Bradyrhizobium

About: Bradyrhizobium is a research topic. Over the lifetime, 1872 publications have been published within this topic receiving 49420 citations. The topic is also known as: P. carboxydohydrogena.

Infection and Invasion of Roots by Symbiotic, Nitrogen-Fixing Rhizobia during Nodulation of Temperate Legumes

Abstract: Bacteria belonging to the genera Rhizobium, Mesorhizobium, Sinorhizobium, Bradyrhizobium, and Azorhizobium (collectively referred to as rhizobia) grow in the soil as free-living organisms but can also live as nitrogen-fixing symbionts inside root nodule cells of legume plants. The interactions between several rhizobial species and their host plants have become models for this type of nitrogen-fixing symbiosis. Temperate legumes such as alfalfa, pea, and vetch form indeterminate nodules that arise from root inner and middle cortical cells and grow out from the root via a persistent meristem. During the formation of functional indeterminate nodules, symbiotic bacteria must gain access to the interior of the host root. To get from the outside to the inside, rhizobia grow and divide in tubules called infection threads, which are composite structures derived from the two symbiotic partners. This review focuses on symbiotic infection and invasion during the formation of indeterminate nodules. It summarizes root hair growth, how root hair growth is influenced by rhizobial signaling molecules, infection of root hairs, infection thread extension down root hairs, infection thread growth into root tissue, and the plant and bacterial contributions necessary for infection thread formation and growth. The review also summarizes recent advances concerning the growth dynamics of rhizobial populations in infection threads.

Legumes Symbioses: Absence of Nod Genes in Photosynthetic Bradyrhizobia

Abstract: Leguminous plants (such as peas and soybeans) and rhizobial soil bacteria are symbiotic partners that communicate through molecular signaling pathways, resulting in the formation of nodules on legume roots and occasionally stems that house nitrogen-fixing bacteria. Nodule formation has been assumed to be exclusively initiated by the binding of bacterial, host-specific lipochito-oligosaccharidic Nod factors, encoded by the nodABC genes, to kinase-like receptors of the plant. Here we show by complete genome sequencing of two symbiotic, photosynthetic, Bradyrhizobium strains, BTAi1 and ORS278, that canonical nodABC genes and typical lipochito-oligosaccharidic Nod factors are not required for symbiosis in some legumes. Mutational analyses indicated that these unique rhizobia use an alternative pathway to initiate symbioses, where a purine derivative may play a key role in triggering nodule formation.

NOTES: Transfer of Rhizobium japonicum Buchanan 1980 to Bradyrhizobium gen. nov., a Genus of Slow-Growing, Root Nodule Bacteria from Leguminous Plants

Abstract: Recent data indicate that the slow-growing, non-acid-producing root nodule bacteria of leguminous plants should be separated from the fast-growing, acid-producing strains and placed in a new genus. The separation is warranted by numerical taxonomy, deoxyribonucleic acid base ratio determinations, nucleic acid hybridization, ribosomal ribonucleic acid cistron similarities, serology, composition of extracellular gum, carbohydrate utilization and metabolism, bacteriophage and antibiotic susceptibilities, protein composition, and types of intracellular inclusion bodies in the bacteroid forms. The name proposed for the new genus is Bradyrhizobium. The type species of the genus is B. japonicum (Buchanan 1980) comb. nov. (basonym: Rhizobium japonicum Buchanan 1980), the type strain of which is ATCC 10324.