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 hosts, 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.
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.
Agromyces is a genus in the phylum Actinomycetota (Bacteria).
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.
Mesorhizobium tianshanense, formerly known as Rhizobium tianshanense, is a Gram negative species of bacteria found in the root nodules of many plant species. Its type strain is A-1BS.
Mesorhizobium plurifarium is a species of root nodule bacteria first isolated from Acacia species in Senegal. Its type strain is ORS 1032.
Rhizobium hainanense is a Gram negative root nodule bacteria. Strain CCBAU 57015 (166) is the type strain.
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.
Mesorhizobium mediterraneum is a bacterium from the genus Mesorhizobium, which was isolated from root nodule of the Chickpea in Spain. The species Rhizobium mediterraneum was subsequently transferred to Mesorhizobium mediterraneum. This species, along with many other closely related taxa, have been found to promote production of chickpea and other crops worldwide by forming symbiotic relationships.
Virgibacillus is a genus of Gram-positive, rod-shaped (bacillus) bacteria and a member of the phylum Bacillota. Virgibacillus species can be obligate aerobes, or facultative anaerobes and catalase enzyme positive. Under stressful environmental conditions, the bacteria can produce oval or ellipsoidal endospores in terminal, or sometimes subterminal, swollen sporangia. The genus was recently reclassified from the genus Bacillus in 1998 following an analysis of the species V. pantothenticus. Subsequently, a number of new species have been discovered or reclassified as Virgibacillus species.
Rhizobium indigoferae is a Gram negative root nodule bacteria, which nodulates and forms nitrogen-fixing symbioses with Indigofera species. Its type strain is CCBAU 71714(T).
Ensifer medicae is a species of gram-negative, nitrogen-fixing, rod-shaped bacteria. They can be free-living or symbionts of leguminous plants in root nodules. E.medicae was first isolated from root nodules on plants in the genus Medicago. Some strains of E.medicae, like WSM419, are aerobic. They are chemoorganotrophic mesophiles that prefer temperatures around 28 °C. In addition to their primary genome, these organisms also have three known plasmids, sized 1,570,951 bp, 1,245,408 bp and 219,313 bp.
Ancylobacter polymorphus is a bacterium from the family of Xanthobacteraceae.
Ancylobacter vacuolatus is a bacterium from the family of Xanthobacteraceae which has been isolated from soil.
Azospirillum is a Gram-negative, microaerophilic, non-fermentative and nitrogen-fixing bacterial genus from the family of Rhodospirillaceae. Azospirillum bacteria can promote plant growth.
Ensifer numidicus is a nitrogen fixing symbiont of Fabaceae. gram-negative, aerobic, non-spore forming, rod-shaped bacterium of the family Rhizobiaceae. First described in 2010; more biovars have since been isolated and described with ORS 1407 considered the representative organism. Most examples have been found in arid and infra-arid regions of Tunisia.
