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 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.
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.
Root hairs or absorbent hairs, are outgrowths of epidermal cells, specialized cells at the tip of a plant root. They are lateral extensions of a single cell and are only rarely branched. They are found in the region of maturation, of the root. Root hair cells improve plant water absorption by increasing root surface area to volume ratio which allows the root hair cell to take in more water. The large vacuole inside root hair cells makes this intake much more efficient. Root hairs are also important for nutrient uptake as they are main interface between plants and mycorrhizal fungi.
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.
Horizontal transmission is the transmission of organisms between biotic and/or abiotic members of an ecosystem that are not in a parent-progeny relationship. Because the evolutionary fate of the agent is not tied to reproductive success of the host, horizontal transmission tends to evolve virulence. It is therefore a critical concept for evolutionary medicine.
Jeffery Lee Dangl is an American biologist. He is currently John N. Couch Professor of Biology at the University of North Carolina at Chapel Hill.
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.
Rhizobium hainanense is a Gram negative root nodule bacteria. Strain CCBAU 57015 (166) is the type strain.
Ulrike Mathesius is a German–Australian plant microbiologist in the Division of Plant Sciences at Australian National University (ANU). She is an Australian Research Council (ARC) Future Fellow at the ANU, National Tertiary Education Union (NTEU) member and Professor at the ANU in plant science, biotechnology and plant-microbe interactions. Her research focuses on root microbe interactions and symbionts to parasites. Mathesius won the 2013 Fenner Medal awarded by the ARC for research in biology for outstanding early-career researchers under the age of 40.
Giles Edward Dixon Oldroyd is a professor at the University of Cambridge, working on beneficial Legume symbioses in Medicago truncatula. He has been a Royal Society Wolfson Research Merit Award winner and the Society of Biology (SEB) President's Medal winner. From 2014 Oldroyd has been in the top 1% of highly cited plant scientists across the world.
Martin Parniske is a German biologist with a specialisation in genetics, microbiology and biochemistry. He is university professor and head of the Institute of Genetics at the Faculty of Biology of the Ludwig Maximilian University of Munich. Parniske's scientific focus is on the molecular interaction between plants and symbiotic and pathogenic organisms including bacteria, fungi, oomycetes and insects.
A symbiosome is a specialised compartment in a host cell that houses an endosymbiont in a symbiotic relationship.
Felix Dapare Dakora, is a Ghanaian plant biologist investigating biological nitrogen fixation at the Tshwane University of Technology in South Africa. He currently serves as President of The African Academy of Sciences for the 2017–2023 terms. Dakora was awarded the UNESCO-Equatorial Guinea International Prize for Research in the Life Sciences and the African Union Kwame Nkrumah Scientific Award. Dakora is a Fellow of the Academy of Science of South Africa.
Ilona Banga (1906–1998) was a Hungarian biochemist known for co-discovering actomyosin and working to characterize how actin and myosin interact to produce muscle contraction. She and her husband József Mátyás Baló discovered the first elastase – an enzyme capable of degrading the protein elastin which gives tissues like veins their flexibility. She also contributed to work that earned Albert Szent-Györgyi the Nobel Prize in Physiology or Medicine in 1937, including by developing methods for the purification and characterization of large quantities of vitamin C. During World War II she saved the equipment of the Institute of Chemistry of the University of Szeged.
Jean Dénarié is a French biologist, member of the French Academy of sciences since December 2008.
Regine Kahmann is a German microbiologist and was Director at the Max Planck Institute for Terrestrial Microbiology in Marburg from 2000 to 2019. She was made a Foreign Member of the Royal Society (ForMRS) in 2020.
Esperanza Martínez-Romero is a researcher and head of the Genomic Ecology Program at the Center for Genomic Sciences (CCG) of the National Autonomous University of Mexico (UNAM) in Cuernavaca, Mexico. She was awarded the L'Oréal-UNESCO For Women in Science Award in 2020.
