| betaine use by rhizosphere bacteria: genes essential for trigonelline, stachydrine, and carnitine catabolism in rhizobium meliloti are located on psym in the symbiotic region. | rhizobium meliloti is known to use betaines synthesized by its host, medicago sativa, as osmoprotectants and sources of energy. it is shown in the present report that the symbiotic megaplasmid (psym) of r. meliloti rcr2011 encodes functions essential to the catabolism of three betaines, trigonelline (nicotinic acid n-methylbetaine), stachydrine (proline betaine or dimethylproline), and carnitine (gamma-trimethyl-beta-hydroxybutyrobetaine). preliminary evidence is presented showing that functions ... | 1991 | 1804402 |
| induction of rhizobium meliloti nodc expression by plant exudate requires nodd. | the soil bacterium rhizobium meliloti invades and establishes a symbiosis with host plants such as alfalfa. bacterial nodulation (nod) genes are required for this invasion, but their mechanism of action and the timing of their expression are not known. we have used translational lacz fusions to monitor expression of nodd and nodc, which are located in the cluster of four nod genes on the r. meliloti megaplasmid (psym). nodd is expressed at comparable levels by broth-grown bacterial cells and by ... | 1985 | 3931078 |
| isolation and characterization of a dna replication origin from the 1,700-kilobase-pair symbiotic megaplasmid psym-b of rhizobium meliloti. | a 4-kb fragment active as an autonomously replicating sequence (ars) from the rhizobium meliloti symbiotic megaplasmid psym-b was isolated by selecting for sequences that allowed a normally nonreplicative pbr322 derivative to replicate in r. meliloti. the resulting escherichia coli-r. meliloti shuttle plasmid (mini-psym-b) containing the ars also replicated in the closely related agrobacterium tumefaciens, but only in strains carrying psym-b, suggesting that a megaplasmid-encoded trans-acting fa ... | 1993 | 8407832 |
| rhizobium meliloti genes encoding catabolism of trigonelline are induced under symbiotic conditions. | rhizobium meliloti trc genes controlling the catabolism of trigonelline, a plant secondary metabolite often abundant in legumes, are closely linked to nif-nod genes on the symbiotic megaplasmid psym [boivin, c., malpica, c., rosenberg, c., denarie, j., goldman, a., fleury, v., maille, m., message, b., and tepfer, d. (1989). in molecular signals in the microbe-plant symbiotic and pathogenic systems. (berlin: springer-verlag), pp. 401-407]. to investigate the role of trigonelline catabolism in the ... | 1990 | 12354952 |