Azospirillum brasilense: A species of motile, free-living, gram-negative bacteria that occur in the soil. They are aerobic or microaerophilic and are sometimes capable of nitrogen fixation.Azospirillum: A genus of gram-negative aerobic bacteria that occurs free-living in the soil or associated with the roots of cereal crops or grasses (POACEAE).Gram-Negative Aerobic Bacteria: A large group of aerobic bacteria which show up as pink (negative) when treated by the gram-staining method. This is because the cell walls of gram-negative bacteria are low in peptidoglycan and thus have low affinity for violet stain and high affinity for the pink dye safranine.Glutamate Synthase: An enzyme that catalyzes the formation of 2 molecules of glutamate from glutamine plus alpha-ketoglutarate in the presence of NADPH. EC 184.108.40.206.Nitrogen Fixation: The process in certain BACTERIA; FUNGI; and CYANOBACTERIA converting free atmospheric NITROGEN to biologically usable forms of nitrogen, such as AMMONIA; NITRATES; and amino compounds.PII Nitrogen Regulatory Proteins: A family of signal transducing adaptor proteins that control the METABOLISM of NITROGEN. They are primarily found in prokaryotes.Flocculation: The aggregation of suspended solids into larger clumps.Nitrogenase: An enzyme system that catalyzes the fixing of nitrogen in soil bacteria and blue-green algae (CYANOBACTERIA). EC 220.127.116.11.Dinitrogenase Reductase: A non-heme iron-sulfur protein isolated from Clostridium pasteurianum and other bacteria. It is a component of NITROGENASE along with molybdoferredoxin and is active in nitrogen fixation.Spirillum: A genus of gram-negative, curved and spiral-shaped bacteria found in stagnant, freshwater environments. These organisms are motile by bipolar tufts of flagella having a long wavelength and about one helical turn. Some species of Spirillum cause a form of RAT-BITE FEVER.Hydroxybutyrates: Salts and esters of hydroxybutyric acid.Polyesters: Polymers of organic acids and alcohols, with ester linkages--usually polyethylene terephthalate; can be cured into hard plastic, films or tapes, or fibers which can be woven into fabrics, meshes or velours.Plant Roots: The usually underground portions of a plant that serve as support, store food, and through which water and mineral nutrients enter the plant. (From American Heritage Dictionary, 1982; Concise Dictionary of Biology, 1990)Gene Expression Regulation, Bacterial: Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in bacteria.Genes, Bacterial: The functional hereditary units of BACTERIA.Atriplex: A plant genus in the CHENOPODIACEAE family.Triticum: A plant genus of the family POACEAE that is the source of EDIBLE GRAIN. A hybrid with rye (SECALE CEREALE) is called TRITICALE. The seed is ground into FLOUR and used to make BREAD, and is the source of WHEAT GERM AGGLUTININS.Quaternary Ammonium Compounds: Derivatives of ammonium compounds, NH4+ Y-, in which all four of the hydrogens bonded to nitrogen have been replaced with hydrocarbyl groups. These are distinguished from IMINES which are RN=CR2.Ammonia: A colorless alkaline gas. It is formed in the body during decomposition of organic materials during a large number of metabolically important reactions. Note that the aqueous form of ammonia is referred to as AMMONIUM HYDROXIDE.Chemotaxis: The movement of cells or organisms toward or away from a substance in response to its concentration gradient.Bacterial Proteins: Proteins found in any species of bacterium.Glutamate-Ammonia Ligase: An enzyme that catalyzes the conversion of ATP, L-glutamate, and NH3 to ADP, orthophosphate, and L-glutamine. It also acts more slowly on 4-methylene-L-glutamate. (From Enzyme Nomenclature, 1992) EC 18.104.22.168.