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.
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.
Nod factors, are signaling molecules produced by soil bacteria known as rhizobia in response to flavonoid exudation from plants under nitrogen limited conditions. Nod factors initiate the establishment of a symbiotic relationship between legumes and rhizobia by inducing nodulation. Nod factors produce the differentiation of plant tissue in root hairs into nodules where the bacteria reside and are able to fix nitrogen from the atmosphere for the plant in exchange for photosynthates and the appropriate environment for nitrogen fixation. One of the most important features provided by the plant in this symbiosis is the production of leghemoglobin, which maintains the oxygen concentration low and prevents the inhibition of nitrogenase activity.
Sharon Rugel Long is an American plant biologist. She is the Steere-Pfizer Professor of Biological Science in the Department of Biology at Stanford University, and the Principal Investigator of the Long Laboratory at Stanford.
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.
Ensifer is a genus of nitrogen-fixing bacteria (rhizobia), three of which have been sequenced.
Medicago intertexta, the hedgehog medick, Calvary clover, or Calvary medick, is a flowering plant of the family Fabaceae. It is found primarily in the western Mediterranean basin. It forms a symbiotic relationship with the bacterium Sinorhizobium medicae, which is capable of nitrogen fixation.
Medicago murex, the spiny medick, is a plant species of the genus Medicago. It is found throughout the Mediterranean basin. It forms a symbiotic relationship with the bacterium Sinorhizobium medicae, which is capable of nitrogen fixation.
Medicago orbicularis is a plant species found throughout the Mediterranean basin and along the European Black Sea coast. It forms a symbiotic relationship with the bacterium Sinorhizobium medicae, which is capable of nitrogen fixation. Common names include blackdisk medick, button clover, button medick, and round-fruited medick.
Medicago rotata is a species of flowering plant in the Fabaceae family. It is found throughout the eastern Mediterranean from Turkey to Israel. It forms a symbiotic relationship with the bacterium Sinorhizobium medicae, which is capable of nitrogen fixation.
Medicago ciliaris, the ciliate medick, is a plant species of the genus Medicago. It is found throughout the Mediterranean basin. It forms a symbiotic relationship with the bacterium Sinorhizobium medicae, which is capable of nitrogen fixation. It is considered by some to be a subspecies of Medicago intertexta.
Actinorhizal plants are a group of angiosperms characterized by their ability to form a symbiosis with the nitrogen fixing actinomycetota Frankia. This association leads to the formation of nitrogen-fixing root nodules.
Within genetics, post-genomic research has rendered bacterial small non-coding RNAs (sRNAs) as major players in post-transcriptional regulation of gene expression in response to environmental stimuli. The Alphaproteobacteria includes Gram-negative microorganisms with diverse life styles; frequently involving long-term interactions with higher eukaryotes.
Trigonella suavissima is a herbaceous plant that is endemic to Australia. It is a member of the genus Trigonella and the family Fabaceae. Common names include Cooper clover, Menindee clover, calomba, Darling trigonella, sweet fenugreek, channel clover, sweet-scented clover and Australian shamrock.
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.
Microvirga lotononidis is a nitrogen fixing, Gram-negative, rod-shaped and non-spore-forming root-nodule bacteria from the genus of Microvirga. Microvirga lotononidis lives in symbiosis with Listia angolensis.
Microvirga lupini is a nitrogen-fixing, Gram-negative, aerobic rod-shaped and non-spore-forming bacteria from the genus of Microvirga.
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.
