobium fredii exhibit a broad host-range and are able to nodulate both determinant hosts such as soy as well as indeterminate hosts including the pigeon pea. Because of their ease of host infection there is interest in their genetics and the symbiotic role in host infection and nodule formation.
Pararhizobium giardinii is a Gram negative root nodule bacteria. It forms nitrogen-fixing root nodules on legumes, being first isolated from those of Phaseolus vulgaris.
Rhizobium mongolense is a Gram negative root nodule bacteria, which nodulates and forms nitrogen-fixing symbioses with Medicago ruthenica. Its type strain is USDA 1844.
Neorhizobium huautlense is a Gram negative root nodule bacterium. It forms nitrogen-fixing root nodules on Sesbania herbacea.
Mesorhizobium ciceri is a gram-negative, nitrogen-fixing motile bacteria from the genus of Mesorhizobium which was isolated from Chickpea nodules of Cicer arietinum in Spain. Rhizobium cicero was transferred to Mesorhizobium ciceri.
Pararhizobium is a genus of Gram-negative soil bacteria that fix nitrogen. Some species of Pararhizobium form an endosymbiotic nitrogen-fixing association with roots of legumes.
Allorhizobium is a genus of Gram-negative soil bacteria. Some species of Allorhizobium form an endosymbiotic nitrogen-fixing association with roots of legumes, while others are known to cause crown gall.